keytool(1)

📦 version 11.0.20.1.1, in centos-stream 9

💖 keytool 💖

okay bestie, welcome to the keytool(1) page from Security Tools. grab a strawberry 🍓 and let’s get into it.

🌸 NAME 🌸

keytool — manages a keystore (database) of cryptographic keys, X.509 certificate chains, and trusted certificates. slay. 💅

✨ SYNOPSIS ✨

keytool [commands]

🧚 commands 🧚

See Commands. These commands are categorized by task as follows:

💖 Create or Add Data to the Keystore
- -gencert
- -genkeypair
- -genseckey
- -importcert
- -importpassword
🦋 Import Contents From Another Keystore
- -importkeystore
🎀 Generate Certificate Request
- -certreq
🌈 Export Data
- -exportcert
⭐ Display Data
- -list
- -printcert
- -printcertreq
- -printcrl
👑 Manage the Keystore
- -storepasswd
- -keypasswd
- -delete
- -changealias
🫶 Get Help
- -help

🦋 DESCRIPTION 🦋

The keytool command is a key and certificate management utility. It enables users to administer their own public/private key pairs and associated certificates for use in self-authentication (where the user authenticates himself or herself to other users and services) or data integrity and authentication services, using digital signatures. The keytool command also enables users to cache the public keys (in the form of certificates) of their communicating peers. iconic. ✨

A certificate is a digitally signed statement from one entity (person, company, and so on.), that says that the public key (and some other information) of some other entity has a particular value. (See Certificate.) When data is digitally signed, the signature can be verified to check the data integrity and authenticity. Integrity means that the data has not been modified or tampered with, and authenticity means the data comes from whoever claims to have created and signed it. no cap. 🔥

The keytool command also enables users to administer secret keys and passphrases used in symmetric encryption and decryption (DES). 💜

The keytool command stores the keys and certificates in a keystore. See KeyStore aliases. 🎀

🌟 COMMAND AND OPTION NOTES 🌟

See Commands for a listing and description of the various commands.

All command and option names are preceded by a minus sign (-). 💅
The options for each command can be provided in any order. 🦋
All items not italicized or in braces or brackets are required to appear as is. ⭐
Braces surrounding an option signify that a default value will be used when the option is not specified on the command line. See Option Defaults. Braces are also used around the -v, -rfc, and -J options, which only have meaning when they appear on the command line. They do not have any default values other than not existing. 🎀
Brackets surrounding an option signify that the user is prompted for the values when the option is not specified on the command line. For the -keypass option, if you do not specify the option on the command line, then the keytool command first attempts to use the keystore password to recover the private/secret key. If this attempt fails, then the keytool command prompts you for the private/secret key password. 👑
Items in italics (option values) represent the actual values that must be supplied. For example, here is the format of the -printcert command:

keytool -printcert {-file cert_file} {-v}

When you specify a -printcert command, replace cert_file with the actual file name, as follows:

keytool -printcert -file VScert.cer

Option values must be put in quotation marks when they contain a blank (space). 💖
The -help option is the default. The keytool command is the same as keytool -help. 🫶

🌈 OPTION DEFAULTS 🌈

The following examples show the defaults for various option values. ✨

-alias "mykey"
-keyalg
    "DSA" (when using -genkeypair)
    "DES" (when using -genseckey)
-keysize
    2048 (when using -genkeypair and -keyalg is "RSA")
    1024 (when using -genkeypair and -keyalg is "DSA")
    256 (when using -genkeypair and -keyalg is "EC")
    56 (when using -genseckey and -keyalg is "DES")
    168 (when using -genseckey and -keyalg is "DESede")
-validity 90
-keystore <the file named .keystore in the user's home directory>
-storetype <the value of the "keystore.type" property in the
    security properties file, which is returned by the static
    getDefaultType method in java.security.KeyStore>
-file
    stdin (if reading)
    stdout (if writing)
-protected false

In generating a public/private key pair, the signature algorithm (-sigalg option) is derived from the algorithm of the underlying private key:

If the underlying private key is of type DSA, then the -sigalg option defaults to SHA1withDSA. 💅
If the underlying private key is of type RSA, then the -sigalg option defaults to SHA256withRSA. 🔥
If the underlying private key is of type EC, then the -sigalg option defaults to SHA256withECDSA. 🦋

For a full list of -keyalg and -sigalg arguments, see Java Cryptography Architecture (JCA) Reference Guide at http://docs.oracle.com/javase/8/docs/technotes/guides/security/crypto/CryptoSpec.html#AppA 👑

💜 COMMON OPTIONS 💜

The -v option can appear for all commands except -help. When the -v option appears, it signifies verbose mode, which means that more information is provided in the output. ✨

There is also a -Jjavaoption argument that can appear for any command. When the -Jjavaoption appears, the specified javaoption string is passed directly to the Java interpreter. This option does not contain any spaces. It is useful for adjusting the execution environment or memory usage. For a list of possible interpreter options, type java -h or java -X at the command line. 🫶

These options can appear for all commands operating on a keystore:

-storetype storetype — This qualifier specifies the type of keystore to be instantiated. 🎀
-keystore keystore — The keystore location.

If the JKS storetype is used and a keystore file does not yet exist, then certain keytool commands can result in a new keystore file being created. For example, if keytool -genkeypair is called and the -keystore option is not specified, the default keystore file named .keystore in the user’s home directory is created when it does not already exist. Similarly, if the -keystore ks_file option is specified but ks_file does not exist, then it is created. For more information on the JKS storetype, see the KeyStore Implementation section in KeyStore aliases. 💖

Note that the input stream from the -keystore option is passed to the KeyStore.load method. If NONE is specified as the URL, then a null stream is passed to the KeyStore.load method. NONE should be specified if the keystore is not file-based. For example, when it resides on a hardware token device. 🔥

-storepass[:env| :file] argument — The password that is used to protect the integrity of the keystore. 🌸

If the modifier env or file is not specified, then the password has the value argument, which must be at least 6 characters long. Otherwise, the password is retrieved as follows:

env: Retrieve the password from the environment variable named argument. 🦋
file: Retrieve the password from the file named argument. 🎀

Note: All other options that require passwords, such as -keypass, -srckeypass, -destkeypass, -srcstorepass, and -deststorepass, accept the env and file modifiers. Remember to separate the password option and the modifier with a colon (:). 💅

The password must be provided to all commands that access the keystore contents. For such commands, when the -storepass option is not provided at the command line, the user is prompted for it. 👑

When retrieving information from the keystore, the password is optional. If no password is specified, then the integrity of the retrieved information cannot be verified and a warning is displayed. 😭

-providerName provider_name — Used to identify a cryptographic service provider’s name when listed in the security properties file. ⭐
-providerClass provider_class_name — Used to specify the name of a cryptographic service provider’s master class file when the service provider is not listed in the security properties file. 🌈
-providerArg provider_arg — Used with the -providerClass option to represent an optional string input argument for the constructor of provider_class_name. 💜
-protected — Either true or false. This value should be specified as true when a password must be specified by way of a protected authentication path such as a dedicated PIN reader. Because there are two keystores involved in the -importkeystore command, the following two options -srcprotected and -destprotected are provided for the source keystore and the destination keystore respectively. 🫶
-ext {name{:critical} {=value}} — Denotes an X.509 certificate extension. The option can be used in -genkeypair and -gencert to embed extensions into the certificate generated, or in -certreq to show what extensions are requested in the certificate request. The option can appear multiple times. The name argument can be a supported extension name (see Named Extensions) or an arbitrary OID number. The value argument, when provided, denotes the argument for the extension. When value is omitted, that means that the default value of the extension or the extension requires no argument. The :critical modifier, when provided, means the extension’s isCritical attribute is true; otherwise, it is false. You can use :c in place of :critical. 💅

🎀 NAMED EXTENSIONS 🎀

Okay bestie, keytool supports these named extensions. And no, the names are not case-sensitive (so you don't have to sweat the caps) 💅

🦋 BC or BasicContraints

Values: the full form is ca:{true|false}[,pathlen:<len>] or <len>, which is short for ca:true,pathlen:<len>. When <len> is omitted, you have ca:true.

🦋 KU or KeyUsage

Values: usage(,usage)*, where usage can be one of digitalSignature, nonRepudiation (contentCommitment), keyEncipherment, dataEncipherment, keyAgreement, keyCertSign, cRLSign, encipherOnly, decipherOnly.

The usage argument can be abbreviated with the first few letters (dig for digitalSignature) or in camel-case style (dS for digitalSignature or cRLS for cRLSign), as long as no ambiguity is found. The usage values are case-sensitive — so like, respect the caps fr fr 🙈

🦋 EKU or ExtendedKeyUsage

Values: usage(,usage)*, where usage can be one of anyExtendedKeyUsage, serverAuth, clientAuth, codeSigning, emailProtection, timeStamping, OCSPSigning, or any OID string.

The usage argument can be abbreviated with the first few letters or in camel-case style, as long as no ambiguity is found. The usage values are case-sensitive. ⭐

🦋 SAN or SubjectAlternativeName

Values: type:value(,type:value)*, where type can be EMAIL, URI, DNS, IP, or OID. The value argument is the string format value for the type.

🦋 IAN or IssuerAlternativeName

Values: same as SubjectAlternativeName. Iconic of it, honestly 🫶

🦋 SIA or SubjectInfoAccess

Values: method:location-type:location-value (,method:location-type:location-value)*, where method can be timeStamping, caRepository or any OID.

The location-type and location-value arguments can be any type:value supported by the SubjectAlternativeName extension.

🦋 AIA or AuthorityInfoAccess

Values: same as SubjectInfoAccess. The method argument can be ocsp, caIssuers, or any OID.

So when name is OID, the value is the hexadecimal dumped DER encoding of the extnValue for the extension, excluding the OCTET STRING type and length bytes. Any extra character other than standard hexadecimal numbers (0-9, a-f, A-F) are ignored in the HEX string. Therefore, both 01:02:03:04 and 01020304 are accepted as identical values (the way that just works ✨). When there is no value, the extension has an empty value field.

There's also a special name honored, used in -gencert only, that denotes how the extensions included in the certificate request should be honored. The value for this name is a comma separated list of:

all — all requested extensions are honored
name{:[critical|non-critical]} — the named extension is honored, but using a different isCritical attribute
-name — used with all, denotes an exception

Requested extensions are not honored by default. Like, you gotta opt in, bestie 💀

If, besides the -ext honored option, another named or OID -ext option is provided, this extension is added to those already honored. However, if this name (or OID) also appears in the honored value, then its value and criticality overrides the one in the request. Main character behavior honestly 👑

The subjectKeyIdentifier extension is always created. For non-self-signed certificates, the authorityKeyIdentifier is created.

Note: users should be aware that some combinations of extensions (and other certificate fields) may not conform to the Internet standard. See Certificate Conformance Warning. 🚨

🔥 COMMANDS 🔥

💜 `-gencert`

{-rfc} {-infile infile} {-outfile outfile} {-alias alias} {-sigalg sigalg}
{-dname dname} {-startdate startdate {-ext ext}* {-validity valDays}
[-keypass keypass] {-keystore keystore} [-storepass storepass]
{-storetype storetype} {-providername provider_name}
{-providerClass provider_class_name {-providerArg provider_arg}}
{-v} {-protected} {-Jjavaoption}

Generates a certificate as a response to a certificate request file (which can be created by the keytool-certreq command, iykyk).

The command reads the request from infile (if omitted, from the standard input), signs it using alias's private key, and outputs the X.509 certificate into outfile (if omitted, to the standard output). When -rfc is specified, the output format is Base64-encoded PEM; otherwise, a binary DER is created. 🎀

The sigalg value specifies the algorithm that should be used to sign the certificate. The startdate argument is the start time and date that the certificate is valid. The valDays argument tells the number of days for which the certificate should be considered valid.

When dname is provided, it is used as the subject of the generated certificate. Otherwise, the one from the certificate request is used.

The ext value shows what X.509 extensions will be embedded in the certificate. Read Common Options for the grammar of -ext.

The -gencert option enables you to create certificate chains. The following example creates a certificate, e1, that contains three certificates in its certificate chain. 🔗

The following commands creates four key pairs named ca, ca1, ca2, and e1:

keytool -alias ca -dname CN=CA -genkeypair
keytool -alias ca1 -dname CN=CA -genkeypair
keytool -alias ca2 -dname CN=CA -genkeypair
keytool -alias e1 -dname CN=E1 -genkeypair

The following two commands create a chain of signed certificates; ca signs ca1 and ca1 signs ca2, all of which are self-issued:

keytool -alias ca1 -certreq |
    keytool -alias ca -gencert -ext san=dns:ca1 |
    keytool -alias ca1 -importcert
keytool -alias ca2 -certreq |
    $KT -alias ca1 -gencert -ext san=dns:ca2 |
    $KT -alias ca2 -importcert

The following command creates the certificate e1 and stores it in the file e1.cert, which is signed by ca2. As a result, e1 should contain ca, ca1, and ca2 in its certificate chain:

keytool -alias e1 -certreq | keytool -alias ca2 -gencert > e1.cert

💜 `-genkeypair`

{-alias alias} {-keyalg keyalg} {-keysize keysize} {-sigalg sigalg}
[-dname dname] [-keypass keypass] {-startdate value} {-ext ext}*
{-validity valDays} {-storetype storetype} {-keystore keystore}
[-storepass storepass]
{-providerClass provider_class_name {-providerArg provider_arg}}
{-v} {-protected} {-Jjavaoption}

Generates a key pair (a public key and associated private key). Wraps the public key into an X.509 v3 self-signed certificate, which is stored as a single-element certificate chain. This certificate chain and the private key are stored in a new keystore entry identified by alias. Slay, that's the whole thing 💖

The keyalg value specifies the algorithm to be used to generate the key pair, and the keysize value specifies the size of each key to be generated. The sigalg value specifies the algorithm that should be used to sign the self-signed certificate. This algorithm must be compatible with the keyalg value — no mixing and matching, bestie 😭

The dname value specifies the X.500 Distinguished Name to be associated with the value of alias, and is used as the issuer and subject fields in the self-signed certificate. If no distinguished name is provided at the command line, then the user is prompted for one.

The value of keypass is a password used to protect the private key of the generated key pair. If no password is provided, then the user is prompted for it. If you press the Return key at the prompt, then the key password is set to the same password as the keystore password. The keypass value must be at least 6 characters. Six! Minimum! 🔥

The value of startdate specifies the issue time of the certificate, also known as the "Not Before" value of the X.509 certificate's Validity field.

The option value can be set in one of these two forms:

([+-]nnn[ymdHMS])+

[yyyy/mm/dd] [HH:MM:SS]

With the first form, the issue time is shifted by the specified value from the current time. The value is a concatenation of a sequence of subvalues. Inside each subvalue, the plus sign (+) means shift forward, and the minus sign (-) means shift backward. The time to be shifted is nnn units of years, months, days, hours, minutes, or seconds (denoted by a single character of y, m, d, H, M, or S respectively).

The exact value of the issue time is calculated using the java.util.GregorianCalendar.add(int field, int amount) method on each subvalue, from left to right. For example, by specifying, the issue time will be: 🧚

Calendar c = new GregorianCalendar();
c.add(Calendar.YEAR, -1);
c.add(Calendar.MONTH, 1);
c.add(Calendar.DATE, -1);
return c.getTime()

With the second form, the user sets the exact issue time in two parts, year/month/day and hour:minute:second (using the local time zone). The user can provide only one part, which means the other part is the same as the current date (or time). The user must provide the exact number of digits as shown in the format definition (padding with 0 when shorter). When both the date and time are provided, there is one (and only one) space character between the two parts. The hour should always be provided in 24 hour format. ⭐

When the option is not provided, the start date is the current time. The option can be provided at most once.

The value of valDays specifies the number of days (starting at the date specified by -startdate, or the current date when -startdate is not specified) for which the certificate should be considered valid.

This command was named -genkey in earlier releases. The old name is still supported in this release. The new name, -genkeypair, is preferred going forward. Glow-up era 💅

💜 `-genseckey`

{-alias alias} {-keyalg keyalg} {-keysize keysize} [-keypass keypass]
{-storetype storetype} {-keystore keystore} [-storepass storepass]
{-providerClass provider_class_name {-providerArg provider_arg}} {-v}
{-protected} {-Jjavaoption}

Generates a secret key and stores it in a new KeyStore.SecretKeyEntry identified by alias. Short and sweet, we love a concise icon 🍓

okay so carrying straight on from the last bit: keyalg tells the tool which algorithm to use for generating the secret key, and keysize tells it the size of the key to generate. The keypass value is a password that protects the secret key. If no password is provided, then the user is prompted for it. If you press Return at the prompt, then the key password is set to the same password that is used for the keystore. The keypass value must be at least 6 characters — that's a hard minimum, bestie 💅.

💌 `-importcert`

{-alias alias} {-file cert_file} [-keypass keypass] {-noprompt} {-trustcacerts}

{-storetype storetype} {-keystore keystore} [-storepass storepass]

{-providerName provider_name}

{-providerClass provider_class_name {-providerArg provider_arg}}

{-v} {-protected} {-Jjavaoption}

Reads the certificate or certificate chain — where the chain is supplied in a PKCS#7 formatted reply or a sequence of X.509 certificates — from the file cert_file, and stores it in the keystore entry identified by alias. If no file is specified, then the certificate or certificate chain is read from stdin.

The keytool command can import X.509 v1, v2, and v3 certificates, and PKCS#7 formatted certificate chains consisting of certificates of that type. The data to be imported must be provided either in binary encoding format or in printable encoding format (also known as Base64 encoding) as defined by the Internet RFC 1421 standard. In the latter case, the encoding must be bounded at the beginning by a string that starts with -----BEGIN, and bounded at the end by a string that starts with -----END. iconic little fences, honestly 🎀.

You import a certificate for two reasons: to add it to the list of trusted certificates, and to import a certificate reply received from a certificate authority (CA) as the result of submitting a Certificate Signing Request to that CA (see the -certreq option in Commands).

Which type of import is intended is indicated by the value of the -alias option. If the alias does not point to a key entry, then the keytool command assumes you are adding a trusted certificate entry. In this case, the alias should not already exist in the keystore. If the alias does already exist, then the keytool command outputs an error because there is already a trusted certificate for that alias, and does not import the certificate. If the alias points to a key entry, then the keytool command assumes you are importing a certificate reply. yes bestie, context is everything 💖.

🔐 `-importpassword`

{-alias alias} [-keypass keypass] {-storetype storetype} {-keystore keystore}

[-storepass storepass]

{-providerClass provider_class_name {-providerArg provider_arg}}

{-v} {-protected} {-Jjavaoption}

Imports a passphrase and stores it in a new KeyStore.SecretKeyEntry identified by alias. The passphrase may be supplied via the standard input stream; otherwise the user is prompted for it. keypass is a password used to protect the imported passphrase. If no password is provided, the user is prompted for it. If you press Return at the prompt, the key password is set to the same password as that used for the keystore. keypass must be at least 6 characters long. short passwords are not the vibe 🙈.

🚚 `-importkeystore`

{-srcstoretype srcstoretype} {-deststoretype deststoretype}

[-srcstorepass srcstorepass] [-deststorepass deststorepass] {-srcprotected}

{-destprotected}

{-srcalias srcalias {-destalias destalias} [-srckeypass srckeypass]}

[-destkeypass destkeypass] {-noprompt}

{-srcProviderName src_provider_name} {-destProviderName dest_provider_name}

{-providerClass provider_class_name {-providerArg provider_arg}} {-v}

{-protected} {-Jjavaoption}

Imports a single entry or all entries from a source keystore to a destination keystore. moving day, but for keys 🧳✨.

When the -srcalias option is provided, the command imports the single entry identified by the alias to the destination keystore. If a destination alias is not provided with destalias, then srcalias is used as the destination alias. If the source entry is protected by a password, then srckeypass is used to recover the entry. If srckeypass is not provided, then the keytool command attempts to use srcstorepass to recover the entry. If srcstorepass is either not provided or is incorrect, then the user is prompted for a password. The destination entry is protected with destkeypass. If destkeypass is not provided, then the destination entry is protected with the source entry password. For example, most third-party tools require storepass and keypass in a PKCS #12 keystore to be the same. In order to create a PKCS #12 keystore for these tools, always specify a -destkeypass to be the same as -deststorepass. no cap, that matching-password trick is the whole game for those tools 🔥.

If the -srcalias option is not provided, then all entries in the source keystore are imported into the destination keystore. Each destination entry is stored under the alias from the source entry. If the source entry is protected by a password, then srcstorepass is used to recover the entry. If srcstorepass is either not provided or is incorrect, then the user is prompted for a password. If a source keystore entry type is not supported in the destination keystore, or if an error occurs while storing an entry into the destination keystore, then the user is prompted whether to skip the entry and continue or to quit. The destination entry is protected with the source entry password.

If the destination alias already exists in the destination keystore, then the user is prompted to either overwrite the entry or to create a new entry under a different alias name. lowkey a "bestie decide" moment 💀.

If the -noprompt option is provided, then the user is not prompted for a new destination alias. Existing entries are overwritten with the destination alias name. Entries that cannot be imported are skipped and a warning is displayed.

🖨️ `-printcertreq`

{-file file}

Prints the content of a PKCS #10 format certificate request, which can be generated by the keytool-certreq command. The command reads the request from file. If there is no file, then the request is read from the standard input.

📝 `-certreq`

{-alias alias} {-dname dname} {-sigalg sigalg} {-file certreq_file}

[-keypass keypass] {-storetype storetype} {-keystore keystore}

[-storepass storepass] {-providerName provider_name}

{-providerClass provider_class_name {-providerArg provider_arg}}

{-v} {-protected} {-Jjavaoption}

Generates a Certificate Signing Request (CSR) using the PKCS #10 format. it's giving "please sign me" energy ✨.

A CSR is intended to be sent to a certificate authority (CA). The CA authenticates the certificate requestor (usually off-line) and will return a certificate or certificate chain, used to replace the existing certificate chain (which initially consists of a self-signed certificate) in the keystore.

The private key associated with alias is used to create the PKCS #10 certificate request. To access the private key, the correct password must be provided. If keypass is not provided at the command line and is different from the password used to protect the integrity of the keystore, then the user is prompted for it. If dname is provided, then it is used as the subject in the CSR. Otherwise, the X.500 Distinguished Name associated with alias is used.

The sigalg value specifies the algorithm that should be used to sign the CSR.

The CSR is stored in the file certreq_file. If no file is specified, then the CSR is output to stdout.

Use the importcert command to import the response from the CA. full circle moment 🫶.

📤 `-exportcert`

{-alias alias} {-file cert_file} {-storetype storetype} {-keystore keystore}

[-storepass storepass] {-providerName provider_name}

{-providerClass provider_class_name {-providerArg provider_arg}}

{-rfc} {-v} {-protected} {-Jjavaoption}

Reads from the keystore the certificate associated with alias and stores it in the cert_file file. When no file is specified, the certificate is output to stdout.

The certificate is by default output in binary encoding. If the -rfc option is specified, then the output is in the printable encoding format defined by the Internet RFC 1421 Certificate Encoding Standard.

If alias refers to a trusted certificate, then that certificate is output. Otherwise, alias refers to a key entry with an associated certificate chain. In that case, the first certificate in the chain is returned. This certificate authenticates the public key of the entity addressed by alias.

This command was named -export in earlier releases. The old name is still supported in this release. The new name, -exportcert, is preferred going forward. glow-up complete 👑.

📋 `-list`

{-alias alias} {-storetype storetype} {-keystore keystore} [-storepass storepass]

{-providerName provider_name}

{-providerClass provider_class_name {-providerArg provider_arg}}

{-v | -rfc} {-protected} {-Jjavaoption}

Prints to stdout the contents of the keystore entry identified by alias. If no alias is specified, then the contents of the entire keystore are printed.

This command by default prints the SHA1 fingerprint of a certificate. If the -v option is specified, then the certificate is printed in human-readable format, with additional information such as the owner, issuer, serial number, and any extensions. If the -rfc option is specified, then the certificate contents are printed using the printable encoding format, as defined by the Internet RFC 1421 Certificate Encoding Standard.

You cannot specify both -v and -rfc. pick one, bestie, this is not a choose-both situation 😭.

🔎 `-printcert`

{-file cert_file | -sslserver host[:port]} {-jarfile JAR_file {-rfc} {-v}

{-Jjavaoption}

So -printcert is a literal ✨certificate reveal✨ ritual: it reads the certificate from the file cert_file, from the SSL server chillin' at host:port, or from the signed JAR file JAR_file (that's the -jarfile option, bestie), and then prints the whole thing in a human-readable format. 🎀 If you don't give it a port, it just assumes the standard HTTPS port 443 — no cap. And heads up: you can't pass -sslserver and -file at the same time, like, ever. Try it and it just throws an error at you. 🙈 If you specify neither? Then the certificate gets read from stdin. Iconic lazy-girl behavior.

When -rfc is specified, the keytool command prints the certificate in PEM mode, as defined by the Internet RFC 1421 Certificate Encoding standard. See Internet RFC 1421 Certificate Encoding Standard. 💅

If the certificate is read from a file or stdin, then it might be either binary encoded or in printable encoding format, as defined by the RFC 1421 Certificate Encoding standard. Both vibes are valid.

If the SSL server is behind a firewall, then the -J-Dhttps.proxyHost=proxyhost and -J-Dhttps.proxyPort=proxyport options can be specified on the command line for proxy tunneling. See Java Secure Socket Extension (JSSE) Reference Guide at http://docs.oracle.com/javase/8/docs/technotes/guides/security/jsse/JSSERefGuide.html 🧚

Note: This option can be used independently of a keystore. Like, it doesn't even need one. Independent queen. 👑

💀 `-printcrl`

-file crl_ {-v}

Reads the Certificate Revocation List (CRL) from the file crl_. So what even is a CRL? It's literally a list of digital certificates that were revoked by the CA that issued them 😭 — the CA is the one who generates the crl_ file, so you don't have to.

Note: This option can be used independently of a keystore. Same energy as above, fr fr.

🔐 `-storepasswd`

[-new new_storepass] {-storetype storetype} {-keystore keystore}
[-storepass storepass] {-providerName provider_name}
{-providerClass provider_class_name {-providerArg provider_arg}}
{-v} {-Jjavaoption}

Changes the password used to protect the integrity of the keystore contents. The new password is new_storepass, and it must be at least 6 characters — no three-letter shortcuts, bestie, that's not the vibe. 💅

🗝️ `-keypasswd`

{-alias alias} [-keypass old_keypass] [-new new_keypass] {-storetype storetype}
{-keystore keystore} [-storepass storepass] {-providerName provider_name}
{-providerClass provider_class_name {-providerArg provider_arg}} {-v}
{-Jjavaoption}

Changes the password under which the private/secret key identified by alias is protected — from old_keypass to new_keypass, which must be at least 6 characters. Same minimum, no exceptions. 🎀

If the -keypass option is not provided at the command line, and the key password is different from the keystore password, then the user is prompted for it. So it'll ask, don't worry. 🙈

If the -new option is not provided at the command line, then the user is prompted for it. Yeah, it double-checks with you. Very "are you sure, bestie?" energy.

🗑️ `-delete`

[-alias alias] {-storetype storetype} {-keystore keystore} [-storepass storepass]
{-providerName provider_name}
{-providerClass provider_class_name {-providerArg provider_arg}}
{-v} {-protected} {-Jjavaoption}

Deletes from the keystore the entry identified by alias. Straight-up removal, no takebacks. 😭 The user is prompted for the alias when no alias is provided at the command line — so if you forget, it'll just ask you which one you want gone.

🦋 `-changealias`

{-alias alias} [-destalias destalias] [-keypass keypass] {-storetype storetype}
{-keystore keystore} [-storepass storepass] {-providerName provider_name}
{-providerClass provider_class_name {-providerArg provider_arg}} {-v}
{-protected} {-Jjavaoption}

Move an existing keystore entry from the specified alias to a new alias, destalias. It's giving rebrand era, honestly. ✨ If no destination alias is provided, then the command prompts for one. If the original entry is protected with an entry password, then the password can be supplied with the -keypass option. If no key password is provided, then the storepass (if provided) is attempted first. If that attempt fails, then the user is prompted for a password. 🫶

🌸 `-help`

Lists the basic commands and their options. The "so what can this thing even do" energy check. 👑

For more information about a specific command, enter the following, where command_name is the name of the command:

keytool -command_name -help

Literal cheat code. iykyk 💜

✨ EXAMPLES ✨

Okay bestie, this is the fun part — we're gonna walk through the whole glow-up journey of making a keystore that manages a public/private key pair and certificates from trusted entities. Follow along, it's giving tutorial era 💅

🎀 GENERATE THE KEY PAIR 🎀

First things first: make a keystore and generate the key pair. You can use a command like the following, typed as a single line:

keytool -genkeypair -dname "cn=Mark Jones, ou=Java, o=Oracle, c=US"
    -alias business -keypass <new password for private key>
    -keystore /working/mykeystore
    -storepass <new password for keystore> -validity 180

So what did that actually do, bestie? It creates the keystore named mykeystore in the working directory (assuming it doesn't already exist, obviously), and assigns it the password specified by <new password for keystore>. Then it generates a public/private key pair for the entity whose distinguished name has a common name of Mark Jones, organizational unit of Java, organization of Oracle and two-letter country code of US. It uses the default DSA key generation algorithm to create the keys — both are 1024 bits, no cap.

The command uses the default SHA1withDSA signature algorithm to create a self-signed certificate that includes the public key and the distinguished name info. That certificate is valid for 180 days, and it's associated with the private key in a keystore entry referred to by the alias business. The private key gets the password specified by <new password for private key>. Iconic, everything's slotted in 🫶

Now — the command is significantly shorter when you just accept the option defaults. In that case, no options are required at all, and the defaults are used for unspecified options that have default values. You get prompted for any required values. So you could literally just do:

keytool -genkeypair

And in this case, a keystore entry with the alias mykey is created, with a newly generated key pair and a certificate that's valid for 90 days. This entry goes into the keystore named .keystore in your home directory. The keystore is created when it doesn't already exist. You get prompted for the distinguished name info, the keystore password, and the private key password. Lowkey the lazy route but it works ✨

The rest of the examples assume you executed the -genkeypair command without options specified, and that you responded to the prompts with values equal to those specified in the first -genkeypair command. For example, a distinguished name of cn=Mark Jones, ou=Java, o=Oracle, c=US.

🦋 REQUEST A SIGNED CERTIFICATE FROM A CA 🦋

So generating the key pair created a self-signed certificate. Cute, but a certificate is way more likely to be trusted by others when it's signed by a Certification Authority (CA). To get that CA signature, first generate a Certificate Signing Request (CSR), like this:

keytool -certreq -file MarkJ.csr

This creates a CSR for the entity identified by the default alias mykey and drops the request in the file named MarkJ.csr. Submit this file to a CA, such as VeriSign. The CA authenticates you, the requestor (usually off-line, ngl), and returns a certificate, signed by them, authenticating your public key. In some cases, the CA returns a chain of certificates, each one authenticating the public key of the signer of the previous certificate in the chain. It's giving linked list energy 🔥

🌸 IMPORT A CERTIFICATE FOR THE CA 🌸

Now you need to replace that self-signed certificate with a certificate chain, where each certificate in the chain authenticates the public key of the signer of the previous certificate in the chain, all the way up to a root CA.

Before you import the certificate reply from a CA, you need one or more trusted certificates in your keystore or in the cacerts keystore file. See -importcert in COMMANDS.

If the certificate reply is a certificate chain, then you need the top certificate of the chain. The root CA certificate that authenticates the public key of the CA.
If the certificate reply is a single certificate, then you need a certificate for the issuing CA (the one that signed it). If that certificate is not self-signed, then you need a certificate for its signer, and so on, up to a self-signed root CA certificate.

The cacerts keystore file ships with several VeriSign root CA certificates, so you probably won't need to import a VeriSign certificate as a trusted certificate in your keystore. But if you request a signed certificate from a different CA, and a certificate authenticating that CA's public key was not added to cacerts, then you must import a certificate from the CA as a trusted certificate.

A certificate from a CA is usually either self-signed or signed by another CA, in which case you need a certificate that authenticates that CA's public key. Suppose company ABC, Inc., is a CA, and you obtain a file named ABCCA.cer that is supposed to be a self-signed certificate from ABC, that authenticates that CA's public key.

⚠️ Bestie, be careful to ensure the certificate is valid before you import it as a trusted certificate. View it first with the keytool -printcert command or the keytool -importcert command without the -noprompt option, and make sure that the displayed certificate fingerprints match the expected ones. You can call the person who sent the certificate, and compare the fingerprints that you see with the ones that they show or that a secure public key repository shows. Only when the fingerprints are equal is it guaranteed that the certificate was not replaced in transit with somebody else's (for example, an attacker's) certificate. If such an attack takes place, and you did not check the certificate before you imported it, then you would be trusting anything the attacker has signed. Like, genuinely not the vibe 💀

If you trust that the certificate is valid, then you can add it to your keystore with the following command:

keytool -importcert -alias abc -file ABCCA.cer

This command creates a trusted certificate entry in the keystore, with the data from the file ABCCA.cer, and assigns the alias abc to the entry. Slay, done 🌟

💜 IMPORT THE CERTIFICATE REPLY FROM THE CA 💜

After you import a certificate that authenticates the public key of the CA you submitted your certificate signing request to (or there's already such a certificate in the cacerts file), you can import the certificate reply and replace your self-signed certificate with a certificate chain. This chain is the one returned by the CA in response to your request (when the CA reply is a chain), or one constructed (when the CA reply is a single certificate) using the certificate reply and trusted certificates that are already available in the keystore where you import the reply or in the cacerts keystore file.

For example, if you sent your certificate signing request to VeriSign, then you can import the reply with the following, which assumes the returned certificate is named VSMarkJ.cer:

keytool -importcert -trustcacerts -file VSMarkJ.cer

🧚 EXPORT A CERTIFICATE THAT AUTHENTICATES THE PUBLIC KEY 🧚

If you used the jarsigner command to sign a Java Archive (JAR) file, then clients that want to use the file will want to authenticate your signature. One way the clients can authenticate you is by first importing your public key certificate into their keystore as a trusted entry.

You can export the certificate and supply it to your clients. As an example, you can copy your certificate to a file named MJ.cer with the following command, which assumes the entry has an alias of mykey:

keytool -exportcert -alias mykey -file MJ.cer

With the certificate and the signed JAR file, a client can use the jarsigner command to authenticate your signature. Sharing is caring fr fr 🫶

🍓 IMPORT KEYSTORE 🍓

The command importkeystore is used to import an entire keystore into another keystore — meaning all entries from the source keystore, including keys and certificates, are all imported to the destination keystore within a single command. One command, everything, periodt. You can use this command to import entries from a different type of keystore. During the import, all new entries in the destination keystore will have the same alias names and protection passwords (for secret keys and private keys). If the keytool command cannot recover the private keys or secret keys from the source keystore, then it prompts you for a password. If it detects alias duplication, then it asks you for a new alias, and you can specify a new alias or simply allow the keytool command to overwrite the existing one.

For example, to import entries from a typical JKS type keystore key.jks into a PKCS #11 type hardware-based keystore, use the command:

keytool -importkeystore
    -srckeystore key.jks -destkeystore NONE
    -srcstoretype JKS -deststoretype PKCS11
    -srcstorepass <src keystore password>
    -deststorepass <destination keystore pwd>

The importkeystore command can also be used to import a single entry from a source keystore to a destination keystore. In this case, besides the options you see in the previous example, you need to specify the alias you want to import. With the -srcalias option specified, you can also specify the destination alias name in the command line, as well as protection password for a secret/private key and the destination protection password you want. The following command demonstrates this:

keytool -importkeystore
    -srckeystore key.jks -destkeystore NONE
    -srcstoretype JKS -deststoretype PKCS11
    -srcstorepass <src keystore password>
    -deststorepass <destination keystore pwd>
    -srcalias myprivatekey -destalias myoldprivatekey
    -srckeypass <source entry password>
    -destkeypass <destination entry password>
    -noprompt

Look at all those flags. She's thorough, she's organized, she's that girl 💅

👑 GENERATE CERTIFICATES FOR AN SSL SERVER 👑

The following are keytool commands to generate key pairs and certificates for three entities: Root CA (root), Intermediate CA (ca), and SSL server (server). Make sure you store all the certificates in the same keystore, bestie. In these examples, RSA is the recommended the key algorithm.

keytool -genkeypair -keystore root.jks -alias root -ext bc:c
keytool -genkeypair -keystore ca.jks -alias ca -ext bc:c
keytool -genkeypair -keystore server.jks -alias server
keytool -keystore root.jks -alias root -exportcert -rfc > root.pem
keytool -storepass <storepass> -keystore ca.jks -certreq -alias ca |
    keytool -storepass <storepass> -keystore root.jks
    -gencert -alias root -ext BC=0 -rfc > ca.pem
keytool -keystore ca.jks -importcert -alias ca -file ca.pem
keytool -storepass <storepass> -keystore server.jks -certreq -alias server |
    keytool -storepass <storepass> -keystore ca.jks -gencert -alias ca
    -ext ku:c=dig,kE -rfc > server.pem
cat root.pem ca.pem server.pem |
    keytool -keystore server.jks -importcert -alias server

Whole trust chain, built from scratch, in eight commands. The way that's a full PKI in a single scroll 😭🔥

🌈 TERMS 🌈

Keystore

A keystore is a storage facility for cryptographic keys and certificates.

Keystore entries

Keystores can have different types of entries. The two most applicable entry types for the keytool command include the following:

Key entries: these are the most sensitive vibe in the whole keystore 💀 each one holds cryptographic key material, stored in a protected format specifically so nobody unauthorized can get at it. Typically it's a secret key, or a private key hanging out with the certificate chain for its matching public key. Peep Certificate Chains. keytool can handle both flavors of entry, but jarsigner only handles the second one — that is, private keys and their associated certificate chains.
Trusted certificate entries: each of these holds exactly one public key certificate that belongs to somebody else. It's called a "trusted certificate" because the keystore owner trusts that the public key inside that certificate really belongs to the identity named by the certificate's subject (owner). The certificate's issuer vouches for all of that by signing the certificate. 🫶

KeyStore aliases ✨

Okay so every single keystore entry — key entries and trusted certificate entries — gets accessed through a unique alias. That's the whole system.

You specify the alias when you add an entity to the keystore:

with the -genseckey command, to generate a secret key
with the -genkeypair command, to generate a key pair (public and private key)
with the -importcert command, to add a certificate or certificate chain to the list of trusted certificates

Every keytool command after that must use this same alias to refer to that entity. No nicknames, no vibes-based shorthand, the alias is the alias. 💅

Example time — say you use the alias duke to generate a new public/private key pair and wrap the public key into a self-signed certificate. That's this command right here. (Also see Certificate Chains.)

keytool -genkeypair -alias duke -keypass dukekeypasswd

So this example specifies an initial password of dukekeypasswd that later commands need in order to access the private key associated with the alias duke. And if you later want to switch up Duke's private key password, you'd use a command like this one:

keytool -keypasswd -alias duke -keypass dukekeypasswd -new newpass

That flips the password from dukekeypasswd to newpass. 🎀

⚠️ Bestie, listen — a password should not be specified on a command line or in a script unless it's for testing purposes, or you're on a secure system. For real. If you don't specify a required password option on the command line, then you get prompted for it, which is the way.

KeyStore implementation 🧚

The KeyStore class, provided in the java.security package, supplies well-defined interfaces to access and modify the information in a keystore. And here's the cute part: there can be multiple different concrete implementations, where each implementation is for one particular type of keystore. 🌈

Currently, two command-line tools (keytool and jarsigner) and a GUI-based tool named Policy Tool make use of keystore implementations. And because the KeyStore class is public, users can write additional security applications that use it. Go off, honestly.

There's a built-in default implementation, provided by Oracle. It implements the keystore as a file with a proprietary keystore type (format) named JKS. It protects each private key with its own individual password, and it also protects the integrity of the entire keystore with a (possibly different) password.

Keystore implementations are provider-based. More specifically, the application interfaces supplied by KeyStore are implemented in terms of a Service Provider Interface (SPI). So like — there's a corresponding abstract KeystoreSpi class, also in the java.security package, which defines the Service Provider Interface methods that providers must implement. The term provider refers to a package or a set of packages that supply a concrete implementation of a subset of services that can be accessed by the Java Security API. To provide a keystore implementation, clients must implement a provider and supply a KeystoreSpi subclass implementation, as described in How to Implement a Provider in the Java Cryptography Architecture at http://docs.oracle.com/javase/8/docs/technotes/guides/security/crypto/HowToImplAProvider.html

Applications can choose different types of keystore implementations from different providers, using the getInstance factory method supplied in the KeyStore class. A keystore type defines the storage and data format of the keystore information, plus the algorithms used to protect private/secret keys in the keystore and the integrity of the keystore itself. And heads up — keystore implementations of different types are not compatible. Not even a little. 💀

The keytool command works on any file-based keystore implementation. It treats the keystore location that's passed to it at the command line as a file name and converts it to a FileInputStream, from which it loads the keystore information.)The jarsigner command, meanwhile, can read a keystore from any location that can be specified with a URL.

For keytool and jarsigner, you can specify a keystore type at the command line with the -storetype option. For Policy Tool, you can specify a keystore type with the Keystore menu.

If you don't explicitly specify a keystore type, then the tools choose a keystore implementation based on the value of the keystore.type property specified in the security properties file. That security properties file is called java.security, and it resides in the security properties directory — java.home\lib\security on Windows and java.home/lib/security on Oracle Solaris, where java.home is the runtime environment directory. That's the jre directory in the SDK, or the top-level directory of the Java Runtime Environment (JRE).

Each tool gets the keystore.type value and then examines all the currently installed providers until it finds one that implements a keystores of that type. Then it uses the keystore implementation from that provider.The KeyStore class defines a static method named getDefaultType that lets applications and applets retrieve the value of the keystore.type property. This line of code creates an instance of the default keystore type as specified in the keystore.type property:

KeyStore keyStore = KeyStore.getInstance(KeyStore.getDefaultType());

The default keystore type is jks, which is the proprietary type of the keystore implementation provided by Oracle. This is specified by the following line in the security properties file:

keystore.type=jks

To have the tools utilize a keystore implementation other than the default, you can change that line to specify a different keystore type. For example, if you've got a provider package that supplies a keystore implementation for a keystore type called pkcs12, then change the line to the following:

keystore.type=pkcs12

📌 Note: Case does not matter in keystore type designations. For example, JKS would be considered the same as jks.

Certificate 🦋

A certificate (or public-key certificate) is a digitally signed statement from one entity (the issuer), saying that the public key and some other information of another entity (the subject) has some specific value. Iconic concept, honestly. Here are the terms related to certificates:

Public Keys: These are numbers associated with a particular entity, and they're intended to be known to everyone who needs to have trusted interactions with that entity. Public keys are used to verify signatures.

Digitally Signed: If some data is digitally signed, then it's stored with the identity of an entity and a signature that proves that entity knows about the data. The data is rendered unforgeable by signing with the entity's private key. ✨

Identity: A known way of addressing an entity. In some systems, the identity is the public key, and in others it can be anything from an Oracle Solaris UID to an email address to an X.509 distinguished name.

Signature: A signature is computed over some data using the private key of an entity — the signer, which in the case of a certificate is also known as the issuer.

Private Keys: These are numbers, each of which is supposed to be known only to the particular entity whose private key it is (that is, it's supposed to be kept secret 🤫). Private and public keys exist in pairs in all public key cryptography systems (also referred to as public key crypto systems). In a typical public key crypto system, such as DSA, a private key corresponds to exactly one public key. Private keys are used to compute signatures.

Entity: An entity is a person, organization, program, computer, business, bank, or something else you are trusting to some degree.

Public key cryptography requires access to users' public keys. In a large-scale networked environment, it's impossible to guarantee that prior relationships between communicating entities were established, or that a trusted repository exists with all used public keys. Certificates were invented as a solution to this public key distribution problem. Now a Certification Authority (CA) can act as a trusted third party. CAs are entities such as businesses that are trusted to sign (issue) certificates for other entities. It's assumed that CAs only create valid and reliable certificates because they're bound by legal agreements. There are many public Certification Authorities, such as VeriSign, Thawte, Entrust, and so on. 👑

You can also run your own Certification Authority using products such as Microsoft Certificate Server or the Entrust CA product for your organization. With the keytool command, it's possible to display, import, and export certificates. It's also possible to generate self-signed certificates. Main character CA energy, honestly.

The keytool command currently handles X.509 certificates. 🎀

💅 X.509 Certificates

Okay so the X.509 standard is the one that defines what info can even go into a certificate, and it also describes how to write it down — that's the data format part. And literally all the data in a certificate is encoded with two related standards called ASN.1/DER: Abstract Syntax Notation 1 describes data, and the Definite Encoding Rules describe a single way to store and transfer that data. Two besties, one job. 🫶

Every X.509 certificate has the following data, in addition to the signature:

Version — this identifies which version of the X.509 standard applies to this certificate, which decides what info can be specified in it. So far three versions are defined. The keytool command can import and export v1, v2, and v3 certificates, and it generates v3 certificates. 👑
- X.509 Version 1 has been around since 1988, is widely deployed, and is the most generic.
- X.509 Version 2 introduced the concept of subject and issuer unique identifiers to handle the possibility of reuse of subject or issuer names over time. Most certificate profile documents strongly recommend that names not be reused and that certificates should not make use of unique identifiers. Version 2 certificates are not widely used — lowkey kinda forgotten.
- X.509 Version 3 is the most recent (1996) and supports the notion of extensions, where anyone can define an extension and include it in the certificate. Some common extensions are: KeyUsage (limits the use of the keys to particular purposes such as signing-only) and AlternativeNames (allows other identities to also be associated with this public key — for example, DNS names, email addresses, IP addresses). Extensions can be marked critical to indicate that the extension should be checked and enforced or used. For example, if a certificate has the KeyUsage extension marked critical and set to keyCertSign, then when this certificate is presented during SSL communication, it should be rejected, because the certificate extension indicates that the associated private key should only be used for signing certificates and not for SSL use. It said what it said and we respect it. 💀
Serial number — the entity that created the certificate is responsible for assigning it a serial number to distinguish it from other certificates it issues. This info is used in numerous ways. For example, when a certificate is revoked, its serial number is placed in a Certificate Revocation List (CRL).
Signature algorithm identifier — this identifies the algorithm used by the CA to sign the certificate.
Issuer name — the X.500 Distinguished Name of the entity that signed the certificate. See X.500 Distinguished Names. This is typically a CA. Using this certificate implies trusting the entity that signed this certificate. In some cases, such as root or top-level CA certificates, the issuer signs its own certificate — main character energy, honestly.
Validity period — each certificate is valid only for a limited amount of time. This period is described by a start date and time and an end date and time, and can be as short as a few seconds or almost as long as a century 😭. The validity period chosen depends on a number of factors, such as the strength of the private key used to sign the certificate, or the amount one is willing to pay for a certificate. This is the expected period that entities can rely on the public value, when the associated private key has not been compromised.
Subject name — the name of the entity whose public key the certificate identifies. This name uses the X.500 standard, so it is intended to be unique across the Internet. This is the X.500 Distinguished Name (DN) of the entity. See X.500 Distinguished Names. For example:

CN=Java Duke, OU=Java Software Division, O=Oracle Corporation, C=US

These refer to the subject's common name (CN), organizational unit (OU), organization (O), and country (C).

Subject public key information — this is the public key of the entity being named, with an algorithm identifier that specifies which public key crypto system this key belongs to and any associated key parameters.

🔗 Certificate Chains

The keytool command can create and manage keystore key entries that each contain a private key and an associated certificate chain. The first certificate in the chain contains the public key that corresponds to the private key.

When keys are first generated, the chain starts off containing a single element: a self-signed certificate. See -genkeypair in Commands. A self-signed certificate is one for which the issuer (signer) is the same as the subject. The subject is the entity whose public key is being authenticated by the certificate. Whenever the -genkeypair command is called to generate a new public/private key pair, it also wraps the public key into a self-signed certificate. It's giving "I made myself, actually." ✨

Later, after a Certificate Signing Request (CSR) was generated with the -certreq command and sent to a Certification Authority (CA), the response from the CA is imported with -importcert, and the self-signed certificate is replaced by a chain of certificates. See the -certreq and -importcert options in Commands. At the bottom of the chain is the certificate (reply) issued by the CA authenticating the subject's public key. The next certificate in the chain is one that authenticates the CA's public key.

In many cases, this is a self-signed certificate, which is a certificate from the CA authenticating its own public key, and the last certificate in the chain. In other cases, the CA might return a chain of certificates. In this case, the bottom certificate in the chain is the same (a certificate signed by the CA, authenticating the public key of the key entry), but the second certificate in the chain is a certificate signed by a different CA that authenticates the public key of the CA you sent the CSR to. The next certificate in the chain is a certificate that authenticates the second CA's key, and so on, until a self-signed root certificate is reached. Each certificate in the chain (after the first) authenticates the public key of the signer of the previous certificate in the chain. It's a literal chain of trust, like a group chat where everyone vouches for the next person. 🫶

Many CAs only return the issued certificate, with no supporting chain, especially when there is a flat hierarchy (no intermediates CAs). In this case, the certificate chain must be established from trusted certificate information already stored in the keystore.

A different reply format (defined by the PKCS #7 standard) includes the supporting certificate chain in addition to the issued certificate. Both reply formats can be handled by the keytool command.

The top-level (root) CA certificate is self-signed. However, the trust into the root's public key does not come from the root certificate itself, but from other sources such as a newspaper 📰. This is because anybody could generate a self-signed certificate with the distinguished name of, for example, the VeriSign root CA. The root CA public key is widely known. The only reason it is stored in a certificate is because this is the format understood by most tools, so the certificate in this case is only used as a vehicle to transport the root CA's public key. Before you add the root CA certificate to your keystore, you should view it with the -printcert option and compare the displayed fingerprint with the well-known fingerprint obtained from a newspaper, the root CA's Web page, and so on. Do not skip the vibe check on this one, fr fr. 🔥

🗂️ The cacerts Certificates File

A certificates file named cacerts resides in the security properties directory, java.home\lib\security on Windows and java.home/lib/security on Oracle Solaris, where java.home is the runtime environment's directory, which would be the jre directory in the SDK or the top-level directory of the JRE.

The cacerts file represents a system-wide keystore with CA certificates. System administrators can configure and manage that file with the keytool command by specifying jks as the keystore type. The cacerts keystore file ships with a default set of root CA certificates. You can list the default certificates with the following command:

keytool -list -keystore java.home/lib/security/cacerts

The initial password of the cacerts keystore file is changeit. System administrators should change that password and the default access permission of that file upon installing the SDK. Yes bestie, changeit is a password, and yes, it's as iconic as it is unserious. 🎀

Note: It is important to verify your cacerts file. Because you trust the CAs in the cacerts file as entities for signing and issuing certificates to other entities, you must manage the cacerts file carefully. The cacerts file should contain only certificates of the CAs you trust. It is your responsibility to verify the trusted root CA certificates bundled in the cacerts file and make your own trust decisions. 🙈

To remove an untrusted CA certificate from the cacerts file, use the delete option of the keytool command. You can find the cacerts file in the JRE installation directory. Contact your system administrator if you do not have permission to edit this file.

📮 Internet RFC 1421 Certificate Encoding Standard

Certificates are often stored using the printable encoding format defined by the Internet RFC 1421 standard, instead of their binary encoding. This certificate format, also known as Base64 encoding, makes it easy to export certificates to other applications by email or through some other mechanism. Slay, mobile-friendly certs. 💅

Certificates read by the -importcert and -printcert commands can be in either this format or binary encoded. The -exportcert command by default outputs a certificate in binary encoding, but will instead output a certificate in the printable encoding format when the -rfc option is specified. Choose your fighter. 🌈

The -list command, by default, prints the SHA1 fingerprint of a certificate. If the -v option is specified, then the certificate is printed in human-readable format. If the -rfc option is specified, then the certificate is output in the printable encoding format.

In its printable encoding format, the encoded certificate is bounded at the beginning and end by the following text:

-----BEGIN CERTIFICATE-----
encoded certificate goes here.
-----END CERTIFICATE-----

🪪 X.500 Distinguished Names 🪪

X.500 Distinguished Names are used to identify entities, such as those that are named by the subject and issuer (signer) fields of X.509 certificates. The keytool command supports the following subparts:

commonName: The common name of a person such as Susan Jones.
organizationUnit: The small organization (such as department or division) name. For example, Purchasing.
localityName: The locality (city) name, for example, Palo Alto.
stateName: State or province name, for example, California.
country: Two-letter country code, for example, CH.

When you supply a distinguished name string as the value of a -dname option, such as for the -genkeypair command, the string must be in the following format:

CN=cName, OU=orgUnit, O=org, L=city, S=state, C=countryCode

All the italicized items represent actual values and the previous keywords are abbreviations for the following:

CN=commonName
OU=organizationUnit
O=organizationName
L=localityName
S=stateName
C=country

A sample distinguished name string is:

CN=Mark Smith, OU=Java, O=Oracle, L=Cupertino, S=California, C=US

A sample command using such a string is:

keytool -genkeypair -dname "CN=Mark Smith, OU=Java, O=Oracle, L=Cupertino,
S=California, C=US" -alias mark

Case does not matter for the keyword abbreviations. For example, CN, cn, and Cn are all treated the same.

Order matters; each subcomponent must appear in the designated order. However, it is not necessary to have all the subcomponents. You can use a subset, for example:

CN=Steve Meier, OU=Java, O=Oracle, C=US

If a distinguished name string value contains a comma, then the comma must be escaped by a backslash (\) character when you specify the string on a command line, as in:

cn=Peter Schuster, ou=Java\, Product Development, o=Oracle, c=US

It is never necessary to specify a distinguished name string on a command line. When the distinguished name is needed for a command, but not supplied on the command line, the user is prompted for each of the subcomponents. In this case, a comma does not need to be escaped by a backslash (\).

🚨 WARNINGS 🚨

👑 IMPORTING TRUSTED CERTIFICATES WARNING 👑

Important: Be sure to check a certificate very carefully before importing it as a trusted certificate.

Windows Example:

View the certificate first with the -printcert command or the -importcert command without the -noprompt option. Ensure that the displayed certificate fingerprints match the expected ones. For example, suppose someone sends or emails you a certificate that you put in a file named \tmp\cert. Before you consider adding the certificate to your list of trusted certificates, you can execute a -printcert command to view its fingerprints, as follows:

keytool -printcert -file \tmp\cert
  Owner: CN=ll, OU=ll, O=ll, L=ll, S=ll, C=ll
  Issuer: CN=ll, OU=ll, O=ll, L=ll, S=ll, C=ll
  Serial Number: 59092b34
  Valid from: Thu Sep 25 18:01:13 PDT 1997 until: Wed Dec 24 17:01:13 PST 1997
  Certificate Fingerprints:
       MD5:  11:81:AD:92:C8:E5:0E:A2:01:2E:D4:7A:D7:5F:07:6F
       SHA1: 20:B6:17:FA:EF:E5:55:8A:D0:71:1F:E8:D6:9D:C0:37:13:0E:5E:FE
       SHA256: 90:7B:70:0A:EA:DC:16:79:92:99:41:FF:8A:FE:EB:90:
               17:75:E0:90:B2:24:4D:3A:2A:16:A6:E4:11:0F:67:A4

Oracle Solaris Example:

View the certificate first with the -printcert command or the -importcert command without the -noprompt option. Ensure that the displayed certificate fingerprints match the expected ones. For example, suppose someone sends or emails you a certificate that you put in a file named /tmp/cert. Before you consider adding the certificate to your list of trusted certificates, you can execute a -printcert command to view its fingerprints, as follows:

keytool -printcert -file /tmp/cert
  Owner: CN=ll, OU=ll, O=ll, L=ll, S=ll, C=ll
  Issuer: CN=ll, OU=ll, O=ll, L=ll, S=ll, C=ll
  Serial Number: 59092b34
  Valid from: Thu Sep 25 18:01:13 PDT 1997 until: Wed Dec 24 17:01:13 PST 1997
  Certificate Fingerprints:
       MD5:  11:81:AD:92:C8:E5:0E:A2:01:2E:D4:7A:D7:5F:07:6F
       SHA1: 20:B6:17:FA:EF:E5:55:8A:D0:71:1F:E8:D6:9D:C0:37:13:0E:5E:FE
       SHA256: 90:7B:70:0A:EA:DC:16:79:92:99:41:FF:8A:FE:EB:90:
               17:75:E0:90:B2:24:4D:3A:2A:16:A6:E4:11:0F:67:A4

Then call or otherwise contact the person who sent the certificate and compare the fingerprints that you see with the ones that they show. Only when the fingerprints are equal is it guaranteed that the certificate was not replaced in transit with somebody else's certificate such as an attacker's certificate. If such an attack took place, and you did not check the certificate before you imported it, then you would be trusting anything the attacker signed, for example, a JAR file with malicious class files inside. 💀 that is not the vibe.

Note: It is not required that you execute a -printcert command before importing a certificate. This is because before you add a certificate to the list of trusted certificates in the keystore, the -importcert command prints out the certificate information and prompts you to verify it. You can then stop the import operation. However, you can do this only when you call the -importcert command without the -noprompt option. If the -noprompt option is specified, then there is no interaction with the user.

🔐 PASSWORDS WARNING 🔐

Most commands that operate on a keystore require the store password. Some commands require a private/secret key password. Passwords can be specified on the command line in the -storepass and -keypass options. However, a password should not be specified on a command line or in a script unless it is for testing, or you are on a secure system. When you do not specify a required password option on a command line, you are prompted for it.

📜 CERTIFICATE CONFORMANCE WARNING 📜

The Internet standard RFC 5280 has defined a profile on conforming X.509 certificates, which includes what values and value combinations are valid for certificate fields and extensions. See the standard at http://tools.ietf.org/rfc/rfc5280.txt

The keytool command does not enforce all of these rules so it can generate certificates that do not conform to the standard. Certificates that do not conform to the standard might be rejected by JRE or other applications. Users should ensure that they provide the correct options for -dname, -ext, and so on.

📝 NOTES 📝

🎀 IMPORT A NEW TRUSTED CERTIFICATE 🎀

okay so before the keytool command even thinks about dropping that certificate into your keystore, it does a whole vibe-check first: it tries to build a chain of trust from that certificate up to a self-signed certificate (like, one belonging to a root CA), using trusted certificates that are already in the keystore. very "show me your references" of it 💅

and if you passed the -trustcacerts option? then extra certificates get pulled into the chain-of-trust deliberation, specifically the ones in a file named cacerts. more friends at the party ✨

now — if the keytool command can't establish a trust path from the certificate you're trying to import all the way up to a self-signed certificate (whether from the keystore or from the cacerts file), it prints out the certificate info and then prompts you, the user, to verify it by comparing the displayed certificate fingerprints against fingerprints you got from some other (trusted) source — which might be, like, the certificate owner themselves.

⚠️ bestie be so careful here. make absolutely sure the certificate is valid before you import it as a trusted certificate. See Importing Trusted Certificates Warning. no cap, this is the part where you don't just click "yes" 😭

after that you get the option of stopping the import operation entirely. and if you specified the -noprompt option, then there's zero interaction with the user — it just goes 🏃‍♀️💨

🦋 IMPORT A CERTIFICATE REPLY 🦋

when you import a certificate reply, that reply gets validated against trusted certificates from the keystore — and, optionally, against the certificates configured in the cacerts keystore file when the -trustcacerts option is specified. See The cacerts Certificates File. 🫶

the ways it decides whether a certificate reply is trusted are giving very much "let me check my sources":

if the reply is a single X.509 certificate, then the keytool command attempts to establish a trust chain, starting at the certificate reply and ending at a self-signed certificate (belonging to a root CA). The certificate reply and the hierarchy of certificates is used to authenticate the certificate reply from the new certificate chain of aliases. If a trust chain can't be established, then the certificate reply is not imported. In this case, the keytool command does not print the certificate and prompt the user to verify it, because it is very difficult for a user to determine the authenticity of the certificate reply. (fr fr, it's protecting you from yourself 🙈)
if the reply is a PKCS #7 formatted certificate chain or a sequence of X.509 certificates, then the chain is ordered with the user certificate first followed by zero or more CA certificates. If the chain ends with a self-signed root CA certificate and the -trustcacerts option was specified, the keytool command attempts to match it with any of the trusted certificates in the keystore or the cacerts keystore file. If the chain does not end with a self-signed root CA certificate and the -trustcacerts option was specified, the keytool command tries to find one from the trusted certificates in the keystore or the cacerts keystore file and add it to the end of the chain. If the certificate is not found and the -noprompt option is not specified, the information of the last certificate in the chain is printed, and the user is prompted to verify it. 👑

and then the swap: if the public key in the certificate reply matches the user's public key already stored with alias, then the old certificate chain is replaced with the new certificate chain in the reply. iconic behavior honestly.

💀 heads up though — the old chain can only be replaced with a valid keypass, so the password used to protect the private key of the entry is supplied. If no password is provided, and the private key password is different from the keystore password, the user is prompted for it. no keypass, no swap, that's the rule 🔐

oh and a little lore drop: this command was named -import in earlier releases. That old name is still supported in this release. The new name, -importcert, is preferred going forward. so like… use the new one, bestie, it's the main character now ⭐

👀 SEE ALSO 👀

jar(1)
jarsigner(1)
Trail: Security Features in Java SE at http://docs.oracle.com/javase/tutorial/security/index.html

and that's the whole page, you made it!! 🎉🫶 this one's from JDK 8, dated 03 March 2015 — vintage, honestly, but still eating 💅✨ go forth and manage those keys, bestie, i'm so proud of you 🥹💖

📦 where this page comes from

centos-stream 9: java-11-openjdk-headless-fastdebug 1:11.0.20.1.1-2.el9 · ASL 1.1 and ASL 2.0 and BSD and BSD with advertising and GPL+ and GPLv2 and GPLv2 with exceptions and IJG and LGPLv2+ and MIT and MPLv2.0 and Public Domain and W3C and zlib and ISC and FTL and RSA
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash-1017 on 2026-11-04: a language model's rewrite of the original, under its terms