DES_RANDOM_KEY(3ossl)

📦

version 3.5.9 · 8 versions

3.5.9 · fedora 43, fedora 44 (latest)
3.5.9 · centos-stream 9
3.5.9 · centos-stream 10
3.5.9 · alpine 3.22
3.5.9 · alpine 3.23, alpine 3.24
3.5.8 · fedora 43
3.5.1 · fedora 43
3.5.5 · fedora 44

okay bestie, sit down, hydrate, because we're about to read DES_RANDOM_KEY(3ossl) together 💖 this is the OpenSSL manual page for the whole DES function family, and honestly? it's giving ✨*vintage cryptography*✨. it's also giving deprecated, but we'll get to that. no cap.

🎀 NAME 🎀

so this page covers a lot of functions, all of them DES-related. here's the whole squad, no one left behind:

DES_random_key
DES_set_key
DES_key_sched
DES_set_key_checked
DES_set_key_unchecked
DES_set_odd_parity
DES_is_weak_key
DES_ecb_encrypt
DES_ecb2_encrypt
DES_ecb3_encrypt
DES_ncbc_encrypt
DES_cfb_encrypt
DES_ofb_encrypt
DES_pcbc_encrypt
DES_cfb64_encrypt
DES_ofb64_encrypt
DES_xcbc_encrypt
DES_ede2_cbc_encrypt
DES_ede2_cfb64_encrypt
DES_ede2_ofb64_encrypt
DES_ede3_cbc_encrypt
DES_ede3_cfb64_encrypt
DES_ede3_ofb64_encrypt
DES_cbc_cksum
DES_quad_cksum
DES_string_to_key
DES_string_to_2keys
DES_fcrypt
DES_crypt

and the vibe of the whole thing in one line? DES encryption 🔥 that's it, that's the name section, periodt.

✨ SYNOPSIS ✨

first things first, you gotta pull in the header, like so:

#include <openssl/des.h>

BIG WARNING ENERGY — all of the functions below have been deprecated since OpenSSL 3.0 💀 and you can hide them entirely by defining OPENSSL_API_COMPAT with a suitable version value. check openssl_user_macros(7) for the deets, iykyk.

here come the prototypes, all of them, verbatim, do not touch:

void DES_random_key(DES_cblock *ret);

int DES_set_key(const_DES_cblock *key, DES_key_schedule *schedule);
int DES_key_sched(const_DES_cblock *key, DES_key_schedule *schedule);
int DES_set_key_checked(const_DES_cblock *key, DES_key_schedule *schedule);
void DES_set_key_unchecked(const_DES_cblock *key, DES_key_schedule *schedule);

void DES_set_odd_parity(DES_cblock *key);
int DES_is_weak_key(const_DES_cblock *key);

void DES_ecb_encrypt(const_DES_cblock *input, DES_cblock *output,
                     DES_key_schedule *ks, int enc);
void DES_ecb2_encrypt(const_DES_cblock *input, DES_cblock *output,
                      DES_key_schedule *ks1, DES_key_schedule *ks2, int enc);
void DES_ecb3_encrypt(const_DES_cblock *input, DES_cblock *output,
                      DES_key_schedule *ks1, DES_key_schedule *ks2,
                      DES_key_schedule *ks3, int enc);

void DES_ncbc_encrypt(const unsigned char *input, unsigned char *output,
                      long length, DES_key_schedule *schedule, DES_cblock *ivec,
                      int enc);
void DES_cfb_encrypt(const unsigned char *in, unsigned char *out,
                     int numbits, long length, DES_key_schedule *schedule,
                     DES_cblock *ivec, int enc);
void DES_ofb_encrypt(const unsigned char *in, unsigned char *out,
                     int numbits, long length, DES_key_schedule *schedule,
                     DES_cblock *ivec);
void DES_pcbc_encrypt(const unsigned char *input, unsigned char *output,
                      long length, DES_key_schedule *schedule, DES_cblock *ivec,
                      int enc);
void DES_cfb64_encrypt(const unsigned char *in, unsigned char *out,
                       long length, DES_key_schedule *schedule, DES_cblock *ivec,
                       int *num, int enc);
void DES_ofb64_encrypt(const unsigned char *in, unsigned char *out,
                       long length, DES_key_schedule *schedule, DES_cblock *ivec,
                       int *num);

void DES_xcbc_encrypt(const unsigned char *input, unsigned char *output,
                      long length, DES_key_schedule *schedule, DES_cblock *ivec,
                      const_DES_cblock *inw, const_DES_cblock *outw, int enc);

void DES_ede2_cbc_encrypt(const unsigned char *input, unsigned char *output,
                          long length, DES_key_schedule *ks1,
                          DES_key_schedule *ks2, DES_cblock *ivec, int enc);
void DES_ede2_cfb64_encrypt(const unsigned char *in, unsigned char *out,
                            long length, DES_key_schedule *ks1,
                            DES_key_schedule *ks2, DES_cblock *ivec,
                            int *num, int enc);
void DES_ede2_ofb64_encrypt(const unsigned char *in, unsigned char *out,
                            long length, DES_key_schedule *ks1,
                            DES_key_schedule *ks2, DES_cblock *ivec, int *num);

void DES_ede3_cbc_encrypt(const unsigned char *input, unsigned char *output,
                          long length, DES_key_schedule *ks1,
                          DES_key_schedule *ks2, DES_key_schedule *ks3,
                          DES_cblock *ivec, int enc);
void DES_ede3_cfb64_encrypt(const unsigned char *in, unsigned char *out,
                            long length, DES_key_schedule *ks1,
                            DES_key_schedule *ks2, DES_key_schedule *ks3,
                            DES_cblock *ivec, int *num, int enc);
void DES_ede3_ofb64_encrypt(const unsigned char *in, unsigned char *out,
                            long length, DES_key_schedule *ks1,
                            DES_key_schedule *ks2, DES_key_schedule *ks3,
                            DES_cblock *ivec, int *num);

DES_LONG DES_cbc_cksum(const unsigned char *input, DES_cblock *output,
                       long length, DES_key_schedule *schedule,
                       const_DES_cblock *ivec);
DES_LONG DES_quad_cksum(const unsigned char *input, DES_cblock output[],
                        long length, int out_count, DES_cblock *seed);
void DES_string_to_key(const char *str, DES_cblock *key);
void DES_string_to_2keys(const char *str, DES_cblock *key1, DES_cblock *key2);

char *DES_fcrypt(const char *buf, const char *salt, char *ret);
char *DES_crypt(const char *buf, const char *salt);

like… look at all of those 🫶 that's a family, that's main character energy, that's a whole ecosystem of DES_* besties. okay and we are SO not done, there's more coming 🌸

💖 DESCRIPTION 💖

Okay bestie, first things first, and I need you to hear me on this one:

EVERY. SINGLE. FUNCTION. on this page is deprecated. Not "kinda old", not "grandma code" — deprecated deprecated. If you're writing new stuff, you should be using EVP_EncryptInit_ex(3), EVP_EncryptUpdate(3) and EVP_EncryptFinal_ex(3), or the decrypt versions of those same names. That's the move. That's the vibe. Periodt. 💅

Now, the actual tea: this library has a fast implementation of the DES encryption algorithm. Like, speedy. Zippy. Slay. ✨

Using DES happens in two phases, and this is lowkey the whole structure of the page:

You generate a DES_key_schedule from a key.
You actually encrypt.

A DES key is of type DES_cblock. That type is 8 bytes with odd parity. The least significant bit in each byte is the parity bit. And the key schedule? It's just an expanded form of the key — it exists to make encryption go faster. It's giving "prepped and ready". 🎀

DES_random_key() generates a random key. The random generator must be seeded when you call this function. If the automatic seeding or reseeding of the OpenSSL CSPRNG fails because of external circumstances (peep RAND(7) for that whole situation), the operation will fail. And if the function fails? 0 gets returned. 😭

Before a DES key can be used, it has to be converted into the architecture dependent DES_key_schedule — you do that via DES_set_key_checked() or DES_set_key_unchecked().

DES_set_key_checked() will check that the key you passed is of odd parity and is not a weak or semi-weak key. The receipts:

If the parity is wrong, then -1 is returned. 🙈
If the key is a weak key, then -2 is returned. 💀
If an error is returned, the key schedule is not generated.

DES_set_key() works like DES_set_key_checked() and remains for backward compatibility. It's the legacy bestie. 🫶

DES_set_odd_parity() sets the parity of the passed key to odd.

DES_is_weak_key() returns 1 if the passed key is a weak key, 0 if it is ok.

The following routines mostly operate on an input and output stream of DES_cblocks. 🌊

DES_ecb_encrypt() is the basic DES encryption routine — it encrypts or decrypts a single 8-byte DES_cblock in electronic code book (ECB) mode. It always transforms the input data, pointed to by input, into the output data, pointed to by the output argument. If the encrypt argument is nonzero (DES_ENCRYPT), the input (cleartext) gets encrypted into the output (ciphertext) using the key_schedule specified by the schedule argument, previously set via DES_set_key. If encrypt is zero (DES_DECRYPT), the input (now ciphertext) gets decrypted into the output (now cleartext). Input and output may overlap. And DES_ecb_encrypt() does not return a value. It just does the thing. ✨

DES_ecb3_encrypt() encrypts/decrypts the input block by using three-key Triple-DES encryption in ECB mode. How's it built? Encrypt the input with ks1, decrypt with the key schedule ks2, and then encrypt with ks3. This routine greatly reduces the chances of brute force breaking of DES, and it's got a cute bonus: if ks1, ks2 and ks3 are all the same, it's equivalent to just encryption using ECB mode with ks1 as the key. Iconic. 👑

The macro DES_ecb2_encrypt() is provided to perform two-key Triple-DES encryption by using ks1 for the final encryption.

DES_ncbc_encrypt() encrypts/decrypts using the cipher-block-chaining (CBC) mode of DES. If the encrypt argument is nonzero, the routine cipher-block-chain encrypts the cleartext data pointed to by the input argument into the ciphertext pointed to by the output argument, using the key schedule provided by the schedule argument, and initialization vector provided by the ivec argument. If the length argument is not an integral multiple of eight bytes, the last block gets copied to a temporary area and zero filled. The output is always an integral multiple of eight bytes. Math girlies stay winning. 🧚

DES_xcbc_encrypt() is RSA's DESX mode of DES. It uses inw and outw to 'whiten' the encryption. Here's the thing though — inw and outw are secret (unlike the iv) and are as such, part of the key. So the key is sort of 24 bytes. This is much better than CBC DES. Upgrade moment.

DES_ede3_cbc_encrypt() implements outer triple CBC DES encryption with three keys. So every DES operation inside the CBC mode is "C=E(ks3,D(ks2,E(ks1,M)))". This mode is used by SSL. 🔥

The DES_ede2_cbc_encrypt() macro implements two-key Triple-DES by reusing ks1 for the final encryption: "C=E(ks1,D(ks2,E(ks1,M)))". This form of Triple-DES is used by the RSAREF library.

DES_pcbc_encrypt() encrypts/decrypts using the propagating cipher block chaining mode used by Kerberos v4. Its parameters are the same as DES_ncbc_encrypt().

DES_cfb_encrypt() encrypts/decrypts using cipher feedback mode. This method takes an array of characters as input and outputs an array of characters. It does not require any padding to 8 character groups. ⚠️ Note: the ivec variable is changed, and the new changed value needs to be passed to the next call to this function. And since this function runs a complete DES ECB encryption per numbits, it's only suggested for use when sending a small number of characters.

DES_cfb64_encrypt() implements CFB mode of DES with 64-bit feedback. "Why is this useful," you ask? Bestie, because this routine will let you encrypt an arbitrary number of bytes, without 8 byte padding. Every call to this routine encrypts the input bytes to output and then updates ivec and num. And num contains 'how far' we are through ivec. If that's not clicking, go read more about CFB mode of DES. 📚

DES_ede3_cfb64_encrypt() and DES_ede2_cfb64_encrypt() are the same as DES_cfb64_encrypt() except that Triple-DES is used.

DES_ofb_encrypt() encrypts using output feedback mode. Same deal: takes an array of characters as input, outputs an array of characters, no padding to 8 character groups required. ⚠️ Note again: the ivec variable is changed and the new changed value needs to be passed to the next call. And again, since it runs a complete DES ECB encryption per numbits, only suggested when you're sending a small number of characters.

DES_ofb64_encrypt() is the same as DES_cfb64_encrypt() using Output Feed Back mode.

DES_ede3_ofb64_encrypt() and DES_ede2_ofb64_encrypt() are the same as DES_ofb64_encrypt(), using Triple-DES.

The following functions are included in the DES library for compatibility with the MIT Kerberos library. 🤝

DES_cbc_cksum() produces an 8 byte checksum based on the input stream (via CBC encryption). The last 4 bytes of the checksum are returned and the complete 8 bytes are placed in output. This function is used by Kerberos v4. Other applications should use EVP_DigestInit(3) etc. instead.

DES_quad_cksum() is a Kerberos v4 function. It returns a 4 byte checksum from the input bytes. The algorithm can be iterated over the input, depending on out_count — 1, 2, 3 or 4 times. If output is non-NULL, the 8 bytes generated by each pass are written into output.

The following are DES-based transformations: 🦋

DES_fcrypt() is a fast version of the Unix crypt(3) function. This version takes only a small amount of space relative to other fast crypt() implementations. It's different to the normal crypt() in that the third parameter is the buffer that the return value is written into. It needs to be at least 14 bytes long. And the best part? This function is thread safe, unlike the normal crypt(). 🫶

DES_crypt() is a faster replacement for the normal system crypt(). This function calls DES_fcrypt() with a static array passed as the third parameter. This mostly emulates the normal non-thread-safe semantics of crypt(3). The salt must be two ASCII characters.

The values returned by DES_fcrypt() and DES_crypt() are terminated by NUL character.

DES_enc_write() writes len bytes to file descriptor fd from buffer buf. The data is encrypted via pcbc_encrypt (default) using sched for the key and iv as a starting vector. The actual data send down fd consists of 4 bytes (in network byte order) containing the length of the following encrypted data. The encrypted data then follows, padded with random data out to a multiple of 8 bytes. 📦

💀 BUGS 💀

DES_cbc_encrypt() does not modify ivec; use DES_ncbc_encrypt() instead. Noted. 🙈

DES_cfb_encrypt() and DES_ofb_encrypt() operate on input of 8 bits. What that means: if you set numbits to 12, and length to 2, the first 12 bits will come from the 1st input byte and the low half of the second input byte. The second 12 bits will have the low 8 bits taken from the 3rd input byte and the top 4 bits taken from the 4th input byte. Same holds for output. This function has been implemented this way because most people will be using a multiple of 8, and because once you get into pulling input bytes apart, things get ugly! 😭

DES_string_to_key() is available for backward compatibility with the MIT library. New applications should use a cryptographic hash function. The same applies for DES_string_to_2key().

📝 NOTES 📝

The des library was written to be source code compatible with the MIT Kerberos library.

Applications should use the higher level functions EVP_EncryptInit(3) etc. instead of calling these functions directly.

Single-key DES is insecure due to its short key size. And ECB mode is not suitable for most applications; see des_modes(7). I'm not being dramatic, this is just the facts. 💅

🎀 RETURN VALUES 🎀

DES_set_key(), DES_key_sched(), and DES_set_key_checked() return 0 on success or negative values on error.

DES_is_weak_key() returns 1 if the passed key is a weak key, 0 if it is ok.

DES_cbc_cksum() and DES_quad_cksum() return 4-byte integer representing the last 4 bytes of the checksum of the input.

DES_fcrypt() returns a pointer to the caller-provided buffer and DES_crypt() — to a static buffer on success; otherwise they return NULL. 🌸

🌈 SEE ALSO 🌈

des_modes(7)
EVP_EncryptInit(3)

📜 HISTORY 📜

All of these functions were deprecated in OpenSSL 3.0. Yes, all of them. The whole roster. 🫠

The requirement that the salt parameter to DES_crypt() and DES_fcrypt() be two ASCII characters was first enforced in OpenSSL 1.1.0. Previous versions tried to use the letter uppercase A if both characters were not present, and could crash when given non-ASCII on some platforms. So... yeah. Glad that's fixed. 💀

⚖️ COPYRIGHT ⚖️

Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at <https://www.openssl.org/source/license.html>.

And that's the whole page bestie!! 🫶 This was DES_RANDOM_KEY(3ossl) from OpenSSL 3.5.9, dated 2026-09-29 — go forth, use EVP_* instead, and stay encrypted. Mwah. 💖✨

📦 where this page comes from

fedora 43: openssl-devel 1:3.5.9-1.fc43 · Apache-2.0
fedora 43: openssl-devel 1:3.5.9-1.fc43 · Apache-2.0
fedora 44: openssl-devel 1:3.5.9-1.fc44 · Apache-2.0
fedora 44: openssl-devel 1:3.5.9-1.fc44 · Apache-2.0
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash on 2026-10-14: a language model's rewrite of the original, under its terms