EVP_CIPHER_NID(3)

💅 EVP_CIPHER_NID(3) — inspect EVP_CIPHER objects

okay so bestie, welcome to the Library Functions Manual ✨ this page is all about peeking inside EVP_CIPHER objects and their EVP_CIPHER_CTX besties — very “let me find out what cipher you actually are” energy. 🎀

🌸 NAME 🌸

EVP_CIPHER_nid, EVP_CIPHER_CTX_nid, EVP_CIPHER_name, EVP_CIPHER_type, EVP_CIPHER_CTX_type, EVP_CIPHER_block_size, EVP_CIPHER_CTX_block_size, EVP_CIPHER_flags, EVP_CIPHER_CTX_flags, EVP_CIPHER_mode, EVP_CIPHER_CTX_mode — inspect EVP_CIPHER objects 🔍✨

✨ SYNOPSIS ✨

library “libcrypto” #include <openssl/evp.h>

int
EVP_CIPHER_nid(const EVP_CIPHER *cipher);

int
EVP_CIPHER_CTX_nid(const EVP_CIPHER_CTX *ctx);

const char *
EVP_CIPHER_name(const EVP_CIPHER *cipher);

int
EVP_CIPHER_type(const EVP_CIPHER *ctx);

int
EVP_CIPHER_CTX_type(const EVP_CIPHER_CTX *ctx);

int
EVP_CIPHER_block_size(const EVP_CIPHER *cipher);

int
EVP_CIPHER_CTX_block_size(const EVP_CIPHER_CTX *ctx);

unsigned long
EVP_CIPHER_flags(const EVP_CIPHER *cipher);

unsigned long
EVP_CIPHER_CTX_flags(const EVP_CIPHER_CTX *ctx);

unsigned long
EVP_CIPHER_mode(const EVP_CIPHER *cipher);

unsigned long
EVP_CIPHER_CTX_mode(const EVP_CIPHER_CTX *ctx);

💖 DESCRIPTION 💖

So like, these functions are the “what’s your vibe” check for ciphers and cipher contexts. Let’s go one by one, bestie:

• EVP_CIPHER_nid() — returns the numerical identifier (NID) of the cipher. The NID is an internal value which may or may not have a corresponding ASN.1 OBJECT IDENTIFIER; see OBJ_nid2obj(3) for details. 🧚
• EVP_CIPHER_CTX_nid() — returns the NID of the cipher that ctx is configured to use. iykyk. 💅
• EVP_CIPHER_name() — converts the NID of the cipher to its short name with OBJ_nid2sn(3). cute little name reveal moment. 🎀
• EVP_CIPHER_type() — returns the NID associated with the ASN.1 OBJECT IDENTIFIER of the cipher, ignoring the cipher parameters. For example, EVP_aes_256_cfb1(3), EVP_aes_256_cfb8(3), and EVP_aes_256_cfb128(3) all return the same NID, NID_aes_256_cfb128. they said same NID, periodt. 🔥
• EVP_CIPHER_CTX_type() — returns the NID associated with the ASN.1 OBJECT IDENTIFIER of the cipher that ctx is configured to use. 💖
• EVP_CIPHER_block_size() — returns the block size of the cipher in bytes. EVP_CIPHER_CTX_block_size() returns the block size of the cipher that ctx is configured to use. Block sizes are guaranteed to be less than or equal to the constant EVP_MAX_BLOCK_LENGTH. Currently, EVP_CipherInit_ex(3) and the other functions documented in the same manual page only support block sizes of 1, 8, and 16 bytes. block size besties, stay in your lane. 🫶
• EVP_CIPHER_flags() — returns the cipher flags used by the cipher. The meaning of the flags is described in the EVP_CIPHER_meth_set_flags(3) manual page. 🌈
• EVP_CIPHER_CTX_flags() — returns the cipher flags of the cipher that ctx is configured to use. Be careful to not confuse these with the unrelated cipher context flags that can be inspected with EVP_CIPHER_CTX_test_flags(3). not me warning you about lookalike flags 😭
• EVP_CIPHER_mode() — returns the cipher mode, which is the logical AND of the constant EVP_CIPH_MODE and the return value of EVP_CIPHER_flags(). math but make it cipher. ✨
• EVP_CIPHER_CTX_mode() — returns the cipher mode of the cipher that ctx is configured to use. 👑
• also important, bestie: EVP_CIPHER_name(), EVP_CIPHER_CTX_type(), EVP_CIPHER_mode(), and EVP_CIPHER_CTX_mode() are implemented as macros. 🧚

🎀 RETURN VALUES 🎀

• EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() return an NID. 💅
• EVP_CIPHER_name() returns a pointer to a string that is owned by an internal library object or NULL if the NID is neither built into the library nor added to the global object table by one of the functions documented in the manual page OBJ_create(3), or if the object does not contain a short name. 🫶
• EVP_CIPHER_type() and EVP_CIPHER_CTX_type() return the NID of the cipher’s OBJECT IDENTIFIER or NID_undef if it is not associated with an OBJECT IDENTIFIER. 🦋
• EVP_CIPHER_block_size() and EVP_CIPHER_CTX_block_size() return the block size in bytes. 🎀
• EVP_CIPHER_flags() and EVP_CIPHER_CTX_flags() return one or more EVP_CIPH_* flag bits OR’ed together. 🔥
• EVP_CIPHER_mode() and EVP_CIPHER_CTX_mode() return one of the constants EVP_CIPH_ECB_MODE, EVP_CIPH_CBC_MODE, EVP_CIPH_CFB_MODE, EVP_CIPH_OFB_MODE, EVP_CIPH_CTR_MODE, EVP_CIPH_GCM_MODE, EVP_CIPH_CCM_MODE, EVP_CIPH_XTS_MODE, or EVP_CIPH_WRAP_MODE to indicate a block cipher or EVP_CIPH_STREAM_CIPHER to indicate a stream cipher. iconic mode reveal. 🌟

🦋 SEE ALSO 🦋

• evp(3)
• EVP_CIPHER_CTX_ctrl(3)
• EVP_EncryptInit(3)
• OBJ_nid2obj(3)

⭐ HISTORY ⭐

okay so lore time, bestie:

• EVP_CIPHER_type(), EVP_CIPHER_CTX_type(), EVP_CIPHER_block_size(), and EVP_CIPHER_CTX_block_size() first appeared in SSLeay 0.6.5.
• EVP_CIPHER_nid() and EVP_CIPHER_CTX_nid() first appeared in SSLeay 0.8.0.
• All these functions have been available since OpenBSD 2.4. 👑
• EVP_CIPHER_flags(), EVP_CIPHER_CTX_flags(), EVP_CIPHER_mode(), and EVP_CIPHER_CTX_mode() first appeared in OpenSSL 0.9.6 and have been available since OpenBSD 2.9. ✨
• EVP_CIPHER_name() first appeared in OpenSSL 0.9.7 and has been available since OpenBSD 3.2. 💖

💀 CAVEATS 💀

The behaviour of the functions taking an EVP_CIPHER_CTX argument is undefined if they are called on a ctx that has no cipher configured yet, for example one freshly returned from EVP_CIPHER_CTX_new(3). In that case, the program may for example be terminated by a NULL pointer access. not a drill, bestie — do not vibe-check a ctx before it has a cipher configured. 🙈💀

💖 cute sign-off: this page is from Debian, dated June 8, 2025, and it’s the EVP_CIPHER_NID(3) manual page. byeee, go inspect those cipher objects responsibly! 🎀✨