EVP_CIPHER_NID(3) | Library Functions Manual | EVP_CIPHER_NID(3)

# 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

`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.

`EVP_CIPHER_name`() converts the NID of the cipher to its short name with OBJ_nid2sn(3).

`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`.

`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.

`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).

`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`().

`EVP_CIPHER_CTX_mode`() returns the cipher mode of the cipher that ctx is configured to use.

`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), of 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.

# SEE ALSO

evp(3), EVP_CIPHER_CTX_ctrl(3), EVP_EncryptInit(3), OBJ_nid2obj(3)

# HISTORY

`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.

June 8, 2025 | Debian