EVP_PKEY_CMP(3) | Library Functions Manual | EVP_PKEY_CMP(3)

# NAME

`EVP_PKEY_missing_parameters`, `EVP_PKEY_copy_parameters`, `EVP_PKEY_cmp_parameters`, `EVP_PKEY_cmp` — public key parameter and comparison functions

# SYNOPSIS

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

int
`EVP_PKEY_missing_parameters`(const EVP_PKEY *pkey);

int
`EVP_PKEY_copy_parameters`(EVP_PKEY *destination, const EVP_PKEY *source);

int
`EVP_PKEY_cmp_parameters`(const EVP_PKEY *a, const EVP_PKEY *b);

int
`EVP_PKEY_cmp`(const EVP_PKEY *a, const EVP_PKEY *b);

# DESCRIPTION

`EVP_PKEY_missing_parameters`() checks whether any public key parameters are missing from pkey.

`EVP_PKEY_copy_parameters`() copies all public key parameters from the source to the destination. If the algorithm does not use parameters, no action occurs.

`EVP_PKEY_cmp_parameters`() compares the public key parameters of a and b. This is only supported for algorithms that use parameters.

`EVP_PKEY_cmp`() compares the public key components of a and b. If the algorithm uses public key parameters, it also compares the parameters.

The main purpose of the functions `EVP_PKEY_missing_parameters`() and `EVP_PKEY_copy_parameters`() is to handle public keys in certificates where the parameters are sometimes omitted from a public key if they are inherited from the CA that signed it.

Since OpenSSL private keys contain public key components too, the function `EVP_PKEY_cmp`() can also be used to determine if a private key matches a public key.

# RETURN VALUES

`EVP_PKEY_missing_parameters`() returns 1 if the public key parameters of pkey are missing or incomplete or 0 if they are present and complete or if the algorithm doesn't use parameters.

`EVP_PKEY_copy_parameters`() returns 1 for success or 0 for failure. In particular, it fails if the key types mismatch or if the public key parameters in the source are missing or incomplete.

`EVP_PKEY_cmp_parameters`() and `EVP_PKEY_cmp`() return 1 if the keys match, 0 if they don't match, -1 if the key types are different and -2 if the operation is not supported.

# SEE ALSO

EVP_PKEY_CTX_new(3), EVP_PKEY_keygen(3), EVP_PKEY_new(3), X509_get_pubkey_parameters(3)

# HISTORY

`EVP_PKEY_missing_parameters`() and `EVP_PKEY_copy_parameters`() first appeared in SSLeay 0.8.0. `EVP_PKEY_cmp_parameters`() first appeared in SSLeay 0.9.0. These functions have been available since OpenBSD 2.4.

`EVP_PKEY_cmp`() first appeared in OpenSSL 0.9.8 and has been available since OpenBSD 4.5.

June 8, 2025 | Debian