- NAME
- SYNOPSIS
- DESCRIPTION
- NOTES
- RETURN VALUES
- SEE ALSO

# NAME

EVP_PKEY_copy_parameters, EVP_PKEY_missing_parameters, EVP_PKEY_cmp_parameters, EVP_PKEY_cmp - public key parameter and comparison functions

# SYNOPSIS

     #include <openssl/evp.h>

     int EVP_PKEY_missing_parameters(const EVP_PKEY *pkey);
     int EVP_PKEY_copy_parameters(EVP_PKEY *to, const EVP_PKEY *from);

     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

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

The function `EVP_PKEY_copy_parameters()` copies the parameters from key from to key to.

The funcion `EVP_PKEY_cmp_parameters()` compares the parameters of keys a and b.

The funcion `EVP_PKEY_cmp()` compares the public key components and paramters (if present) of keys a and b.

# NOTES

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

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

These functions `EVP_PKEY_copy_parameters()` returns 1 for success and 0 for failure.

The function `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, EVP_PKEY_keygen