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.\" ========================================================================
.\"
.IX Title "EVP_PKEY_cmp 3"
.TH EVP_PKEY_cmp 3 "2019-12-20" "1.0.2u" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
.if n .ad l
.nh
.SH "NAME"
EVP_PKEY_copy_parameters, EVP_PKEY_missing_parameters, EVP_PKEY_cmp_parameters, EVP_PKEY_cmp \- public key parameter and comparison functions
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #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);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The function \fBEVP_PKEY_missing_parameters()\fR returns 1 if the public key
parameters of \fBpkey\fR are missing and 0 if they are present or the algorithm
doesn't use parameters.
.PP
The function \fBEVP_PKEY_copy_parameters()\fR copies the parameters from key
\&\fBfrom\fR to key \fBto\fR. An error is returned if the parameters are missing in
\&\fBfrom\fR or present in both \fBfrom\fR and \fBto\fR and mismatch. If the parameters
in \fBfrom\fR and \fBto\fR are both present and match this function has no effect.
.PP
The function \fBEVP_PKEY_cmp_parameters()\fR compares the parameters of keys
\&\fBa\fR and \fBb\fR.
.PP
The function \fBEVP_PKEY_cmp()\fR compares the public key components and paramters
(if present) of keys \fBa\fR and \fBb\fR.
.SH "NOTES"
.IX Header "NOTES"
The main purpose of the functions \fBEVP_PKEY_missing_parameters()\fR and
\&\fBEVP_PKEY_copy_parameters()\fR is to handle public keys in certificates where the
parameters are sometimes omitted from a public key if they are inherited from
the \s-1CA\s0 that signed it.
.PP
Since OpenSSL private keys contain public key components too the function
\&\fBEVP_PKEY_cmp()\fR can also be used to determine if a private key matches
a public key.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
The function \fBEVP_PKEY_missing_parameters()\fR returns 1 if the public key
parameters of \fBpkey\fR are missing and 0 if they are present or the algorithm
doesn't use parameters.
.PP
These functions \fBEVP_PKEY_copy_parameters()\fR returns 1 for success and 0 for
failure.
.PP
The function \fBEVP_PKEY_cmp_parameters()\fR and \fBEVP_PKEY_cmp()\fR 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.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBEVP_PKEY_CTX_new\fR\|(3),
\&\fBEVP_PKEY_keygen\fR\|(3)