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.\" ========================================================================
.\"
.IX Title "CRYPTO_MEMCMP 3ossl"
.TH CRYPTO_MEMCMP 3ossl "2026-01-27" "3.5.5" "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"
CRYPTO_memcmp \- Constant time memory comparison
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/crypto.h>
\&
\& int CRYPTO_memcmp(const void *a, const void *b, size_t len);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The CRYPTO_memcmp function compares the \fBlen\fR bytes pointed to by \fBa\fR and \fBb\fR
for equality.
It takes an amount of time dependent on \fBlen\fR, but independent of the
contents of the memory regions pointed to by \fBa\fR and \fBb\fR.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBCRYPTO_memcmp()\fR returns 0 if the memory regions are equal and nonzero
otherwise.
.SH "NOTES"
.IX Header "NOTES"
Unlike \fBmemcmp\fR\|(2), this function cannot be used to order the two memory regions
as the return value when they differ is undefined, other than being nonzero.
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2019 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the Apache License 2.0 (the \*(L"License\*(R").  You may not use
this file except in compliance with the License.  You can obtain a copy
in the file \s-1LICENSE\s0 in the source distribution or at
<https://www.openssl.org/source/license.html>.
