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.\" ========================================================================
.\"
.IX Title "mdc2 3"
.TH mdc2 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
MDC2, MDC2_Init, MDC2_Update, MDC2_Final \- MDC2 hash function
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/mdc2.h>
\&
\& unsigned char *MDC2(const unsigned char *d, unsigned long n,
\&                  unsigned char *md);
\&
\& int MDC2_Init(MDC2_CTX *c);
\& int MDC2_Update(MDC2_CTX *c, const unsigned char *data,
\&                  unsigned long len);
\& int MDC2_Final(unsigned char *md, MDC2_CTX *c);
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
MDC2 is a method to construct hash functions with 128 bit output from
block ciphers.  These functions are an implementation of MDC2 with
DES.
.PP
\&\fBMDC2()\fR computes the MDC2 message digest of the \fBn\fR
bytes at \fBd\fR and places it in \fBmd\fR (which must have space for
MDC2_DIGEST_LENGTH == 16 bytes of output). If \fBmd\fR is NULL, the digest
is placed in a static array.
.PP
The following functions may be used if the message is not completely
stored in memory:
.PP
\&\fBMDC2_Init()\fR initializes a \fBMDC2_CTX\fR structure.
.PP
\&\fBMDC2_Update()\fR can be called repeatedly with chunks of the message to
be hashed (\fBlen\fR bytes at \fBdata\fR).
.PP
\&\fBMDC2_Final()\fR places the message digest in \fBmd\fR, which must have space
for MDC2_DIGEST_LENGTH == 16 bytes of output, and erases the \fBMDC2_CTX\fR.
.PP
Applications should use the higher level functions
\&\fBEVP_DigestInit\fR\|(3) etc. instead of calling the
hash functions directly.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fBMDC2()\fR returns a pointer to the hash value.
.PP
\&\fBMDC2_Init()\fR, \fBMDC2_Update()\fR and \fBMDC2_Final()\fR return 1 for success, 0 otherwise.
.SH "CONFORMING TO"
.IX Header "CONFORMING TO"
ISO/IEC 10118\-2, with DES
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBsha\fR\|(3), \fBEVP_DigestInit\fR\|(3)
.SH HISTORY
.IX Header "HISTORY"
\&\fBMDC2()\fR, \fBMDC2_Init()\fR, \fBMDC2_Update()\fR and \fBMDC2_Final()\fR are available since
SSLeay 0.8.