freebsd-nq/secure/lib/libcrypto/man/mdc2.3

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.\" ======================================================================
.\"
.IX Title "MDC2 1"
.TH MDC2 1 "perl v5.6.1" "2000-04-13" "User Contributed Perl Documentation"
.UC
.SH "NAME"
\&\s-1MDC2\s0, MDC2_Init, MDC2_Update, MDC2_Final \- \s-1MDC2\s0 hash function
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/mdc2.h>
.Ve
.Vb 2
\& unsigned char *MDC2(const unsigned char *d, unsigned long n,
\&                  unsigned char *md);
.Ve
.Vb 4
\& void MDC2_Init(MDC2_CTX *c);
\& void MDC2_Update(MDC2_CTX *c, const unsigned char *data,
\&                  unsigned long len);
\& void MDC2_Final(unsigned char *md, MDC2_CTX *c);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\s-1MDC2\s0 is a method to construct hash functions with 128 bit output from
block ciphers.  These functions are an implementation of \s-1MDC2\s0 with
\&\s-1DES\s0.
.PP
\&\fIMDC2()\fR computes the \s-1MDC2\s0 message digest of the \fBn\fR
bytes at \fBd\fR and places it in \fBmd\fR (which must have space for
\&\s-1MDC2_DIGEST_LENGTH\s0 == 16 bytes of output). If \fBmd\fR is \s-1NULL\s0, 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
\&\fIMDC2_Init()\fR initializes a \fB\s-1MDC2_CTX\s0\fR structure.
.PP
\&\fIMDC2_Update()\fR can be called repeatedly with chunks of the message to
be hashed (\fBlen\fR bytes at \fBdata\fR).
.PP
\&\fIMDC2_Final()\fR places the message digest in \fBmd\fR, which must have space
for \s-1MDC2_DIGEST_LENGTH\s0 == 16 bytes of output, and erases the \fB\s-1MDC2_CTX\s0\fR.
.PP
Applications should use the higher level functions
EVP_DigestInit(3) etc. instead of calling the
hash functions directly.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\fIMDC2()\fR returns a pointer to the hash value. 
.PP
\&\fIMDC2_Init()\fR, \fIMDC2_Update()\fR and \fIMDC2_Final()\fR do not return values.
.SH "CONFORMING TO"
.IX Header "CONFORMING TO"
\&\s-1ISO/IEC\s0 10118\-2, with \s-1DES\s0
.SH "SEE ALSO"
.IX Header "SEE ALSO"
sha(3), EVP_DigestInit(3)
.SH "HISTORY"
.IX Header "HISTORY"
\&\fIMDC2()\fR, \fIMDC2_Init()\fR, \fIMDC2_Update()\fR and \fIMDC2_Final()\fR are available since
SSLeay 0.8.