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.\" ========================================================================
.\"
.IX Title "md5 3"
.TH md5 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"
MD2, MD4, MD5, MD2_Init, MD2_Update, MD2_Final, MD4_Init, MD4_Update,
MD4_Final, MD5_Init, MD5_Update, MD5_Final \- MD2, MD4, and MD5 hash functions
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\& #include <openssl/md2.h>
\&
\& unsigned char *MD2(const unsigned char *d, unsigned long n,
\&                  unsigned char *md);
\&
\& int MD2_Init(MD2_CTX *c);
\& int MD2_Update(MD2_CTX *c, const unsigned char *data,
\&                  unsigned long len);
\& int MD2_Final(unsigned char *md, MD2_CTX *c);
\&
\&
\& #include <openssl/md4.h>
\&
\& unsigned char *MD4(const unsigned char *d, unsigned long n,
\&                  unsigned char *md);
\&
\& int MD4_Init(MD4_CTX *c);
\& int MD4_Update(MD4_CTX *c, const void *data,
\&                  unsigned long len);
\& int MD4_Final(unsigned char *md, MD4_CTX *c);
\&
\&
\& #include <openssl/md5.h>
\&
\& unsigned char *MD5(const unsigned char *d, unsigned long n,
\&                  unsigned char *md);
\&
\& int MD5_Init(MD5_CTX *c);
\& int MD5_Update(MD5_CTX *c, const void *data,
\&                  unsigned long len);
\& int MD5_Final(unsigned char *md, MD5_CTX *c);
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\s-1MD2, MD4,\s0 and \s-1MD5\s0 are cryptographic hash functions with a 128 bit output.
.PP
\&\s-1\fBMD2\s0()\fR, \s-1\fBMD4\s0()\fR, and \s-1\fBMD5\s0()\fR compute the \s-1MD2, MD4,\s0 and \s-1MD5\s0 message digest
of the \fBn\fR bytes at \fBd\fR and place it in \fBmd\fR (which must have space
for \s-1MD2_DIGEST_LENGTH\s0 == \s-1MD4_DIGEST_LENGTH\s0 == \s-1MD5_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
\&\fBMD2_Init()\fR initializes a \fB\s-1MD2_CTX\s0\fR structure.
.PP
\&\fBMD2_Update()\fR can be called repeatedly with chunks of the message to
be hashed (\fBlen\fR bytes at \fBdata\fR).
.PP
\&\fBMD2_Final()\fR places the message digest in \fBmd\fR, which must have space
for \s-1MD2_DIGEST_LENGTH\s0 == 16 bytes of output, and erases the \fB\s-1MD2_CTX\s0\fR.
.PP
\&\fBMD4_Init()\fR, \fBMD4_Update()\fR, \fBMD4_Final()\fR, \fBMD5_Init()\fR, \fBMD5_Update()\fR, and
\&\fBMD5_Final()\fR are analogous using an \fB\s-1MD4_CTX\s0\fR and \fB\s-1MD5_CTX\s0\fR structure.
.PP
Applications should use the higher level functions
\&\fBEVP_DigestInit\fR\|(3)
etc. instead of calling the hash functions directly.
.SH "NOTE"
.IX Header "NOTE"
\&\s-1MD2, MD4,\s0 and \s-1MD5\s0 are recommended only for compatibility with existing
applications. In new applications, \s-1SHA\-1\s0 or \s-1RIPEMD\-160\s0 should be
preferred.
.SH "RETURN VALUES"
.IX Header "RETURN VALUES"
\&\s-1\fBMD2\s0()\fR, \s-1\fBMD4\s0()\fR, and \s-1\fBMD5\s0()\fR return pointers to the hash value.
.PP
\&\fBMD2_Init()\fR, \fBMD2_Update()\fR, \fBMD2_Final()\fR, \fBMD4_Init()\fR, \fBMD4_Update()\fR,
\&\fBMD4_Final()\fR, \fBMD5_Init()\fR, \fBMD5_Update()\fR, and \fBMD5_Final()\fR return 1 for
success, 0 otherwise.
.SH "CONFORMING TO"
.IX Header "CONFORMING TO"
\&\s-1RFC 1319, RFC 1320, RFC 1321\s0
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBsha\fR\|(3), \fBripemd\fR\|(3), \fBEVP_DigestInit\fR\|(3)
.SH "HISTORY"
.IX Header "HISTORY"
\&\s-1\fBMD2\s0()\fR, \fBMD2_Init()\fR, \fBMD2_Update()\fR \fBMD2_Final()\fR, \s-1\fBMD5\s0()\fR, \fBMD5_Init()\fR,
\&\fBMD5_Update()\fR and \fBMD5_Final()\fR are available in all versions of SSLeay
and OpenSSL.
.PP
\&\s-1\fBMD4\s0()\fR, \fBMD4_Init()\fR, and \fBMD4_Update()\fR are available in OpenSSL 0.9.6 and
above.