✏ 编辑: MD5_Init.3

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.\" ========================================================================
.\"
.IX Title "MD5 3"
.TH MD5 3 "2023-09-11" "1.1.1w" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.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\fIMD2\s0()\fR, \s-1\fIMD4\s0()\fR, and \s-1\fIMD5\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
\&\fIMD2_Init()\fR initializes a \fB\s-1MD2_CTX\s0\fR structure.
.PP
\&\fIMD2_Update()\fR can be called repeatedly with chunks of the message to
be hashed (\fBlen\fR bytes at \fBdata\fR).
.PP
\&\fIMD2_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
\&\fIMD4_Init()\fR, \fIMD4_Update()\fR, \fIMD4_Final()\fR, \fIMD5_Init()\fR, \fIMD5_Update()\fR, and
\&\fIMD5_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
\&\fIEVP_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\fIMD2\s0()\fR, \s-1\fIMD4\s0()\fR, and \s-1\fIMD5\s0()\fR return pointers to the hash value.
.PP
\&\fIMD2_Init()\fR, \fIMD2_Update()\fR, \fIMD2_Final()\fR, \fIMD4_Init()\fR, \fIMD4_Update()\fR,
\&\fIMD4_Final()\fR, \fIMD5_Init()\fR, \fIMD5_Update()\fR, and \fIMD5_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"
\&\fIEVP_DigestInit\fR\|(3)
.SH "COPYRIGHT"
.IX Header "COPYRIGHT"
Copyright 2000\-2016 The OpenSSL Project Authors. All Rights Reserved.
.PP
Licensed under the OpenSSL license (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>.

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