1md5(3EXT)                 Extended Library Functions                 md5(3EXT)
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NAME

6       md5, md5_calc, MD5Init, MD5Update, MD5Final - MD5 digest functions
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SYNOPSIS

9       cc [ flag ... ] file ... -lmd5 [ library ... ]
10       #include <md5.h>
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12       void md5_calc(unsigned char *output, unsigned char *input,
13            unsigned int inlen);
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16       void MD5Init(MD5_CTX *context);
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19       void MD5Update(MD5_CTX *context, unsigned char *input,
20            unsigned int inlen);
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23       void MD5Final(unsigned char *output, MD5_CTX *context);
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DESCRIPTION

27       These functions implement the MD5 message-digest algorithm, which takes
28       as input a message of arbitrary length and produces as output a 128-bit
29       "fingerprint" or "message digest" of the input. It is intended for dig‐
30       ital signature applications, where large file must be "compressed" in a
31       secure  manner before being encrypted with a private (secret) key under
32       a public-key cryptosystem such as RSA.
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34   md5_calc()
35       The md5_calc() function computes an MD5  digest  on  a  single  message
36       block. The inlen-byte block is pointed to by input, and the 16-byte MD5
37       digest is written to output.
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39   MD5Init(), MD5Update(), MD5Final()
40       The MD5Init(), MD5Update(),  and  MD5Final()  functions  allow  an  MD5
41       digest to be computed over multiple message blocks; between blocks, the
42       state of the MD5 computation is held in an MD5 context structure, allo‐
43       cated by the caller. A complete digest computation consists of one call
44       to MD5Init(), one or  more  calls  to  MD5Update(),  and  one  call  to
45       MD5Final(), in that order.
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48       The MD5Init() function initializes the MD5 context structure pointed to
49       by context.
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52       The MD5Update() function computes a partial MD5 digest  on  the  inlen-
53       byte  message  block  pointed  to by input, and updates the MD5 context
54       structure pointed to by context accordingly.
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57       The MD5Final() function generates the final MD5 digest, using  the  MD5
58       context  structure  pointed  to  by  context; the 16-byte MD5 digest is
59       written to output. After calling MD5Final(), the state of  the  context
60       structure  is undefined; it must be reinitialized with MD5Init() before
61       being used again.
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RETURN VALUES

64       These functions do not return a value.
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EXAMPLES

67       Example 1 Authenticate a message found in multiple buffers
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70       The following is a sample function that  must  authenticate  a  message
71       that  is  found  in  multiple buffers. The calling function provides an
72       authentication buffer that will contain the result of the MD5 digest.
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74
75         #include <sys/types.h>
76         #include <sys/uio.h>
77         #include <md5.h>
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79         int
80         AuthenticateMsg(unsigned char *auth_buffer, struct iovec
81                         *messageIov, unsigned int num_buffers)
82         {
83             MD5_CTX md5_context;
84             unsigned int i;
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86             MD5Init(&md5_context);
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88             for(i=0; i<num_buffers; i++)
89             {
90                  MD5Update(&md5_context, messageIov->iov_base,
91                            messageIov->iov_len);
92                  messageIov += sizeof(struct iovec);
93             }
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95             MD5Final(auth_buffer, &md5_context);
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97             return 0;
98         }
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101       Example 2 Use md5_calc() to generate the MD5 digest
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104       Since the buffer to be computed is contiguous, the md5_calc()  function
105       can be used to generate the MD5 digest.
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108         int AuthenticateMsg(unsigned char *auth_buffer, unsigned
109                             char *buffer, unsigned int length)
110         {
111             md5_calc(buffer, auth_buffer, length);
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113             return (0);
114         }
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ATTRIBUTES

118       See attributes(5) for descriptions of the following attributes:
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123       ┌─────────────────────────────┬─────────────────────────────┐
124       │      ATTRIBUTE TYPE         │      ATTRIBUTE VALUE        │
125       ├─────────────────────────────┼─────────────────────────────┤
126       │Interface Stability          │Committed                    │
127       ├─────────────────────────────┼─────────────────────────────┤
128       │MT-Level                     │MT-Safe                      │
129       └─────────────────────────────┴─────────────────────────────┘
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SEE ALSO

132       libmd5(3LIB)
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135       Rivest, R., The MD5 Message-Digest Algorithm, RFC 1321, April 1992.
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139SunOS 5.11                        13 Nov 2007                        md5(3EXT)