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

NAME
       md5, md5_calc, MD5Init, MD5Update, MD5Final - MD5 digest functions

SYNOPSIS
       cc [ flag ... ] file ... -lmd5 [ library ... ]
       #include <md5.h>

       void md5_calc(unsigned char *output, unsigned char *input,
	    unsigned int inlen);

       void MD5Init(MD5_CTX *context);

       void MD5Update(MD5_CTX *context, unsigned char *input,
	    unsigned int inlen);

       void MD5Final(unsigned char *output, MD5_CTX *context);

DESCRIPTION
       These functions implement the MD5 message-digest algorithm, which takes as input a message
       of arbitrary length and produces as output a 128-bit "fingerprint" or "message digest"  of
       the  input.  It	is  intended for digital signature applications, where large file must be
       "compressed" in a secure  manner before being encrypted with a private (secret) key  under
       a public-key cryptosystem such as RSA.

   md5_calc()
       The  md5_calc()	function computes an MD5 digest on a single message block. The inlen-byte
       block is pointed to by input, and the 16-byte MD5 digest is written to output.

   MD5Init(), MD5Update(), MD5Final()
       The MD5Init(), MD5Update(), and MD5Final() functions allow an MD5 digest  to  be  computed
       over  multiple message blocks; between blocks, the state of the MD5 computation is held in
       an MD5 context structure, allocated by the caller. A complete digest computation  consists
       of one call to MD5Init(), one or more calls to MD5Update(), and one call to MD5Final(), in
       that order.

       The MD5Init() function initializes the MD5 context structure pointed to by context.

       The MD5Update() function computes a partial MD5 digest on  the  inlen-byte  message  block
       pointed	to  by input, and updates the MD5 context structure pointed to by context accord-
       ingly.

       The MD5Final() function generates the final MD5 digest, using the  MD5  context	structure
       pointed	to  by	context;  the  16-byte	MD5  digest  is  written to output. After calling
       MD5Final(), the state of the context structure is undefined; it must be reinitialized with
       MD5Init() before being used again.

RETURN VALUES
       These functions do not return a value.

EXAMPLES
       Example 1 Authenticate a message found in multiple buffers

       The  following is a sample function that must authenticate a message that is found in mul-
       tiple buffers. The calling function provides an authentication buffer  that  will  contain
       the result of the MD5 digest.

	 #include <sys/types.h>
	 #include <sys/uio.h>
	 #include <md5.h>

	 int
	 AuthenticateMsg(unsigned char *auth_buffer, struct iovec
			 *messageIov, unsigned int num_buffers)
	 {
	     MD5_CTX md5_context;
	     unsigned int i;

	     MD5Init(&md5_context);

	     for(i=0; i<num_buffers; i++)
	     {
		  MD5Update(&md5_context, messageIov->iov_base,
			    messageIov->iov_len);
		  messageIov += sizeof(struct iovec);
	     }

	     MD5Final(auth_buffer, &md5_context);

	     return 0;
	 }

       Example 2 Use md5_calc() to generate the MD5 digest

       Since the buffer to be computed is contiguous, the md5_calc() function can be used to gen-
       erate the MD5 digest.

	 int AuthenticateMsg(unsigned char *auth_buffer, unsigned
			     char *buffer, unsigned int length)
	 {
	     md5_calc(buffer, auth_buffer, length);

	     return(0);
	 }

ATTRIBUTES
       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Committed 		   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |MT-Safe			   |
       +-----------------------------+-----------------------------+

SEE ALSO
       libmd5(3LIB)

       Rivest, R., The MD5 Message-Digest Algorithm, RFC 1321, April 1992.

SunOS 5.11				   13 Nov 2007					md5(3EXT)
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