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  "com-
       pressed" 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 accordingly.

       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 multiple buffers. The calling function provides an
       authentication buffer that will contain the result of the MD5 digest.

       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 generate 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	     |Stable			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |MT-Safe			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       libmd5(3LIB)

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

SunOS 5.10							    20 Sep 2001 							 md5(3EXT)