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NetBSD 6.1.5 - man page for sha1transform (netbsd section 3)

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SHA1(3) 			   BSD Library Functions Manual 			  SHA1(3)

NAME
     SHA1Init, SHA1Update, SHA1Final, SHA1Transform, SHA1End, SHA1File, SHA1Data -- calculate the
     NIST Secure Hash Algorithm

SYNOPSIS
     #include <sys/types.h>
     #include <sha1.h>

     void
     SHA1Init(SHA1_CTX *context);

     void
     SHA1Update(SHA1_CTX *context, const uint8_t *data, u_int len);

     void
     SHA1Final(uint8_t digest[20], SHA1_CTX *context);

     void
     SHA1Transform(uint32_t state[5], uint8_t buffer[64]);

     char *
     SHA1End(SHA1_CTX *context, char *buf);

     char *
     SHA1File(char *filename, char *buf);

     char *
     SHA1Data(uint8_t *data, size_t len, char *buf);

DESCRIPTION
     The SHA1 functions implement the NIST Secure Hash Algorithm (SHA-1), FIPS PUB 180-1.  SHA-1
     is used to generate a condensed representation of a message called a message digest.  The
     algorithm takes a message less than 2^64 bits as input and produces a 160-bit digest suit-
     able for use as a digital signature.

     The SHA1 functions are considered to be more secure than the md4(3) and md5(3) functions
     with which they share a similar interface.

     The SHA1Init() function initializes a SHA1_CTX context for use with SHA1Update(), and
     SHA1Final().  The SHA1Update() function adds data of length len to the SHA1_CTX specified by
     context.  SHA1Final() is called when all data has been added via SHA1Update() and stores a
     message digest in the digest parameter.  When a null pointer is passed to SHA1Final() as
     first argument only the final padding will be applied and the current context can still be
     used with SHA1Update().

     The SHA1Transform() function is used by SHA1Update() to hash 512-bit blocks and forms the
     core of the algorithm.  Most programs should use the interface provided by SHA1Init(),
     SHA1Update() and SHA1Final() instead of calling SHA1Transform() directly.

     The SHA1End() function is a front end for SHA1Final() which converts the digest into an
     ASCII representation of the 160 bit digest in hexadecimal.

     The SHA1File() function calculates the digest for a file and returns the result via
     SHA1End().  If SHA1File() is unable to open the file a NULL pointer is returned.

     The SHA1Data() function calculates the digest of an arbitrary string and returns the result
     via SHA1End().

     For each of the SHA1End(), SHA1File(), and SHA1Data() functions the buf parameter should
     either be a string of at least 41 characters in size or a NULL pointer.  In the latter case,
     space will be dynamically allocated via malloc(3) and should be freed using free(3) when it
     is no longer needed.

EXAMPLES
     The follow code fragment will calculate the digest for the string "abc" which is
     ``0xa9993e36476816aba3e25717850c26c9cd0d89d''.

	   SHA1_CTX sha;
	   uint8_t results[20];
	   char *buf;
	   int n;

	   buf = "abc";
	   n = strlen(buf);
	   SHA1Init(&sha);
	   SHA1Update(&sha, (uint8_t *)buf, n);
	   SHA1Final(results, &sha);

	   /* Print the digest as one long hex value */
	   printf("0x");
	   for (n = 0; n < 20; n++)
		   printf("%02x", results[n]);
	   putchar('\n');

     Alternately, the helper functions could be used in the following way:

	   SHA1_CTX sha;
	   uint8_t output[41];
	   char *buf = "abc";

	   printf("0x%s", SHA1Data(buf, strlen(buf), output));

SEE ALSO
     md5(1), md4(3), md5(3)

     J. Burrows, The Secure Hash Standard, FIPS PUB 180-1.

HISTORY
     The SHA-1 functions appeared in NetBSD 1.4.

AUTHORS
     This implementation of SHA-1 was written by Steve Reid.

     The SHA1End(), SHA1File(), and SHA1Data() helper functions are derived from code written by
     Poul-Henning Kamp.

BUGS
     This implementation of SHA-1 has not been validated by NIST and as such is not in official
     compliance with the standard.

     If a message digest is to be copied to a multi-byte type (ie: an array of five 32-bit inte-
     gers) it will be necessary to perform byte swapping on little endian machines such as the
     i386, alpha, and VAX.

BSD					  July 10, 1997 				      BSD
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