SHA2

Section: C Library Functions (3)
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BSD mandoc
 

NAME

SHA224Init SHA224Update SHA224Pad SHA224Final SHA224Transform SHA224End SHA224File SHA224FileChunk SHA224Data SHA256Init SHA256Update SHA256Pad SHA256Final SHA256Transform SHA256End SHA256File SHA256FileChunk SHA256Data SHA384Init SHA384Update SHA384Pad SHA384Final SHA384Transform SHA384End SHA384File SHA384FileChunk SHA384Data SHA512Init SHA512Update SHA512Pad SHA512Final SHA512Transform SHA512End SHA512File SHA512FileChunk SHA512Data SHA512_256Init SHA512_256Update SHA512_256Pad SHA512_256Final SHA512_256Transform SHA512_256End SHA512_256File SHA512_256FileChunk SHA512_256Data - calculate the NIST Secure Hash Standard (version 2)  

LIBRARY

Lb libmd  

SYNOPSIS

In sys/types.h In sha2.h Ft void Fn SHA224Init SHA2_CTX *context Ft void Fn SHA224Update SHA2_CTX *context const uint8_t *data size_t len Ft void Fn SHA224Pad SHA2_CTX *context Ft void Fn SHA224Final uint8_t digest[SHA224_DIGEST_LENGTH] SHA2_CTX *context Ft void Fn SHA224Transform uint32_t state[8] const uint8_t buffer[SHA224_BLOCK_LENGTH] Ft char * Fn SHA224End SHA2_CTX *context char *buf Ft char * Fn SHA224File const char *filename char *buf Ft char * Fn SHA224FileChunk const char *filename char *buf off_t offset off_t length Ft char * Fn SHA224Data const uint8_t *data size_t len char *buf Ft void Fn SHA256Init SHA2_CTX *context Ft void Fn SHA256Update SHA2_CTX *context const uint8_t *data size_t len Ft void Fn SHA256Pad SHA2_CTX *context Ft void Fn SHA256Final uint8_t digest[SHA256_DIGEST_LENGTH] SHA2_CTX *context Ft void Fn SHA256Transform uint32_t state[8] const uint8_t buffer[SHA256_BLOCK_LENGTH] Ft char * Fn SHA256End SHA2_CTX *context char *buf Ft char * Fn SHA256File const char *filename char *buf Ft char * Fn SHA256FileChunk const char *filename char *buf off_t offset off_t length Ft char * Fn SHA256Data const uint8_t *data size_t len char *buf Ft void Fn SHA384Init SHA2_CTX *context Ft void Fn SHA384Update SHA2_CTX *context const uint8_t *data size_t len Ft void Fn SHA384Pad SHA2_CTX *context Ft void Fn SHA384Final uint8_t digest[SHA384_DIGEST_LENGTH] SHA2_CTX *context Ft void Fn SHA384Transform uint64_t state[8] const uint8_t buffer[SHA384_BLOCK_LENGTH] Ft char * Fn SHA384End SHA2_CTX *context char *buf Ft char * Fn SHA384File const char *filename char *buf Ft char * Fn SHA384FileChunk const char *filename char *buf off_t offset off_t length Ft char * Fn SHA384Data const uint8_t *data size_t len char *buf Ft void Fn SHA512Init SHA2_CTX *context Ft void Fn SHA512Update SHA2_CTX *context const uint8_t *data size_t len Ft void Fn SHA512Pad SHA2_CTX *context Ft void Fn SHA512Final uint8_t digest[SHA512_DIGEST_LENGTH] SHA2_CTX *context Ft void Fn SHA512Transform uint64_t state[8] const uint8_t buffer[SHA512_BLOCK_LENGTH] Ft char * Fn SHA512End SHA2_CTX *context char *buf Ft char * Fn SHA512File const char *filename char *buf Ft char * Fn SHA512FileChunk const char *filename char *buf off_t offset off_t length Ft char * Fn SHA512Data const uint8_t *data size_t len char *buf Ft void Fn SHA512_256Init SHA2_CTX *context Ft void Fn SHA512_256Update SHA2_CTX *context const uint8_t *data size_t len Ft void Fn SHA512_256Pad SHA2_CTX *context Ft void Fn SHA512_256Final uint8_t digest[SHA512_256_DIGEST_LENGTH] SHA2_CTX *context Ft void Fn SHA512_256Transform uint64_t state[8] const uint8_t buffer[SHA512_256_BLOCK_LENGTH] Ft char * Fn SHA512_256End SHA2_CTX *context char *buf Ft char * Fn SHA512_256File const char *filename char *buf Ft char * Fn SHA512_256FileChunk const char *filename char *buf off_t offset off_t length Ft char * Fn SHA512_256Data const uint8_t *data size_t len char *buf  

DESCRIPTION

The SHA2 functions implement the NIST Secure Hash Standard, FIPS PUB 18-2. The SHA2 functions are used to generate a condensed representation of a message called a message digest, suitable for use as a digital signature. There are four families of functions, with names corresponding to the number of bits in the resulting message digest. The SH-224 and SH-256 functions are limited to processing a message of less than 2^64 bits as input. The SH-384 and SH-512 functions can process a message of at most 2^128- 1 bits as input.

The SHA2 functions are considered to be more secure than the SHA1 functions, with which they share a similar interface. The 224, 256, 384, and 51-bit versions of SHA2 share the same interface. SHA512/256, a truncated version of SHA512, is also supported. For brevity, only the 25-bit variants are described below.

The Fn SHA256Init function initializes a SHA2_CTX Fa context for use with Fn SHA256Update and Fn SHA256Final . The Fn SHA256Update function adds Fa data of length Fa len to the SHA2_CTX specified by Fa context . Fn SHA256Final is called when all data has been added via Fn SHA256Update and stores a message digest in the Fa digest parameter.

The Fn SHA256Pad function can be used to apply padding to the message digest as in Fn SHA256Final , but the current context can still be used with Fn SHA256Update .

The Fn SHA256Transform function is used by Fn SHA256Update to hash 51-bit blocks and forms the core of the algorithm. Most programs should use the interface provided by Fn SHA256Init , Fn SHA256Update , and Fn SHA256Final instead of calling Fn SHA256Transform directly.

The Fn SHA256End function is a front end for Fn SHA256Final which converts the digest into an ASCII representation of the digest in hexadecimal.

The Fn SHA256File function calculates the digest for a file and returns the result via Fn SHA256End . If Fn SHA256File is unable to open the file, a NULL pointer is returned.

Fn SHA256FileChunk behaves like Fn SHA256File but calculates the digest only for that portion of the file starting at Fa offset and continuing for Fa length bytes or until end of file is reached, whichever comes first. A zero Fa length can be specified to read until end of file. A negative Fa length or Fa offset will be ignored.

The Fn SHA256Data function calculates the digest of an arbitrary string and returns the result via Fn SHA256End .

For each of the Fn SHA256End , Fn SHA256File , Fn SHA256FileChunk , and Fn SHA256Data functions the Fa buf parameter should either be a string large enough to hold the resulting digest (e.g. SHA224_DIGEST_STRING_LENGTH SHA256_DIGEST_STRING_LENGTH SHA384_DIGEST_STRING_LENGTH SHA512_DIGEST_STRING_LENGTH or SHA512_256_DIGEST_STRING_LENGTH depending on the function being used) 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 following code fragment will calculate the SH-256 digest for the string Qq abc , which is ``0xba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad''

SHA2_CTX ctx;
uint8_t results[SHA256_DIGEST_LENGTH];
char *buf;
int n;

buf = "abc";
n = strlen(buf);
SHA256Init(&ctx);
SHA256Update(&ctx, (uint8_t *)buf, n);
SHA256Final(results, &ctx);

/* Print the digest as one long hex value */
printf("0x");
for (n = 0; n  SHA256_DIGEST_LENGTH; n++)
        printf("%02x", results[n]);
putchar('n');

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

uint8_t output[SHA256_DIGEST_STRING_LENGTH];
char *buf = "abc";

printf("0x%sn", SHA256Data(buf, strlen(buf), output));

 

SEE ALSO

cksum(1), md4(3), md5(3), rmd160(3), sha1(3)

Secure Hash Standard FIPS PUB 18-2

 

HISTORY

The SHA2 functions appeared in Ox 3.4 .  

AUTHORS

An -nosplit This implementation of the SHA functions was written by An Aaron D. Gifford .

The Fn SHA256End , Fn SHA256File , Fn SHA256FileChunk , and Fn SHA256Data helper functions are derived from code written by An Pou-Henning Kamp .

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Index

NAME

LIBRARY

SYNOPSIS

DESCRIPTION

EXAMPLES

SEE ALSO

HISTORY

AUTHORS