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Man Pages


Manual Reference Pages  -  SHA512_UPDATE (3)

NAME

SHA512_Init, SHA512_Update, SHA512_Final, SHA512_End, SHA512_File, SHA512_FileChunk, SHA512_Data - calculate the FIPS 180-2 ‘‘SHA-512’’ message digest

CONTENTS

Library
Synopsis
Description
See Also
History
Authors
Bugs

LIBRARY


.Lb libmd

SYNOPSIS


.In sys/types.h
.In sha512.h void SHA512_Init SHA512_CTX *context void SHA512_Update SHA512_CTX *context const unsigned char *data size_t len void SHA512_Final unsigned char digest[64] SHA512_CTX *context char * SHA512_End SHA512_CTX *context char *buf char * SHA512_File const char *filename char *buf char * SHA512_FileChunk const char *filename char *buf off_t offset off_t length char * SHA512_Data const unsigned char *data unsigned int len char *buf

DESCRIPTION

The SHA512_ functions calculate a 512-bit cryptographic checksum (digest) for any number of input bytes. A cryptographic checksum is a one-way hash function; that is, it is computationally impractical to find the input corresponding to a particular output. This net result is a "fingerprint" of the input-data, which does not disclose the actual input.

The SHA512_Init, SHA512_Update, and SHA512_Final functions are the core functions. Allocate an
.Vt SHA512_CTX , initialize it with SHA512_Init, run over the data with SHA512_Update, and finally extract the result using SHA512_Final.

SHA512_End is a wrapper for SHA512_Final which converts the return value to a 65-character (including the terminating ’\0’) ASCII string which represents the 512 bits in hexadecimal.

SHA512_File calculates the digest of a file, and uses SHA512_End to return the result. If the file cannot be opened, a null pointer is returned. SHA512_FileChunk is similar to SHA512_File, but it only calculates the digest over a byte-range of the file specified, starting at offset and spanning length bytes. If the length parameter is specified as 0, or more than the length of the remaining part of the file, SHA512_FileChunk calculates the digest from offset to the end of file. SHA512_Data calculates the digest of a chunk of data in memory, and uses SHA512_End to return the result.

When using SHA512_End, SHA512_File, or SHA512_Data, the buf argument can be a null pointer, in which case the returned string is allocated with malloc(3) and subsequently must be explicitly deallocated using free(3) after use. If the buf argument is non-null it must point to at least 65 characters of buffer space.

SEE ALSO

md4(3), md5(3), ripemd(3), sha(3)

HISTORY

These functions appeared in
.Fx 9.0 .

AUTHORS

The core hash routines were implemented by Colin Percival based on the published FIPS 180-2 standard.

BUGS

No method is known to exist which finds two files having the same hash value, nor to find a file with a specific hash value. There is on the other hand no guarantee that such a method does not exist.
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