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RedHat 9 (Linux i386) - man page for sha1_init (redhat section 3)

sha(3)								      OpenSSL								    sha(3)

NAME
SHA1, SHA1_Init, SHA1_Update, SHA1_Final - Secure Hash Algorithm
SYNOPSIS
#include <openssl/sha.h> unsigned char *SHA1(const unsigned char *d, unsigned long n, unsigned char *md); void SHA1_Init(SHA_CTX *c); void SHA1_Update(SHA_CTX *c, const void *data, unsigned long len); void SHA1_Final(unsigned char *md, SHA_CTX *c);
DESCRIPTION
SHA-1 (Secure Hash Algorithm) is a cryptographic hash function with a 160 bit output. SHA1() computes the SHA-1 message digest of the n bytes at d and places it in md (which must have space for SHA_DIGEST_LENGTH == 20 bytes of output). If md is NULL, the digest is placed in a static array. The following functions may be used if the message is not completely stored in memory: SHA1_Init() initializes a SHA_CTX structure. SHA1_Update() can be called repeatedly with chunks of the message to be hashed (len bytes at data). SHA1_Final() places the message digest in md, which must have space for SHA_DIGEST_LENGTH == 20 bytes of output, and erases the SHA_CTX. Applications should use the higher level functions EVP_DigestInit(3) etc. instead of calling the hash functions directly. The predecessor of SHA-1, SHA, is also implemented, but it should be used only when backward compatibility is required.
RETURN VALUES
SHA1() returns a pointer to the hash value. SHA1_Init(), SHA1_Update() and SHA1_Final() do not return values.
CONFORMING TO
SHA: US Federal Information Processing Standard FIPS PUB 180 (Secure Hash Standard), SHA-1: US Federal Information Processing Standard FIPS PUB 180-1 (Secure Hash Standard), ANSI X9.30
SEE ALSO
ripemd(3), hmac(3), EVP_DigestInit(3)
HISTORY
SHA1(), SHA1_Init(), SHA1_Update() and SHA1_Final() are available in all versions of SSLeay and OpenSSL. 0.9.7a 2000-02-25 sha(3)