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=pod
=head1 NAME
SHA1, SHA1_Init, SHA1_Update, SHA1_Final - Secure Hash Algorithm
=head1 SYNOPSIS
#include <openssl/sha.h>
unsigned char *SHA1(const unsigned char *d, unsigned long n,
unsigned char *md);
int SHA1_Init(SHA_CTX *c);
int SHA1_Update(SHA_CTX *c, const void *data,
unsigned long len);
int SHA1_Final(unsigned char *md, SHA_CTX *c);
=head1 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 B<n>
bytes at B<d> and places it in B<md> (which must have space for
SHA_DIGEST_LENGTH == 20 bytes of output). If B<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 B<SHA_CTX> structure.
SHA1_Update() can be called repeatedly with chunks of the message to
be hashed (B<len> bytes at B<data>).
SHA1_Final() places the message digest in B<md>, which must have space
for SHA_DIGEST_LENGTH == 20 bytes of output, and erases the B<SHA_CTX>.
Applications should use the higher level functions
L<EVP_DigestInit(3)|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.
=head1 RETURN VALUES
SHA1() returns a pointer to the hash value.
SHA1_Init(), SHA1_Update() and SHA1_Final() return 1 for success, 0 otherwise.
=head1 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
=head1 SEE ALSO
L<ripemd(3)|ripemd(3)>, L<hmac(3)|hmac(3)>, L<EVP_DigestInit(3)|EVP_DigestInit(3)>
=head1 HISTORY
SHA1(), SHA1_Init(), SHA1_Update() and SHA1_Final() are available in all
versions of SSLeay and OpenSSL.
=cut
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