1=pod
2
3=head1 NAME
4
5SHA1, SHA1_Init, SHA1_Update, SHA1_Final - Secure Hash Algorithm
6
7=head1 SYNOPSIS
8
9 #include <openssl/sha.h>
10
11 unsigned char *SHA1(const unsigned char *d, unsigned long n,
12                  unsigned char *md);
13
14 int SHA1_Init(SHA_CTX *c);
15 int SHA1_Update(SHA_CTX *c, const void *data,
16                  unsigned long len);
17 int SHA1_Final(unsigned char *md, SHA_CTX *c);
18
19=head1 DESCRIPTION
20
21SHA-1 (Secure Hash Algorithm) is a cryptographic hash function with a
22160 bit output.
23
24SHA1() computes the SHA-1 message digest of the B<n>
25bytes at B<d> and places it in B<md> (which must have space for
26SHA_DIGEST_LENGTH == 20 bytes of output). If B<md> is NULL, the digest
27is placed in a static array.
28
29The following functions may be used if the message is not completely
30stored in memory:
31
32SHA1_Init() initializes a B<SHA_CTX> structure.
33
34SHA1_Update() can be called repeatedly with chunks of the message to
35be hashed (B<len> bytes at B<data>).
36
37SHA1_Final() places the message digest in B<md>, which must have space
38for SHA_DIGEST_LENGTH == 20 bytes of output, and erases the B<SHA_CTX>.
39
40Applications should use the higher level functions
41L<EVP_DigestInit(3)|EVP_DigestInit(3)>
42etc. instead of calling the hash functions directly.
43
44The predecessor of SHA-1, SHA, is also implemented, but it should be
45used only when backward compatibility is required.
46
47=head1 RETURN VALUES
48
49SHA1() returns a pointer to the hash value.
50
51SHA1_Init(), SHA1_Update() and SHA1_Final() return 1 for success, 0 otherwise.
52
53=head1 CONFORMING TO
54
55SHA: US Federal Information Processing Standard FIPS PUB 180 (Secure Hash
56Standard),
57SHA-1: US Federal Information Processing Standard FIPS PUB 180-1 (Secure Hash
58Standard),
59ANSI X9.30
60
61=head1 SEE ALSO
62
63L<ripemd(3)|ripemd(3)>, L<hmac(3)|hmac(3)>, L<EVP_DigestInit(3)|EVP_DigestInit(3)>
64
65=head1 HISTORY
66
67SHA1(), SHA1_Init(), SHA1_Update() and SHA1_Final() are available in all
68versions of SSLeay and OpenSSL.
69
70=cut
71