Update the SHA* documentation

=head1 NAME

SHA1, SHA1_Init, SHA1_Update, SHA1_Final - Secure Hash Algorithm

SHA1, SHA1_Init, SHA1_Update, SHA1_Final, SHA224, SHA224_Init, SHA224_Update,

SHA224_Final, SHA256, SHA256_Init, SHA256_Update, SHA256_Final, SHA384,

SHA384_Init, SHA384_Update, SHA384_Final, SHA512, SHA512_Init, SHA512_Update,

SHA512_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_Update(SHA_CTX *c, const void *data, size_t len);

 int SHA1_Final(unsigned char *md, SHA_CTX *c);

 unsigned char *SHA1(const unsigned char *d, size_t n,

      unsigned char *md);

 int SHA224_Init(SHA256_CTX *c);

 int SHA224_Update(SHA256_CTX *c, const void *data, size_t len);

 int SHA224_Final(unsigned char *md, SHA256_CTX *c);

 unsigned char *SHA224(const unsigned char *d, size_t n,

      unsigned char *md);

 int SHA256_Init(SHA256_CTX *c);

 int SHA256_Update(SHA256_CTX *c, const void *data, size_t len);

 int SHA256_Final(unsigned char *md, SHA256_CTX *c);

 unsigned char *SHA256(const unsigned char *d, size_t n,

      unsigned char *md);

 int SHA384_Init(SHA512_CTX *c);

 int SHA384_Update(SHA512_CTX *c, const void *data, size_t len);

 int SHA384_Final(unsigned char *md, SHA512_CTX *c);

 unsigned char *SHA384(const unsigned char *d, size_t n,

      unsigned char *md);

 int SHA512_Init(SHA512_CTX *c);

 int SHA512_Update(SHA512_CTX *c, const void *data, size_t len);

 int SHA512_Final(unsigned char *md, SHA512_CTX *c);

 unsigned char *SHA512(const unsigned char *d, size_t n,

      unsigned char *md);

=head1 DESCRIPTION

Applications should use the higher level functions

L<EVP_DigestInit(3)|EVP_DigestInit(3)> etc. instead of calling the hash

functions directly.

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.

is placed in a static array. Note: setting B<md> to NULL is B<not thread safe>.

The following functions may be used if the message is not completely

stored in memory:

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 SHA224, SHA256, SHA384 and SHA512 families of functions operate in the

same way as for the SHA1 functions. Note that SHA224 and SHA256 use a

B<SHA256_CTX> object instead of B<SHA_CTX>. SHA384 and SHA512 use B<SHA512_CTX>.

The buffer B<md> must have space for the output from the SHA variant being used

(defined by SHA224_DIGEST_LENGTH, SHA256_DIGEST_LENGTH, SHA384_DIGEST_LENGTH and

SHA512_DIGEST_LENGTH). Also note that, as for the SHA1() function above, the

SHA224(), SHA256(), SHA384() and SHA512() functions are not thread safe if

B<md> is NULL.

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(), SHA224(), SHA256(), SHA384() and SHA512() return a pointer to the hash

value. 

SHA1_Init(), SHA1_Update() and SHA1_Final() return 1 for success, 0 otherwise.

SHA1_Init(), SHA1_Update() and SHA1_Final() and equivalent SHA224, SHA256,

SHA384 and SHA512 functions 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

US Federal Information Processing Standard FIPS PUB 180-4 (Secure Hash

Standard),

ANSI X9.30