- NAME
- SYNOPSIS
- DESCRIPTION
- RETURN VALUES
- CONFORMING TO
- SEE ALSO
- HISTORY

# 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);

     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);

# 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 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()` return 1 for success, 0 otherwise.

# 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, hmac, EVP_DigestInit

# HISTORY

SHA1(), SHA1_Init(), `SHA1_Update()` and `SHA1_Final()` are available in all versions of SSLeay and OpenSSL.