SHA256(3)

NAME

       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

SYNOPSIS

        #include <openssl/sha.h>

        int SHA1_Init(SHA_CTX *c);
        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);

DESCRIPTION

       Applications should use the higher level functions 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 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. Note:
       setting md to NULL is not thread safe.

       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.

       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 SHA256_CTX object instead of SHA_CTX. SHA384 and SHA512 use
       SHA512_CTX.  The buffer 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 md is
       NULL.

       The predecessor of SHA-1, SHA, is also implemented, but it should be
       used only when backward compatibility is required.

RETURN VALUES

       SHA1(), SHA224(), SHA256(), SHA384() and SHA512() return a pointer to
       the hash value.

       SHA1_Init(), SHA1_Update() and SHA1_Final() and equivalent SHA224,
       SHA256, SHA384 and SHA512 functions return 1 for success, 0 otherwise.

CONFORMING TO

       US Federal Information Processing Standard FIPS PUB 180-4 (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.

1.0.2t                            2019-09-10                            sha(3)