MirOS Manual: HMAC(3), HMAC_cleanup(3), HMAC_Final(3), HMAC_Init(3), HMAC_Update(3)


HMAC(3)                      OpenSSL                      HMAC(3)

NAME

     HMAC, HMAC_Init, HMAC_Update, HMAC_Final, HMAC_cleanup -
     HMAC message authentication code

SYNOPSIS

      #include <openssl/hmac.h>

      unsigned char *HMAC(const EVP_MD *evp_md, const void *key,
                    int key_len, const unsigned char *d, int n,
                    unsigned char *md, unsigned int *md_len);

      void HMAC_CTX_init(HMAC_CTX *ctx);

      void HMAC_Init(HMAC_CTX *ctx, const void *key, int key_len,
                    const EVP_MD *md);
      void HMAC_Init_ex(HMAC_CTX *ctx, const void *key, int key_len,
                        const EVP_MD *md, ENGINE *impl);
      void HMAC_Update(HMAC_CTX *ctx, const unsigned char *data, int len);
      void HMAC_Final(HMAC_CTX *ctx, unsigned char *md, unsigned int *len);

      void HMAC_CTX_cleanup(HMAC_CTX *ctx);
      void HMAC_cleanup(HMAC_CTX *ctx);

DESCRIPTION

     HMAC is a MAC (message authentication code), i.e. a keyed
     hash function used for message authentication, which is
     based on a hash function.

     HMAC() computes the message authentication code of the n
     bytes at d using the hash function evp_md and the key key
     which is key_len bytes long.

     It places the result in md (which must have space for the
     output of the hash function, which is no more than
     EVP_MAX_MD_SIZE bytes). If md is NULL, the digest is placed
     in a static array.  The size of the output is placed in
     md_len, unless it is NULL.

     evp_md can be EVP_sha1(), EVP_ripemd160() etc. key and
     evp_md may be NULL if a key and hash function have been set
     in a previous call to HMAC_Init() for that HMAC_CTX.

     HMAC_CTX_init() initialises a HMAC_CTX before first use. It
     must be called.

     HMAC_CTX_cleanup() erases the key and other data from the
     HMAC_CTX and releases any associated resources. It must be
     called when an HMAC_CTX is no longer required.

     HMAC_cleanup() is an alias for HMAC_CTX_cleanup() included
     for back compatibility with 0.9.6b, it is deprecated.

MirOS BSD #10-current      2006-09-20                           1

HMAC(3)                      OpenSSL                      HMAC(3)

     The following functions may be used if the message is not
     completely stored in memory:

     HMAC_Init() initializes a HMAC_CTX structure to use the hash
     function evp_md and the key key which is key_len bytes long.
     It is deprecated and only included for backward compatibil-
     ity with OpenSSL 0.9.6b.

     HMAC_Init_ex() initializes or reuses a HMAC_CTX structure to
     use the function evp_md and key key. Either can be NULL, in
     which case the existing one will be reused. HMAC_CTX_init()
     must have been called before the first use of an HMAC_CTX in
     this function. N.B. HMAC_Init() had this undocumented
     behaviour in previous versions of OpenSSL - failure to
     switch to HMAC_Init_ex() in programs that expect it will
     cause them to stop working.

     HMAC_Update() can be called repeatedly with chunks of the
     message to be authenticated (len bytes at data).

     HMAC_Final() places the message authentication code in md,
     which must have space for the hash function output.

RETURN VALUES

     HMAC() returns a pointer to the message authentication code.

     HMAC_CTX_init(), HMAC_Init_ex(), HMAC_Update(), HMAC_Final()
     and HMAC_CTX_cleanup() do not return values.

CONFORMING TO

     RFC 2104

SEE ALSO

     SHA1(3), EVP_DigestInit(3)

HISTORY

     HMAC(), HMAC_Init(), HMAC_Update(), HMAC_Final() and
     HMAC_cleanup() are available since SSLeay 0.9.0.

     HMAC_CTX_init(), HMAC_Init_ex() and HMAC_CTX_cleanup() are
     available since OpenSSL 0.9.7.

MirOS BSD #10-current      2006-09-20                           2

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