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HMAC_Init (3)
  • >> HMAC_Init (3) ( Разные man: Библиотечные вызовы )
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    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.

    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 compatibility 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

    sha(3), evp(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.


     

    Index

    NAME
    SYNOPSIS
    DESCRIPTION
    RETURN VALUES
    CONFORMING TO
    SEE ALSO
    HISTORY


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