NAME

       CMAC_CTX, CMAC_CTX_new, CMAC_CTX_cleanup, CMAC_CTX_free, CMAC_CTX_get0_cipher_ctx, CMAC_CTX_copy,
       CMAC_Init, CMAC_Update, CMAC_Final, CMAC_resume - create cipher-based message authentication codes

SYNOPSIS

        #include <openssl/cmac.h>

       The following functions have been deprecated since OpenSSL 3.0, and can be disabled entirely by defining
       OPENSSL_API_COMPAT with a suitable version value, see openssl_user_macros(7).

        typedef struct CMAC_CTX_st CMAC_CTX;

        CMAC_CTX *CMAC_CTX_new(void);
        void CMAC_CTX_cleanup(CMAC_CTX *ctx);
        void CMAC_CTX_free(CMAC_CTX *ctx);
        EVP_CIPHER_CTX *CMAC_CTX_get0_cipher_ctx(CMAC_CTX *ctx);
        int CMAC_CTX_copy(CMAC_CTX *out, const CMAC_CTX *in);
        int CMAC_Init(CMAC_CTX *ctx, const void *key, size_t keylen,
                      const EVP_CIPHER *cipher, ENGINE *impl);
        int CMAC_Update(CMAC_CTX *ctx, const void *data, size_t dlen);
        int CMAC_Final(CMAC_CTX *ctx, unsigned char *out, size_t *poutlen);
        int CMAC_resume(CMAC_CTX *ctx);

DESCRIPTION

       The low-level MAC functions documented on this page are deprecated.  Applications should use the new
       EVP_MAC(3) interface.  Specifically, utilize the following functions for MAC operations:

       EVP_MAC_CTX_new(3) to create a new MAC context.
       EVP_MAC_CTX_free(3) to free the MAC context.
       EVP_MAC_init(3) to initialize the MAC context.
       EVP_MAC_update(3) to update the MAC with data.
       EVP_MAC_final(3) to finalize the MAC and retrieve the output.

       Alternatively, for a single-step MAC computation, use the EVP_Q_mac(3) function.

       The  CMAC_CTX  type  is  a  structure used for the provision of CMAC (Cipher-based Message Authentication
       Code) operations.

       CMAC_CTX_new() creates a new CMAC_CTX structure and returns a pointer to it.

       CMAC_CTX_cleanup() resets the CMAC_CTX  structure,  clearing  any  internal  data  but  not  freeing  the
       structure itself.

       CMAC_CTX_free()  frees  the CMAC_CTX structure and any associated resources.  If the argument is NULL, no
       action is taken.

       CMAC_CTX_get0_cipher_ctx() returns  a  pointer  to  the  internal  EVP_CIPHER_CTX  structure  within  the
       CMAC_CTX.

       CMAC_CTX_copy() copies the state from one CMAC_CTX structure to another.

       CMAC_Init()  initializes  the  CMAC_CTX  structure for a new CMAC calculation with the specified key, key
       length, and cipher type.  Optionally, an ENGINE can be provided.

       CMAC_Update() processes data to be included in  the  CMAC  calculation.   This  function  can  be  called
       multiple times to update the context with additional data.

       CMAC_Final()  finalizes  the CMAC calculation and retrieves the resulting MAC value. The output is stored
       in the provided buffer, and the length is stored in the variable pointed to by poutlen. To determine  the
       required  buffer  size,  call  with  out set to NULL, which stores only the length in poutlen. Allocate a
       buffer of this size and call CMAC_Final() again with the allocated buffer to retrieve the MAC.

       CMAC_resume() resumes a previously finalized CMAC calculation, allowing additional data to  be  processed
       and a new MAC to be generated.

RETURN VALUES

       CMAC_CTX_new() returns a pointer to a new CMAC_CTX structure or NULL if an error occurs.

       CMAC_CTX_get0_cipher_ctx()  returns  a  pointer  to  the internal EVP_CIPHER_CTX structure, or NULL if an
       error occurs.

       CMAC_CTX_copy(), CMAC_Init(), CMAC_Update(), CMAC_Final() and CMAC_resume() return 1 for success or 0  if
       an error occurs.

HISTORY

       All  functions  described  here were deprecated in OpenSSL 3.0. For replacements, see EVP_MAC_CTX_new(3),
       EVP_MAC_CTX_free(3), EVP_MAC_init(3), EVP_MAC_update(3), and EVP_MAC_final(3).

COPYRIGHT

       Copyright 2024 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the Apache License 2.0 (the "License").  You may not use this file  except  in  compliance
       with  the  License.   You  can  obtain  a  copy  in  the  file  LICENSE  in the source distribution or at
       <https://www.openssl.org/source/license.html>.

3.4.1                                              2025-04-03                                     CMAC_CTX(3SSL)