EVP_MAC-KMAC¶

NAME¶

EVP_MAC-KMAC, EVP_MAC-KMAC128, EVP_MAC-KMAC256 - The KMAC EVP_MAC implementations

DESCRIPTION¶

Support for computing KMAC MACs through the EVP_MAC API.

Identity¶

These implementations are identified with one of these names and properties, to be used with EVP_MAC_fetch():

"KMAC-128", "provider=default" or "provider=fips"
"KMAC-256", "provider=default" or "provider=fips"

Supported parameters¶

The general description of these parameters can be found in "PARAMETERS" in EVP_MAC(3).

All these parameters (except for "block-size") can be set with EVP_MAC_CTX_set_params(). Furthermore, the "size" parameter can be retrieved with EVP_MAC_CTX_get_params(), or with EVP_MAC_CTX_get_mac_size(). The length of the "size" parameter should not exceed that of a size_t. Likewise, the "block-size" parameter can be retrieved with EVP_MAC_CTX_get_params(), or with EVP_MAC_CTX_get_block_size().

"key" (OSSL_MAC_PARAM_KEY) <octet string>
Sets the MAC key. Setting this parameter is identical to passing a key to EVP_MAC_init(3). The length of the key (in bytes) must be in the range 4...512.
"custom" (OSSL_MAC_PARAM_CUSTOM) <octet string>
Sets the customization string. It is an optional value with a length of at most 512 bytes, and is empty by default.
"size" (OSSL_MAC_PARAM_SIZE) <unsigned integer>
Sets the MAC size. By default, it is 32 for KMAC-128 and 64 for KMAC-256.
"block-size" (OSSL_MAC_PARAM_BLOCK_SIZE) <unsigned integer>
Gets the MAC block size. It is 168 for KMAC-128 and 136 for KMAC-256.
"xof" (OSSL_MAC_PARAM_XOF) <integer>
The "xof" parameter value is expected to be 1 or 0. Use 1 to enable XOF mode. The default value is 0.

The "custom" parameter must be set as part of or before the EVP_MAC_init() call. The "xof" and "size" parameters can be set at any time before EVP_MAC_final(). The "key" parameter is set as part of the EVP_MAC_init() call, but can be set before it instead.

EXAMPLES¶

#include <openssl/evp.h>
#include <openssl/params.h>

static int do_kmac(const unsigned char *in, size_t in_len,
                   const unsigned char *key, size_t key_len,
                   const unsigned char *custom, size_t custom_len,
                   int xof_enabled, unsigned char *out, int out_len)
{
    EVP_MAC_CTX *ctx = NULL;
    EVP_MAC *mac = NULL;
    OSSL_PARAM params[4], *p;
    int ret = 0;
    size_t l = 0;

    mac = EVP_MAC_fetch(NULL, "KMAC-128", NULL);
    if (mac == NULL)
        goto err;
    ctx = EVP_MAC_CTX_new(mac);
    /* The mac can be freed after it is used by EVP_MAC_CTX_new */
    EVP_MAC_free(mac);
    if (ctx == NULL)
        goto err;

    /*
     * Setup parameters required before calling EVP_MAC_init()
     * The parameters OSSL_MAC_PARAM_XOF and OSSL_MAC_PARAM_SIZE may also be
     * used at this point.
     */
    p = params;
    *p++ = OSSL_PARAM_construct_octet_string(OSSL_MAC_PARAM_KEY,
                                             (void *)key, key_len);
    if (custom != NULL && custom_len != 0)
      *p++ = OSSL_PARAM_construct_octet_string(OSSL_MAC_PARAM_CUSTOM,
                                               (void *)custom, custom_len);
    *p = OSSL_PARAM_construct_end();
    if (!EVP_MAC_CTX_set_params(ctx, params))
        goto err;

    if (!EVP_MAC_init(ctx))
        goto err;

    /*
     * Note: the following optional parameters can be set any time
     * before EVP_MAC_final().
     */
    p = params;
    *p++ = OSSL_PARAM_construct_int(OSSL_MAC_PARAM_XOF, &xof_enabled);
    *p++ = OSSL_PARAM_construct_int(OSSL_MAC_PARAM_SIZE, &out_len);
    *p = OSSL_PARAM_construct_end();
    if (!EVP_MAC_CTX_set_params(ctx, params))
        goto err;

    /* The update may be called multiple times here for streamed input */
    if (!EVP_MAC_update(ctx, in, in_len))
        goto err;
    if (!EVP_MAC_final(ctx, out, &l, out_len))
        goto err;
    ret = 1;
err:
    EVP_MAC_CTX_free(ctx);
    return ret;
}

COPYRIGHT¶

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.