NAME

EVP_RAND-SEED-SRC - The randomness seed source EVP_RAND implementation

DESCRIPTION

Support for deterministic random number generator seeding through the EVP_RAND API.

The seed sources used are specified at the time OpenSSL is configured for building using the --with-rand-seed= option. By default, operating system randomness sources are used.

Identity

"SEED-SRC" is the name for this implementation; it can be used with the EVP_RAND_fetch() function.

Supported parameters

The supported parameters are:

"state" (OSSL_RAND_PARAM_STATE) <integer>
"strength" (OSSL_RAND_PARAM_STRENGTH) <unsigned integer>
"max_request" (OSSL_RAND_PARAM_MAX_REQUEST) <unsigned integer>: These parameters work as described in "PARAMETERS" in EVP_RAND(3).

NOTES

A context for the seed source can be obtained by calling:

 EVP_RAND *rand = EVP_RAND_fetch(NULL, "SEED-SRC", NULL);
 EVP_RAND_CTX *rctx = EVP_RAND_CTX_new(rand, NULL);

EXAMPLES

 EVP_RAND *rand;
 EVP_RAND_CTX *seed, *rctx;
 unsigned char bytes[100];
 OSSL_PARAM params[2], *p = params;
 unsigned int strength = 128;

 /* Create and instantiate a seed source */
 rand = EVP_RAND_fetch(NULL, "SEED-SRC", NULL);
 seed = EVP_RAND_CTX_new(rand, NULL);
 EVP_RAND_instantiate(seed, strength, 0, NULL, 0, NULL);
 EVP_RAND_free(rand);

 /* Feed this into a DRBG */
 rand = EVP_RAND_fetch(NULL, "CTR-DRBG", NULL);
 rctx = EVP_RAND_CTX_new(rand, seed);
 EVP_RAND_free(rand);

 /* Configure the DRBG */
 *p++ = OSSL_PARAM_construct_utf8_string(OSSL_DRBG_PARAM_CIPHER,
                                         SN_aes_256_ctr, 0);
 *p = OSSL_PARAM_construct_end();
 EVP_RAND_instantiate(rctx, strength, 0, NULL, 0, params);

 EVP_RAND_generate(rctx, bytes, sizeof(bytes), strength, 0, NULL, 0);

 EVP_RAND_CTX_free(rctx);
 EVP_RAND_CTX_free(seed);

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.