| =pod |
| |
| =head1 NAME |
| |
| EVP_RAND-SEED-SRC - The randomness seed source EVP_RAND implementation |
| |
| =head1 DESCRIPTION |
| |
| Support for deterministic random number generator seeding through the |
| B<EVP_RAND> API. |
| |
| The seed sources used are specified at the time OpenSSL is configured for |
| building using the B<--with-rand-seed=> option. By default, operating system |
| randomness sources are used. |
| |
| =head2 Identity |
| |
| "SEED-SRC" is the name for this implementation; it can be used with the |
| EVP_RAND_fetch() function. |
| |
| =head2 Supported parameters |
| |
| The supported parameters are: |
| |
| =over 4 |
| |
| =item "state" (B<OSSL_RAND_PARAM_STATE>) <integer> |
| |
| =item "strength" (B<OSSL_RAND_PARAM_STRENGTH>) <unsigned integer> |
| |
| =item "max_request" (B<OSSL_RAND_PARAM_MAX_REQUEST>) <unsigned integer> |
| |
| These parameters work as described in L<EVP_RAND(3)/PARAMETERS>. |
| |
| =back |
| |
| =head1 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); |
| |
| =head1 EXAMPLES |
| |
| EVP_RAND *rand; |
| EVP_RAND_CTX *seed, *rctx; |
| unsigned char bytes[100]; |
| OSSL_PARAM params[2], *p = params; |
| unsigned int strength = 128; |
| |
| /* Create a seed source */ |
| rand = EVP_RAND_fetch(NULL, "SEED-SRC", NULL); |
| seed = EVP_RAND_CTX_new(rand, 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); |
| |
| =head1 SEE ALSO |
| |
| L<EVP_RAND(3)>, |
| L<EVP_RAND(3)/PARAMETERS> |
| |
| =head1 COPYRIGHT |
| |
| Copyright 2020-2021 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 |
| L<https://www.openssl.org/source/license.html>. |
| |
| =cut |
