1=pod 2 3=head1 NAME 4 5EVP_RAND-SEED-SRC - The randomness seed source EVP_RAND implementation 6 7=head1 DESCRIPTION 8 9Support for deterministic random number generator seeding through the 10B<EVP_RAND> API. 11 12The seed sources used are specified at the time OpenSSL is configured for 13building using the B<--with-rand-seed=> option. By default, operating system 14randomness sources are used. 15 16=head2 Identity 17 18"SEED-SRC" is the name for this implementation; it can be used with the 19EVP_RAND_fetch() function. 20 21=head2 Supported parameters 22 23The supported parameters are: 24 25=over 4 26 27=item "state" (B<OSSL_RAND_PARAM_STATE>) <integer> 28 29=item "strength" (B<OSSL_RAND_PARAM_STRENGTH>) <unsigned integer> 30 31=item "max_request" (B<OSSL_RAND_PARAM_MAX_REQUEST>) <unsigned integer> 32 33These parameters work as described in L<EVP_RAND(3)/PARAMETERS>. 34 35=back 36 37=head1 NOTES 38 39A context for the seed source can be obtained by calling: 40 41 EVP_RAND *rand = EVP_RAND_fetch(NULL, "SEED-SRC", NULL); 42 EVP_RAND_CTX *rctx = EVP_RAND_CTX_new(rand); 43 44=head1 EXAMPLES 45 46 EVP_RAND *rand; 47 EVP_RAND_CTX *seed, *rctx; 48 unsigned char bytes[100]; 49 OSSL_PARAM params[2], *p = params; 50 unsigned int strength = 128; 51 52 /* Create a seed source */ 53 rand = EVP_RAND_fetch(NULL, "SEED-SRC", NULL); 54 seed = EVP_RAND_CTX_new(rand, NULL); 55 EVP_RAND_free(rand); 56 57 /* Feed this into a DRBG */ 58 rand = EVP_RAND_fetch(NULL, "CTR-DRBG", NULL); 59 rctx = EVP_RAND_CTX_new(rand, seed); 60 EVP_RAND_free(rand); 61 62 /* Configure the DRBG */ 63 *p++ = OSSL_PARAM_construct_utf8_string(OSSL_DRBG_PARAM_CIPHER, 64 SN_aes_256_ctr, 0); 65 *p = OSSL_PARAM_construct_end(); 66 EVP_RAND_instantiate(rctx, strength, 0, NULL, 0, params); 67 68 EVP_RAND_generate(rctx, bytes, sizeof(bytes), strength, 0, NULL, 0); 69 70 EVP_RAND_CTX_free(rctx); 71 EVP_RAND_CTX_free(seed); 72 73=head1 SEE ALSO 74 75L<EVP_RAND(3)>, 76L<EVP_RAND(3)/PARAMETERS> 77 78=head1 COPYRIGHT 79 80Copyright 2020-2021 The OpenSSL Project Authors. All Rights Reserved. 81 82Licensed under the Apache License 2.0 (the "License"). You may not use 83this file except in compliance with the License. You can obtain a copy 84in the file LICENSE in the source distribution or at 85L<https://www.openssl.org/source/license.html>. 86 87=cut 88