1EVP_RAND-SEED-SRC(7ossl)            OpenSSL           EVP_RAND-SEED-SRC(7ossl)
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NAME

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

9       Support for deterministic random number generator seeding through the
10       EVP_RAND API.
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12       The seed sources used are specified at the time OpenSSL is configured
13       for building using the --with-rand-seed= option.  By default, operating
14       system randomness sources are used.
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16   Identity
17       "SEED-SRC" is the name for this implementation; it can be used with the
18       EVP_RAND_fetch() function.
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20   Supported parameters
21       The supported parameters are:
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23       "state" (OSSL_RAND_PARAM_STATE) <integer>
24       "strength" (OSSL_RAND_PARAM_STRENGTH) <unsigned integer>
25       "max_request" (OSSL_RAND_PARAM_MAX_REQUEST) <unsigned integer>
26           These parameters work as described in "PARAMETERS" in EVP_RAND(3).
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NOTES

29       A context for the seed source can be obtained by calling:
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31        EVP_RAND *rand = EVP_RAND_fetch(NULL, "SEED-SRC", NULL);
32        EVP_RAND_CTX *rctx = EVP_RAND_CTX_new(rand);
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EXAMPLES

35        EVP_RAND *rand;
36        EVP_RAND_CTX *seed, *rctx;
37        unsigned char bytes[100];
38        OSSL_PARAM params[2], *p = params;
39        unsigned int strength = 128;
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41        /* Create a seed source */
42        rand = EVP_RAND_fetch(NULL, "SEED-SRC", NULL);
43        seed = EVP_RAND_CTX_new(rand, NULL);
44        EVP_RAND_free(rand);
45
46        /* Feed this into a DRBG */
47        rand = EVP_RAND_fetch(NULL, "CTR-DRBG", NULL);
48        rctx = EVP_RAND_CTX_new(rand, seed);
49        EVP_RAND_free(rand);
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51        /* Configure the DRBG */
52        *p++ = OSSL_PARAM_construct_utf8_string(OSSL_DRBG_PARAM_CIPHER,
53                                                SN_aes_256_ctr, 0);
54        *p = OSSL_PARAM_construct_end();
55        EVP_RAND_instantiate(rctx, strength, 0, NULL, 0, params);
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57        EVP_RAND_generate(rctx, bytes, sizeof(bytes), strength, 0, NULL, 0);
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59        EVP_RAND_CTX_free(rctx);
60        EVP_RAND_CTX_free(seed);
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SEE ALSO

63       EVP_RAND(3), "PARAMETERS" in EVP_RAND(3)
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66       Copyright 2020-2021 The OpenSSL Project Authors. All Rights Reserved.
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68       Licensed under the Apache License 2.0 (the "License").  You may not use
69       this file except in compliance with the License.  You can obtain a copy
70       in the file LICENSE in the source distribution or at
71       <https://www.openssl.org/source/license.html>.
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753.0.5                             2022-07-05          EVP_RAND-SEED-SRC(7ossl)
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