EVP_RAND-CTR-DRBG - The CTR DRBG EVP_RAND implementation
Support for the counter deterministic random bit generator through the
  EVP_RAND API.
"CTR-DRBG" is the name for this implementation; it can be used with
  the EVP_RAND_fetch() function.
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>
- "reseed_requests" (OSSL_DRBG_PARAM_RESEED_REQUESTS)
    <unsigned integer>
- "reseed_time_interval"
    (OSSL_DRBG_PARAM_RESEED_TIME_INTERVAL) <integer>
- "min_entropylen" (OSSL_DRBG_PARAM_MIN_ENTROPYLEN)
    <unsigned integer>
- "max_entropylen" (OSSL_DRBG_PARAM_MAX_ENTROPYLEN)
    <unsigned integer>
- "min_noncelen" (OSSL_DRBG_PARAM_MIN_NONCELEN)
    <unsigned integer>
- "max_noncelen" (OSSL_DRBG_PARAM_MAX_NONCELEN)
    <unsigned integer>
- "max_perslen" (OSSL_DRBG_PARAM_MAX_PERSLEN) <unsigned
    integer>
- "max_adinlen" (OSSL_DRBG_PARAM_MAX_ADINLEN) <unsigned
    integer>
- "reseed_counter" (OSSL_DRBG_PARAM_RESEED_COUNTER)
    <unsigned integer>
- "properties" (OSSL_DRBG_PARAM_PROPERTIES) <UTF8
    string>
- "cipher" (OSSL_DRBG_PARAM_CIPHER) <UTF8
    string>
- These parameters work as described in "PARAMETERS" in
      EVP_RAND(3).
- "use_derivation_function" (OSSL_DRBG_PARAM_USE_DF)
    <integer>
- This Boolean indicates if a derivation function should be used or not. A
      nonzero value (the default) uses the derivation function. A zero value
      does not.
A context for CTR DRBG can be obtained by calling:
 EVP_RAND *rand = EVP_RAND_fetch(NULL, "CTR-DRBG", NULL);
 EVP_RAND_CTX *rctx = EVP_RAND_CTX_new(rand);
 EVP_RAND *rand;
 EVP_RAND_CTX *rctx;
 unsigned char bytes[100];
 OSSL_PARAM params[2], *p = params;
 unsigned int strength = 128;
 rand = EVP_RAND_fetch(NULL, "CTR-DRBG", NULL);
 rctx = EVP_RAND_CTX_new(rand, NULL);
 EVP_RAND_free(rand);
 *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);
NIST SP 800-90A and SP 800-90B
EVP_RAND(3), "PARAMETERS" in EVP_RAND(3)
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
    <https://www.openssl.org/source/license.html>.