EVP_RAND-JITTER - The randomness seed source EVP_RAND implementation

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       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>.

3.5.0                                              2025-06-04                              EVP_RAND-JITTER(7SSL)

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

       This software seed source produces randomness based on tiny CPU "jitter" fluctuations.

       It is available when OpenSSL is compiled with enable-jitter option. When available it is listed in
       openssllist-random-generators and opensslinfo-seeds.

   Identity
       "JITTER" is the name for this implementation; it can be used with the EVP_RAND_fetch() function.

   Supportedparameters
       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).

        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, "JITTER", 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);

       EVP_RAND-JITTER - The randomness seed source EVP_RAND implementation

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

        EVP_RAND *rand = EVP_RAND_fetch(NULL, "JITTER", NULL);
        EVP_RAND_CTX *rctx = EVP_RAND_CTX_new(rand, NULL);

       The enable-jitter option was added in OpenSSL 3.4.

       By  specifying the enable-fips-jitter configuration option, the FIPS provider will use an internal jitter
       source for its entropy.  Enabling this option will cause the FIPS provider to operate in a  non-compliant
       mode  unless  an  entropy assessment ESV <https://csrc.nist.gov/Projects/cryptographic-module-validation-
       program/entropy-validations>          and          validation          through          the          CMVP
       <https://csrc.nist.gov/projects/cryptographic-module-validation-program>   are   additionally  conducted.
       This option was added in OpenSSL 3.5.

EVP_RAND(3), "PARAMETERS" in EVP_RAND(3)