EVP_RAND-JITTER7ssl

Overview

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 openssl list -random-generators and openssl info -seeds.

Notes

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.

Examples

 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);