EVP_RAND-JITTER¶

NAME¶

EVP_RAND-JITTER - The randomness seed source EVP_RAND implementation

DESCRIPTION¶

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.

Identity¶

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

Supported parameters¶

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).

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);

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);

COPYRIGHT¶

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.