OSSL_DIGEST_PARAM_BLOCK_SIZE
params[0] = OSSL_PARAM_construct_size_t(OSSL_DIGEST_PARAM_BLOCK_SIZE, &blksz);
p = OSSL_PARAM_locate(params, OSSL_DIGEST_PARAM_BLOCK_SIZE);
OSSL_PARAM_size_t(OSSL_DIGEST_PARAM_BLOCK_SIZE, NULL),
p = OSSL_PARAM_locate(params, OSSL_DIGEST_PARAM_BLOCK_SIZE);