105 lines
2.8 KiB
C
105 lines
2.8 KiB
C
//
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// rng.c
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//
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// Created by Bassham, Lawrence E (Fed) on 8/29/17.
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// Copyright © 2017 Bassham, Lawrence E (Fed). All rights reserved.
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// Modified for liboqs by Douglas Stebila
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//
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#include <assert.h>
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#include <string.h>
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#include "aes.h"
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#include "randombytes.h"
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typedef struct {
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uint8_t Key[32];
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uint8_t V[16];
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int reseed_counter;
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} AES256_CTR_DRBG_struct;
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static AES256_CTR_DRBG_struct DRBG_ctx;
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static void AES256_CTR_DRBG_Update(const uint8_t *provided_data, uint8_t *Key, uint8_t *V);
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// Use whatever AES implementation you have. This uses AES from openSSL library
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// key - 256-bit AES key
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// ctr - a 128-bit plaintext value
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// buffer - a 128-bit ciphertext value
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static void AES256_ECB(uint8_t *key, uint8_t *ctr, uint8_t *buffer) {
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aes256ctx ctx;
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aes256_ecb_keyexp(&ctx, key);
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aes256_ecb(buffer, ctr, 1, &ctx);
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aes256_ctx_release(&ctx);
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}
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void nist_kat_init(uint8_t *entropy_input, const uint8_t *personalization_string, int security_strength);
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void nist_kat_init(uint8_t *entropy_input, const uint8_t *personalization_string, int security_strength) {
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uint8_t seed_material[48];
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assert(security_strength == 256);
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memcpy(seed_material, entropy_input, 48);
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if (personalization_string) {
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for (int i = 0; i < 48; i++) {
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seed_material[i] ^= personalization_string[i];
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}
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}
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memset(DRBG_ctx.Key, 0x00, 32);
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memset(DRBG_ctx.V, 0x00, 16);
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AES256_CTR_DRBG_Update(seed_material, DRBG_ctx.Key, DRBG_ctx.V);
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DRBG_ctx.reseed_counter = 1;
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}
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int randombytes(uint8_t *buf, size_t xlen) {
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uint8_t block[16];
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int i = 0;
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while (xlen > 0) {
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//increment V
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for (int j = 15; j >= 0; j--) {
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if (DRBG_ctx.V[j] == 0xff) {
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DRBG_ctx.V[j] = 0x00;
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} else {
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DRBG_ctx.V[j]++;
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break;
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}
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}
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AES256_ECB(DRBG_ctx.Key, DRBG_ctx.V, block);
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if (xlen > 15) {
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memcpy(buf + i, block, 16);
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i += 16;
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xlen -= 16;
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} else {
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memcpy(buf + i, block, xlen);
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xlen = 0;
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}
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}
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AES256_CTR_DRBG_Update(NULL, DRBG_ctx.Key, DRBG_ctx.V);
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DRBG_ctx.reseed_counter++;
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return 0;
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}
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static void AES256_CTR_DRBG_Update(const uint8_t *provided_data, uint8_t *Key, uint8_t *V) {
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uint8_t temp[48];
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for (int i = 0; i < 3; i++) {
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//increment V
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for (int j = 15; j >= 0; j--) {
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if (V[j] == 0xff) {
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V[j] = 0x00;
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} else {
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V[j]++;
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break;
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}
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}
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AES256_ECB(Key, V, temp + 16 * i);
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}
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if (provided_data != NULL) {
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for (int i = 0; i < 48; i++) {
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temp[i] ^= provided_data[i];
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}
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}
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memcpy(Key, temp, 32);
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memcpy(V, temp + 32, 16);
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}
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