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ocb_shared_lib.c
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/*
* ocb_shared_lib.c
*
* Created on: Mar 10, 2015
* Author: lauril
*/
/*------------------------------------------------------------------------
/ OCB Version 3 Reference Code (Unoptimized C) Last modified 12-JUN-2013
/-------------------------------------------------------------------------
/ Copyright (c) 2013 Ted Krovetz.
/
/ Permission to use, copy, modify, and/or distribute this software for any
/ purpose with or without fee is hereby granted, provided that the above
/ copyright notice and this permission notice appear in all copies.
/
/ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
/ WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
/ MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
/ ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
/ WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
/ ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
/ OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
/
/ Phillip Rogaway holds patents relevant to OCB. See the following for
/ his free patent grant: http://www.cs.ucdavis.edu/~rogaway/ocb/grant.htm
/
/ Comments are welcome: Ted Krovetz <[email protected]>
/------------------------------------------------------------------------- */
/* This implementation is not optimized and is suceptible to timing attack.
/ It mirrors the OCB RFC to aid in understanding and should not be used
/ for any other purpose. This implementation manipulates data as bytes
/ rather than machine words, which avoids endian issues entirely.
/ To compile: gcc -lcrypto ocb_ref.c */
#include <string.h>
#include <openssl/aes.h>
#include <stdint.h>
#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
#define KEYBYTES (128/8)
#define NONCEBYTES (96/8)
#define TAGBYTES (128/8)
typedef uint8_t block[16];
/* ------------------------------------------------------------------------- */
static void xor_block(block d, block s1, block s2) {
unsigned i;
for (i=0; i<16; i++)
d[i] = s1[i] ^ s2[i];
}
/* ------------------------------------------------------------------------- */
static void double_block(block d, block s) {
unsigned i;
uint8_t tmp = s[0];
for (i=0; i<15; i++)
d[i] = (s[i] << 1) | (s[i+1] >> 7);
d[15] = (s[15] << 1) ^ ((tmp >> 7) * 135);
}
/* ------------------------------------------------------------------------- */
static void calc_L_i(block l, block ldollar, unsigned i) {
double_block(l, ldollar); /* l is now L_0 */
for ( ; (i&1)==0 ; i>>=1)
double_block(l,l); /* double for each trailing 0 */
}
/* ------------------------------------------------------------------------- */
static void hash(block result, uint8_t *k,
uint8_t *a, unsigned abytes) {
AES_KEY aes_key;
block lstar, ldollar, offset, sum, tmp;
unsigned i;
/* Key-dependent variables */
/* L_* = ENCIPHER(K, zeros(128)) */
AES_set_encrypt_key(k, KEYBYTES*8, &aes_key);
memset(tmp, 0, 16);
AES_encrypt(tmp, lstar, &aes_key);
/* L_$ = double(L_*) */
double_block(ldollar, lstar);
/* Process any whole blocks */
/* Sum_0 = zeros(128) */
memset(sum, 0, 16);
/* Offset_0 = zeros(128) */
memset(offset, 0, 16);
for (i=1; i<=abytes/16; i++, a = a + 16) {
/* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
calc_L_i(tmp, ldollar, i);
xor_block(offset, offset, tmp);
/* Sum_i = Sum_{i-1} xor ENCIPHER(K, A_i xor Offset_i) */
xor_block(tmp, offset, a);
AES_encrypt(tmp, tmp, &aes_key);
xor_block(sum, sum, tmp);
}
/* Process any final partial block; compute final hash value */
abytes = abytes % 16; /* Bytes in final block */
if (abytes > 0) {
/* Offset_* = Offset_m xor L_* */
xor_block(offset, offset, lstar);
/* tmp = (A_* || 1 || zeros(127-bitlen(A_*))) xor Offset_* */
memset(tmp, 0, 16);
memcpy(tmp, a, abytes);
tmp[abytes] = 0x80;
xor_block(tmp, offset, tmp);
/* Sum = Sum_m xor ENCIPHER(K, tmp) */
AES_encrypt(tmp, tmp, &aes_key);
xor_block(sum, tmp, sum);
}
memcpy(result, sum, 16);
}
/* ------------------------------------------------------------------------- */
static int ocb_crypt(uint8_t *out, uint8_t *k, uint8_t *n,
uint8_t *a, unsigned abytes,
uint8_t *in, unsigned inbytes, int encrypting) {
AES_KEY aes_encrypt_key, aes_decrypt_key;
block lstar, ldollar, sum, offset, ktop, pad, nonce, tag, tmp;
uint8_t stretch[24];
unsigned bottom, byteshift, bitshift, i;
/* Setup AES and strip ciphertext of its tag */
if ( ! encrypting ) {
if (inbytes < TAGBYTES) return -1;
inbytes -= TAGBYTES;
AES_set_decrypt_key(k, KEYBYTES*8, &aes_decrypt_key);
}
AES_set_encrypt_key(k, KEYBYTES*8, &aes_encrypt_key);
/* L_* = ENCIPHER(K, zeros(128)) */
memset(tmp, 0, 16);
AES_encrypt(tmp, lstar, &aes_encrypt_key);
/* L_$ = double(L_*) */
double_block(ldollar, lstar);
/* Nonce-dependent and per-encryption variables */
/* Nonce = zeros(127-bitlen(N)) || 1 || N */
memset(nonce,0,16);
memcpy(&nonce[16-NONCEBYTES],n,NONCEBYTES);
nonce[0] = (uint8_t)(((TAGBYTES * 8) % 128) << 1);
nonce[16-NONCEBYTES-1] |= 0x01;
/* bottom = str2num(Nonce[123..128]) */
bottom = nonce[15] & 0x3F;
/* Ktop = ENCIPHER(K, Nonce[1..122] || zeros(6)) */
nonce[15] &= 0xC0;
AES_encrypt(nonce, ktop, &aes_encrypt_key);
/* Stretch = Ktop || (Ktop[1..64] xor Ktop[9..72]) */
memcpy(stretch, ktop, 16);
memcpy(tmp, &ktop[1], 8);
xor_block(tmp, tmp, ktop);
memcpy(&stretch[16],tmp,8);
/* Offset_0 = Stretch[1+bottom..128+bottom] */
byteshift = bottom/8;
bitshift = bottom%8;
if (bitshift != 0)
for (i=0; i<16; i++)
offset[i] = (stretch[i+byteshift] << bitshift) |
(stretch[i+byteshift+1] >> (8-bitshift));
else
for (i=0; i<16; i++)
offset[i] = stretch[i+byteshift];
/* Checksum_0 = zeros(128) */
memset(sum, 0, 16);
/* Process any whole blocks */
for (i=1; i<=inbytes/16; i++, in=in+16, out=out+16) {
/* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
calc_L_i(tmp, ldollar, i);
xor_block(offset, offset, tmp);
xor_block(tmp, offset, in);
if (encrypting) {
/* P_i = Offset_i xor DECIPHER(K, C_i xor Offset_i) */
AES_encrypt(tmp, tmp, &aes_encrypt_key);
xor_block(out, offset, tmp);
/* Checksum_i = Checksum_{i-1} xor P_i */
xor_block(sum, in, sum);
} else {
/* P_i = Offset_i xor DECIPHER(K, C_i xor Offset_i) */
AES_decrypt(tmp, tmp, &aes_decrypt_key);
xor_block(out, offset, tmp);
/* Checksum_i = Checksum_{i-1} xor P_i */
xor_block(sum, out, sum);
}
}
/* Process any final partial block and compute raw tag */
inbytes = inbytes % 16; /* Bytes in final block */
if (inbytes > 0) {
/* Offset_* = Offset_m xor L_* */
xor_block(offset, offset, lstar);
/* Pad = ENCIPHER(K, Offset_*) */
AES_encrypt(offset, pad, &aes_encrypt_key);
if (encrypting) {
/* Checksum_* = Checksum_m xor (P_* || 1 || zeros(127-bitlen(P_*))) */
memset(tmp, 0, 16);
memcpy(tmp, in, inbytes);
tmp[inbytes] = 0x80;
xor_block(sum, tmp, sum);
/* C_* = P_* xor Pad[1..bitlen(P_*)] */
xor_block(pad, tmp, pad);
memcpy(out, pad, inbytes);
out = out + inbytes;
} else {
/* P_* = C_* xor Pad[1..bitlen(C_*)] */
memcpy(tmp, pad, 16);
memcpy(tmp, in, inbytes);
xor_block(tmp, pad, tmp);
tmp[inbytes] = 0x80; /* tmp == P_* || 1 || zeros(127-bitlen(P_*)) */
memcpy(out, tmp, inbytes);
/* Checksum_* = Checksum_m xor (P_* || 1 || zeros(127-bitlen(P_*))) */
xor_block(sum, tmp, sum);
in = in + inbytes;
}
}
/* Tag = ENCIPHER(K, Checksum xor Offset xor L_$) xor HASH(K,A) */
xor_block(tmp, sum, offset);
xor_block(tmp, tmp, ldollar);
AES_encrypt(tmp, tag, &aes_encrypt_key);
hash(tmp, k, a, abytes);
xor_block(tag, tmp, tag);
if (encrypting) {
memcpy(out, tag, TAGBYTES);
return 0;
} else
return (memcmp(in,tag,TAGBYTES) ? -1 : 0); /* Check for validity */
}
/* ------------------------------------------------------------------------- */
#define OCB_ENCRYPT 1
#define OCB_DECRYPT 0
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#define KEYSIZE 16
#define DATASIZE 32
#define TAGSIZE 16
#define CIPHERSIZE DATASIZE+TAGSIZE
typedef struct CryptoData
{
uint32_t datalenght;
uint8_t key[KEYSIZE];
uint8_t nonce[KEYSIZE];
uint8_t assoc[DATASIZE];
uint8_t cipher[CIPHERSIZE];
uint8_t cleartext[DATASIZE];
} CryptoData;
int py_ocb_decrypt(CryptoData *cryptodata)
{
int i;
i = ocb_crypt(cryptodata->cleartext,
cryptodata->key,
cryptodata->nonce,
cryptodata->assoc,
cryptodata->datalenght,
cryptodata->cipher,
cryptodata->datalenght+16,
OCB_DECRYPT);
return i;
}
#define PLAIN_SIZE 32
//function to test OCB on ero vectors, just sanity check
static void testOCB(){
static uint32_t s_ticks;
static uint32_t e_ticks;
static uint32_t r_ticks;
uint32_t err = 0;
uint8_t text[PLAIN_SIZE] = { 0, };
uint8_t zeroes[16] = { 0, };
uint8_t nonce[16] = { 0, };
uint8_t keyArray[KEYBYTES] = { 0, };
uint8_t *c;
unsigned i;
/* Encrypt and output RFC vector */
c = malloc(PLAIN_SIZE + TAGBYTES);
ocb_crypt(c, keyArray, nonce, zeroes, PLAIN_SIZE, text, PLAIN_SIZE, OCB_ENCRYPT);
for (i = 0; i < (PLAIN_SIZE + TAGBYTES); i++)
printf("%d, ", (unsigned int) *(c + i));
printf("\n");
free(c);
}
int py_ocb_encrypt(CryptoData *cryptodata)
{
return ocb_crypt(cryptodata->cipher,
cryptodata->key,
cryptodata->nonce,
cryptodata->assoc,
cryptodata->datalenght,
cryptodata->cleartext,
cryptodata->datalenght,
OCB_ENCRYPT);
}