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athena/src/aes.c

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/* Rijndael Block Cipher - aes.c
Written by Mike Scott 21st April 1999
mike@compapp.dcu.ie
Permission for free direct or derivative use is granted subject
to compliance with any conditions that the originators of the
algorithm place on its exploitation.
*/
#include "aes.h"
#include <stdio.h>
//#include <stdlib.h>
#include <string.h>
/* rotates x one bit to the left */
#define ROTL(x) (((x)>>7)|((x)<<1))
/* Rotates 32-bit word left by 1, 2 or 3 byte */
#define ROTL8(x) (((x)<<8)|((x)>>24))
#define ROTL16(x) (((x)<<16)|((x)>>16))
#define ROTL24(x) (((x)<<24)|((x)>>8))
/* Fixed Data */
static atUint8 InCo[4] = {0xB, 0xD, 0x9, 0xE}; /* Inverse Coefficients */
static atUint8 fbsub[256];
static atUint8 rbsub[256];
static atUint8 ptab[256], ltab[256];
static atUint32 ftable[256];
static atUint32 rtable[256];
static atUint32 rco[30];
/* Parameter-dependent data */
int Nk, Nb, Nr;
atUint8 fi[24], ri[24];
atUint32 fkey[120];
atUint32 rkey[120];
static atUint32 pack(const atUint8* b)
{
/* pack bytes into a 32-bit Word */
return ((atUint32)b[3] << 24) | ((atUint32)b[2] << 16) | ((atUint32)b[1] << 8) | (atUint32)b[0];
}
static void unpack(atUint32 a, atUint8* b)
{
/* unpack bytes from a word */
b[0] = (atUint8)a;
b[1] = (atUint8)(a >> 8);
b[2] = (atUint8)(a >> 16);
b[3] = (atUint8)(a >> 24);
}
static atUint8 xtime(atUint8 a)
{
atUint8 b;
if (a & 0x80) b = 0x1B;
else b = 0;
a <<= 1;
a ^= b;
return a;
}
static atUint8 bmul(atUint8 x, atUint8 y)
{
/* x.y= AntiLog(Log(x) + Log(y)) */
if (x && y) return ptab[(ltab[x] + ltab[y]) % 255];
else return 0;
}
static atUint32 SubByte(atUint32 a)
{
atUint8 b[4];
unpack(a, b);
b[0] = fbsub[b[0]];
b[1] = fbsub[b[1]];
b[2] = fbsub[b[2]];
b[3] = fbsub[b[3]];
return pack(b);
}
static atUint8 product(atUint32 x, atUint32 y)
{
/* dot product of two 4-byte arrays */
atUint8 xb[4], yb[4];
unpack(x, xb);
unpack(y, yb);
return bmul(xb[0], yb[0])^bmul(xb[1], yb[1])^bmul(xb[2], yb[2])^bmul(xb[3], yb[3]);
}
static atUint32 InvMixCol(atUint32 x)
{
/* matrix Multiplication */
atUint32 y, m;
atUint8 b[4];
m = pack(InCo);
b[3] = product(m, x);
m = ROTL24(m);
b[2] = product(m, x);
m = ROTL24(m);
b[1] = product(m, x);
m = ROTL24(m);
b[0] = product(m, x);
y = pack(b);
return y;
}
atUint8 ByteSub(atUint8 x)
{
atUint8 y = ptab[255 - ltab[x]]; /* multiplicative inverse */
x = y;
x = ROTL(x);
y ^= x;
x = ROTL(x);
y ^= x;
x = ROTL(x);
y ^= x;
x = ROTL(x);
y ^= x;
y ^= 0x63;
return y;
}
void gentables(void)
{
/* generate tables */
int i;
atUint8 y, b[4];
/* use 3 as primitive root to generate power and log tables */
ltab[0] = 0;
ptab[0] = 1;
ltab[1] = 0;
ptab[1] = 3;
ltab[3] = 1;
for (i = 2; i < 256; i++)
{
ptab[i] = ptab[i - 1] ^ xtime(ptab[i - 1]);
ltab[ptab[i]] = i;
}
/* affine transformation:- each bit is xored with itself shifted one bit */
fbsub[0] = 0x63;
rbsub[0x63] = 0;
for (i = 1; i < 256; i++)
{
y = ByteSub((atUint8)i);
fbsub[i] = y;
rbsub[y] = i;
}
for (i = 0, y = 1; i < 30; i++)
{
rco[i] = y;
y = xtime(y);
}
/* calculate forward and reverse tables */
for (i = 0; i < 256; i++)
{
y = fbsub[i];
b[3] = y ^ xtime(y);
b[2] = y;
b[1] = y;
b[0] = xtime(y);
ftable[i] = pack(b);
y = rbsub[i];
b[3] = bmul(InCo[0], y);
b[2] = bmul(InCo[1], y);
b[1] = bmul(InCo[2], y);
b[0] = bmul(InCo[3], y);
rtable[i] = pack(b);
}
}
void gkey(int nb, int nk, const atUint8* key)
{
/* blocksize=32*nb bits. Key=32*nk bits */
/* currently nb,bk = 4, 6 or 8 */
/* key comes as 4*Nk bytes */
/* Key Scheduler. Create expanded encryption key */
int i, j, k, m, N;
int C1, C2, C3;
atUint32 CipherKey[8];
Nb = nb;
Nk = nk;
/* Nr is number of rounds */
if (Nb >= Nk) Nr = 6 + Nb;
else Nr = 6 + Nk;
C1 = 1;
if (Nb < 8) { C2 = 2; C3 = 3; }
else { C2 = 3; C3 = 4; }
/* pre-calculate forward and reverse increments */
for (m = j = 0; j < nb; j++, m += 3)
{
fi[m] = (j + C1) % nb;
fi[m + 1] = (j + C2) % nb;
fi[m + 2] = (j + C3) % nb;
ri[m] = (nb + j - C1) % nb;
ri[m + 1] = (nb + j - C2) % nb;
ri[m + 2] = (nb + j - C3) % nb;
}
N = Nb * (Nr + 1);
for (i = j = 0; i < Nk; i++, j += 4)
{
CipherKey[i] = pack(key + j);
}
for (i = 0; i < Nk; i++) fkey[i] = CipherKey[i];
for (j = Nk, k = 0; j < N; j += Nk, k++)
{
fkey[j] = fkey[j - Nk] ^ SubByte(ROTL24(fkey[j - 1]))^rco[k];
if (Nk <= 6)
{
for (i = 1; i < Nk && (i + j) < N; i++)
fkey[i + j] = fkey[i + j - Nk] ^ fkey[i + j - 1];
}
else
{
for (i = 1; i < 4 && (i + j) < N; i++)
fkey[i + j] = fkey[i + j - Nk] ^ fkey[i + j - 1];
if ((j + 4) < N) fkey[j + 4] = fkey[j + 4 - Nk] ^ SubByte(fkey[j + 3]);
for (i = 5; i < Nk && (i + j) < N; i++)
fkey[i + j] = fkey[i + j - Nk] ^ fkey[i + j - 1];
}
}
/* now for the expanded decrypt key in reverse order */
for (j = 0; j < Nb; j++) rkey[j + N - Nb] = fkey[j];
for (i = Nb; i < N - Nb; i += Nb)
{
k = N - Nb - i;
for (j = 0; j < Nb; j++) rkey[k + j] = InvMixCol(fkey[i + j]);
}
for (j = N - Nb; j < N; j++) rkey[j - N + Nb] = fkey[j];
}
/* There is an obvious time/space trade-off possible here. *
* Instead of just one ftable[], I could have 4, the other *
* 3 pre-rotated to save the ROTL8, ROTL16 and ROTL24 overhead */
void encrypt(atUint8* buff)
{
int i, j, k, m;
atUint32 a[8], b[8], *x, *y, *t;
for (i = j = 0; i < Nb; i++, j += 4)
{
a[i] = pack(buff + j);
a[i] ^= fkey[i];
}
k = Nb;
x = a;
y = b;
/* State alternates between a and b */
for (i = 1; i < Nr; i++)
{
/* Nr is number of rounds. May be odd. */
/* if Nb is fixed - unroll this next
loop and hard-code in the values of fi[] */
for (m = j = 0; j < Nb; j++, m += 3)
{
/* deal with each 32-bit element of the State */
/* This is the time-critical bit */
y[j] = fkey[k++] ^ ftable[(atUint8)x[j]] ^
ROTL8(ftable[(atUint8)(x[fi[m]] >> 8)])^
ROTL16(ftable[(atUint8)(x[fi[m + 1]] >> 16)])^
ROTL24(ftable[(atUint8)(x[fi[m + 2]] >> 24)]);
}
t = x;
x = y;
y = t; /* swap pointers */
}
/* Last Round - unroll if possible */
for (m = j = 0; j < Nb; j++, m += 3)
{
y[j] = fkey[k++] ^ (atUint32)fbsub[(atUint8)x[j]] ^
ROTL8((atUint32)fbsub[(atUint8)(x[fi[m]] >> 8)])^
ROTL16((atUint32)fbsub[(atUint8)(x[fi[m + 1]] >> 16)])^
ROTL24((atUint32)fbsub[(atUint8)(x[fi[m + 2]] >> 24)]);
}
for (i = j = 0; i < Nb; i++, j += 4)
{
unpack(y[i], (atUint8*)&buff[j]);
x[i] = y[i] = 0; /* clean up stack */
}
return;
}
void decrypt(atUint8* buff)
{
int i, j, k, m;
atUint32 a[8], b[8], *x, *y, *t;
for (i = j = 0; i < Nb; i++, j += 4)
{
a[i] = pack(buff + j);
a[i] ^= rkey[i];
}
k = Nb;
x = a;
y = b;
/* State alternates between a and b */
for (i = 1; i < Nr; i++)
{
/* Nr is number of rounds. May be odd. */
/* if Nb is fixed - unroll this next
loop and hard-code in the values of ri[] */
for (m = j = 0; j < Nb; j++, m += 3)
{
/* This is the time-critical bit */
y[j] = rkey[k++] ^ rtable[(atUint8)x[j]] ^
ROTL8(rtable[(atUint8)(x[ri[m]] >> 8)])^
ROTL16(rtable[(atUint8)(x[ri[m + 1]] >> 16)])^
ROTL24(rtable[(atUint8)(x[ri[m + 2]] >> 24)]);
}
t = x;
x = y;
y = t; /* swap pointers */
}
/* Last Round - unroll if possible */
for (m = j = 0; j < Nb; j++, m += 3)
{
y[j] = rkey[k++] ^ (atUint32)rbsub[(atUint8)x[j]] ^
ROTL8((atUint32)rbsub[(atUint8)(x[ri[m]] >> 8)])^
ROTL16((atUint32)rbsub[(atUint8)(x[ri[m + 1]] >> 16)])^
ROTL24((atUint32)rbsub[(atUint8)(x[ri[m + 2]] >> 24)]);
}
for (i = j = 0; i < Nb; i++, j += 4)
{
unpack(y[i], (atUint8*)&buff[j]);
x[i] = y[i] = 0; /* clean up stack */
}
return;
}
void aes_set_key(const atUint8* key)
{
gentables();
gkey(4, 4, key);
}
// CBC mode decryption
void aes_decrypt(atUint8* iv, const atUint8* inbuf, atUint8* outbuf, atUint64 len)
{
atUint8 block[16];
atUint8* ctext_ptr;
unsigned int blockno = 0, i;
//fprintf( stderr,"aes_decrypt(%p, %p, %p, %lld)\n", iv, inbuf, outbuf, len );
//printf("aes_decrypt(%p, %p, %p, %lld)\n", iv, inbuf, outbuf, len);
for (blockno = 0; blockno <= (len / sizeof(block)); blockno++)
{
unsigned int fraction;
if (blockno == (len / sizeof(block))) // last block
{
fraction = len % sizeof(block);
if (fraction == 0) break;
memset(block, 0, sizeof(block));
}
else fraction = 16;
// debug_printf("block %d: fraction = %d\n", blockno, fraction);
memcpy(block, inbuf + blockno * sizeof(block), fraction);
decrypt(block);
if (blockno == 0) ctext_ptr = iv;
else ctext_ptr = (atUint8*)(inbuf + (blockno - 1) * sizeof(block));
for (i = 0; i < fraction; i++)
outbuf[blockno * sizeof(block) + i] =
ctext_ptr[i] ^ block[i];
// debug_printf("Block %d output: ", blockno);
// hexdump(outbuf + blockno*sizeof(block), 16);
}
}
// CBC mode encryption
void aes_encrypt(atUint8* iv, const atUint8* inbuf, atUint8* outbuf, atUint64 len)
{
atUint8 block[16];
unsigned int blockno = 0, i;
//printf("aes_decrypt(%p, %p, %p, %lld)\n", iv, inbuf, outbuf, len);
//fprintf( stderr,"aes_encrypt(%p, %p, %p, %lld)\n", iv, inbuf, outbuf, len);
for (blockno = 0; blockno <= (len / sizeof(block)); blockno++)
{
unsigned int fraction;
if (blockno == (len / sizeof(block))) // last block
{
fraction = len % sizeof(block);
if (fraction == 0) break;
memset(block, 0, sizeof(block));
}
else fraction = 16;
// debug_printf("block %d: fraction = %d\n", blockno, fraction);
memcpy(block, inbuf + blockno * sizeof(block), fraction);
for (i = 0; i < fraction; i++)
block[i] = inbuf[blockno * sizeof(block) + i] ^ iv[i];
encrypt(block);
memcpy(iv, block, sizeof(block));
memcpy(outbuf + blockno * sizeof(block), block, sizeof(block));
// debug_printf("Block %d output: ", blockno);
// hexdump(outbuf + blockno*sizeof(block), 16);
}
}
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