/* This is an independent implementation of the encryption algorithm: */
/* */
/* RC6 by Ron Rivest and RSA Labs */
/* */
/* which is a candidate algorithm in the Advanced Encryption Standard */
/* programme of the US National Institute of Standards and Technology. */
/* */
/* Copyright in this implementation is held by Dr B R Gladman but I */
/* hereby give permission for its free direct or derivative use subject */
/* to acknowledgment of its origin and compliance with any conditions */
/* that the originators of the algorithm place on its exploitation. */
/* */
/* Dr Brian Gladman ([email protected]) 14th January 1999 */
/* Timing data for RC6 (rc6.c)
128 bit key:
Key Setup: 1632 cycles
Encrypt: 270 cycles = 94.8 mbits/sec
Decrypt: 226 cycles = 113.3 mbits/sec
Mean: 248 cycles = 103.2 mbits/sec
192 bit key:
Key Setup: 1885 cycles
Encrypt: 267 cycles = 95.9 mbits/sec
Decrypt: 235 cycles = 108.9 mbits/sec
Mean: 251 cycles = 102.0 mbits/sec
256 bit key:
Key Setup: 1877 cycles
Encrypt: 270 cycles = 94.8 mbits/sec
Decrypt: 227 cycles = 112.8 mbits/sec
Mean: 249 cycles = 103.0 mbits/sec
*/
#include "../std_defs.h"
static char *alg_name[] = { "rc6", "rc6.c", "rc6" };
char **cipher_name()
{
return alg_name;
}
#define f_rnd(i,a,b,c,d) \
u = rotl(d * (d + d + 1), 5); \
t = rotl(b * (b + b + 1), 5); \
a = rotl(a ^ t, u) + l_key[i]; \
c = rotl(c ^ u, t) + l_key[i + 1]
#define i_rnd(i,a,b,c,d) \
u = rotl(d * (d + d + 1), 5); \
t = rotl(b * (b + b + 1), 5); \
c = rotr(c - l_key[i + 1], t) ^ u; \
a = rotr(a - l_key[i], u) ^ t
u4byte l_key[44]; /* storage for the key schedule */
/* initialise the key schedule from the user supplied key */
u4byte *set_key(const u4byte in_key[], const u4byte key_len)
{ u4byte i, j, k, a, b, l[8], t;
l_key[0] = 0xb7e15163;
for(k = 1; k < 44; ++k)
l_key[k] = l_key[k - 1] + 0x9e3779b9;
for(k = 0; k < key_len / 32; ++k)
l[k] = in_key[k];
t = (key_len / 32) - 1; // t = (key_len / 32);
a = b = i = j = 0;
for(k = 0; k < 132; ++k)
{ a = rotl(l_key[i] + a + b, 3); b += a;
b = rotl(l[j] + b, b);
l_key[i] = a; l[j] = b;
i = (i == 43 ? 0 : i + 1); // i = (i + 1) % 44;
j = (j == t ? 0 : j + 1); // j = (j + 1) % t;
}
return l_key;
};
/* encrypt a block of text */
void encrypt(const u4byte in_blk[4], u4byte out_blk[4])
{ u4byte a,b,c,d,t,u;
a = in_blk[0]; b = in_blk[1] + l_key[0];
c = in_blk[2]; d = in_blk[3] + l_key[1];
f_rnd( 2,a,b,c,d); f_rnd( 4,b,c,d,a);
f_rnd( 6,c,d,a,b); f_rnd( 8,d,a,b,c);
f_rnd(10,a,b,c,d); f_rnd(12,b,c,d,a);
f_rnd(14,c,d,a,b); f_rnd(16,d,a,b,c);
f_rnd(18,a,b,c,d); f_rnd(20,b,c,d,a);
f_rnd(22,c,d,a,b); f_rnd(24,d,a,b,c);
f_rnd(26,a,b,c,d); f_rnd(28,b,c,d,a);
f_rnd(30,c,d,a,b); f_rnd(32,d,a,b,c);
f_rnd(34,a,b,c,d); f_rnd(36,b,c,d,a);
f_rnd(38,c,d,a,b); f_rnd(40,d,a,b,c);
out_blk[0] = a + l_key[42]; out_blk[1] = b;
out_blk[2] = c + l_key[43]; out_blk[3] = d;
};
/* decrypt a block of text */
void decrypt(const u4byte in_blk[4], u4byte out_blk[4])
{ u4byte a,b,c,d,t,u;
d = in_blk[3]; c = in_blk[2] - l_key[43];
b = in_blk[1]; a = in_blk[0] - l_key[42];
i_rnd(40,d,a,b,c); i_rnd(38,c,d,a,b);
i_rnd(36,b,c,d,a); i_rnd(34,a,b,c,d);
i_rnd(32,d,a,b,c); i_rnd(30,c,d,a,b);
i_rnd(28,b,c,d,a); i_rnd(26,a,b,c,d);
i_rnd(24,d,a,b,c); i_rnd(22,c,d,a,b);
i_rnd(20,b,c,d,a); i_rnd(18,a,b,c,d);
i_rnd(16,d,a,b,c); i_rnd(14,c,d,a,b);
i_rnd(12,b,c,d,a); i_rnd(10,a,b,c,d);
i_rnd( 8,d,a,b,c); i_rnd( 6,c,d,a,b);
i_rnd( 4,b,c,d,a); i_rnd( 2,a,b,c,d);
out_blk[3] = d - l_key[1]; out_blk[2] = c;
out_blk[1] = b - l_key[0]; out_blk[0] = a;
};
