i search how to implement the RC6 encryption algorithm on avr microcontroller "ATMEGA16" Or another as possible please help me
and thank you
the code of RC6:
/* rc6 (TM)
* Unoptimized sample implementation of Ron Rivest's submission to the
* AES bakeoff.
*/
#include <stdio.h>
/* RC6 is parameterized for w-bit words, b bytes of key, and
* r rounds. The AES version of RC6 specifies b=16, 24, or 32;
* w=32; and r=20.
*/
#define w 32 /* word size in bits */
#define r 20 /* based on security estimates */
#define P32 0xB7E15163 /* Magic constants for key setup */
#define Q32 0x9E3779B9
/* derived constants */
#define bytes (w /
/* bytes per word */#define c ((b + bytes - 1) / bytes) /* key in words, rounded up */
#define R24 (2 * r + 4)
#define lgw 5 /* log2(w) -- wussed out */
/* Rotations */
#define ROTL(x,y) (((x)<<(y&(w-1))) | ((x)>>(w-(y&(w-1)))))
#define ROTR(x,y) (((x)>>(y&(w-1))) | ((x)<<(w-(y&(w-1)))))
unsigned int S[R24 - 1]; /* Key schedule */
void rc6_key_setup(unsigned char *K, int b)
{
int i, j, s, v;
unsigned int L[(32 + bytes - 1) / bytes]; /* Big enough for max b */
unsigned int A, B;
L[c - 1] = 0;
for (i = b - 1; i >= 0; i--)
L[i / bytes] = (L[i / bytes] <<
+ K;S[0] = P32;
for (i = 1; i <= 2 * r + 3; i++)
S = S + Q32;
A = B = i = j = 0;
v = R24;
if (c > v) v = c;
v *= 3;
for (s = 1; s <= v; s++)
{
A = S = ROTL(S + A + B, 3);
B = L[j] = ROTL(L[j] + A + B, A + B);
i = (i + 1) % R24;
j = (j + 1) % c;
}
}
void rc6_block_encrypt(unsigned int *pt, unsigned int *ct)
{
unsigned int A, B, C, D, t, u, x;
int i, j;
A = pt[0];
B = pt[1];
C = pt[2];
D = pt[3];
B += S[0];
D += S[1];
for (i = 2; i <= 2 * r; i += 2)
{
t = ROTL(B * (2 * B + 1), lgw);
u = ROTL(D * (2 * D + 1), lgw);
A = ROTL(A ^ t, u) + S;
C = ROTL(C ^ u, t) + S[i + 1];
x = A;
A = B;
B = C;
C = D;
D = x;
}
A += S[2 * r + 2];
C += S[2 * r + 3];
ct[0] = A;
ct[1] = B;
ct[2] = C;
ct[3] = D;
}
void rc6_block_decrypt(unsigned int *ct, unsigned int *pt)
{
unsigned int A, B, C, D, t, u, x;
int i, j;
A = ct[0];
B = ct[1];
C = ct[2];
D = ct[3];
C -= S[2 * r + 3];
A -= S[2 * r + 2];
for (i = 2 * r; i >= 2; i -= 2)
{
x = D;
D = C;
C = B;
B = A;
A = x;
u = ROTL(D * (2 * D + 1), lgw);
t = ROTL(B * (2 * B + 1), lgw);
C = ROTR(C - S[i + 1], t) ^ u;
A = ROTR(A - S, u) ^ t;
}
D -= S[1];
B -= S[0];
pt[0] = A;
pt[1] = B;
pt[2] = C;
pt[3] = D;
}
struct test_struct
{
int keylen;
unsigned char key[32];
unsigned int pt[4];
unsigned int ct[4];
} tests[] =
{
{ 16, {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00},
{0x00000000, 0x00000000, 0x00000000, 0x00000000},
{0x36a5c38f, 0x78f7b156, 0x4edf29c1, 0x1ea44898},
},
{ 16, {0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef,
0x01, 0x12, 0x23, 0x34, 0x45, 0x56, 0x67, 0x78},
{0x35241302, 0x79685746, 0xbdac9b8a, 0xf1e0dfce},
{0x2f194e52, 0x23c61547, 0x36f6511f, 0x183fa47e},
},
{ 24, {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00},
{0x00000000, 0x00000000, 0x00000000, 0x00000000},
{0xcb1bd66c, 0x38300b19, 0x163f8a4e, 0x82ae9086},
},
{ 24, {0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef,
0x01, 0x12, 0x23, 0x34, 0x45, 0x56, 0x67, 0x78,
0x89, 0x9a, 0xab, 0xbc, 0xcd, 0xde, 0xef, 0xf0},
{0x35241302, 0x79685746, 0xbdac9b8a, 0xf1e0dfce},
{0xd0298368, 0x0405e519, 0x2ae9521e, 0xd49152f9},
},
{ 32, {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00},
{0x00000000, 0x00000000, 0x00000000, 0x00000000},
{0x05bd5f8f, 0xa85fd110, 0xda3ffa93, 0xc27e856e},
},
{ 32, {0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef,
0x01, 0x12, 0x23, 0x34, 0x45, 0x56, 0x67, 0x78,
0x89, 0x9a, 0xab, 0xbc, 0xcd, 0xde, 0xef, 0xf0,
0x10, 0x32, 0x54, 0x76, 0x98, 0xba, 0xdc, 0xfe},
{0x35241302, 0x79685746, 0xbdac9b8a, 0xf1e0dfce},
{0x161824c8, 0x89e4d7f0, 0xa116ad20, 0x485d4e67},
},
{ 0,
}
};
int
main()
{
unsigned int ct[4], pt[4];
int i;
struct test_struct *p;
for (p = tests, i = 1; p->keylen; p++, i++)
{
rc6_key_setup(p->key, p->keylen);
rc6_block_encrypt(p->pt, ct);
printf("Test %d: %08x %08x %08x %08x\n",
i, ct[0], ct[1], ct[2], ct[3]);
printf("Should be: %08x %08x %08x %08x\n",
p->ct[0], p->ct[1], p->ct[2], p->ct[3]);
rc6_block_decrypt(ct, pt);
printf("Plain: %08x %08x %08x %08x\n",
pt[0], pt[1], pt[2], pt[3]);
printf("Should be: %08x %08x %08x %08x\n\n",
p->pt[0], p->pt[1], p->pt[2], p->pt[3]);
}
return 0;
}
