4 * email: daniel.otte@rub.de
12 #include <avr/pgmspace.h>
16 #define GRAIN_REVERSEKEY
18 /* s0, s1, s2, ..., s78, s79 */
19 #define S(i) ((ctx->lfsr[9-((i)/8)])>>(7-((i)%8)))
20 /* b0, b1, b2, ..., b78, b79 */
21 #define B(i) ((ctx->nfsr[9-((i)/8)])>>(7-((i)%8)))
22 #define _B(i) (((ctx->nfsr[9-((i)/8)])>>(7-((i)%8)))&1)
25 uint8_t h_lut[4] PROGMEM = {0x4C, 0xB6, 0xD3, 0x26};
27 #ifdef GRAIN_BADOPTIMISATION
28 uint8_t g_lut[128] PROGMEM = {
29 0xF0, 0xA5, 0x0F, 0x5A, 0x0F, 0x5A, 0xF0, 0xA5, 0x0F, 0x5A, 0xF0, 0xA5, 0xF0, 0x5A, 0x0F, 0x0F,
30 0xC3, 0x96, 0x3C, 0x69, 0x3C, 0x69, 0xC3, 0x96, 0x9C, 0xC9, 0x63, 0x36, 0x63, 0xC9, 0x9C, 0x9C,
31 0x0F, 0x5A, 0x0F, 0x5A, 0xF0, 0xA5, 0xF0, 0x5A, 0xF0, 0xA5, 0xF0, 0xA5, 0x0F, 0xA5, 0x0F, 0xF0,
32 0x3C, 0x69, 0x3C, 0x69, 0xC3, 0x96, 0xC3, 0x69, 0x63, 0x36, 0x63, 0x36, 0x9C, 0x36, 0x9C, 0x63,
33 0x0F, 0xD2, 0xF0, 0x2D, 0xF0, 0x2D, 0x0F, 0xD2, 0xF0, 0x2D, 0x0F, 0xD2, 0x0F, 0x2D, 0xF0, 0x78,
34 0x3C, 0xE1, 0xC3, 0x1E, 0xC3, 0x1E, 0x3C, 0xE1, 0x63, 0xBE, 0x9C, 0x41, 0x9C, 0xBE, 0x63, 0xEB,
35 0x00, 0xDD, 0x00, 0xDD, 0xFF, 0x22, 0xFF, 0xDD, 0xFF, 0x22, 0xFF, 0x22, 0x00, 0x22, 0xF0, 0x87,
36 0xF3, 0x2E, 0xF3, 0x2E, 0x0C, 0xD1, 0x0C, 0x2E, 0xAC, 0x71, 0xAC, 0x71, 0x53, 0x71, 0xA3, 0xD4 };
39 uint8_t grain_enc(grain_ctx_t* ctx){
40 uint8_t s80, s0, c1, c2;
44 s80 =S(62) ^ S(51) ^ S(38) ^ S(23) ^ S(13) ^ s0;
48 c2 = (ctx->lfsr[i])>>7;
49 ctx->lfsr[i] = ((ctx->lfsr[i])<<1) | c1;
54 /* 778 Byte in this variant / 617 clks enc_time */
55 #ifndef GRAIN_BADOPTIMISATION
57 b80 = B(62) ^ B(60) ^ B(52) ^ B(45) ^
58 B(37) ^ B(33) ^ B(28) ^ B(21) ^
59 B(14) ^ B( 9) ^ B( 0) ^ s0;
60 b80 ^= (a = B(63) & B(60));
61 b80 ^= (b = B(37) & B(33));
62 b80 ^= B(15) & B( 9); // c
63 b80 ^= (d = B(60) & B(52) & B(45));
64 b80 ^= (e = B(33) & B(28) & B(21));
65 b80 ^= B(63) & B(45) & B(28) & B(9); // f
67 b80 ^= b & B(60) & B(52); // g
68 b80 ^= a & B(21) & B(15); // h
69 b80 ^= d & B(63) & B(37); // i
70 b80 ^= e & B(15) & B( 9); // j
71 b80 ^= e & B(52) & B(45) & B(37); // k
73 /* let's reorder the bits */
88 x = ((ctx->nfsr[8])&0x41)<<1; // B15 & B09
89 x |= ((ctx->nfsr[2])&0x09); // B63 & B60
90 // x |= ((ctx->nfsr[4])&0x04)<<4; // B45
91 x |= (((ctx->nfsr[5])&0x44) |
92 ((ctx->nfsr[3])&0x08) |
93 (((((ctx->nfsr[7])&0x04)<<3) |((ctx->nfsr[4])&0x04))<<2) )<<2; // B37 & B33
94 // x |= ((ctx->nfsr[3])&0x08)<<2; // B52
95 x |= ((ctx->nfsr[6])&0x08)>>1; // B28
96 // x |= ((ctx->nfsr[7])&0x04)<<7; // B21
99 b80 = pgm_read_byte(g_lut+(x/8))>>(x%8);
100 b80 ^= s0 ^ B(62) ^ B(14) ^ B(0);
104 c2 = (ctx->nfsr[i])>>7;
105 ctx->nfsr[i] = ((ctx->nfsr[i])<<1) | c1;
108 /* now the h function */
116 h = (pgm_read_byte(h_lut+(i/8)))>>(i%8);
118 h ^= B(0) ^ B(1) ^ B(3) ^ B(9) ^ B(30) ^ B(42) ^ B(55);
122 #ifdef GRAIN_REVERSEKEY
125 uint8_t reverse_bits(uint8_t a){
127 0x0, 0x8, 0x4, 0xC, /* 0000 1000 0100 1100 */
128 0x2, 0xA, 0x6, 0xE, /* 0010 1010 0110 1110 */
129 0x1, 0x9, 0x5, 0xD, /* 0001 1001 0101 1101 */
130 0x3, 0xB, 0x7, 0xF }; /* 0011 1011 0111 1111 */
132 x = ((lut[a&0xf]) << 4) | lut[a>>4];
137 #define reverse_bits(a) (a)
141 void grain_init(const void* key, const void* iv, grain_ctx_t* ctx){
144 /* load the 80bit key */
146 ctx->nfsr[9-i] = reverse_bits(((uint8_t*)key)[i]);
148 /* load the 64bit iv */
150 ctx->lfsr[9-i] = reverse_bits(((uint8_t*)iv)[i]);
152 /* set the other bits of iv to 1 */
153 ctx->lfsr[0] = ctx->lfsr[1] = 0xFF;
155 /* run it 160 times */
156 for(i=0; i<160; ++i){