Originally Posted by
DanAmrich
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It's not Silversun Pickups. But if you speak code...
uint32_t P[18]; // P-array uint32_t S[4][256]; // S-boxes uint32_t f (uint32_t x) { uint32_t h = S[0][x >> 24] + S[1][x >> 16 & 0xff]; return ( h ^ S[2][x >> 8 & 0xff] ) + S[3][x & 0xff]; } void encrypt (uint32_t & L, uint32_t & R) { for (int i=0 ; i<16 ; i += 2) { L ^= P[i]; R ^= f(L); R ^= P[i+1]; L ^= f(R); } L ^= P[16]; R ^= P[17]; swap (L, R); } void decrypt (uint32_t & L, uint32_t & R) { for (int i=16 ; i > 0 ; i -= 2) { L ^= P[i+1]; R ^= f(L); R ^= P[i]; L ^= f(R); } L ^= P[1]; R ^= P[0]; swap (L, R); } void key_schedule (uint32_t key[], int keylen) { // ... // initializing the P-array and S-boxes with values derived from pi; omitted in the example // ... for (int i=0 ; i<18 ; ++i) P[i] ^= key[i % keylen]; uint32_t L = 0, R = 0; for (int i=0 ; i<18 ; i+=2) { encrypt (L, R); P[i] = L; P[i+1] = R; } for (int i=0 ; i<4 ; ++i) for (int j=0 ; j<256; j+=2) { encrypt (L, R); S[i][j] = L; S[i][j+1] = R; } }
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