permutations.h

#ifndef PERMUTATIONS_H_
#define PERMUTATIONS_H_

#ifdef DEBUG
#include <stdio.h>
#endif

typedef unsigned char u8;
typedef unsigned long long u64;

typedef struct {
  u64 x0, x1, x2, x3, x4;
} state;

static inline void printstate(const char* text, const state s) {
#ifdef DEBUG
  printf("%s\n", text);
  printf("  x0=%016llx\n", s.x0);
  printf("  x1=%016llx\n", s.x1);
  printf("  x2=%016llx\n", s.x2);
  printf("  x3=%016llx\n", s.x3);
  printf("  x4=%016llx\n", s.x4);
#else
  // disable warning about unused parameters
  (void)text;
  (void)s;
#endif
}

static inline u64 BYTES_TO_U64(const u8* bytes, int n) {
  int i;
  u64 x = 0;
  for (i = 0; i < n; i++) x |= ((u64)bytes[i]) << (56 - 8 * i);
  return x;
}

static inline void U64_TO_BYTES(u8* bytes, const u64 x, int n) {
  int i;
  for (i = 0; i < n; i++) bytes[i] = (u8)(x >> (56 - 8 * i));
}

static inline u64 BYTE_MASK(int n) {
  int i;
  u64 x = 0;
  for (i = 0; i < n; i++) x |= 0xffull << (56 - 8 * i);
  return x;
}

static inline u64 ROTR64(u64 x, int n) { return (x << (64 - n)) | (x >> n); }

static inline void ROUND(u8 C, state* p) {
  state s = *p;
  state t;
  // addition of round constant
  s.x2 ^= C;
  printstate(" addition of round constant:", s);
  // substitution layer
  s.x0 ^= s.x4;
  s.x4 ^= s.x3;
  s.x2 ^= s.x1;
  // start of keccak s-box
  t.x0 = ~s.x0;
  t.x1 = ~s.x1;
  t.x2 = ~s.x2;
  t.x3 = ~s.x3;
  t.x4 = ~s.x4;
  t.x0 &= s.x1;
  t.x1 &= s.x2;
  t.x2 &= s.x3;
  t.x3 &= s.x4;
  t.x4 &= s.x0;
  s.x0 ^= t.x1;
  s.x1 ^= t.x2;
  s.x2 ^= t.x3;
  s.x3 ^= t.x4;
  s.x4 ^= t.x0;
  // end of keccak s-box
  s.x1 ^= s.x0;
  s.x0 ^= s.x4;
  s.x3 ^= s.x2;
  s.x2 = ~s.x2;
  printstate(" substitution layer:", s);
  // linear diffusion layer
  s.x0 ^= ROTR64(s.x0, 19) ^ ROTR64(s.x0, 28);
  s.x1 ^= ROTR64(s.x1, 61) ^ ROTR64(s.x1, 39);
  s.x2 ^= ROTR64(s.x2, 1) ^ ROTR64(s.x2, 6);
  s.x3 ^= ROTR64(s.x3, 10) ^ ROTR64(s.x3, 17);
  s.x4 ^= ROTR64(s.x4, 7) ^ ROTR64(s.x4, 41);
  printstate(" linear diffusion layer:", s);
  *p = s;
}

static inline void P12(state* s) {
  printstate(" permutation input:", *s);
  ROUND(0xf0, s);
  ROUND(0xe1, s);
  ROUND(0xd2, s);
  ROUND(0xc3, s);
  ROUND(0xb4, s);
  ROUND(0xa5, s);
  ROUND(0x96, s);
  ROUND(0x87, s);
  ROUND(0x78, s);
  ROUND(0x69, s);
  ROUND(0x5a, s);
  ROUND(0x4b, s);
}

static inline void P8(state* s) {
  printstate(" permutation input:", *s);
  ROUND(0xb4, s);
  ROUND(0xa5, s);
  ROUND(0x96, s);
  ROUND(0x87, s);
  ROUND(0x78, s);
  ROUND(0x69, s);
  ROUND(0x5a, s);
  ROUND(0x4b, s);
}

static inline void P6(state* s) {
  printstate(" permutation input:", *s);
  ROUND(0x96, s);
  ROUND(0x87, s);
  ROUND(0x78, s);
  ROUND(0x69, s);
  ROUND(0x5a, s);
  ROUND(0x4b, s);
}

#endif  // PERMUTATIONS_H_