sky_keygen.c

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <inttypes.h>

#if defined(__APPLE__)
#include <libkern/OSByteOrder.h>
#define bswap_16(x) OSSwapInt16(x)
#define bswap_32(x) OSSwapInt32(x)
#define bswap_64(x) OSSwapInt64(x)
#else
#include <byteswap.h>
#endif

#define HEX 0x10
#define UID_LEN 4
#define SECTOR_COUNT 16
#define KEY_MASK 0xFFFFFFFFFFFF

#define POLY UINT64_C(0x42f0e1eba9ea3693)
#define TOP UINT64_C(0x800000000000)

uint64_t crc64_like(uint64_t result, uint8_t sector) {
  result ^= (uint64_t)sector << 40;
  for(int i = 0; i < 8; i++) {
    result = (result & TOP) ? (result << 1) ^ POLY : result << 1;
  }
  return result;
}

uint64_t taghash(uint32_t uid) {
  uint64_t result = 0x9AE903260CC4;
  uint8_t uidBytes[UID_LEN] = {0};
  memcpy(uidBytes, &uid, UID_LEN);

  for(int i = 0; i < UID_LEN; i++) {
    result = crc64_like(result, uidBytes[i]);
  }
  return result;
}

int main(int argc, char *argv[]) {
  if (argc != 2) {
    printf("%s <4 byte uid in hex>\n", argv[0]);
    return 1;
  }
  uint32_t uid = strtoul(argv[1], NULL, HEX);

  printf("uid = %08x\n", uid);
  printf("Sector 0: 4b0b20107ccb\n"); //Fixed sector 0 key

  uid = bswap_32(uid);
  uint64_t hash = taghash(uid);
  for(uint8_t sector = 1; sector < SECTOR_COUNT; sector++) {
    uint64_t sectorhash = crc64_like(hash, sector);
    uint64_t key = bswap_64(sectorhash & KEY_MASK) >> 16;

    printf("Sector %u: %012" PRIx64 "\n", sector, key);
  }
}