siphash.py raw

   1  #!/usr/bin/env python3
   2  # Copyright (c) 2016-present The Bitcoin Core developers
   3  # Distributed under the MIT software license, see the accompanying
   4  # file COPYING or http://www.opensource.org/licenses/mit-license.php.
   5  """SipHash-2-4 implementation.
   6  
   7  This implements SipHash-2-4. For convenience, an interface taking 256-bit
   8  integers is provided in addition to the one accepting generic data.
   9  """
  10  
  11  def rotl64(n, b):
  12      return n >> (64 - b) | (n & ((1 << (64 - b)) - 1)) << b
  13  
  14  
  15  def siphash_round(v0, v1, v2, v3):
  16      v0 = (v0 + v1) & ((1 << 64) - 1)
  17      v1 = rotl64(v1, 13)
  18      v1 ^= v0
  19      v0 = rotl64(v0, 32)
  20      v2 = (v2 + v3) & ((1 << 64) - 1)
  21      v3 = rotl64(v3, 16)
  22      v3 ^= v2
  23      v0 = (v0 + v3) & ((1 << 64) - 1)
  24      v3 = rotl64(v3, 21)
  25      v3 ^= v0
  26      v2 = (v2 + v1) & ((1 << 64) - 1)
  27      v1 = rotl64(v1, 17)
  28      v1 ^= v2
  29      v2 = rotl64(v2, 32)
  30      return (v0, v1, v2, v3)
  31  
  32  
  33  def siphash(k0, k1, data):
  34      assert type(data) is bytes
  35      v0 = 0x736f6d6570736575 ^ k0
  36      v1 = 0x646f72616e646f6d ^ k1
  37      v2 = 0x6c7967656e657261 ^ k0
  38      v3 = 0x7465646279746573 ^ k1
  39      c = 0
  40      t = 0
  41      for d in data:
  42          t |= d << (8 * (c % 8))
  43          c = (c + 1) & 0xff
  44          if (c & 7) == 0:
  45              v3 ^= t
  46              v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
  47              v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
  48              v0 ^= t
  49              t = 0
  50      t = t | (c << 56)
  51      v3 ^= t
  52      v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
  53      v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
  54      v0 ^= t
  55      v2 ^= 0xff
  56      v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
  57      v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
  58      v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
  59      v0, v1, v2, v3 = siphash_round(v0, v1, v2, v3)
  60      return v0 ^ v1 ^ v2 ^ v3
  61  
  62  
  63  def siphash256(k0, k1, num):
  64      assert type(num) is int
  65      return siphash(k0, k1, num.to_bytes(32, 'little'))
  66