TupleHash256.py 2.8 KB

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  1. # ===================================================================
  2. #
  3. # Copyright (c) 2021, Legrandin <helderijs@gmail.com>
  4. # All rights reserved.
  5. #
  6. # Redistribution and use in source and binary forms, with or without
  7. # modification, are permitted provided that the following conditions
  8. # are met:
  9. #
  10. # 1. Redistributions of source code must retain the above copyright
  11. # notice, this list of conditions and the following disclaimer.
  12. # 2. Redistributions in binary form must reproduce the above copyright
  13. # notice, this list of conditions and the following disclaimer in
  14. # the documentation and/or other materials provided with the
  15. # distribution.
  16. #
  17. # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  18. # "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  19. # LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  20. # FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  21. # COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  22. # INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  23. # BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  24. # LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  25. # CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  26. # LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  27. # ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  28. # POSSIBILITY OF SUCH DAMAGE.
  29. # ===================================================================
  30. from . import cSHAKE256
  31. from .TupleHash128 import TupleHash
  32. def new(**kwargs):
  33. """Create a new TupleHash256 object.
  34. Args:
  35. digest_bytes (integer):
  36. Optional. The size of the digest, in bytes.
  37. Default is 64. Minimum is 8.
  38. digest_bits (integer):
  39. Optional and alternative to ``digest_bytes``.
  40. The size of the digest, in bits (and in steps of 8).
  41. Default is 512. Minimum is 64.
  42. custom (bytes):
  43. Optional.
  44. A customization bytestring (``S`` in SP 800-185).
  45. :Return: A :class:`TupleHash` object
  46. """
  47. digest_bytes = kwargs.pop("digest_bytes", None)
  48. digest_bits = kwargs.pop("digest_bits", None)
  49. if None not in (digest_bytes, digest_bits):
  50. raise TypeError("Only one digest parameter must be provided")
  51. if (None, None) == (digest_bytes, digest_bits):
  52. digest_bytes = 64
  53. if digest_bytes is not None:
  54. if digest_bytes < 8:
  55. raise ValueError("'digest_bytes' must be at least 8")
  56. else:
  57. if digest_bits < 64 or digest_bits % 8:
  58. raise ValueError("'digest_bytes' must be at least 64 "
  59. "in steps of 8")
  60. digest_bytes = digest_bits // 8
  61. custom = kwargs.pop("custom", b'')
  62. return TupleHash(custom, cSHAKE256, digest_bytes)