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The FFX Mode of Operation for Format-Preserving Encryption

License: GNU General Public License v3.0

Python 100.00%

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karlpilkington sinchb longnight robmagee innoteq adityag3 lribeiro beny23m jamespic n-mca

libffx's Issues

pycrypto dependency should be updated to pycryptodome

pycrypto (currently a dependency) is a defunct project and has been continued by pycryptodome. This project should be updated to use pycryptodome instead (should be a drop replacement)

over padding when right block is 2^16

seems to over pad when right block is 2^16

    plain = FFXInteger('0000065536', radix=10)
    tweak = FFXInteger('0000000000', radix=10)
    key = FFXInteger('2b7e151628aed2a6abf7158809cf4f3c', radix=16, blocksize=32)

    ffx_obj = ffx.new(key.to_bytes(16), 10)
    cypher = ffx_obj.encrypt(tweak, plain)

Implementation differs from the paper for input with a range that exceeds 8^24

While working on a PHP implementation of the FFX[radix] algorithm, I compared the output of my implementation with this implementation. I noticed that the output begin to differ if the input range exceeds 8^24. This is due to a wrong implementation of the "expansion" of the Y variable.

In the paper Addendum to “The FFX Mode of Operation for Format-Preserving Encryption” it says:

Y ← first d + 4 bytes of (Y || AESK(Y ⊕ [1]16) || AESK(Y ⊕ [2]16) || AESK(Y ⊕ [3]16)··· )

However this implementation does actually:

Y ← first d + 4 bytes of (Y || AESK(Y ⊞ [1]16) || AESK(Y ⊞ [2]16) || AESK(Y ⊞ [3]16)··· )

Notice the difference between ⊕ and ⊞. The paper states that for the scheme FFX[radix] ⊞ is block-wise addition. While it is nowhere explicitly stated in the paper that ⊕ means an XOR operation. However, it could be interpreted from the description of the CBC-MACK(X) algorithm (on page 2) as it states: for j ← 1 to m, set Y ← AESK(Y ⊕ Xi).

To correct this implementation these lines:

            left = FFXInteger(bytes_to_long(Y), radix=self._radix, blocksize=32)
            right = FFXInteger(str(i), radix=10, blocksize=16)
            X = self.add(left, right)
            TMP += self._ecb.encrypt(X.to_bytes(16))

should be replaced with:

            I = FFXInteger(str(i), radix=10, blocksize=16).to_bytes(16)
            X = "".join(chr(ord(Yi) ^ ord(Ii)) for Yi, Ii in zip(Y, I))
            TMP += self._ecb.encrypt(X)

Test data:

radix=16 key=0x00000000000000000000000000000000 tweak=

Current implementation
input  000000000000000000000000000000000000000000000000
output ddb77d3be91a8e255fca9389a3d48da2b4476919744febea
input  0000000000000000000000000000000000000000000000000
output 1dad7e05f03706e8af695246afa40a49876c1d3e0699c5be1

Expected
input  000000000000000000000000000000000000000000000000
output ddb77d3be91a8e255fca9389a3d48da2b4476919744febea
input  0000000000000000000000000000000000000000000000000
output 1f7b9459d22b2bee17d5b5616e03241467767c9dcbc424c21

encrypting special characters

I am not able to encrypt email addresses with libffx.
Am I doing something wrong?

Radix > 36 raises ValueError

If I run benchmark.py --radix 62 it raises a ValueError.

Traceback (most recent call last):
  File "benchmark.py", line 68, in <module>
    main()
  File "benchmark.py", line 47, in main
    C = ffx.encrypt(T, M1)
  File "FFX/__init__.py", line 262, in encrypt
    C = self.add(A, self.F(n, T, i, B))
  File "FFX/__init__.py", line 199, in F
    if T == 0:
  File "FFX/__init__.py", line 117, in __eq__
    retval = (self.to_int() == other)
  File "FFX/__init__.py", line 143, in to_int
    self._as_int = int(self._x, self._radix)
ValueError: int() base must be >= 2 and <= 36

Need to update libffx on PyPI

Please update libffx package on PyPI. The source is ready.

There is old version:

$ pip search libffx
libffx (0.0.1)  - FFX

Thank you!

typo in setup.py

I can't install this lib because__init__.pyx doesn't exist, there is just__init__.py：

$$$:/tmp/libffx$ sudo python setup.py build
Traceback (most recent call last):
  File "setup.py", line 8, in <module>
    ext_modules = cythonize("FFX/__init__.pyx"),
  File "/usr/local/lib/python2.7/dist-packages/Cython/Build/Dependencies.py", line 758, in cythonize
    aliases=aliases)
  File "/usr/local/lib/python2.7/dist-packages/Cython/Build/Dependencies.py", line 651, in create_extension_list
    for file in nonempty(sorted(extended_iglob(filepattern)), "'%s' doesn't match any files" % filepattern):
  File "/usr/local/lib/python2.7/dist-packages/Cython/Build/Dependencies.py", line 103, in nonempty
    raise ValueError(error_msg)
ValueError: 'FFX/__init__.pyx' doesn't match any files

this is useful; would you like to put it on PyPI?

PyPI ffx right now is this:

https://pypi.python.org/pypi/ffx

Would you like to publish this library to PyPI?
https://packaging.python.org/distributing/#uploading-your-project-to-pypi

Keys with prefix \x00 raises ValueError

Hi,

with zero key ('0'*128) libFFX raises a ValueError:

import FFX
ffx_key = FFX.FFXInteger('0'*128, radix=2, blocksize = 128)
ffx = FFX.new(ffx_key.to_bytes(), 2)

ValueError: AES key must be either 16, 24, or 32 bytes long

This is caused by FFXInteger.to_bytes(), which strips leading null bytes:

>>> FFXInteger('1'*8+'0'*8, radix=2, blocksize=16).to_bytes()
'\xff\x00'
>>> FFXInteger('0'*8+'1'*8, radix=2, blocksize=16).to_bytes()
'\xff'

RADIX 62

Is it possible to support RADIX 62 and hove?