AES encryption

Bryan Olson fakeaddress at nowhere.org
Sat Mar 11 02:01:10 CET 2006


I wrote:
> Tuvas wrote:
> [...]
> 
>> I've tested my function with a thousand random texts, it
>> seems to return the same result as received every time.
> 
> 
> Unfortunately, the results seem incorrect, self-consistent
> as they may be. The following will call your code, and
> check the results against 3 popular test vectors.
> 
> --Bryan
> 
> 
>     # Assert false if test fails
> 
>     test_key = (
>         0x2b, 0x7e, 0x15, 0x16, 0x28, 0xae, 0xd2, 0xa6,
>         0xab, 0xf7, 0x15, 0x88, 0x09, 0xcf, 0x4f, 0x3c,
>         0x76, 0x2e, 0x71, 0x60, 0xf3, 0x8b, 0x4d, 0xa5,
>         0x6a, 0x78, 0x4d, 0x90, 0x45, 0x19, 0x0c, 0xfe)
> 
>     test_plaintext = (
>         0x32, 0x43, 0xf6, 0xa8, 0x88, 0x5a, 0x30, 0x8d,
>         0x31, 0x31, 0x98, 0xa2, 0xe0, 0x37, 0x07, 0x34)
> 
>     expected = (
>             (0x39, 0x25, 0x84, 0x1d, 0x02, 0xdc, 0x09, 0xfb,
>             0xdc, 0x11, 0x85, 0x97, 0x19, 0x6a, 0x0b, 0x32),
> 
>             (0xf9, 0xfb, 0x29, 0xae, 0xfc, 0x38, 0x4a, 0x25,
>             0x03, 0x40, 0xd8, 0x33, 0xb8, 0x7e, 0xbc, 0x00),
> 
>             (0x1a, 0x6e, 0x6c, 0x2c, 0x66, 0x2e, 0x7d, 0xa6,
>             0x50, 0x1f, 0xfb, 0x62, 0xbc, 0x9e, 0x93, 0xf3))
> 
>     key_sizes = (16, 24, 32)
>     plaintext = s2num(''.join([chr(c) for c in test_plaintext]))
>     for i in range(len(key_sizes)):
>         key_size = key_sizes[i]
>         key = s2num(''.join([chr(c) for c in test_key[:key_size]]))
>         expected = s2num(''.join([chr(c) for c in expected[i]]))
>         ciphertext = encryptb(plaintext, key)
>         assert ciphertext == expected
>         deciphertext = decryptb(ciphertext, key)
>         assert deciphertext == plaintext

Oops, introduced a bug by shadowing "expected". Make the for loop:

    for i in range(len(key_sizes)):
         key_size = key_sizes[i]
         key = s2num(''.join([chr(c) for c in test_key[:key_size]]))
         expect = s2num(''.join([chr(c) for c in expected[i]]))
         ciphertext = encryptb(plaintext, key)
         assert ciphertext == expect
         deciphertext = decryptb(ciphertext, key)
         assert deciphertext == plaintext


-- 
--Bryan



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