On Monday, December 3, 2018 at 6:13:40 PM UTC-5, Jeffrey Walton wrote:
>
>
> On Monday, December 3, 2018 at 11:58:54 AM UTC-5, rums.da...@gmail.com
> wrote:
>>
>> Hi,
>> when decrypting using pipelines I would normally do something like:
>>
>> StringSource ss(cipher_hex, true, new HexDecoder(new
>> StreamTransformationFilter(dec, new StringSink(recover))));
>>
>> Now i ran into a problem using the Panama Stream Cipher:
>>
>> AutoSeededRandomPool prng;
>> std::string plain("High-school students – who have been protesting
>> against changes to colleges and the university system – also seized on the
>> mood of protest and stepped up their blockades.");
>> std::string cipher_hex, recover1, recover2, cipher_bin;
>>
>> SecByteBlock key(32), iv(32);
>> prng.GenerateBlock(key, key.size());
>> prng.GenerateBlock(iv, iv.size());
>>
>> PanamaCipher<LittleEndian>::Encryption enc;
>> enc.SetKeyWithIV(key, key.size(), iv, iv.size());
>> PanamaCipher<LittleEndian>::Decryption dec;
>> dec.SetKeyWithIV(key, key.size(), iv, iv.size());
>>
>> StringSource (plain, true, new StreamTransformationFilter(enc, new
>> HexEncoder(new StringSink(cipher_hex))));
>>
>> // works fine, recover1 = plain
>> StringSource (cipher_hex, true, new HexDecoder(new StringSink(
>> cipher_bin)));
>> StringSource (cipher_bin, true, new StreamTransformationFilter(dec,
>> new StringSink(recover1)));
>>
>> dec.Resynchronize(iv, iv.size());
>>
>> // does not work, recover2 = "High-school students – who have been
>> protesting against changes –Ö)‘à« ç›áS` ¥¨~]Šm Qÿö:Û (...) "
>> StringSource (cipher_hex, true, new HexDecoder(new
>> StreamTransformationFilter(dec, new StringSink(recover2))));
>>
>> Is this expected behaviour? Is it not possible to use a Decoder inside
>> the decryption pipeline of a stream cipher?
>>
>
> No, its not expected behavior.
>
> I can duplicate it with GCC 8.2.1 on Fedora 29. Clang 6.0.1 is OK on
> Fedora 29.
>
> GCC 6 and Clang 6 are OK on OS X.
>
> Let me see if I can find a workaround in the code.
>
I'm still looking for a solution.
The unusual thing I'm seeing is, it is happening at character 70. I would
expect something unusual to happen on a simd-word or block boundary.
$ echo 'Two: High-school students – who have been protesting against
change' | wc -c
70
For the moment you can work around the issue by opening panama.h, and
defining CRYPTOPP_DISABLE_PANAMA_ASM. It is a safety for X32 and Clang, but
it works for GCC as well.
Jeff
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