Suggestion: implement ciphertext stealing (CTS) for ECB and CBC

[prusnak]

There is a method called ciphertext stealing (https://en.wikipedia.org/wiki/Ciphertext_stealing) which allows encryption of plaintext of artibrary length (the length does not have to be a multiply of blocksize) using ECB and CBC.

I see three ways how this can be integrated into the existing code:
a) add enable_cts=False parameter to constructors of AESModeOfOperationECB and AESModeOfOperationCBC, store the value in class and handle encryption/decryption with respect to this value
b) always perform CTS when len(plaintext) % blocksize > 0 or len(ciphertext) % blocksize > 0
c) create separate classes AESModeOfOperationECBCTS and AESModeOfOperationCBCCTS

Btw. Thanks for the library! Exactly what I was looking for after I realised that slowaes is dead. And your provide much more pleasant API. Thumbs up!

[ricmoo]

Awesome! I will look into it and hopefully get it done this week.

I will probably do the (b) method... But I have to research first. :)

Thanks a lot!

RicMoo

[ricmoo]

Oh sorry. Misread the email. I meant option (c).

[ricmoo]

We now have an optional parameter to specify padding options, so I will likely just add a PADDING_CTS in the non-distant future. If anyone wants this functionality soon-than-later, please +1 this issue. :)