Re: SymmetricCipher Decoder is not working if created dynamically.

[Voronkov Konstantin]

Hello Russell! I wanted to ask you question about padding. IFAIK the CFB encryption  mode produces the same output buffer size and input, and in the sample: http://www.eskimo.com/~weidai/cgi-bin/fom-serve/cache/79.html there is the same size for output buffer as for input. This is the CFB mode  design to produce the same length buffer, am I wrong? Best Regards, Konstantion ----- Original Message ----- From: Russell Robinson To: Cornel Maftuleac Sent: Wednesday, June 02, 2004 3:05 AM Subject: Re: SymmetricCipher Decoder is not working if created dynamically. Hi Cornel, Cornel>         cfbEncryption.ProcessData(chiper, plain,bSize); Cornel>         cfbDecryption.ProcessData(out_plain, chiper,bSize); Cornel>         cfbEncrypt->ProcessData(chiper2, plain, bSize); Cornel>         cfbDecrypt->ProcessData(out_plain, chiper2, bSize); I'm not sure, but I'm surprised that either works....you've assumed that the ciphertext is the same length as the plaintext.  That, in general, is not true.  I think it can only be true if the plaintext is a multiple of a block size for the underlying cipher. If it isn't (which ususally isn't), you need to use padding. In any case, decryption with    ProcessData(out_plain, chiper2, bSize) is almost certainly wrong. In fact, your call to    cfbEncryption.ProcessData(chiper, plain,bSize); is probably scribbling over the stack.  That's why CrytoPP has the Source and Sink classes to work with variable length data. You really need to be using those. -- Russell Robinson (mailto:[EMAIL PROTECTED]) Author of Tectite (CRM and Licensing for Software Developers) Download your free CRM from: http://www.tectite.com/