AES encryption problem in Debug and Release mode

I am 开发者_开发问答using AES encryption algorithm (Rijndael implementation). I am using MS Visual Studio 2008 IDE for my development work. I could see a strange problem in my Debug and Release mode. When I encrypt a string in Debug mode it generates different bytes than Release mode. But fortunately decrypting will result same string. I have tried in Mac, it generates one more byte sequence but able to decrypt all byte sequences correctly.

Is this problem related to encryption algorithm or Debug/Release settings? Is there any solution to avoid this?

Regards Devara Gudda

AES is a block cipher. You can encrypt and decrypt blocks of a fixed size of 128 bits with it. To encrypt and decrypt longer sequences you typically use a certain "mode of operation" and a certain "padding scheme" which both might involve some randonmess via the IV (initialization vector) and padding. In those cases the cipher text will be a bit longer and different each time due to the "randomness" that is involved. Actually, it's not a bad property that the same message encrypts to different cipher texts. You even need this to protect yourself from certain attacks.

You should verify the difference between your "release" and "debug" settings, the most problems occour at "Configuration Properties -> C/C++ -> Code Generation" and also the "Character Set" under "Configuration Properties -> General".

I have my implementation of AES and it compiles fine under both default configurations of VC2008.

You might want to verify how you're specifying buffer sizes for the plain text/cipher text. In debug builds the compiler usually initializes buffers to a known value (to detect overflow errors typically). In VC++ 2008 Express for instance, I find that char buffers are initialized to 0xCD in debug builds. In release builds of course, no such thing is done. I am not saying this is the cause for what you are observing - just something you might want to check out.