Question

I’m developing a application to Windows(C#), Iphone, Android and Iphone which will connect to a SOAP WebService, that store information on a Database.

I’m looking for a way to encrypt/decrypt the information between those platforms. Is there any cross platforms library?

Answer 1

As @Sascha says, AES is available on pretty much every platform. What you have to do is to make sure that everything else is the same on both platforms:

1. The same mode; use either CBC or CTR mode.
2. The same IV; set it explicitly, don’t use the default because it will often be different on different systems.
3. The same key; obvious, but they need to be the same at the byte level because text can be encoded differently on different systems. Explicitly state the encoding you are using.
4. The same padding; for AES use PKCS7, again don’t rely on the default which may be different on different systems.

Whatever you chose do set things explicitly and don’t rely on defaults. Defaults can differ between systems and any difference will cause decryption to fail.