Using padding in encryption: "The most common query we get about cryptography concerns padding with a block cipher.
If you have to encrypt some data to send to another user and everything else works OK except the last few bytes, your problem is probably one of padding. Read on.
This article describes the mechanics of padding with examples using common block encryption algorithms like DES, Triple DES, Blowfish and AES. It considers where you should use padding and where you don't need to."