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When Is A Block Cipher Not A Block Cipher?

Ask most people about whether AES is a block cipher or a stream cipher, and they will typically say that it’s a block cipher. But that’s not quite true, as some of the AES modes implement with a 128-bit block, while other methods implement a stream cipher. The block cipher modes are then ECB (Electronic Code Book) and CBC (Cipher Block Chaining). These modes then require padding, in order to make sure that we fill…