How can padding be disambiguated from data, when encrypting using a block cipher?
I'm by no means an expert in cryptography, but rather a programmer with a keen interest.
X bytes of data, message
M, that I want to encrypt using an
N-byte block cipher, where
N >> X.
M be padded using
N-X bytes of padding
O, such that there would be no ambiguity between decrypting the padded message
M´ and the (concatenated) message
How is this done in practice? Normally, when encrypting using a block cipher, I don't see a header being output describing the original length of the message