4870847 in decryption5/29/2023 ![]() No information is lost during the encryption process, the one-way function is simply used to mask each half in turn in an interleaved fashion (which can be done again during decryption in the opposite direction, but only if you have the key). Then you keep doing that for each round (using the round keys in reverse) and you end up with the plaintext. In this case, $L_$, but still becomes one half of the ciphertext, which lets you use it again during decryption to undo the XOR operation you used to mask the other half of the ciphertext. ![]() ![]() Look at this diagram, specifically the decryption one:Īs you can see, even though one half of the ciphertext is passed through the one-way function, there's always a copy of it remaining. one-way, you don't need to reverse it at all to "decrypt" (otherwise you are correct we would have a problem). DES is based on a Feistel construction - while the one-way function used is.
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