4 ms·
> there is no meaningful sense in which OTP fails any of these IND-CPA/CCA1/CCA2 games That’s factually wrong. A CCA oracle can easily determine the key. > en
by l33t2328 5y ago
> there is no meaningful sense in which OTP fails any of these IND-CPA/CCA1/CCA2 games
That’s factually wrong. A CCA oracle can easily determine the key.
> enc_k(m) is defined as taking the next length(m) unused bits from the pad
No, it is not. It’s defined as m \xor k.
You are describing another cipher, but not Vernan’s OTP.
> Yes, this means enc_k and dec_k carry some extra implicit state and are not simply functions in (k × m) → c
Then you aren’t describing an encryption and decryption function. Those depend only on k and m.
Someone must be able to have the algorithm and the key and decrypt any message. Your “hidden state” cannot(and indeed should not) be a part of the algorithm as it violates the principle of kerckhoff.
Stepping out of the theoretical for a moment, your proposed scheme also makes no sense in reality. How am I to know what part of the pad you’re using if I’m in a bunker picking up your encrypted signal?