News for hackers. Stuff that matters.

A comment on "Unbreakable" Encryption Almost Certainly Isn't. Parent comment

Re:"Unbreakable" Encryption Almost Certainly Isn't by darkmighty on Tuesday April 08, 2014 @12:26PM (#7554385)
"If we expand the definition of "encryption scheme" sufficiently to allow transmission of secrets outside of cryptographic channels, then OTP is not even close to the only unbreakable system."

Any scheme which allows sharing arbitrary amounts of random information is less than or equally secure as an OTP (security defined per symbol) since OTP reveals no information per symbol; also, it uses the minimum amount shared information to do so, provided your symbols are equiprobable.

[ Parent | on HN ]
Re:"Unbreakable" Encryption Almost Certainly Isn't by andrewla on Tuesday April 08, 2014 @04:57PM (#7555954)
I agree, OTP is optimal, it's just not unique, even by a very broad definition of what an OTP is. Sending a Turing machine to the other party through a secondary channel, for example, would produce an equivalently (not more) secure mechanism. Or sending a normal real number as the key, and the ciphertext is an index into the base26 expansion.

Technically, either of these could be slightly more secure, in that they need not leak the length of the plaintext. For transmitting a single "yes" vs. "no" answer, that could be a fatal attack vector for a naive OTP.

[ Parent | on HN ]