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> 6. Fundamental cryptanalytics in the solution of aperiodic systems. That section is white. Is there any information on cyphers that generate codes indistingu
by ffhhj 5y ago
> 6. Fundamental cryptanalytics in the solution of aperiodic systems.
That section is white. Is there any information on cyphers that generate codes indistinguishable from absolute randomness based on the properties of entropy?
- thaumasiotes 5y agohttps://en.wikipedia.org/wiki/One-time_pad https://en.wikipedia.org/wiki/One-time_pad Note that for the code to be indistinguishable from absolute randomness, you need the key to be as long as the text.
- hanche 5y agoIn theory, yes. You might say that cryptography exists in the gap between the theoretically impossible and the practically achievable.
- qsort 5y agoThe only cypher that satisfies your request is "XOR the signal with noise, where the noise is a shared secret". Generally, you only require a weaker property: that a time-bounded attacker is unable to assert that the cyphertext is random with neglegible probability.
- anchpop 5y agoI think modular addition also has that property
- sirsar 5y agoXOR is modular addition on single bits!
- adrian_b 5y agoFor this kind of encryption, any operation between plaintext symbols and the random masking symbols that belongs to a commutative group can be used. Nevertheless, modular addition, including addition modulo 2, a.k.a. XOR, is almost always chosen, because any other kind of operations are slower in hardware without having any advantages over modular addition (when the masking symbols cannot be distinguished from a random sequence). For example, instead of using modular addition, you can use multiplication modulo 2^16+1 (a Fermat prime number), to encrypt each 16-bit plaintext symbol, but that is slower than modular addition without being better (unless your method of generating the pseudo-random mask is weak, which is easy to avoid).
- AnotherGoodName 5y agoI mean all working (non broken) cyphers are indistinguishable from randomness since you could simply do an entropy attack against a cypher that didn't have this property.