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Is it better to XOR rounds or just to make round by round in cipher?

tf flag
Tom

Let's consider we have keyed PRNG's and we want to build a cipher. What is better:

  • to xor let's say ten such generators with some input as a plaintext (every generator got different key, but the same input),
  • make 10 rounds, in which every generator output is new input to the next generator.

We see that usually ciphers have a round design. Is it because this is better?

Paul Uszak avatar
cn flag
I think that you have to tighten up on the language somewhat. What exactly is a keyed PRNG?
Tom avatar
tf flag
Tom
PRNG with parameters. You can choose some some different parameters and generate many independent pseudo random numbers, with let's say the maximum period (n-bit generator has a period $2^n$), no matter what seed you will choose. One keyed PRNG is not cryptographically secure, we should assume it can broken with more or less effort. Usually in PRNG we choose only the seed, in such a generator we can also choose, say, an n-bit key for an n-bit generator.
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