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> One of the not-ideal aspects of the design is that SHISHUA is not reversible. Why is irreversibility a bad thing? Is it just the loss of useful state which r
by kortex 7y ago
> One of the not-ideal aspects of the design is that SHISHUA is not reversible.
Why is irreversibility a bad thing? Is it just the loss of useful state which reduces the internal entropy?
Is irreversibility ever useful? Wouldn't some amount of discarded bits make it harder for an adversary to infer the state?
- KMag 7y agoCSRNGs are mentioned a few times in TFA, but cryptographic security doesn't appear to be among the design criteria for SHISHUA. There's no mention of linear or differential crpytanalisis, which is table stakes for a CSPRNG.
- espadrine 7y agoI added a warning in the GitHub’s Readme. SHISHUA is not to be used for cryptographic purposes. You mentioned the lack of cryptanalysis; there is also the lack of rounds (which prevents researchers from breaking partial versions to ease their study, and allows setting a security margin).
- HAPMCEZ 7y agoIntuitively, yes. If something is irreversible then it's not 1 to 1 and you don't use the whole state space, so you'll likely have short cycles. Second part, again yes. But you can add that useful irreversible transform in the finalization of the output, and not in the state transform itself. I'm self taught so my understanding and terminology may not mesh with the people who have been taught this.