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I'm looking for a non-invertible bijective function mapping a 64bit value into another 64bit value.

I can't use a hash because it isn't bijective.

Could this be done with public key cryptography ? The key and function may be big. It's just the data that would be small. I would destroy the private key as I never need to decipher.

Since the application is distributed, using a public key or equivalent would be great for security.

chmike
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I'm looking for a non-invertible bijective function mapping a 64bit value into another 64bit value.

Actually, if the function is public, then it obviously can be inverted with $O(2^{64})$ work (by simply trying every possible input). That amount of work is achievable by dedicated adversaries, hence it would indicate that what you're asking for is impossible.

poncho
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