What's the deal with conditional and jump operations in homomorphic encryption?

Asked Feb 17 '20 at 10:31

Active Mar 01 '20 at 12:54

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I'm doing some research about full homomorphic encryption (FHE). As I figured out, algorithms are implemented in circuits. I suppose that they are called circuits because the Holy Grail is to realize a NAND gate and then be able to do any kind of logic with that.

My question is: how does homomorphic encryption deal with conditions and jump operations? How could you calculate the nth item of a Fibonacci series recursively with a circuit?

Most of the manuals of FHE implementations don't talk about conditions and jumps. Is the idea that some instances do some preparation of the circuit before execution?

edited Mar 01 '20 at 12:54

Patriot

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asked Feb 17 '20 at 10:31

Robin

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Might me related Representing a function as FHE circuit. Due to the semantic security, you calculate both and combine them since the evaluator cannot know the jump. – kelalaka Feb 17 '20 at 13:02
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Also related: Can Fully Homomorphic Encryption do comparisons? – Geoffroy Couteau Feb 18 '20 at 08:28
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Unroll all loops, convert into circuit. There's nothing specific about FHE here. – Maeher Mar 01 '20 at 13:30
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@Robin: since you added a bounty to your question, can you explain why the two other questions linked to in the comments, and their answer, do not already answer your question? – Geoffroy Couteau Mar 03 '20 at 18:28
@GeoffroyCouteau: In my opinion it doesn't, but I think the question arose because of a misunderstanding on my side. Jumps are not handled directly within a circuit. – Robin Mar 07 '20 at 10:09

What's the deal with conditional and jump operations in homomorphic encryption?

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