alt Hacker Newscan you build a conditional swap in FHE in a small size though? FHE is always circuit like, ie no dynamic control flow anyway I think?
can you build a conditional swap in FHE in a small size though? FHE is always circuit like, ie no dynamic control flow anyway I think?
Once you calculate which value is smaller, the conditional swap itself is trivial. Let's say inputs A and B, comparison result is a boolean C. Outputs X and Y.
Bitwise: X = A&C | B&¬C, Y = A&¬C | B&C
Arithmetic: X = A*C + B*(1-C), Y = A*(1-C) + B*C
Edit: Or to put it another way, one of the most basic things you can make in a circuit is a multiplexer, and a conditional swap is two minimum size multiplexers next to each other.