Comment by sillysaurusx
Comment by sillysaurusx 4 days ago
I was going to make my usual comment of FHE being nice in theory but too slow in practice, and then the article points out that there’s now SHE (somewhat homomorphic encryption). I wasn’t aware that the security guarantees of FHE could be relaxed without sacrificing them. That’s pretty cool.
Is there any concrete info about noise budgets? It seems like that’s the critical concern, and I’d like to understand at what point precisely the security breaks down if you have too little (or too much?) noise.
SHE vs FHE has nothing to do with security. Instead, it’s about how many operations (eg homomorphic multiplications and additions) can be performed before the correctness of the scheme fails due to too much noise accumulating in the ciphertext. Indeed all FHE schemes are also SHE schemes.
What typically makes FHE expensive computationally is a “bootstrapping” step for removing the noise that accumulated after X operations and threatening correctness. After bootstrapping you can do another X operations. Rinse and repeat until you finish the computation to you want to perform.