how fhe works.

Fully homomorphic encryption lets you add and multiply encrypted numbers and get back an encrypted result. Since any computation is just adds and multiplies, you can run a whole model on ciphertext — and only the key holder ever sees the answer.

the catch, honestly

FHE is slower than plaintext compute — roughly a lot. Void's whole engineering job is hiding that cost with faster hardware, better bootstrapping, and batching. The proof time you see on the benchmarks is that work, in public.