ot

Oblivious Transfer

This module implements the Oblivous Transfer with the following algorithms:

• RSA: simple RSA encryption based OT. Each transfer requires one RSA operation.
• Chou Orlandi OT: Diffie-Hellman - like fast OT algorithm.

Pure CO helpers

The CO implementation now exposes pure helper functions so applications can prepare, encrypt, and decrypt OT payloads without depending on the streaming IO API. Use:

1. GenerateCOSenderSetup to sample the sender's randomness and public point.
2. EncryptCOCiphertexts to turn Wire labels and evaluator points into OT ciphertexts.
3. BuildCOChoices to build evaluator curve points deterministically from the sender's public key.
4. DecryptCOCiphertexts to decode the evaluator's chosen labels.

These helpers accept any io.Reader for randomness, which makes deterministic testing straightforward. The streaming CO type is now a small wrapper around the same helpers, so both styles always share the exact same cryptographic core.

Performance

goos: darwin
goarch: amd64
pkg: github.com/markkurossi/mpc/ot
cpu: Intel(R) Core(TM) i5-8257U CPU @ 1.40GHz

Algorithm	ns/op	ops/s
RSA-2048	8,086,829	124
CO	152,745	6,545
COT semi-honest	3,007	332,600
COT malicious	3,703	270,000

IKNP OT Extension

The COTSender and COTReceiver implement correlated OT with the IKNP protocol.

TODO

• malicious IKNP
• COT send / receive
• random send / receive
• rename COTSender and COTReceiver to IKNPSender and IKNPReceiver
• new COTSender and COTReceiver for correlated OT send and receive
• new ROTSender and ROTReceiver for random OT send and receive
• SoftSpokenOT