sha2pc

sha2pc

sha2pc is a pure-Go two-party protocol that privately computes SHA256(XOR(a, b)) for two 32-byte inputs. The package exposes round handlers that return explicit Go structs, so callers can exchange the typed payloads (Round1Payload, Round2Payload, etc.) using any transport they like (sockets, gRPC, files, etc.).

Example

package main

import (
	crand "crypto/rand"
	"fmt"
	"log"

	"github.com/markkurossi/mpc/sha2pc"
)

func main() {
	var a, b [32]byte
	for i := 0; i < len(a); i++ {
		a[i] = byte(i)
		b[i] = byte(len(a) - i)
	}

	msg1, gState, err := sha2pc.GarblerRound1(crand.Reader, sha2pc.CurveP256)
	if err != nil {
		log.Fatalf("round1: %v", err)
	}
	fmt.Printf("Round1: curve=%s\n", msg1.OT.CurveName)

	msg2, eState, err := sha2pc.EvaluatorRound2(crand.Reader, sha2pc.CurveP256, msg1, b)
	if err != nil {
		log.Fatalf("round2: %v", err)
	}
	fmt.Printf("Round2: choices=%d\n", len(msg2.Choices))

	msg3, err := sha2pc.GarblerRound3(crand.Reader, sha2pc.CurveP256, gState, a, msg2)
	if err != nil {
		log.Fatalf("round3: %v", err)
	}
	fmt.Printf("Round3: ciphertexts=%d tables=%d\n", len(msg3.Ciphertexts), len(msg3.GarbledTables))

	hashEval, err := sha2pc.EvaluatorRound4(sha2pc.CurveP256, eState, msg3)
	if err != nil {
		log.Fatalf("round4: %v", err)
	}

	fmt.Printf("Evaluator hash: %x\n", hashEval)
}