Fix the neff shuffle

[lbarman]

https://github.com/dedis/kyber/blob/master/shuffle/shuffle_test.go

[lbarman]

We need the kyber v2 library to support it on gopkg.in, then courtesy from Alejandro:

package main

import (
    "encoding/hex"
    "fmt"
    "github.com/dedis/kyber"
    "github.com/dedis/kyber/proof"
    "github.com/dedis/kyber/shuffle"
    "github.com/dedis/kyber/suites"
    "github.com/lbarman/prifi/prifi-lib/crypto"
    //"gopkg.in/dedis/kyber.v2"
    //"gopkg.in/dedis/kyber.v2/suites"
    //"gopkg.in/dedis/kyber.v2/proof/dleq"
)

func main() {
    //var err error
    var suite = suites.MustFind("Ed25519")
    rand := suite.RandomStream()
    k := 5
    N := 10

    H, h := crypto.NewKeyPair()

    c := make([]kyber.Scalar, k) //prv
    C := make([]kyber.Point, k)  // pbl

    for i := 0; i < k; i++ {
        C[i], c[i] = crypto.NewKeyPair()
    }

    X := make([]kyber.Point, k)
    Y := make([]kyber.Point, k)
    r := suite.Scalar() // temporary
    for i := 0; i < k; i++ {
        r.Pick(rand)
        X[i] = suite.Point().Mul(r, nil)
        Y[i] = suite.Point().Mul(r, H) // ElGamal blinding factor
        Y[i].Add(Y[i], C[i])           // Encrypted client public key
    }

    for i := 0; i < N; i++ {
        // Do a key-shuffle
        Xbar, Ybar, prover := shuffle.Shuffle(suite, nil, H, X, Y, rand)
        prf, err := proof.HashProve(suite, "PairShuffle", prover)
        if err != nil {
            panic("Shuffle proof failed: " + err.Error())
        }
        fmt.Printf("proof:\n%s\n", hex.Dump(prf))

        fmt.Printf("%v", h) // here to avoid golang yelling

        // Check it
        verifier := shuffle.Verifier(suite, nil, H, X, Y, Xbar, Ybar)
        err = proof.HashVerify(suite, "PairShuffle", verifier, prf)
        if err != nil {
            panic("Shuffle verify failed: " + err.Error())
        }
    }
}