gistfile1.txt

import verificatum.eio.ByteTree;
import verificatum.eio.ByteTreeBasic;
import verificatum.eio.ByteTreeReader;
import verificatum.arithm.ModPGroup;
import verificatum.arithm.PGroup;
import verificatum.arithm.PGroupElement;
import verificatum.arithm.PGroupElementArray;
import verificatum.arithm.PPGroup;
import verificatum.arithm.PPGroupElement;
import verificatum.arithm.PRing;
import verificatum.arithm.PFieldElement;
import verificatum.arithm.PRingElement;
import verificatum.arithm.PRingElementArray;
import verificatum.crypto.RandomOracle;
import verificatum.crypto.CryptoKeyGen;
import verificatum.crypto.CryptoKeyGenCramerShoup;
import verificatum.crypto.CryptoKeyPair;
import verificatum.crypto.Hashfunction;
import verificatum.crypto.HashfunctionHeuristic;
import verificatum.crypto.PRG;
import verificatum.crypto.PRGHeuristic;
import verificatum.crypto.RandomSource;
import verificatum.protocol.mixnet.MixNetElGamalInterface;
import verificatum.protocol.mixnet.MixNetElGamalInterfaceNative;
import verificatum.eio.Marshalizer;
import verificatum.eio.Hex;

import org.apache.commons.codec.binary.Base64;


// https://github.com/benadida/js-voting-crypto/blob/master/lib/elgamal.js
// https://github.com/agoraciudadana/applet-verificatum/blob/master/src/org/agora/VotingApplet.java

public class Vote {
    protected static final String interfaceName = "native";        
    protected static final int certainty = 100;
    protected RandomSource mRandomSource = null;
    
    protected int mVote = -1;
    protected int mProposal = -1;
    protected PGroupElement mFullPublicKey = null;
    protected String mFullPublicKeyString = null;
    protected String mEncryptedVote = null;
    protected String mHash = null;
    protected String mAFactor = null;
    protected String mDFactor = null;
    protected String mUFactor = null;

    public Vote(int vote, int proposal, String publicKeyString) throws Exception {
        mVote = vote;
        mProposal = proposal;
        mFullPublicKeyString = publicKeyString;

        obtainPublicKey();
        encrypt();
    }

    // Obtain the public key for this proposal/voting
    protected void obtainPublicKey() throws Exception {
        // mFullPublicKey = MixNetElGamalInterface.stringToPublicKey(interfaceName, mFullPublicKeyString, mRandomSource, certainty);
        this.readPublicKey(mFullPublicKeyString, mRandomSource, certainty);
    }

    protected void encrypt() throws Exception {
        String plaintext = Integer.toString(mVote);

        // Recover key from input
        PGroupElement basicPublicKey =
            ((PPGroupElement)mFullPublicKey).project(0);
        PGroupElement publicKey =
            ((PPGroupElement)mFullPublicKey).project(1);

        PGroup basicPublicKeyPGroup = basicPublicKey.getPGroup();
        PGroup publicKeyPGroup = publicKey.getPGroup();

        // Get interface (added cast)
        MixNetElGamalInterfaceNative mixnetInterface =
            (MixNetElGamalInterfaceNative) MixNetElGamalInterface.getInterface(interfaceName);

        // Generate plaintext
        byte[] iBytes = plaintext.getBytes();
        PGroupElement a_plaintext = publicKeyPGroup.encode(iBytes, 0, iBytes.length);

        // Encrypt the result.
        PRG prg = new PRGHeuristic(); // this uses SecureRandom internally
        PRing randomizerPRing = basicPublicKeyPGroup.getPRing();

        PRingElement r = randomizerPRing.randomElement(prg, 20);

        PGroupElement u = basicPublicKey.exp(r);
        PGroupElement v = publicKey.exp(r).mul(a_plaintext);

        PGroupElement ciph =
            ((PPGroup)mFullPublicKey.getPGroup()).product(u, v);

        // set ciphertext using the format of the interface.
        mEncryptedVote = mixnetInterface.ciphertextToString(ciph);

        // Calculate hash and convert it to readable hex String
        RandomOracle ro = new RandomOracle(new HashfunctionHeuristic("SHA-256"), 2048);
        String HEXES = "0123456789abcdef";
        byte[] raw = ro.hash(mEncryptedVote.getBytes());
        StringBuilder hex = new StringBuilder(2 * raw.length);
        for (byte b : raw) {
            hex.append(HEXES.charAt((b & 0xF0) >> 4))
            .append(HEXES.charAt((b & 0x0F)));
        }
        mHash = hex.toString();


        // Create a verifiable proof of knowledge of the cleartext
        PRingElement s = randomizerPRing.randomElement(prg, 20);
        PGroupElement a = basicPublicKey.exp(s);
        // c = hash(prefix, g, u*v, a)
        ByteTree cTree = new ByteTree(
            new ByteTree(basicPublicKeyPGroup.toByteTree().toByteArray()),
            new ByteTree(ciph.toByteTree().toByteArray()),
            new ByteTree(a.toByteTree().toByteArray())
        );
        // ro = new RandomOracle(new HashfunctionHeuristic("SHA-256"), 2048, ByteTree.intToByteTree(mProposal));
        Hashfunction roHashfunction = Marshalizer.unmarshalAux_Hashfunction(ByteTree.intToByteTree(mProposal).getByteTreeReader(), mRandomSource, certainty);
                
        byte[] cHash = ro.hash(cTree.toByteArray());
        // d = cr+s
        prg.setSeed(cHash);
        PRingElement c = randomizerPRing.randomElement(prg, 20);
        PRingElement d = c.mul(r).add(s);

        mAFactor = encode(a.toByteTree().toByteArray());
        mDFactor = encode(d.toByteTree().toByteArray());
        mUFactor = encode(u.toByteTree().toByteArray());
    }

    public String getAFactor() {
        return mAFactor;
    }

    public String getDFactor() {
        return mDFactor;
    }

    public String getUFactor() {
        return mUFactor;
    }

    public int getVote() {
        return mVote;
    }

    public int getProposal() {
        return mProposal;
    }

    public String getEncryptedVote() {
        return mEncryptedVote;
    }

    public String getHash() {
        return mHash;
    }

    public String toString() {
        return "vote id = " + mVote + ", proposal id = " + mProposal;
    }
    
    // from mixnetinterfacenative
    private PGroupElement readPublicKey(String publicKeyString, RandomSource randomSource, int certainty) throws Exception {
        byte[] keyBytes = Hex.toByteArray(publicKeyString);
        ByteTreeReader btr =
            (new ByteTree(keyBytes, null)).getByteTreeReader();

        PGroup pGroup = Marshalizer.unmarshalAux_PGroup(btr.getNextChild(),
                                                        randomSource,
                                                        certainty);
        return (new PPGroup(pGroup, 2)).toElement(btr.getNextChild());
    }
    
    public static String encode(byte[] bytes) throws Exception {
        byte[] encoded = Base64.encodeBase64(bytes);
        return new String(encoded, "ASCII");
    }
    
    public static void main(String[] args) throws Exception {
        String publicKeyString = "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";
        Vote vote = new Vote(-1, 23, publicKeyString);        
        
        // String ballotStr = "0,1," + publicKeyString;
        // applet.vote(ballotStr, args[0]);
        return;
    }
 }