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Replaced generic RandomOracle with explicit SHA-256 to make description of random oracle simpler for external verifiers

mixer
Tal Moran 2017-01-21 23:07:20 +02:00
parent 43d4fb75b2
commit 2744005263
8 changed files with 31 additions and 31 deletions
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11
mixer/src/main/java/meerkat/mixer/main/Mix.java
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@ -13,8 +13,6 @@ import meerkat.mixer.MixerOutput;
import meerkat.mixer.proofs.concrete.Mix2nizk;
import meerkat.protobuf.ConcreteCrypto;
import meerkat.protobuf.Crypto;
import org.factcenter.qilin.primitives.RandomOracle;
import org.factcenter.qilin.primitives.concrete.DigestOracle;
import org.factcenter.qilin.primitives.concrete.ECElGamal;
import org.factcenter.qilin.primitives.concrete.ECGroup;
import org.slf4j.Logger;
@ -30,17 +28,17 @@ import java.util.List;
import java.util.Random;
import static java.lang.System.exit;
import static java.lang.System.in;
/**
* Command-line mixProverVerifier and verifier.
*/
public class Mix {
final static String DEFAULT_ECGROUP = "secp256k1";
final static Logger logger = LoggerFactory.getLogger(Mix.class);
public Random rand;
public ECGroup group;
public ECElGamalEncryption enc;
public RandomOracle randomOracle;
public ConcreteCrypto.ElGamalPublicKey serializedPk;
public ECElGamal.SK secretKey;
public Mix2nizk mixProverVerifier;
@ -49,7 +47,6 @@ public class Mix {
public Mix() {
rand = new SecureRandom();
randomOracle = new DigestOracle();
enc = new ECElGamalEncryption();
serializedPk = null;
secretKey = null;
@ -108,7 +105,7 @@ public class Mix {
exit(-2);
}
mixProverVerifier = new Mix2nizk(rand, enc, randomOracle);
mixProverVerifier = new Mix2nizk(rand, enc);
}
/**
@ -117,7 +114,7 @@ public class Mix {
* @param outFile
*/
public void createKeypair(File outFile) throws IOException {
group = new ECGroup("secp256k1");
group = new ECGroup(DEFAULT_ECGROUP);
BigInteger sk = ECElGamal.generateSecretKey(group, rand);
secretKey = new ECElGamal.SK(group, sk);

6
mixer/src/main/java/meerkat/mixer/proofs/concrete/Mix2nizk.java
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@ -7,7 +7,6 @@ import meerkat.mixer.proofs.Mix2nizk.Verifier;
import meerkat.mixer.proofs.generic.SigmaFiatShamir;
import meerkat.protobuf.Crypto;
import meerkat.protobuf.Mixing;
import org.factcenter.qilin.primitives.RandomOracle;
import org.factcenter.qilin.primitives.concrete.ECGroup;
import java.util.Random;
@ -28,15 +27,14 @@ public class Mix2nizk implements Prover, Verifier {
/**
* @param rand
* @param encryptor
* @param randomOracle - use for Fiat–Shamir heuristic
*/
public Mix2nizk(Random rand, ECElGamalEncryption encryptor, RandomOracle randomOracle) {
public Mix2nizk(Random rand, ECElGamalEncryption encryptor) {
this.rand = rand;
this.encryptor = encryptor;
this.group = this.encryptor.getGroup();
this.mixParams = new Statements(encryptor);
this.mix2NIZK = new SigmaFiatShamir(ProtobufConcatenators.concatNIZK, randomOracle);
this.mix2NIZK = new SigmaFiatShamir(ProtobufConcatenators.concatNIZK);
}
/**

27
mixer/src/main/java/meerkat/mixer/proofs/generic/SigmaFiatShamir.java
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@ -3,20 +3,28 @@ package meerkat.mixer.proofs.generic;
import com.google.protobuf.Message;
import meerkat.mixer.proofs.Concatenator;
import meerkat.mixer.proofs.SigmaProtocol;
import org.factcenter.qilin.primitives.RandomOracle;
import java.math.BigInteger;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
/**
* Transform a Sigma protocol into a NIZK using Fiat-Shamir
* We use SHA-256 explicitly to make it easier to verify in other codebases
*/
public class SigmaFiatShamir<NIZKMsgType, FirstMsgType extends Message, FinalMessageType> {
final RandomOracle randomOracle;
final static String DIGEST_ALG = "SHA-256";
final MessageDigest md;
final Concatenator.Pair<NIZKMsgType, FirstMsgType, FinalMessageType> concat;
public SigmaFiatShamir(Concatenator.Pair<NIZKMsgType, FirstMsgType, FinalMessageType> concat, RandomOracle randomOracle) {
public SigmaFiatShamir(Concatenator.Pair<NIZKMsgType, FirstMsgType, FinalMessageType> concat) {
this.concat = concat;
this.randomOracle = randomOracle;
try {
md = MessageDigest.getInstance(DIGEST_ALG);
} catch (NoSuchAlgorithmException e) {
// Should never happen
throw new RuntimeException("Error in instantiating " + DIGEST_ALG + " digest", e);
}
}
/**
@ -24,21 +32,24 @@ public class SigmaFiatShamir<NIZKMsgType, FirstMsgType extends Message, FinalMes
* @param input - protobuf contains all parameters from the first step of the current proof
* @return randomOracle.hash(input)
*/
public static BigInteger hash(Message input, RandomOracle randomOracle) {
public BigInteger hash(Message input) {
md.reset();
byte[] arr = input.toByteArray();
return new BigInteger(1,randomOracle.hash(arr,arr.length));
byte[] digest = md.digest(arr);
return new BigInteger(1,digest);
}
public NIZKMsgType generateNizk(SigmaProtocol.Prover<FirstMsgType, FinalMessageType> prover) {
FirstMsgType firstMessage = prover.getFirstMessage();
BigInteger challenge = hash(firstMessage, randomOracle);
BigInteger challenge = hash(firstMessage);
FinalMessageType finalMessage = prover.getFinalMessage(challenge);
return concat.concatenate(firstMessage, finalMessage);
}
public boolean verifyNizk(NIZKMsgType NIZK, SigmaProtocol.Verifier<FirstMsgType, FinalMessageType> verifier) {
FirstMsgType firstMessage = concat.getMsg1(NIZK);
BigInteger challenge = hash(firstMessage, randomOracle);
BigInteger challenge = hash(firstMessage);
return verifier.verify(firstMessage, challenge, concat.getMsg2(NIZK));
}
}

1
mixer/src/test/java/meerkat/mixer/ECParamTestBase.java
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@ -21,7 +21,6 @@ public class ECParamTestBase {
public ECElGamal.SK key;
public ECGroup group;
public ECElGamalEncryption enc;
public RandomOracle randomOracle = new DigestOracle();
public ConcreteCrypto.ElGamalPublicKey serializedPk;
public ECParamTestBase() {

2
mixer/src/test/java/meerkat/mixer/MixingTest.java
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@ -29,7 +29,7 @@ public class MixingTest extends ECParamTestBase {
random = new Random(1);
randomMixer = new Random(2);
randomProver = new Random(3);
mix2nizk = new Mix2nizk(randomProver, enc,randomOracle);
mix2nizk = new Mix2nizk(randomProver, enc);
mixer = new MixGenerator(mix2nizk, enc);
// generate n

8
mixer/src/test/java/meerkat/mixer/proofs/SigmaProtocolTest.java
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@ -2,8 +2,6 @@ package meerkat.mixer.proofs;
import com.google.protobuf.Message;
import meerkat.mixer.proofs.generic.SigmaFiatShamir;
import org.factcenter.qilin.primitives.RandomOracle;
import org.factcenter.qilin.primitives.concrete.DigestOracle;
import org.factcenter.qilin.util.Pair;
import org.junit.Before;
import org.junit.Test;
@ -11,7 +9,7 @@ import org.junit.Test;
import java.math.BigInteger;
import java.util.Random;
import static org.junit.Assert.*;
import static org.junit.Assert.assertTrue;
/**
* Generic test for Sigma Protocol
@ -19,8 +17,6 @@ import static org.junit.Assert.*;
abstract public class SigmaProtocolTest<M1 extends Message, M2> {
public final int NUM_REPEAT = 10;
final protected RandomOracle randomOracle = new DigestOracle();
abstract protected void generateRandomTrueStatement();
abstract protected void generateRandomFalseStatement();
@ -97,7 +93,7 @@ abstract public class SigmaProtocolTest<M1 extends Message, M2> {
for (int i = 0; i < NUM_REPEAT; ++i) {
generateRandomTrueStatement();
SigmaFiatShamir<Pair<M1,M2>, M1, M2> fiatShamir = new SigmaFiatShamir<Pair<M1,M2>, M1, M2>(nizkConcat, randomOracle);
SigmaFiatShamir<Pair<M1,M2>, M1, M2> fiatShamir = new SigmaFiatShamir<Pair<M1,M2>, M1, M2>(nizkConcat);
prover = getNewProver();
Pair<M1,M2> nizk = fiatShamir.generateNizk(prover);

2
mixer/src/test/java/meerkat/mixer/proofs/concrete/Mix2ProofTest.java
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@ -26,7 +26,7 @@ public class Mix2ProofTest extends ECParamTestBase {
@Before
public void setup() throws Exception {
nizk = new Mix2nizk(rand, enc, randomOracle);
nizk = new Mix2nizk(rand, enc);
verifier = nizk;
prover = nizk;
}

5
mixer/src/test/java/profiling/ZeroKnowledgeProof.java
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@ -35,15 +35,14 @@ public class ZeroKnowledgeProof {
Crypto.RerandomizableEncryptedMessage[] reencryptedMessage;
public void setup() throws Exception {
rand = new Random();
rand = new Random(1);
group = new ECGroup("secp256k1");
BigInteger sk = ECElGamal.generateSecretKey(group, rand);
key = new ECElGamal.SK(group, sk);
serializedPk = Util.encodePK(group, key);
enc = new ECElGamalEncryption();
enc.init(serializedPk);
RandomOracle randomOracle = new DigestOracle();
prover = new Mix2nizk(new Random(),enc,randomOracle);
prover = new Mix2nizk(rand,enc);
int LogVotes = 12;
int layers = 2*LogVotes - 1;
n = layers * (1<<LogVotes) / 2;