Introduction to Bulletproofs
Bulletproofs are non-interactive zero-knowledge proof protocols that require no trusted setup. They are particularly efficient for proving statements about committed values, such as range proofs (proving a value lies within a specific range without revealing the value itself). This makes them invaluable for confidential transactions in blockchain systems.
Prerequisites
- Java 11 or later
- Understanding of cryptography concepts (elliptic curves, commitments, zero-knowledge proofs)
- Basic knowledge of finite field arithmetic
Step 1: Project Setup and Dependencies
Maven Configuration (pom.xml)
<properties>
<maven.compiler.source>11</maven.compiler.source>
<maven.compiler.target>11</maven.compiler.target>
<bouncycastle.version>1.75</bouncycastle.version>
<apache.commons.version>3.13.0</apache.commons.version>
</properties>
<dependencies>
<!-- Bouncy Castle for cryptographic primitives -->
<dependency>
<groupId>org.bouncycastle</groupId>
<artifactId>bcprov-jdk18on</artifactId>
<version>${bouncycastle.version}</version>
</dependency>
<!-- Apache Commons for utilities -->
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>${apache.commons.version}</version>
</dependency>
<!-- For JSON processing -->
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-databind</artifactId>
<version>2.15.2</version>
</dependency>
<!-- Logging -->
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>2.0.7</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-simple</artifactId>
<version>2.0.7</version>
</dependency>
<!-- Testing -->
<dependency>
<groupId>org.junit.jupiter</groupId>
<artifactId>junit-jupiter</artifactId>
<version>5.9.3</version>
<scope>test</scope>
</dependency>
</dependencies>
Step 2: Cryptographic Primitives and Utilities
Elliptic Curve Point Implementation
package com.example.bulletproofs.crypto;
import org.bouncycastle.jce.ECNamedCurveTable;
import org.bouncycastle.jce.spec.ECParameterSpec;
import org.bouncycastle.math.ec.ECCurve;
import org.bouncycastle.math.ec.ECPoint;
import java.math.BigInteger;
import java.security.SecureRandom;
import java.util.Objects;
/**
* Represents an elliptic curve point with operations needed for Bulletproofs
*/
public class ECPointWrapper {
private final ECPoint point;
private final ECParameterSpec curveSpec;
private final ECCurve curve;
private final BigInteger fieldSize;
private static final SecureRandom random = new SecureRandom();
private static final String CURVE_NAME = "secp256k1";
public ECParameterSpec getCurveSpec() {
return curveSpec;
}
public ECCurve getCurve() {
return curve;
}
public BigInteger getFieldSize() {
return fieldSize;
}
public ECPointWrapper(ECPoint point, ECParameterSpec curveSpec) {
this.point = point;
this.curveSpec = curveSpec;
this.curve = curveSpec.getCurve();
this.fieldSize = curve.getField().getCharacteristic();
}
public static ECParameterSpec getDefaultCurve() {
return ECNamedCurveTable.getParameterSpec(CURVE_NAME);
}
public static ECPointWrapper getGenerator() {
ECParameterSpec curveSpec = getDefaultCurve();
return new ECPointWrapper(curveSpec.getG(), curveSpec);
}
public static ECPointWrapper fromBytes(byte[] data, ECParameterSpec curveSpec) {
ECPoint point = curveSpec.getCurve().decodePoint(data);
return new ECPointWrapper(point, curveSpec);
}
public ECPointWrapper multiply(BigInteger scalar) {
return new ECPointWrapper(point.multiply(scalar), curveSpec);
}
public ECPointWrapper add(ECPointWrapper other) {
if (!this.curveSpec.equals(other.curveSpec)) {
throw new IllegalArgumentException("Points are on different curves");
}
return new ECPointWrapper(point.add(other.point), curveSpec);
}
public ECPointWrapper subtract(ECPointWrapper other) {
if (!this.curveSpec.equals(other.curveSpec)) {
throw new IllegalArgumentException("Points are on different curves");
}
return new ECPointWrapper(point.subtract(other.point), curveSpec);
}
public byte[] toBytes() {
return point.getEncoded(true);
}
public boolean equals(ECPointWrapper other) {
return this.point.equals(other.point);
}
public static BigInteger randomScalar(ECParameterSpec curveSpec) {
BigInteger n = curveSpec.getN();
BigInteger result;
do {
result = new BigInteger(n.bitLength(), random);
} while (result.compareTo(n) >= 0 || result.equals(BigInteger.ZERO));
return result;
}
@Override
public String toString() {
return "ECPoint[" + point.toString() + "]";
}
}
Pedersen Commitment Scheme
package com.example.bulletproofs.crypto;
import java.math.BigInteger;
/**
* Implementation of Pedersen commitments
* Com(msg, blinding) = G*msg + H*blinding
*/
public class PedersenCommitment {
private final ECPointWrapper generatorG;
private final ECPointWrapper generatorH;
private final ECParameterSpec curveSpec;
public PedersenCommitment(ECPointWrapper generatorG, ECPointWrapper generatorH) {
if (!generatorG.getCurveSpec().equals(generatorH.getCurveSpec())) {
throw new IllegalArgumentException("Generators must be on the same curve");
}
this.generatorG = generatorG;
this.generatorH = generatorH;
this.curveSpec = generatorG.getCurveSpec();
}
public static PedersenCommitment createDefault() {
ECParameterSpec curveSpec = ECPointWrapper.getDefaultCurve();
ECPointWrapper G = ECPointWrapper.getGenerator();
// Create a random generator H (in practice, this should be generated verifiably)
BigInteger hScalar = ECPointWrapper.randomScalar(curveSpec);
ECPointWrapper H = G.multiply(hScalar);
return new PedersenCommitment(G, H);
}
public Commitment commit(BigInteger value, BigInteger blindingFactor) {
ECPointWrapper commitmentPoint = generatorG.multiply(value)
.add(generatorH.multiply(blindingFactor));
return new Commitment(commitmentPoint, value, blindingFactor);
}
public boolean verify(Commitment commitment) {
ECPointWrapper recomputed = generatorG.multiply(commitment.getValue())
.add(generatorH.multiply(commitment.getBlindingFactor()));
return recomputed.equals(commitment.getCommitmentPoint());
}
public static class Commitment {
private final ECPointWrapper commitmentPoint;
private final BigInteger value;
private final BigInteger blindingFactor;
public Commitment(ECPointWrapper commitmentPoint, BigInteger value, BigInteger blindingFactor) {
this.commitmentPoint = commitmentPoint;
this.value = value;
this.blindingFactor = blindingFactor;
}
public ECPointWrapper getCommitmentPoint() { return commitmentPoint; }
public BigInteger getValue() { return value; }
public BigInteger getBlindingFactor() { return blindingFactor; }
public byte[] toBytes() { return commitmentPoint.toBytes(); }
}
}
Step 3: Core Bulletproofs Implementation
Inner Product Proof (Core of Bulletproofs)
package com.example.bulletproofs.core;
import com.example.bulletproofs.crypto.ECPointWrapper;
import com.example.bulletproofs.crypto.PedersenCommitment;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.List;
/**
* Inner Product Proof implementation - the core component of Bulletproofs
*/
public class InnerProductProof {
private final List<ECPointWrapper> L;
private final List<ECPointWrapper> R;
private final BigInteger a;
private final BigInteger b;
public InnerProductProof(List<ECPointWrapper> L, List<ECPointWrapper> R, BigInteger a, BigInteger b) {
this.L = L;
this.R = R;
this.a = a;
this.b = b;
}
public List<ECPointWrapper> getL() { return L; }
public List<ECPointWrapper> getR() { return R; }
public BigInteger getA() { return a; }
public BigInteger getB() { return b; }
public static class Prover {
private final PedersenCommitment pedersen;
private final ECParameterSpec curveSpec;
public Prover(PedersenCommitment pedersen) {
this.pedersen = pedersen;
this.curveSpec = pedersen.getGeneratorG().getCurveSpec();
}
public InnerProductProof prove(List<BigInteger> a, List<BigInteger> b,
ECPointWrapper P, ECPointWrapper U) {
int n = a.size();
if (n != b.size() || (n & (n - 1)) != 0) {
throw new IllegalArgumentException("Vectors must have same power-of-two length");
}
List<ECPointWrapper> L = new ArrayList<>();
List<ECPointWrapper> R = new ArrayList<>();
List<BigInteger> aCurrent = new ArrayList<>(a);
List<BigInteger> bCurrent = new ArrayList<>(b);
ECPointWrapper PCurrent = P;
while (aCurrent.size() > 1) {
int m = aCurrent.size() / 2;
// Split vectors
List<BigInteger> aLeft = aCurrent.subList(0, m);
List<BigInteger> aRight = aCurrent.subList(m, aCurrent.size());
List<BigInteger> bLeft = bCurrent.subList(0, m);
List<BigInteger> bRight = bCurrent.subList(m, bCurrent.size());
// Compute cross terms
BigInteger cL = innerProduct(aLeft, bRight);
BigInteger cR = innerProduct(aRight, bLeft);
// Compute L and R
ECPointWrapper GL = computeG(aRight);
ECPointWrapper GR = computeG(aLeft);
ECPointWrapper HL = computeH(bRight);
ECPointWrapper HR = computeH(bLeft);
ECPointWrapper LPoint = GL.multiply(cL)
.add(HR.multiply(cL))
.add(U.multiply(cL));
ECPointWrapper RPoint = GR.multiply(cR)
.add(HL.multiply(cR))
.add(U.multiply(cR));
L.add(LPoint);
R.add(RPoint);
// Generate random challenge
BigInteger x = generateChallenge(PCurrent, LPoint, RPoint);
BigInteger xInv = x.modInverse(curveSpec.getN());
// Update vectors and P
aCurrent = vectorAdd(vectorScale(aLeft, x), vectorScale(aRight, xInv));
bCurrent = vectorAdd(vectorScale(bLeft, xInv), vectorScale(bRight, x));
PCurrent = LPoint.multiply(x.multiply(x))
.add(PCurrent)
.add(RPoint.multiply(xInv.multiply(xInv)));
}
return new InnerProductProof(L, R, aCurrent.get(0), bCurrent.get(0));
}
private BigInteger innerProduct(List<BigInteger> a, List<BigInteger> b) {
BigInteger result = BigInteger.ZERO;
for (int i = 0; i < a.size(); i++) {
result = result.add(a.get(i).multiply(b.get(i))).mod(curveSpec.getN());
}
return result;
}
private ECPointWrapper computeG(List<BigInteger> coefficients) {
ECPointWrapper result = pedersen.getGeneratorG().multiply(BigInteger.ZERO);
for (int i = 0; i < coefficients.size(); i++) {
// This is simplified - actual implementation would use proper generator vector
ECPointWrapper term = pedersen.getGeneratorG().multiply(coefficients.get(i));
result = result.add(term);
}
return result;
}
private ECPointWrapper computeH(List<BigInteger> coefficients) {
ECPointWrapper result = pedersen.getGeneratorH().multiply(BigInteger.ZERO);
for (int i = 0; i < coefficients.size(); i++) {
// This is simplified - actual implementation would use proper generator vector
ECPointWrapper term = pedersen.getGeneratorH().multiply(coefficients.get(i));
result = result.add(term);
}
return result;
}
private List<BigInteger> vectorScale(List<BigInteger> vector, BigInteger scalar) {
List<BigInteger> result = new ArrayList<>();
for (BigInteger value : vector) {
result.add(value.multiply(scalar).mod(curveSpec.getN()));
}
return result;
}
private List<BigInteger> vectorAdd(List<BigInteger> a, List<BigInteger> b) {
List<BigInteger> result = new ArrayList<>();
for (int i = 0; i < a.size(); i++) {
result.add(a.get(i).add(b.get(i)).mod(curveSpec.getN()));
}
return result;
}
private BigInteger generateChallenge(ECPointWrapper P, ECPointWrapper L, ECPointWrapper R) {
// In practice, this should use a proper hash function like SHA256
byte[] data = new byte[0];
// data = concat(P.toBytes(), L.toBytes(), R.toBytes());
// return new BigInteger(1, hash(data)).mod(curveSpec.getN());
return ECPointWrapper.randomScalar(curveSpec); // Simplified for example
}
}
}
Range Proof Implementation
package com.example.bulletproofs.core;
import com.example.bulletproofs.crypto.ECPointWrapper;
import com.example.bulletproofs.crypto.PedersenCommitment;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.List;
/**
* Bulletproofs range proof implementation
* Proves that a committed value lies within a specific range [0, 2^n - 1]
*/
public class RangeProof {
private final ECPointWrapper A;
private final ECPointWrapper S;
private final ECPointWrapper T1;
private final ECPointWrapper T2;
private final BigInteger taux;
private final BigInteger mu;
private final InnerProductProof innerProductProof;
private final BigInteger a;
private final BigInteger b;
public RangeProof(ECPointWrapper A, ECPointWrapper S, ECPointWrapper T1, ECPointWrapper T2,
BigInteger taux, BigInteger mu, InnerProductProof innerProductProof,
BigInteger a, BigInteger b) {
this.A = A;
this.S = S;
this.T1 = T1;
this.T2 = T2;
this.taux = taux;
this.mu = mu;
this.innerProductProof = innerProductProof;
this.a = a;
this.b = b;
}
public static class Prover {
private final PedersenCommitment pedersen;
private final int bitLength;
public Prover(PedersenCommitment pedersen, int bitLength) {
this.pedersen = pedersen;
this.bitLength = bitLength;
}
public RangeProof prove(BigInteger value, BigInteger blindingFactor) {
// Step 1: Convert value to binary representation
List<BigInteger> aL = toBinaryVector(value, bitLength);
List<BigInteger> aR = computeAR(aL);
// Step 2: Generate random commitments
BigInteger alpha = ECPointWrapper.randomScalar(pedersen.getGeneratorG().getCurveSpec());
BigInteger rho = ECPointWrapper.randomScalar(pedersen.getGeneratorG().getCurveSpec());
ECPointWrapper A = pedersen.commit(value, blindingFactor).getCommitmentPoint();
// Additional commitments S, T1, T2 would be computed here
// Step 3: Generate challenges (simplified)
BigInteger y = generateYChallenge(A);
BigInteger z = generateZChallenge(A, y);
// Step 4: Compute polynomial coefficients
List<BigInteger> lPoly = computeLPoly(aL, aR, y, z);
List<BigInteger> rPoly = computeRPoly(aL, aR, y, z);
// Step 5: Compute inner product proof
BigInteger t = innerProduct(lPoly, rPoly);
BigInteger tau1 = ECPointWrapper.randomScalar(pedersen.getGeneratorG().getCurveSpec());
BigInteger tau2 = ECPointWrapper.randomScalar(pedersen.getGeneratorG().getCurveSpec());
ECPointWrapper T1 = pedersen.getGeneratorG().multiply(tau1);
ECPointWrapper T2 = pedersen.getGeneratorG().multiply(tau2);
// Step 6: Generate inner product proof
InnerProductProof.Prover innerProver = new InnerProductProof.Prover(pedersen);
InnerProductProof innerProof = innerProver.prove(lPoly, rPoly, A, T1); // Simplified
BigInteger taux = tau1.add(tau2).mod(pedersen.getGeneratorG().getCurveSpec().getN());
BigInteger mu = alpha.add(rho).mod(pedersen.getGeneratorG().getCurveSpec().getN());
return new RangeProof(A, A, T1, T2, taux, mu, innerProof,
innerProduct(lPoly, lPoly), innerProduct(rPoly, rPoly));
}
private List<BigInteger> toBinaryVector(BigInteger value, int length) {
List<BigInteger> result = new ArrayList<>();
for (int i = 0; i < length; i++) {
result.add(value.testBit(i) ? BigInteger.ONE : BigInteger.ZERO);
}
return result;
}
private List<BigInteger> computeAR(List<BigInteger> aL) {
List<BigInteger> aR = new ArrayList<>();
for (BigInteger bit : aL) {
aR.add(bit.subtract(BigInteger.ONE));
}
return aR;
}
private List<BigInteger> computeLPoly(List<BigInteger> aL, List<BigInteger> aR,
BigInteger y, BigInteger z) {
List<BigInteger> lPoly = new ArrayList<>();
BigInteger yPower = BigInteger.ONE;
for (int i = 0; i < aL.size(); i++) {
BigInteger term = aL.get(i).subtract(z).multiply(yPower).mod(pedersen.getGeneratorG().getCurveSpec().getN());
lPoly.add(term);
yPower = yPower.multiply(y).mod(pedersen.getGeneratorG().getCurveSpec().getN());
}
return lPoly;
}
private List<BigInteger> computeRPoly(List<BigInteger> aL, List<BigInteger> aR,
BigInteger y, BigInteger z) {
List<BigInteger> rPoly = new ArrayList<>();
BigInteger yPower = BigInteger.ONE;
BigInteger two = BigInteger.valueOf(2);
BigInteger zSquare = z.multiply(z);
BigInteger zTwoN = zSquare.multiply(two.pow(aL.size()));
for (int i = 0; i < aR.size(); i++) {
BigInteger term = aR.get(i).add(z)
.multiply(yPower)
.add(zSquare.multiply(two.pow(i)))
.mod(pedersen.getGeneratorG().getCurveSpec().getN());
rPoly.add(term);
yPower = yPower.multiply(y).mod(pedersen.getGeneratorG().getCurveSpec().getN());
}
return rPoly;
}
private BigInteger innerProduct(List<BigInteger> a, List<BigInteger> b) {
BigInteger result = BigInteger.ZERO;
BigInteger mod = pedersen.getGeneratorG().getCurveSpec().getN();
for (int i = 0; i < a.size(); i++) {
result = result.add(a.get(i).multiply(b.get(i))).mod(mod);
}
return result;
}
private BigInteger generateYChallenge(ECPointWrapper A) {
// Simplified challenge generation
return ECPointWrapper.randomScalar(pedersen.getGeneratorG().getCurveSpec());
}
private BigInteger generateZChallenge(ECPointWrapper A, BigInteger y) {
// Simplified challenge generation
return ECPointWrapper.randomScalar(pedersen.getGeneratorG().getCurveSpec());
}
}
public static class Verifier {
private final PedersenCommitment pedersen;
private final int bitLength;
public Verifier(PedersenCommitment pedersen, int bitLength) {
this.pedersen = pedersen;
this.bitLength = bitLength;
}
public boolean verify(RangeProof proof, ECPointWrapper commitment) {
try {
// Step 1: Recompute challenges
BigInteger y = generateYChallenge(proof.A);
BigInteger z = generateZChallenge(proof.A, y);
// Step 2: Verify inner product proof
// This would involve reconstructing the commitment
// and verifying the inner product proof structure
// Step 3: Verify the range proof structure
ECPointWrapper P = reconstructP(proof, y, z);
// Simplified verification - actual implementation would be more complex
return verifyInnerProduct(proof.innerProductProof, P);
} catch (Exception e) {
return false;
}
}
private ECPointWrapper reconstructP(RangeProof proof, BigInteger y, BigInteger z) {
// Simplified reconstruction - actual implementation would be more complex
return proof.A.add(proof.S.multiply(y));
}
private boolean verifyInnerProduct(InnerProductProof proof, ECPointWrapper P) {
// Simplified inner product verification
// Actual implementation would properly verify the inner product proof
BigInteger computed = proof.getA().multiply(proof.getB())
.mod(pedersen.getGeneratorG().getCurveSpec().getN());
// Check if the inner product matches some expected value
return computed.compareTo(BigInteger.ZERO) > 0;
}
private BigInteger generateYChallenge(ECPointWrapper A) {
return ECPointWrapper.randomScalar(pedersen.getGeneratorG().getCurveSpec());
}
private BigInteger generateZChallenge(ECPointWrapper A, BigInteger y) {
return ECPointWrapper.randomScalar(pedersen.getGeneratorG().getCurveSpec());
}
}
}
Step 4: Service Layer and API
Bulletproofs Service
package com.example.bulletproofs.service;
import com.example.bulletproofs.core.RangeProof;
import com.example.bulletproofs.crypto.ECPointWrapper;
import com.example.bulletproofs.crypto.PedersenCommitment;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Service;
import java.math.BigInteger;
@Service
public class BulletproofsService {
private static final Logger logger = LoggerFactory.getLogger(BulletproofsService.class);
private final PedersenCommitment pedersen;
private final int defaultBitLength = 64; // Prove range [0, 2^64 - 1]
public BulletproofsService() {
this.pedersen = PedersenCommitment.createDefault();
logger.info("Bulletproofs service initialized with default parameters");
}
public BulletproofsService(PedersenCommitment pedersen, int bitLength) {
this.pedersen = pedersen;
logger.info("Bulletproofs service initialized with custom parameters");
}
public ProofResult generateRangeProof(BigInteger value, BigInteger blindingFactor) {
try {
RangeProof.Prover prover = new RangeProof.Prover(pedersen, defaultBitLength);
// Create commitment
PedersenCommitment.Commitment commitment = pedersen.commit(value, blindingFactor);
// Generate range proof
RangeProof proof = prover.prove(value, blindingFactor);
logger.info("Generated range proof for value: {}", value);
return new ProofResult(proof, commitment.toBytes(), value, blindingFactor);
} catch (Exception e) {
logger.error("Failed to generate range proof", e);
throw new RuntimeException("Proof generation failed", e);
}
}
public boolean verifyRangeProof(byte[] commitmentBytes, RangeProof proof) {
try {
ECPointWrapper commitment = ECPointWrapper.fromBytes(
commitmentBytes,
pedersen.getGeneratorG().getCurveSpec()
);
RangeProof.Verifier verifier = new RangeProof.Verifier(pedersen, defaultBitLength);
boolean isValid = verifier.verify(proof, commitment);
logger.info("Range proof verification result: {}", isValid);
return isValid;
} catch (Exception e) {
logger.error("Failed to verify range proof", e);
return false;
}
}
public static class ProofResult {
private final RangeProof proof;
private final byte[] commitment;
private final BigInteger value;
private final BigInteger blindingFactor;
public ProofResult(RangeProof proof, byte[] commitment,
BigInteger value, BigInteger blindingFactor) {
this.proof = proof;
this.commitment = commitment;
this.value = value;
this.blindingFactor = blindingFactor;
}
// Getters
public RangeProof getProof() { return proof; }
public byte[] getCommitment() { return commitment; }
public BigInteger getValue() { return value; }
public BigInteger getBlindingFactor() { return blindingFactor; }
}
}
Step 5: REST API Controller
Bulletproofs REST API
package com.example.bulletproofs.controller;
import com.example.bulletproofs.core.RangeProof;
import com.example.bulletproofs.service.BulletproofsService;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.*;
import java.math.BigInteger;
import java.util.Base64;
import java.util.HashMap;
import java.util.Map;
@RestController
@RequestMapping("/api/bulletproofs")
public class BulletproofsController {
private static final Logger logger = LoggerFactory.getLogger(BulletproofsController.class);
private final BulletproofsService bulletproofsService;
public BulletproofsController(BulletproofsService bulletproofsService) {
this.bulletproofsService = bulletproofsService;
}
@PostMapping("/prove")
public ResponseEntity<Map<String, Object>> generateProof(
@RequestBody ProofRequest request) {
try {
BigInteger value = new BigInteger(request.getValue());
BigInteger blindingFactor = new BigInteger(request.getBlindingFactor());
var result = bulletproofsService.generateRangeProof(value, blindingFactor);
Map<String, Object> response = new HashMap<>();
response.put("success", true);
response.put("commitment", Base64.getEncoder().encodeToString(result.getCommitment()));
response.put("value", result.getValue().toString());
response.put("proofId", generateProofId(result.getCommitment()));
logger.info("Generated proof for value: {}", result.getValue());
return ResponseEntity.ok(response);
} catch (Exception e) {
logger.error("Proof generation failed", e);
return ResponseEntity.badRequest().body(Map.of(
"success", false,
"error", e.getMessage()
));
}
}
@PostMapping("/verify")
public ResponseEntity<Map<String, Object>> verifyProof(
@RequestBody VerifyRequest request) {
try {
byte[] commitment = Base64.getDecoder().decode(request.getCommitment());
// In a real implementation, you would deserialize the proof from the request
// RangeProof proof = deserializeProof(request.getProof());
// For this example, we'll simulate verification
boolean isValid = bulletproofsService.verifyRangeProof(commitment, null);
Map<String, Object> response = new HashMap<>();
response.put("success", true);
response.put("valid", isValid);
response.put("commitment", request.getCommitment());
logger.info("Proof verification result: {}", isValid);
return ResponseEntity.ok(response);
} catch (Exception e) {
logger.error("Proof verification failed", e);
return ResponseEntity.badRequest().body(Map.of(
"success", false,
"error", e.getMessage()
));
}
}
@GetMapping("/parameters")
public ResponseEntity<Map<String, Object>> getParameters() {
Map<String, Object> params = new HashMap<>();
params.put("curve", "secp256k1");
params.put("maxBits", 64);
params.put("protocol", "Bulletproofs");
params.put("trustedSetup", "None required");
return ResponseEntity.ok(params);
}
private String generateProofId(byte[] commitment) {
return Base64.getEncoder().encodeToString(commitment).substring(0, 16);
}
// Request DTOs
public static class ProofRequest {
private String value;
private String blindingFactor;
// Getters and setters
public String getValue() { return value; }
public void setValue(String value) { this.value = value; }
public String getBlindingFactor() { return blindingFactor; }
public void setBlindingFactor(String blindingFactor) { this.blindingFactor = blindingFactor; }
}
public static class VerifyRequest {
private String commitment;
private String proof;
// Getters and setters
public String getCommitment() { return commitment; }
public void setCommitment(String commitment) { this.commitment = commitment; }
public String getProof() { return proof; }
public void setProof(String proof) { this.proof = proof; }
}
}
Step 6: Testing and Examples
Unit Tests
package com.example.bulletproofs.test;
import com.example.bulletproofs.core.RangeProof;
import com.example.bulletproofs.crypto.ECPointWrapper;
import com.example.bulletproofs.crypto.PedersenCommitment;
import com.example.bulletproofs.service.BulletproofsService;
import org.junit.jupiter.api.Test;
import java.math.BigInteger;
import static org.junit.jupiter.api.Assertions.*;
class BulletproofsTest {
@Test
void testPedersenCommitment() {
PedersenCommitment pedersen = PedersenCommitment.createDefault();
BigInteger value = BigInteger.valueOf(12345);
BigInteger blinding = BigInteger.valueOf(67890);
var commitment = pedersen.commit(value, blinding);
assertTrue(pedersen.verify(commitment));
}
@Test
void testRangeProofGeneration() {
BulletproofsService service = new BulletproofsService();
BigInteger value = BigInteger.valueOf(5000);
BigInteger blinding = ECPointWrapper.randomScalar(ECPointWrapper.getDefaultCurve());
var result = service.generateRangeProof(value, blinding);
assertNotNull(result);
assertNotNull(result.getProof());
assertNotNull(result.getCommitment());
}
@Test
void testRangeProofVerification() {
BulletproofsService service = new BulletproofsService();
BigInteger value = BigInteger.valueOf(1000);
BigInteger blinding = ECPointWrapper.randomScalar(ECPointWrapper.getDefaultCurve());
var result = service.generateRangeProof(value, blinding);
boolean isValid = service.verifyRangeProof(result.getCommitment(), result.getProof());
assertTrue(isValid, "Range proof should be valid");
}
}
Example Usage
package com.example.bulletproofs.example;
import com.example.bulletproofs.crypto.ECPointWrapper;
import com.example.bulletproofs.crypto.PedersenCommitment;
import com.example.bulletproofs.service.BulletproofsService;
import java.math.BigInteger;
public class BulletproofsExample {
public static void main(String[] args) {
// Initialize service
BulletproofsService service = new BulletproofsService();
// Example values
BigInteger secretValue = BigInteger.valueOf(1000000); // $1,000,000
BigInteger blindingFactor = ECPointWrapper.randomScalar(ECPointWrapper.getDefaultCurve());
System.out.println("Generating range proof for value: " + secretValue);
// Generate proof
var result = service.generateRangeProof(secretValue, blindingFactor);
System.out.println("Proof generated successfully!");
System.out.println("Commitment: " +
java.util.Base64.getEncoder().encodeToString(result.getCommitment()));
// Verify proof
boolean isValid = service.verifyRangeProof(result.getCommitment(), result.getProof());
System.out.println("Proof verification: " + (isValid ? "VALID" : "INVALID"));
System.out.println("Value is proven to be in range [0, 2^64-1] without revealing the actual value!");
}
}
Security Considerations
- Random Number Generation: Always use cryptographically secure random number generators
- Side-Channel Attacks: Implement constant-time algorithms where necessary
- Parameter Validation: Validate all inputs to prevent invalid curve attacks
- Memory Management: Securely wipe sensitive data from memory
- Audit Trail: Log all proof generations and verifications for security monitoring
Performance Optimizations
- Batch Verification: Verify multiple proofs simultaneously
- Caching: Cache generator points and precomputed values
- Parallel Processing: Use parallel streams for vector operations
- Memory Pooling: Reuse objects to reduce garbage collection
This implementation provides a foundation for using Bulletproofs in Java applications. Note that this is a simplified version for educational purposes - production implementations would require more robust error handling, proper serialization, and comprehensive security reviews.