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.