MACRO NEPAL
BLS Signatures in Java: Complete Implementation Guide
awiskar acharya
March 6, 2026
8:49 am

Introduction to BLS Signatures

BLS (Boneh-Lynn-Shacham) signatures are a cryptographic signature scheme that enables signature aggregation and verification. They are widely used in blockchain applications, consensus protocols, and distributed systems due to their unique properties:

  • Signature Aggregation: Multiple signatures can be combined into a single signature
  • Key Aggregation: Multiple public keys can be combined
  • Deterministic: Same message always produces the same signature
  • Short Signatures: Signatures are very compact
  • Threshold Signatures: Enable m-of-n signing schemes

Architecture Overview

graph TB
subgraph "BLS Core Components"
SK[Secret Key]
PK[Public Key]
SIG[Signature]
VER[Verification]
AGG[Aggregation]
end
subgraph "Elliptic Curve Operations"
G1[G1 Group - Signatures]
G2[G2 Group - Public Keys]
GT[GT Group - Pairings]
end
subgraph "Applications"
TH[Threshold Signatures]
MU[Multi-Signature]
AG[Aggregate Signatures]
end
SK --> PK
PK --> VER
SK --> SIG
SIG --> VER
SIG --> AGG
AGG --> AG
AGG --> MU
AGG --> TH
style SK fill:#f9f,stroke:#333,stroke-width:2px
style PK fill:#bbf,stroke:#333,stroke-width:2px
style SIG fill:#bfb,stroke:#333,stroke-width:2px

Core Dependencies

<properties>
<bouncycastle.version>1.77</bouncycastle.version>
<milagro.version>3.0.0</milagro.version>
<herumi.version>1.0.0</herumi.version>
</properties>
<dependencies>
<!-- Bouncy Castle for cryptography -->
<dependency>
<groupId>org.bouncycastle</groupId>
<artifactId>bcprov-jdk18on</artifactId>
<version>${bouncycastle.version}</version>
</dependency>
<dependency>
<groupId>org.bouncycastle</groupId>
<artifactId>bcpkix-jdk18on</artifactId>
<version>${bouncycastle.version}</version>
</dependency>
<!-- Milagro for BLS implementation -->
<dependency>
<groupId>org.apache.milagro</groupId>
<artifactId>milagro-crypto-java</artifactId>
<version>${milagro.version}</version>
</dependency>
<!-- Herumi BLS (optional) -->
<dependency>
<groupId>com.herumi</groupId>
<artifactId>bls-java</artifactId>
<version>${herumi.version}</version>
</dependency>
<!-- For SHA-256/512 hashing -->
<dependency>
<groupId>commons-codec</groupId>
<artifactId>commons-codec</artifactId>
<version>1.16.0</version>
</dependency>
<!-- For serialization -->
<dependency>
<groupId>com.google.protobuf</groupId>
<artifactId>protobuf-java</artifactId>
<version>3.25.1</version>
</dependency>
</dependencies>

Core BLS Implementation

BLS Parameters and Curve Configuration

package com.bls.crypto;
import org.bouncycastle.crypto.CryptoException;
import org.bouncycastle.math.ec.ECPoint;
import org.bouncycastle.util.encoders.Hex;
import java.math.BigInteger;
import java.security.SecureRandom;
import java.util.Arrays;
public class BLSParameters {
// BLS12-381 curve parameters (standard for BLS signatures)
public static final BigInteger CURVE_ORDER = new BigInteger(
"73eda753299d7d483339d80809a1d80553bda402fffe5bfeffffffff00000001", 16
);
public static final BigInteger FIELD_MODULUS = new BigInteger(
"1a0111ea397fe69a4b1ba7b6434bacd764774b84f38512bf6730d2a0f6b0f6241eabfffeb153ffffb9feffffffffaaab", 16
);
public static final String CURVE_NAME = "BLS12-381";
public static final int SECURITY_LEVEL = 128; // bits
// Domain separation tags
public static final byte[] DST_G1 = "BLS_SIG_BLS12381G1_XMD:SHA-256_SSWU_RO_".getBytes();
public static final byte[] DST_G2 = "BLS_SIG_BLS12381G2_XMD:SHA-256_SSWU_RO_".getBytes();
// Ciphersuite IDs
public static final String CIPHERSUITE_BLS12381G1 = 
"BLS_SIG_BLS12381G1_XMD:SHA-256_SSWU_RO_NUL_";
public static final String CIPHERSUITE_BLS12381G2 = 
"BLS_SIG_BLS12381G2_XMD:SHA-256_SSWU_RO_NUL_";
// Key lengths in bytes
public static final int SECRET_KEY_LENGTH = 32;
public static final int PUBLIC_KEY_LENGTH_G1 = 48;  // Compressed
public static final int PUBLIC_KEY_LENGTH_G2 = 96;  // Compressed
public static final int SIGNATURE_LENGTH = 96;      // Compressed G1
public static final int AGGREGATED_SIG_LENGTH = 96; // Same as signature
private BLSParameters() {
// Utility class
}
}

BLS Secret Key

package com.bls.crypto;
import org.bouncycastle.crypto.CryptoException;
import org.bouncycastle.crypto.digests.SHA256Digest;
import org.bouncycastle.crypto.generators.HKDFBytesGenerator;
import org.bouncycastle.crypto.params.HKDFParameters;
import java.math.BigInteger;
import java.security.SecureRandom;
import java.util.Arrays;
import java.util.Objects;
public class BLSSecretKey {
private final BigInteger scalar;
private byte[] keyMaterial;
private static final SecureRandom SECURE_RANDOM = new SecureRandom();
public BLSSecretKey() {
// Generate random secret key
this.scalar = generateRandomScalar();
this.keyMaterial = scalar.toByteArray();
}
public BLSSecretKey(byte[] ikm) {
// Key derivation using HKDF
this.scalar = deriveKey(ikm);
this.keyMaterial = scalar.toByteArray();
}
public BLSSecretKey(BigInteger scalar) {
if (scalar.compareTo(BigInteger.ZERO) <= 0 || 
scalar.compareTo(BLSParameters.CURVE_ORDER) >= 0) {
throw new IllegalArgumentException("Invalid scalar value");
}
this.scalar = scalar;
this.keyMaterial = scalar.toByteArray();
}
private BigInteger generateRandomScalar() {
byte[] randomBytes = new byte[BLSParameters.SECRET_KEY_LENGTH];
SECURE_RANDOM.nextBytes(randomBytes);
return deriveKey(randomBytes);
}
private BigInteger deriveKey(byte[] ikm) {
// HKDF-Extract and Expand to get valid scalar
HKDFBytesGenerator hkdf = new HKDFBytesGenerator(new SHA256Digest());
hkdf.init(new HKDFParameters(ikm, null, null));
byte[] okm = new byte[BLSParameters.SECRET_KEY_LENGTH];
hkdf.generateBytes(okm, 0, okm.length);
// Convert to scalar modulo curve order
BigInteger scalar = new BigInteger(1, okm);
return scalar.mod(BLSParameters.CURVE_ORDER);
}
public BLSPublicKey derivePublicKey() {
return new BLSPublicKey(this);
}
public BigInteger getScalar() {
return scalar;
}
public byte[] toBytes() {
return keyMaterial.clone();
}
public static BLSSecretKey fromBytes(byte[] bytes) {
return new BLSSecretKey(new BigInteger(1, bytes));
}
public byte[] sign(byte[] message) {
return sign(message, BLSParameters.DST_G1);
}
public byte[] sign(byte[] message, byte[] dst) {
// Hash message to G1
byte[] hash = hashToG1(message, dst);
// Multiply by secret key scalar
return scalarMult(hash, scalar);
}
private native byte[] scalarMult(byte[] point, BigInteger scalar);
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
BLSSecretKey that = (BLSSecretKey) o;
return scalar.equals(that.scalar);
}
@Override
public int hashCode() {
return Objects.hash(scalar);
}
@Override
public String toString() {
return "BLSSecretKey{" +
"scalar=" + scalar.toString(16).substring(0, 16) + "...}";
}
}

BLS Public Key

package com.bls.crypto;
import org.bouncycastle.math.ec.ECPoint;
import org.bouncycastle.util.encoders.Hex;
import java.math.BigInteger;
import java.util.Arrays;
import java.util.Objects;
public class BLSPublicKey {
private final byte[] point; // Compressed G2 point
public BLSPublicKey(BLSSecretKey secretKey) {
// g^sk where g is generator of G2
this.point = generatePublicKey(secretKey.getScalar());
}
public BLSPublicKey(byte[] compressedPoint) {
validatePublicKey(compressedPoint);
this.point = compressedPoint.clone();
}
private native byte[] generatePublicKey(BigInteger scalar);
private void validatePublicKey(byte[] compressedPoint) {
if (compressedPoint.length != BLSParameters.PUBLIC_KEY_LENGTH_G2) {
throw new IllegalArgumentException("Invalid public key length");
}
// Additional validation (ensure point is on curve, not identity, etc.)
if (!isValidPoint(compressedPoint)) {
throw new IllegalArgumentException("Invalid public key point");
}
}
private native boolean isValidPoint(byte[] compressedPoint);
public boolean verify(byte[] message, byte[] signature) {
return verify(message, signature, BLSParameters.DST_G1);
}
public boolean verify(byte[] message, byte[] signature, byte[] dst) {
// e(g, sig) == e(pk, H(msg))
return verifyPairing(point, signature, hashToG1(message, dst));
}
private native boolean verifyPairing(byte[] pk, byte[] sig, byte[] hash);
public byte[] toBytes() {
return point.clone();
}
public static BLSPublicKey fromBytes(byte[] bytes) {
return new BLSPublicKey(bytes);
}
public String toHex() {
return Hex.toHexString(point);
}
public static BLSPublicKey fromHex(String hex) {
return new BLSPublicKey(Hex.decode(hex));
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
BLSPublicKey that = (BLSPublicKey) o;
return Arrays.equals(point, that.point);
}
@Override
public int hashCode() {
return Arrays.hashCode(point);
}
@Override
public String toString() {
return "BLSPublicKey{" +
"point=" + Hex.toHexString(point).substring(0, 16) + "...}";
}
}

BLS Signature

package com.bls.crypto;
import org.bouncycastle.util.encoders.Hex;
import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.Objects;
public class BLSSignature {
private final byte[] point; // Compressed G1 point
public BLSSignature(byte[] compressedPoint) {
validateSignature(compressedPoint);
this.point = compressedPoint.clone();
}
private void validateSignature(byte[] compressedPoint) {
if (compressedPoint.length != BLSParameters.SIGNATURE_LENGTH) {
throw new IllegalArgumentException("Invalid signature length");
}
// Additional validation (ensure point is on curve, not identity, etc.)
if (!isValidPoint(compressedPoint)) {
throw new IllegalArgumentException("Invalid signature point");
}
}
private native boolean isValidPoint(byte[] compressedPoint);
public boolean verify(BLSPublicKey publicKey, byte[] message) {
return publicKey.verify(message, point);
}
public boolean verify(BLSPublicKey publicKey, byte[] message, byte[] dst) {
return publicKey.verify(message, point, dst);
}
public byte[] toBytes() {
return point.clone();
}
public static BLSSignature fromBytes(byte[] bytes) {
return new BLSSignature(bytes);
}
public String toHex() {
return Hex.toHexString(point);
}
public static BLSSignature fromHex(String hex) {
return new BLSSignature(Hex.decode(hex));
}
public BLSSignature add(BLSSignature other) {
// Add two signatures (elliptic curve point addition)
byte[] sum = pointAddition(this.point, other.point);
return new BLSSignature(sum);
}
private native byte[] pointAddition(byte[] a, byte[] b);
public static BLSSignature aggregate(List<BLSSignature> signatures) {
if (signatures == null || signatures.isEmpty()) {
throw new IllegalArgumentException("No signatures to aggregate");
}
// Start with first signature
BLSSignature result = signatures.get(0);
// Add all other signatures
for (int i = 1; i < signatures.size(); i++) {
result = result.add(signatures.get(i));
}
return result;
}
public static boolean verifyAggregate(List<BLSSignature> signatures, 
List<BLSPublicKey> publicKeys,
List<byte[]> messages) {
if (signatures.size() != publicKeys.size() || 
signatures.size() != messages.size()) {
throw new IllegalArgumentException("List sizes must match");
}
// Verify all signatures individually
for (int i = 0; i < signatures.size(); i++) {
if (!signatures.get(i).verify(publicKeys.get(i), messages.get(i))) {
return false;
}
}
return true;
}
public static boolean verifyAggregateSameMessage(BLSSignature aggregatedSig,
List<BLSPublicKey> publicKeys,
byte[] message) {
// Verify aggregated signature for same message
// e(g, sig) == e(pk1 * pk2 * ... * pkn, H(msg))
BLSPublicKey aggregatedKey = BLSPublicKey.aggregate(publicKeys);
return aggregatedKey.verify(message, aggregatedSig.toBytes());
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
BLSSignature that = (BLSSignature) o;
return Arrays.equals(point, that.point);
}
@Override
public int hashCode() {
return Arrays.hashCode(point);
}
@Override
public String toString() {
return "BLSSignature{" +
"point=" + Hex.toHexString(point).substring(0, 16) + "...}";
}
}

JNI Bridge for Native BLS Operations

package com.bls.nativebridge;
public class BLSJNI {
static {
// Load native library
System.loadLibrary("bls_jni");
}
// Core operations
public static native byte[] hashToG1(byte[] message, byte[] dst);
public static native byte[] hashToG2(byte[] message, byte[] dst);
// G1 operations
public static native byte[] g1Generator();
public static native byte[] g1ScalarMult(byte[] point, byte[] scalar);
public static native byte[] g1Add(byte[] a, byte[] b);
public static native boolean g1IsValid(byte[] point);
public static native byte[] g1Negate(byte[] point);
public static native byte[] g1Serialize(byte[] point);
public static native byte[] g1Deserialize(byte[] data);
// G2 operations
public static native byte[] g2Generator();
public static native byte[] g2ScalarMult(byte[] point, byte[] scalar);
public static native byte[] g2Add(byte[] a, byte[] b);
public static native boolean g2IsValid(byte[] point);
public static native byte[] g2Negate(byte[] point);
public static native byte[] g2Serialize(byte[] point);
public static native byte[] g2Deserialize(byte[] data);
// Pairing operations
public static native byte[] pairing(byte[] g1Point, byte[] g2Point);
public static native boolean verifyPairing(byte[] g1Sig, byte[] g2Pk, byte[] g1Hash);
// Key derivation
public static native byte[] deriveKey(byte[] ikm, byte[] salt, byte[] info);
// Curve parameters
public static native byte[] getCurveOrder();
public static native byte[] getFieldModulus();
}

Complete BLS Implementation with Aggregation

package com.bls.core;
import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.SecureRandom;
import java.util.*;
public class BLS {
private static final SecureRandom SECURE_RANDOM = new SecureRandom();
public static class KeyPair {
private final BLSSecretKey secretKey;
private final BLSPublicKey publicKey;
public KeyPair() {
this.secretKey = new BLSSecretKey();
this.publicKey = secretKey.derivePublicKey();
}
public KeyPair(byte[] seed) {
this.secretKey = new BLSSecretKey(seed);
this.publicKey = secretKey.derivePublicKey();
}
public BLSSecretKey getSecretKey() {
return secretKey;
}
public BLSPublicKey getPublicKey() {
return publicKey;
}
}
public static byte[] sign(BLSSecretKey sk, byte[] message) {
return sk.sign(message);
}
public static byte[] sign(BLSSecretKey sk, byte[] message, byte[] dst) {
return sk.sign(message, dst);
}
public static boolean verify(BLSPublicKey pk, byte[] message, byte[] signature) {
return pk.verify(message, signature);
}
public static BLSSignature aggregateSignatures(List<BLSSignature> signatures) {
return BLSSignature.aggregate(signatures);
}
public static BLSPublicKey aggregatePublicKeys(List<BLSPublicKey> publicKeys) {
return BLSPublicKey.aggregate(publicKeys);
}
public static boolean verifyAggregate(List<BLSSignature> signatures,
List<BLSPublicKey> publicKeys,
List<byte[]> messages) {
return BLSSignature.verifyAggregate(signatures, publicKeys, messages);
}
public static boolean verifyAggregateSameMessage(BLSSignature aggregatedSig,
List<BLSPublicKey> publicKeys,
byte[] message) {
return BLSSignature.verifyAggregateSameMessage(aggregatedSig, publicKeys, message);
}
public static KeyPair generateDeterministicKeyPair(byte[] seed) {
return new KeyPair(seed);
}
public static byte[] hashToG1(byte[] message) {
return hashToG1(message, BLSParameters.DST_G1);
}
public static native byte[] hashToG1(byte[] message, byte[] dst);
public static byte[] hashToG2(byte[] message) {
return hashToG2(message, BLSParameters.DST_G2);
}
public static native byte[] hashToG2(byte[] message, byte[] dst);
}

Threshold BLS Signatures

package com.bls.threshold;
import com.bls.core.*;
import java.math.BigInteger;
import java.util.*;
public class ThresholdBLS {
private final int threshold;
private final int totalParticipants;
private final Map<Integer, BLSSecretKey> participantKeys;
private final Map<Integer, BLSPublicKey> participantPublicKeys;
public ThresholdBLS(int threshold, int totalParticipants) {
if (threshold > totalParticipants) {
throw new IllegalArgumentException("Threshold cannot exceed total participants");
}
this.threshold = threshold;
this.totalParticipants = totalParticipants;
this.participantKeys = new HashMap<>();
this.participantPublicKeys = new HashMap<>();
}
public static class SharedSecret {
private final BigInteger secret;
private final List<ShamirShare> shares;
public SharedSecret(BigInteger secret, List<ShamirShare> shares) {
this.secret = secret;
this.shares = shares;
}
public BigInteger getSecret() { return secret; }
public List<ShamirShare> getShares() { return shares; }
}
public static class ShamirShare {
private final int index;
private final BigInteger value;
public ShamirShare(int index, BigInteger value) {
this.index = index;
this.value = value;
}
public int getIndex() { return index; }
public BigInteger getValue() { return value; }
}
public SharedSecret generateSharedSecret() {
BigInteger secret = new BigInteger(BLSParameters.SECRET_KEY_LENGTH * 8, 
new java.security.SecureRandom());
List<ShamirShare> shares = generateShamirShares(secret);
return new SharedSecret(secret, shares);
}
private List<ShamirShare> generateShamirShares(BigInteger secret) {
// Generate random polynomial of degree threshold-1
List<BigInteger> coefficients = new ArrayList<>();
coefficients.add(secret);
for (int i = 1; i < threshold; i++) {
coefficients.add(new BigInteger(BLSParameters.SECRET_KEY_LENGTH * 8, 
new java.security.SecureRandom()));
}
// Evaluate polynomial at points 1..totalParticipants
List<ShamirShare> shares = new ArrayList<>();
for (int x = 1; x <= totalParticipants; x++) {
BigInteger y = evaluatePolynomial(coefficients, BigInteger.valueOf(x));
shares.add(new ShamirShare(x, y));
}
return shares;
}
private BigInteger evaluatePolynomial(List<BigInteger> coefficients, BigInteger x) {
BigInteger result = BigInteger.ZERO;
BigInteger power = BigInteger.ONE;
for (BigInteger coeff : coefficients) {
result = result.add(coeff.multiply(power)).mod(BLSParameters.CURVE_ORDER);
power = power.multiply(x).mod(BLSParameters.CURVE_ORDER);
}
return result;
}
public void distributeShares(List<ShamirShare> shares) {
for (ShamirShare share : shares) {
BLSSecretKey sk = new BLSSecretKey(share.value);
participantKeys.put(share.index, sk);
participantPublicKeys.put(share.index, sk.derivePublicKey());
}
}
public byte[] signParticipant(int participantId, byte[] message) {
BLSSecretKey sk = participantKeys.get(participantId);
if (sk == null) {
throw new IllegalArgumentException("Participant not found: " + participantId);
}
return sk.sign(message);
}
public byte[] aggregateThresholdSignatures(Map<Integer, byte[]> signatures, 
byte[] message) {
if (signatures.size() < threshold) {
throw new IllegalArgumentException("Insufficient signatures: need " + 
threshold + ", have " + signatures.size());
}
// Lagrange interpolation to reconstruct master signature
List<Integer> indices = new ArrayList<>(signatures.keySet());
// Compute Lagrange coefficients for each participant
Map<Integer, BigInteger> coefficients = computeLagrangeCoefficients(indices);
// Combine signatures using coefficients
byte[] aggregated = null;
for (Map.Entry<Integer, byte[]> entry : signatures.entrySet()) {
int id = entry.getKey();
byte[] sig = entry.getValue();
// Multiply signature by Lagrange coefficient
byte[] weighted = scalarMultiplySignature(sig, coefficients.get(id));
if (aggregated == null) {
aggregated = weighted;
} else {
aggregated = addSignatures(aggregated, weighted);
}
}
return aggregated;
}
private Map<Integer, BigInteger> computeLagrangeCoefficients(List<Integer> indices) {
Map<Integer, BigInteger> coefficients = new HashMap<>();
for (int i : indices) {
BigInteger coeff = BigInteger.ONE;
BigInteger xi = BigInteger.valueOf(i);
for (int j : indices) {
if (j != i) {
BigInteger xj = BigInteger.valueOf(j);
// coeff *= (0 - xj) / (xi - xj)
BigInteger numerator = BigInteger.ZERO.subtract(xj);
BigInteger denominator = xi.subtract(xj);
BigInteger term = numerator.multiply(denominator.modInverse(
BLSParameters.CURVE_ORDER)).mod(BLSParameters.CURVE_ORDER);
coeff = coeff.multiply(term).mod(BLSParameters.CURVE_ORDER);
}
}
coefficients.put(i, coeff);
}
return coefficients;
}
private native byte[] scalarMultiplySignature(byte[] signature, BigInteger scalar);
private native byte[] addSignatures(byte[] a, byte[] b);
public BLSPublicKey getMasterPublicKey() {
// Master public key = g^secret
return aggregatePublicKeys(new ArrayList<>(participantPublicKeys.values()));
}
public boolean verifyThresholdSignature(byte[] signature, byte[] message) {
BLSPublicKey masterPK = getMasterPublicKey();
return masterPK.verify(message, signature);
}
}

Multi-Signature Scheme

package com.bls.multisig;
import com.bls.core.*;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
public class BLSMultiSignature {
private final Map<String, Signer> signers;
private final Map<String, byte[]> pendingSignatures;
public BLSMultiSignature() {
this.signers = new ConcurrentHashMap<>();
this.pendingSignatures = new ConcurrentHashMap<>();
}
public static class Signer {
private final String id;
private final BLSSecretKey secretKey;
private final BLSPublicKey publicKey;
public Signer(String id) {
this.id = id;
this.secretKey = new BLSSecretKey();
this.publicKey = secretKey.derivePublicKey();
}
public Signer(String id, byte[] seed) {
this.id = id;
this.secretKey = new BLSSecretKey(seed);
this.publicKey = secretKey.derivePublicKey();
}
public String getId() { return id; }
public BLSSecretKey getSecretKey() { return secretKey; }
public BLSPublicKey getPublicKey() { return publicKey; }
public byte[] sign(byte[] message) {
return secretKey.sign(message);
}
}
public Signer addSigner(String id) {
Signer signer = new Signer(id);
signers.put(id, signer);
return signer;
}
public Signer addSigner(String id, byte[] seed) {
Signer signer = new Signer(id, seed);
signers.put(id, signer);
return signer;
}
public void requestSignatures(String requestId, byte[] message, List<String> signerIds) {
pendingSignatures.clear();
for (String id : signerIds) {
Signer signer = signers.get(id);
if (signer != null) {
byte[] signature = signer.sign(message);
pendingSignatures.put(id, signature);
}
}
}
public MultiSignatureResult aggregateSignatures(String message) {
List<BLSSignature> signatures = new ArrayList<>();
List<BLSPublicKey> publicKeys = new ArrayList<>();
for (Map.Entry<String, byte[]> entry : pendingSignatures.entrySet()) {
signatures.add(new BLSSignature(entry.getValue()));
publicKeys.add(signers.get(entry.getKey()).getPublicKey());
}
BLSSignature aggregated = BLSSignature.aggregate(signatures);
BLSPublicKey aggregatedKey = BLSPublicKey.aggregate(publicKeys);
return new MultiSignatureResult(aggregated, aggregatedKey, signatures.size());
}
public static class MultiSignatureResult {
private final BLSSignature signature;
private final BLSPublicKey aggregatedKey;
private final int participantCount;
public MultiSignatureResult(BLSSignature signature, BLSPublicKey aggregatedKey,
int participantCount) {
this.signature = signature;
this.aggregatedKey = aggregatedKey;
this.participantCount = participantCount;
}
public BLSSignature getSignature() { return signature; }
public BLSPublicKey getAggregatedKey() { return aggregatedKey; }
public int getParticipantCount() { return participantCount; }
public boolean verify(byte[] message) {
return signature.verify(aggregatedKey, message);
}
}
public boolean verifyIndividualSignatures(byte[] message) {
for (Map.Entry<String, byte[]> entry : pendingSignatures.entrySet()) {
Signer signer = signers.get(entry.getKey());
if (!signer.getPublicKey().verify(message, entry.getValue())) {
return false;
}
}
return true;
}
public Map<String, byte[]> getPendingSignatures() {
return Collections.unmodifiableMap(pendingSignatures);
}
public void clearPending() {
pendingSignatures.clear();
}
}

Proof-of-Possession (PoP) for BLS

package com.bls.pop;
import com.bls.core.*;
import java.nio.charset.StandardCharsets;
import java.util.*;
public class BLSPoP {
private static final byte[] POP_DST = "BLS_POP_BLS12381G1_XMD:SHA-256_SSWU_RO_".getBytes();
public static class PoPKeyPair {
private final BLSSecretKey secretKey;
private final BLSPublicKey publicKey;
private final byte[] proofOfPossession;
public PoPKeyPair() {
this.secretKey = new BLSSecretKey();
this.publicKey = secretKey.derivePublicKey();
this.proofOfPossession = generateProof(secretKey, publicKey);
}
public PoPKeyPair(byte[] seed) {
this.secretKey = new BLSSecretKey(seed);
this.publicKey = secretKey.derivePublicKey();
this.proofOfPossession = generateProof(secretKey, publicKey);
}
public BLSSecretKey getSecretKey() { return secretKey; }
public BLSPublicKey getPublicKey() { return publicKey; }
public byte[] getProofOfPossession() { return proofOfPossession.clone(); }
private byte[] generateProof(BLSSecretKey sk, BLSPublicKey pk) {
// Sign the public key to prove possession of secret key
byte[] message = pk.toBytes();
return sk.sign(message, POP_DST);
}
}
public static boolean verifyPoP(BLSPublicKey publicKey, byte[] proof) {
byte[] message = publicKey.toBytes();
return publicKey.verify(message, proof, POP_DST);
}
public static Set<BLSPublicKey> filterValidPoPs(Map<BLSPublicKey, byte[]> proofs) {
Set<BLSPublicKey> valid = new HashSet<>();
for (Map.Entry<BLSPublicKey, byte[]> entry : proofs.entrySet()) {
if (verifyPoP(entry.getKey(), entry.getValue())) {
valid.add(entry.getKey());
}
}
return valid;
}
public static class PoPRegistry {
private final Map<String, PoPKeyPair> registeredKeys;
private final Map<String, byte[]> proofs;
public PoPRegistry() {
this.registeredKeys = new HashMap<>();
this.proofs = new HashMap<>();
}
public PoPKeyPair register(String id) {
PoPKeyPair keyPair = new PoPKeyPair();
registeredKeys.put(id, keyPair);
proofs.put(id, keyPair.getProofOfPossession());
return keyPair;
}
public boolean verifyRegistration(String id) {
PoPKeyPair keyPair = registeredKeys.get(id);
if (keyPair == null) return false;
byte[] proof = proofs.get(id);
return verifyPoP(keyPair.getPublicKey(), proof);
}
public BLSPublicKey getPublicKey(String id) {
PoPKeyPair keyPair = registeredKeys.get(id);
return keyPair != null ? keyPair.getPublicKey() : null;
}
public List<BLSPublicKey> getAllValidPublicKeys() {
List<BLSPublicKey> valid = new ArrayList<>();
for (String id : registeredKeys.keySet()) {
if (verifyRegistration(id)) {
valid.add(registeredKeys.get(id).getPublicKey());
}
}
return valid;
}
public void revoke(String id) {
registeredKeys.remove(id);
proofs.remove(id);
}
}
}

BLS Serialization

package com.bls.serialization;
import com.bls.core.*;
import com.google.protobuf.ByteString;
import java.io.*;
public class BLSSerializer {
public static byte[] serializeKeyPair(BLS.KeyPair keyPair) {
try (ByteArrayOutputStream baos = new ByteArrayOutputStream();
DataOutputStream dos = new DataOutputStream(baos)) {
byte[] skBytes = keyPair.getSecretKey().toBytes();
byte[] pkBytes = keyPair.getPublicKey().toBytes();
dos.writeInt(skBytes.length);
dos.write(skBytes);
dos.writeInt(pkBytes.length);
dos.write(pkBytes);
return baos.toByteArray();
} catch (IOException e) {
throw new RuntimeException("Failed to serialize key pair", e);
}
}
public static BLS.KeyPair deserializeKeyPair(byte[] data) {
try (ByteArrayInputStream bais = new ByteArrayInputStream(data);
DataInputStream dis = new DataInputStream(bais)) {
int skLen = dis.readInt();
byte[] skBytes = new byte[skLen];
dis.readFully(skBytes);
int pkLen = dis.readInt();
byte[] pkBytes = new byte[pkLen];
dis.readFully(pkBytes);
BLSSecretKey sk = BLSSecretKey.fromBytes(skBytes);
BLSPublicKey pk = BLSPublicKey.fromBytes(pkBytes);
return new BLS.KeyPair(sk, pk);
} catch (IOException e) {
throw new RuntimeException("Failed to deserialize key pair", e);
}
}
public static class AggregatedSignature {
private final BLSSignature signature;
private final List<BLSPublicKey> publicKeys;
private final List<byte[]> messages;
public AggregatedSignature(BLSSignature signature, List<BLSPublicKey> publicKeys,
List<byte[]> messages) {
this.signature = signature;
this.publicKeys = publicKeys;
this.messages = messages;
}
public BLSSignature getSignature() { return signature; }
public List<BLSPublicKey> getPublicKeys() { return publicKeys; }
public List<byte[]> getMessages() { return messages; }
public byte[] serialize() {
try (ByteArrayOutputStream baos = new ByteArrayOutputStream();
DataOutputStream dos = new DataOutputStream(baos)) {
// Write signature
byte[] sigBytes = signature.toBytes();
dos.writeInt(sigBytes.length);
dos.write(sigBytes);
// Write number of participants
dos.writeInt(publicKeys.size());
// Write each public key
for (BLSPublicKey pk : publicKeys) {
byte[] pkBytes = pk.toBytes();
dos.writeInt(pkBytes.length);
dos.write(pkBytes);
}
// Write each message
for (byte[] msg : messages) {
dos.writeInt(msg.length);
dos.write(msg);
}
return baos.toByteArray();
} catch (IOException e) {
throw new RuntimeException("Failed to serialize aggregated signature", e);
}
}
public static AggregatedSignature deserialize(byte[] data) {
try (ByteArrayInputStream bais = new ByteArrayInputStream(data);
DataInputStream dis = new DataInputStream(bais)) {
// Read signature
int sigLen = dis.readInt();
byte[] sigBytes = new byte[sigLen];
dis.readFully(sigBytes);
BLSSignature signature = BLSSignature.fromBytes(sigBytes);
// Read number of participants
int numParticipants = dis.readInt();
List<BLSPublicKey> publicKeys = new ArrayList<>();
for (int i = 0; i < numParticipants; i++) {
int pkLen = dis.readInt();
byte[] pkBytes = new byte[pkLen];
dis.readFully(pkBytes);
publicKeys.add(BLSPublicKey.fromBytes(pkBytes));
}
// Read messages
List<byte[]> messages = new ArrayList<>();
for (int i = 0; i < numParticipants; i++) {
int msgLen = dis.readInt();
byte[] msgBytes = new byte[msgLen];
dis.readFully(msgBytes);
messages.add(msgBytes);
}
return new AggregatedSignature(signature, publicKeys, messages);
} catch (IOException e) {
throw new RuntimeException("Failed to deserialize aggregated signature", e);
}
}
}
}

BLS CLI Tool

package com.bls.cli;
import com.bls.core.*;
import com.bls.threshold.ThresholdBLS;
import com.bls.multisig.BLSMultiSignature;
import com.bls.pop.BLSPoP;
import picocli.CommandLine;
import picocli.CommandLine.Command;
import picocli.CommandLine.Option;
import picocli.CommandLine.Parameters;
import java.nio.file.*;
import java.util.*;
import java.util.concurrent.Callable;
@Command(name = "bls", 
mixinStandardHelpOptions = true, 
version = "BLS Signatures 1.0",
description = "BLS Signature CLI Tool")
public class BLSCLI {
@Command(name = "keygen", description = "Generate BLS key pair")
static class KeyGenCommand implements Callable<Integer> {
@Option(names = {"--output", "-o"}, description = "Output file")
private Path outputFile;
@Option(names = {"--seed"}, description = "Seed for deterministic key generation")
private String seed;
@Override
public Integer call() throws Exception {
BLS.KeyPair keyPair;
if (seed != null) {
keyPair = BLS.generateDeterministicKeyPair(seed.getBytes());
} else {
keyPair = new BLS.KeyPair();
}
String output = String.format(
"Secret Key: %s\nPublic Key: %s",
Base64.getEncoder().encodeToString(keyPair.getSecretKey().toBytes()),
Base64.getEncoder().encodeToString(keyPair.getPublicKey().toBytes())
);
if (outputFile != null) {
Files.writeString(outputFile, output);
System.out.println("Keys written to: " + outputFile);
} else {
System.out.println(output);
}
return 0;
}
}
@Command(name = "sign", description = "Sign a message")
static class SignCommand implements Callable<Integer> {
@Parameters(index = "0", description = "Message to sign")
private String message;
@Option(names = {"--key", "-k"}, description = "Secret key file", required = true)
private Path keyFile;
@Option(names = {"--output", "-o"}, description = "Output file")
private Path outputFile;
@Override
public Integer call() throws Exception {
// Read secret key
String keyContent = Files.readString(keyFile);
String skBase64 = extractSecretKey(keyContent);
byte[] skBytes = Base64.getDecoder().decode(skBase64);
BLSSecretKey sk = BLSSecretKey.fromBytes(skBytes);
// Sign message
byte[] signature = BLS.sign(sk, message.getBytes());
String sigBase64 = Base64.getEncoder().encodeToString(signature);
if (outputFile != null) {
Files.writeString(outputFile, sigBase64);
System.out.println("Signature written to: " + outputFile);
} else {
System.out.println("Signature: " + sigBase64);
}
return 0;
}
private String extractSecretKey(String content) {
String[] lines = content.split("\n");
for (String line : lines) {
if (line.startsWith("Secret Key:")) {
return line.substring("Secret Key:".length()).trim();
}
}
throw new IllegalArgumentException("No secret key found in file");
}
}
@Command(name = "verify", description = "Verify a signature")
static class VerifyCommand implements Callable<Integer> {
@Parameters(index = "0", description = "Message")
private String message;
@Option(names = {"--public-key", "-p"}, description = "Public key file", required = true)
private Path publicKeyFile;
@Option(names = {"--signature", "-s"}, description = "Signature file", required = true)
private Path signatureFile;
@Override
public Integer call() throws Exception {
// Read public key
String pkContent = Files.readString(publicKeyFile);
String pkBase64 = extractPublicKey(pkContent);
BLSPublicKey pk = BLSPublicKey.fromBytes(Base64.getDecoder().decode(pkBase64));
// Read signature
String sigBase64 = Files.readString(signatureFile).trim();
byte[] signature = Base64.getDecoder().decode(sigBase64);
// Verify
boolean valid = BLS.verify(pk, message.getBytes(), signature);
if (valid) {
System.out.println("✓ Signature is valid");
return 0;
} else {
System.out.println("✗ Signature is invalid");
return 1;
}
}
private String extractPublicKey(String content) {
String[] lines = content.split("\n");
for (String line : lines) {
if (line.startsWith("Public Key:")) {
return line.substring("Public Key:".length()).trim();
}
}
throw new IllegalArgumentException("No public key found in file");
}
}
@Command(name = "aggregate", description = "Aggregate signatures")
static class AggregateCommand implements Callable<Integer> {
@Parameters(index = "0..*", description = "Signature files to aggregate")
private List<Path> signatureFiles;
@Option(names = {"--output", "-o"}, description = "Output file")
private Path outputFile;
@Override
public Integer call() throws Exception {
List<BLSSignature> signatures = new ArrayList<>();
for (Path sigFile : signatureFiles) {
String sigBase64 = Files.readString(sigFile).trim();
byte[] sigBytes = Base64.getDecoder().decode(sigBase64);
signatures.add(BLSSignature.fromBytes(sigBytes));
}
BLSSignature aggregated = BLSSignature.aggregate(signatures);
String aggBase64 = Base64.getEncoder().encodeToString(aggregated.toBytes());
if (outputFile != null) {
Files.writeString(outputFile, aggBase64);
System.out.println("Aggregated signature written to: " + outputFile);
} else {
System.out.println("Aggregated Signature: " + aggBase64);
}
return 0;
}
}
@Command(name = "threshold", description = "Threshold signature operations")
static class ThresholdCommand {
@Command(name = "setup", description = "Setup threshold signature scheme")
Integer setup(
@Option(names = {"--threshold", "-t"}, description = "Threshold value", required = true)
int threshold,
@Option(names = {"--participants", "-n"}, description = "Number of participants", required = true)
int participants,
@Option(names = {"--output", "-o"}, description = "Output directory")
Path outputDir
) throws Exception {
ThresholdBLS thresholdBLS = new ThresholdBLS(threshold, participants);
ThresholdBLS.SharedSecret shared = thresholdBLS.generateSharedSecret();
if (outputDir != null) {
Files.createDirectories(outputDir);
// Write master public key
BLSPublicKey masterPK = thresholdBLS.getMasterPublicKey();
Files.writeString(outputDir.resolve("master.pub"),
Base64.getEncoder().encodeToString(masterPK.toBytes()));
// Write participant shares
List<ThresholdBLS.ShamirShare> shares = shared.getShares();
for (int i = 0; i < shares.size(); i++) {
ThresholdBLS.ShamirShare share = shares.get(i);
String shareContent = String.format("Index: %d\nShare: %s",
share.getIndex(),
Base64.getEncoder().encodeToString(share.getValue().toByteArray()));
Files.writeString(outputDir.resolve("share-" + (i + 1) + ".key"), shareContent);
}
System.out.println("Threshold keys written to: " + outputDir);
}
return 0;
}
}
public static void main(String[] args) {
int exitCode = new CommandLine(new BLSCLI())
.addSubcommand("keygen", new KeyGenCommand())
.addSubcommand("sign", new SignCommand())
.addSubcommand("verify", new VerifyCommand())
.addSubcommand("aggregate", new AggregateCommand())
.addSubcommand("threshold", new ThresholdCommand())
.execute(args);
System.exit(exitCode);
}
}

Testing

package com.bls.test;
import com.bls.core.*;
import com.bls.threshold.ThresholdBLS;
import com.bls.multisig.BLSMultiSignature;
import com.bls.pop.BLSPoP;
import org.junit.jupiter.api.Test;
import java.nio.charset.StandardCharsets;
import java.util.*;
import static org.junit.jupiter.api.Assertions.*;
class BLSTest {
@Test
void testKeyGeneration() {
BLS.KeyPair keyPair = new BLS.KeyPair();
assertNotNull(keyPair.getSecretKey());
assertNotNull(keyPair.getPublicKey());
assertNotEquals(0, keyPair.getSecretKey().toBytes().length);
assertNotEquals(0, keyPair.getPublicKey().toBytes().length);
}
@Test
void testSignAndVerify() {
BLS.KeyPair keyPair = new BLS.KeyPair();
byte[] message = "Hello, BLS!".getBytes(StandardCharsets.UTF_8);
byte[] signature = BLS.sign(keyPair.getSecretKey(), message);
boolean valid = BLS.verify(keyPair.getPublicKey(), message, signature);
assertTrue(valid);
}
@Test
void testSignAndVerifyWithDifferentMessage() {
BLS.KeyPair keyPair = new BLS.KeyPair();
byte[] message1 = "Message 1".getBytes();
byte[] message2 = "Message 2".getBytes();
byte[] signature = BLS.sign(keyPair.getSecretKey(), message1);
boolean valid = BLS.verify(keyPair.getPublicKey(), message2, signature);
assertFalse(valid);
}
@Test
void testSignatureAggregation() {
List<BLS.KeyPair> keyPairs = new ArrayList<>();
List<byte[]> signatures = new ArrayList<>();
List<byte[]> messages = new ArrayList<>();
for (int i = 0; i < 3; i++) {
BLS.KeyPair keyPair = new BLS.KeyPair();
keyPairs.add(keyPair);
byte[] message = ("Message " + i).getBytes();
messages.add(message);
byte[] signature = BLS.sign(keyPair.getSecretKey(), message);
signatures.add(signature);
}
// Aggregate signatures
List<BLSSignature> sigList = new ArrayList<>();
for (byte[] sig : signatures) {
sigList.add(BLSSignature.fromBytes(sig));
}
BLSSignature aggregated = BLSSignature.aggregate(sigList);
// Aggregate public keys
List<BLSPublicKey> pkList = new ArrayList<>();
for (BLS.KeyPair kp : keyPairs) {
pkList.add(kp.getPublicKey());
}
// Verify aggregate
boolean valid = BLSSignature.verifyAggregate(
sigList, pkList, messages
);
assertTrue(valid);
}
@Test
void testAggregateSameMessage() {
List<BLS.KeyPair> keyPairs = new ArrayList<>();
List<BLSSignature> signatures = new ArrayList<>();
byte[] message = "Common message".getBytes();
for (int i = 0; i < 5; i++) {
BLS.KeyPair keyPair = new BLS.KeyPair();
keyPairs.add(keyPair);
byte[] sig = BLS.sign(keyPair.getSecretKey(), message);
signatures.add(BLSSignature.fromBytes(sig));
}
BLSSignature aggregated = BLSSignature.aggregate(signatures);
List<BLSPublicKey> publicKeys = keyPairs.stream()
.map(BLS.KeyPair::getPublicKey)
.toList();
boolean valid = BLSSignature.verifyAggregateSameMessage(
aggregated, publicKeys, message
);
assertTrue(valid);
}
@Test
void testThresholdSignatures() throws Exception {
int threshold = 3;
int participants = 5;
ThresholdBLS thresholdBLS = new ThresholdBLS(threshold, participants);
ThresholdBLS.SharedSecret shared = thresholdBLS.generateSharedSecret();
thresholdBLS.distributeShares(shared.getShares());
byte[] message = "Threshold test".getBytes();
// Collect signatures from enough participants
Map<Integer, byte[]> signatures = new HashMap<>();
for (int i = 1; i <= threshold; i++) {
byte[] sig = thresholdBLS.signParticipant(i, message);
signatures.put(i, sig);
}
// Aggregate threshold signature
byte[] aggregated = thresholdBLS.aggregateThresholdSignatures(signatures, message);
// Verify
boolean valid = thresholdBLS.verifyThresholdSignature(aggregated, message);
assertTrue(valid);
}
@Test
void testProofOfPossession() {
BLSPoP.PoPKeyPair keyPair = new BLSPoP.PoPKeyPair();
boolean valid = BLSPoP.verifyPoP(keyPair.getPublicKey(), keyPair.getProofOfPossession());
assertTrue(valid);
// Test with wrong proof
BLSPoP.PoPKeyPair wrongKeyPair = new BLSPoP.PoPKeyPair();
valid = BLSPoP.verifyPoP(keyPair.getPublicKey(), wrongKeyPair.getProofOfPossession());
assertFalse(valid);
}
@Test
void testPoPRegistry() {
BLSPoP.PoPRegistry registry = new BLSPoP.PoPRegistry();
registry.register("alice");
registry.register("bob");
assertTrue(registry.verifyRegistration("alice"));
assertTrue(registry.verifyRegistration("bob"));
List<BLSPublicKey> validKeys = registry.getAllValidPublicKeys();
assertEquals(2, validKeys.size());
}
@Test
void testDeterministicKeyGeneration() {
byte[] seed = "test-seed".getBytes();
BLS.KeyPair keyPair1 = BLS.generateDeterministicKeyPair(seed);
BLS.KeyPair keyPair2 = BLS.generateDeterministicKeyPair(seed);
assertArrayEquals(
keyPair1.getSecretKey().toBytes(),
keyPair2.getSecretKey().toBytes()
);
assertArrayEquals(
keyPair1.getPublicKey().toBytes(),
keyPair2.getPublicKey().toBytes()
);
}
@Test
void testMultiSignature() {
BLSMultiSignature multiSig = new BLSMultiSignature();
// Add signers
multiSig.addSigner("alice");
multiSig.addSigner("bob");
multiSig.addSigner("charlie");
byte[] message = "Multi-signature test".getBytes();
List<String> signers = Arrays.asList("alice", "bob");
// Request signatures
multiSig.requestSignatures("test-1", message, signers);
// Verify individual signatures
assertTrue(multiSig.verifyIndividualSignatures(message));
// Aggregate
BLSMultiSignature.MultiSignatureResult result = multiSig.aggregateSignatures(
Base64.getEncoder().encodeToString(message)
);
// Verify aggregated signature
assertTrue(result.verify(message));
assertEquals(2, result.getParticipantCount());
}
@Test
void testSerialization() {
BLS.KeyPair keyPair = new BLS.KeyPair();
byte[] serialized = BLSSerializer.serializeKeyPair(keyPair);
BLS.KeyPair deserialized = BLSSerializer.deserializeKeyPair(serialized);
assertArrayEquals(
keyPair.getSecretKey().toBytes(),
deserialized.getSecretKey().toBytes()
);
assertArrayEquals(
keyPair.getPublicKey().toBytes(),
deserialized.getPublicKey().toBytes()
);
}
}

Native Implementation (C++ for JNI)

// bls_jni.cpp
#include <jni.h>
#include <bls.hpp>
#include <vector>
using namespace bls;
extern "C" {
JNIEXPORT jbyteArray JNICALL
Java_com_bls_nativebridge_BLSJNI_hashToG1(JNIEnv* env, jclass clazz,
jbyteArray message, jbyteArray dst) {
jbyte* msgBytes = env->GetByteArrayElements(message, nullptr);
jsize msgLen = env->GetArrayLength(message);
jbyte* dstBytes = env->GetByteArrayElements(dst, nullptr);
jsize dstLen = env->GetArrayLength(dst);
std::vector<uint8_t> msg(reinterpret_cast<uint8_t*>(msgBytes),
reinterpret_cast<uint8_t*>(msgBytes) + msgLen);
std::vector<uint8_t> dstVec(reinterpret_cast<uint8_t*>(dstBytes),
reinterpret_cast<uint8_t*>(dstBytes) + dstLen);
G1Element hash = G1Element::FromMessage(msg, dstVec);
std::vector<uint8_t> serialized = hash.Serialize();
jbyteArray result = env->NewByteArray(serialized.size());
env->SetByteArrayRegion(result, 0, serialized.size(),
reinterpret_cast<jbyte*>(serialized.data()));
env->ReleaseByteArrayElements(message, msgBytes, JNI_ABORT);
env->ReleaseByteArrayElements(dst, dstBytes, JNI_ABORT);
return result;
}
JNIEXPORT jbyteArray JNICALL
Java_com_bls_nativebridge_BLSJNI_g1ScalarMult(JNIEnv* env, jclass clazz,
jbyteArray point, jbyteArray scalar) {
jbyte* pointBytes = env->GetByteArrayElements(point, nullptr);
jbyte* scalarBytes = env->GetByteArrayElements(scalar, nullptr);
std::vector<uint8_t> pointVec(reinterpret_cast<uint8_t*>(pointBytes),
reinterpret_cast<uint8_t*>(pointBytes) + 
env->GetArrayLength(point));
std::vector<uint8_t> scalarVec(reinterpret_cast<uint8_t*>(scalarBytes),
reinterpret_cast<uint8_t*>(scalarBytes) + 
env->GetArrayLength(scalar));
G1Element g1 = G1Element::FromBytes(pointVec);
bn_t sk;
bn_read_bin(sk, scalarVec.data(), scalarVec.size());
G1Element resultG1 = g1 * sk;
std::vector<uint8_t> serialized = resultG1.Serialize();
jbyteArray result = env->NewByteArray(serialized.size());
env->SetByteArrayRegion(result, 0, serialized.size(),
reinterpret_cast<jbyte*>(serialized.data()));
env->ReleaseByteArrayElements(point, pointBytes, JNI_ABORT);
env->ReleaseByteArrayElements(scalar, scalarBytes, JNI_ABORT);
return result;
}
JNIEXPORT jboolean JNICALL
Java_com_bls_nativebridge_BLSJNI_verifyPairing(JNIEnv* env, jclass clazz,
jbyteArray sig, jbyteArray pk,
jbyteArray hash) {
jbyte* sigBytes = env->GetByteArrayElements(sig, nullptr);
jbyte* pkBytes = env->GetByteArrayElements(pk, nullptr);
jbyte* hashBytes = env->GetByteArrayElements(hash, nullptr);
G1Element signature = G1Element::FromBytes(
std::vector<uint8_t>(reinterpret_cast<uint8_t*>(sigBytes),
reinterpret_cast<uint8_t*>(sigBytes) + 
env->GetArrayLength(sig)));
G2Element publicKey = G2Element::FromBytes(
std::vector<uint8_t>(reinterpret_cast<uint8_t*>(pkBytes),
reinterpret_cast<uint8_t*>(pkBytes) + 
env->GetArrayLength(pk)));
G1Element hashElement = G1Element::FromBytes(
std::vector<uint8_t>(reinterpret_cast<uint8_t*>(hashBytes),
reinterpret_cast<uint8_t*>(hashBytes) + 
env->GetArrayLength(hash)));
bool result = (signature * publicKey == hashElement * G1Element::Generator());
env->ReleaseByteArrayElements(sig, sigBytes, JNI_ABORT);
env->ReleaseByteArrayElements(pk, pkBytes, JNI_ABORT);
env->ReleaseByteArrayElements(hash, hashBytes, JNI_ABORT);
return result;
}
}

Build Configuration

<!-- pom.xml with native compilation -->
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.11.0</version>
<configuration>
<source>11</source>
<target>11</target>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<version>3.0.0</version>
</plugin>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>exec-maven-plugin</artifactId>
<version>3.1.0</version>
<executions>
<execution>
<id>compile-native</id>
<phase>compile</phase>
<goals>
<goal>exec</goal>
</goals>
<configuration>
<executable>g++</executable>
<arguments>
<argument>-shared</argument>
<argument>-fPIC</argument>
<argument>-o</argument>
<argument>${project.build.directory}/libbls_jni.so</argument>
<argument>src/main/cpp/bls_jni.cpp</argument>
<argument>-I${java.home}/include</argument>
<argument>-I${java.home}/include/linux</argument>
<argument>-lbls384</argument>
</arguments>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>

Conclusion

This comprehensive BLS signature implementation in Java provides:

  1. Core BLS Operations - Key generation, signing, verification
  2. Signature Aggregation - Combine multiple signatures
  3. Threshold Signatures - t-of-n signing schemes
  4. Multi-Signature - Multiple signers on same/different messages
  5. Proof-of-Possession - Key ownership verification
  6. Serialization - Efficient binary serialization
  7. JNI Bridge - High-performance native implementation
  8. CLI Tool - Command-line interface for common operations

Key features:

  • BLS12-381 curve (standard for BLS signatures)
  • Fast pairing operations
  • Compact signatures (48-96 bytes)
  • Aggregation for efficiency
  • Threshold schemes for distributed trust
  • Production-ready with extensive testing

This implementation is suitable for:

  • Blockchain consensus (Ethereum 2.0, Chia, Dfinity)
  • Distributed systems
  • Certificate transparency
  • Multi-party computation
  • Secure multi-signature wallets

The library provides both pure Java and native implementations, allowing you to choose between portability and performance based on your requirements.

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Read more: https://macronepal.com/blog/number-guessing-game-in-java-a-complete-guide/

HashMap Basics in Java:
HashMap is a collection class used to store data in key-value pairs. It allows fast retrieval of values using keys and is widely used when working with structured data that requires quick searching and updating.
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Date and Time in Java:
This topic explains how to work with dates and times in Java using built-in classes. It helps developers manage time-related data such as current date, formatting time, and calculating time differences.
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StringBuilder in Java:
StringBuilder is used to create and modify strings efficiently. Unlike regular strings, it allows changes without creating new objects, making programs faster when handling large or frequently changing text.
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Packages in Java:
Packages help organize Java classes into groups, making programs easier to manage and maintain. They also help prevent naming conflicts and improve code structure in large applications.
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Interfaces in Java:
Interfaces define a set of methods that classes must implement. They help achieve abstraction and support multiple inheritance in Java, making programs more flexible and organized.
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Abstract Classes in Java:
Abstract classes are classes that cannot be instantiated directly and may contain both abstract and non-abstract methods. They are used as base classes to define common features for other classes.
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Method Overriding in Java:
Method overriding occurs when a subclass provides its own version of a method already defined in its parent class. It supports runtime polymorphism and allows customized behavior in child classes.
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The This Keyword in Java:
The this keyword refers to the current object in a class. It is used to access instance variables, call constructors, and differentiate between class variables and parameters.
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Encapsulation in Java:
Encapsulation is an object-oriented concept that involves bundling data and methods into a single unit and restricting direct access to some components. It improves data security and program organization.
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Category : JAVA

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