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BLS Signatures Java

An implementation of BLS signatures using blst Java bindings based on Chia's implementation. This library implements the Minimal Pubkey Size variant.

🚫 Security Disclaimer: This code has not undergone formal security audits. I started this as a hobbyist project primarily for learning and exploration. Please use at your own risk.

It's currently using Consensys' jblst, a packaged cross-platform version of blst for java. You may prefer to build the blst jar from source yourself if you don't trust their package.

Feedback and PR's are very welcome.

Usage

Get instance of scheme

SignatureScheme basicScheme = BasicSignatureScheme.getInstance();
SignatureScheme augScheme = MessageAugmentationSignatureScheme.getInstance();
ProofOfPossessionSignatureScheme popScheme = ProofOfPossessionSignatureScheme.getInstance();

Sign message using message augmentation signature scheme

// Fetch signature scheme instance
SignatureScheme augScheme = MessageAugmentationSignatureScheme.getInstance();

// Generate a keypair
PrivateKey privateKey = MessageAugmentationSignatureScheme.keygen(secureRandom.generateSeed(32));
PublicKey publicKey = augScheme.privateKeyToPublicKey(privateKey);

// A message to sign
Bytes messageBytes = Bytes.secure("Hello, World!".getBytes());

// Sign message with private key
Signature signature = augScheme.sign(privateKey, messageBytes);

// Verify message with public key and signature
boolean verified = augScheme.verify(publicKey, messageBytes, signature);

Verify ownership of public key using Proof of Possession (POP) Signature Scheme

// Fetch POP signature scheme instance
ProofOfPossessionSignatureScheme popScheme = ProofOfPossessionSignatureScheme.getInstance();

// Party A generates keypair and shares their public key
PrivateKey partyAPrivateKey = ProofOfPossessionSignatureScheme.keygen(secureRandom.generateSeed(32));
PublicKey partyAPublicKey = popScheme.privateKeyToPublicKey(privateKey);

// Party A creates a signature to prove they own the shared public key
Signature partyAProofOfPossessionSignature = popScheme.popProve(privateKey);

// Party B verifies that Party A does indeed own the shared public key using the created signature
boolean doTheyOwnThePublicKey = popScheme.popVerify(partyAPublicKey, partyAProofOfPossessionSignature);

Run Tests

mvn test
[INFO] Results:
[INFO] 
[INFO] Tests run: 36, Failures: 0, Errors: 0, Skipped: 0
[INFO] 
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  1.264 s

Examples Adapted From Chia's BLS Signatures Repo

Creating keys and signatures example

// Example seed, used to generate private key. Always use a secure RNG
// with sufficient entropy to generate a seed (at least 32 bytes).
Bytes seed = Bytes.of(
    0, 50, 6, 244, 24, 199, 1, 25, 52, 88, 192, 19, 
    18, 12, 89, 6, 220, 18, 102, 58, 209, 82, 12, 
    62, 89, 110, 182, 9, 44, 20, 254, 22);

PrivateKey privateKey = MessageAugmentationSignatureScheme.keygen(seed);
PublicKey publicKey = augScheme.privateKeyToPublicKey(privateKey);

Bytes message = Bytes.of(1, 2, 3, 4, 5);  // Message is passed in as a bytes
Signature signature = augScheme.sign(privateKey, message);

// Verify the signature
boolean ok = augScheme.verify(publicKey, message, signature);

Serializing keys and signatures to bytes example

Bytes32 privateKeyBytes = privateKey.serialize();
Bytes48 publicKeyBytes = publicKey.serialize();
Bytes signatureBytes = signature.serialize();

System.out.println(privateKeyBytes.toHexString());  // 32 bytes printed in hex
System.out.println(publicKeyBytes.toHexString());   // 48 bytes printed in hex
System.out.println(signatureBytes.toHexString());   // 96 bytes printed in hex

Loading keys and signatures from bytes example

// Takes Bytes32
PrivateKey privateKey = PrivateKey.fromBytes(privateKeyBytes);
PrivateKey privateKey = PrivateKey.fromBytesModOrder(privateKeyBytes);

// Takes Bytes48
PublicKey publicKey = PublicKey.fromBytes(publicKeyBytes);

// Takes Bytes of length 96
Signature signature = Signature.fromBytes(signatureBytes);

Create aggregate signatures example

// Update seed to generate privateKey1
seed = Bytes.concatenate(Bytes.of(1), seed.slice(1, seed.size() - 1));
PrivateKey privateKey1 = MessageAugmentationSignatureScheme.keygen(seed);

// Update seed again to generate privateKey2
seed = Bytes.concatenate(Bytes.of(2), seed.slice(1, seed.size() - 1));
PrivateKey privateKey2 = MessageAugmentationSignatureScheme.keygen(seed);

// Create message to sign
Bytes message2 = Bytes.of(1, 2, 3, 4, 5, 6, 7);

// Generate first sigmature
PublicKey publicKey1 = privateKey1.getPublicKey();
Signature signature1 = augScheme.sign(privateKey1, message);

// Generate second sigmature
PublicKey publicKey2 = privateKey2.getPublicKey();
Signature signature2 = augScheme.sign(privateKey2, message2);

// Signatures can be non-interactively combined by anyone
Signature aggSig = augScheme.aggregateSignatures(List.of(signature1, signature2));

boolean ok = augScheme.aggregateVerify(List.of(publicKey1, publicKey2), List.of(message, message2), aggSig)

Arbitrary trees of aggregates example

Bytes seed = Bytes.concatenate(Bytes.of(3), seed.slice(1, seed.size() - 1));
PrivateKey privateKey3 = MessageAugmentationSignatureScheme.keygen(seed);
PublicKey publicKey3 = privateKey3.getPublicKey();
Bytes message3 = Bytes.of(100, 2, 254, 88, 90, 45, 23);
Signature signature3 = augScheme.sign(privateKey3, message3);

Signature aggSigFinal = augScheme.aggregateSignatures(List.of(aggSig, signature3));
boolean ok = augScheme.aggregateVerify(List.of(publicKey1, publicKey2, publicKey3), List.of(message, message2, message3), aggSigFinal);

Very fast verification with Proof of Possession scheme example

// If the same message is signed, you can use Proof of Posession (PopScheme) for efficiency
// A proof of possession MUST be passed around with the PK to ensure security.
Signature popSignature1 = popScheme.sign(privateKey1, message);
Signature popSignature2 = popScheme.sign(privateKey2, message);
Signature popSignature3 = popScheme.sign(privateKey3, message);
Signature pop1 = popScheme.popProve(privateKey1);
Signature pop2 = popScheme.popProve(privateKey2);
Signature pop3 = popScheme.popProve(privateKey3);

boolean ok = popScheme.popVerify(publicKey1, pop1);
boolean ok = popScheme.popVerify(publicKey2, pop2);
boolean ok = popScheme.popVerify(publicKey3, pop3);
Signature popAggregatedSignature = popScheme.aggregateSignatures(List.of(popSignature1, popSignature2, popSignature3));

boolean ok = popScheme.fastAggregateVerify(List.of(publicKey1, publicKey2, publicKey3), message, popAggregatedSignature);

// Aggregate public key, indistinguishable from a single public key
PublicKey popAggregatedPk = publicKey1.add(publicKey2).add(publicKey3);
boolean ok = popScheme.verify(popAggregatedPk, message, popAggregatedSignature);

// Aggregate private keys
PrivateKey aggregatedPrivateKey = PrivateKey.aggregate(List.of(privateKey1, privateKey2, privateKey3));
boolean ok = popAggregatedSignature, popScheme.sign(aggregatedPrivateKey, message);

HD keys using EIP-2333 example

// You can derive 'child' keys from any key, to create arbitrary trees. 4 byte indeces are used.
// Hardened (more secure, but no parent pk -> child pk)
PrivateKey masterPrivateKey = MessageAugmentationSignatureScheme.keygen(seed);

// Unhardened (less secure, but can go from parent pk -> child pk), BIP32 style
PublicKey masterPublicKey = masterPrivateKey.getPublicKey();
PrivateKey childUnhardenedPrivateKey = augScheme.deriveChildPrivateKeyUnhardened(masterPrivateKey, UInt32.valueOf(22));
PrivateKey grandchildUnhardenedPrivateKey = augScheme.deriveChildPrivateKeyUnhardened(childUnhardenedPrivateKey, UInt32.valueOf(0));
PublicKey childUnhardenedPublicKey = augScheme.deriveChildPublicKeyUnhardened(masterPublicKey, UInt32.valueOf(22));
PublicKey grandchildUnhardenedPublicKey = augScheme.deriveChildPublicKeyUnhardened(childUnhardenedPublicKey, UInt32.valueOf(0));

BLST license

BLST is used with the Apache 2.0 license