Falcon Signatures in Java: Complete Guide

Introduction to Falcon Signatures

Falcon (Fast-Fourier Lattice-based Compact Signatures Over NTRU) is a post-quantum cryptographic signature scheme selected by NIST for standardization. It offers quantum-resistant digital signatures with compact sizes and fast verification, making it ideal for long-term security applications.

System Architecture Overview

Falcon Signature System ├── Key Generation │ ├ - NTRU Lattice Parameters │ ├ - Fast Fourier Transform (FFT) │ └ - Key Pair (Public/Private) ├── Signing Process │ ├ - Message Hashing (SHA-256/512) │ ├ - Gaussian Sampling │ ├ - Lattice Reduction │ └ - Signature Generation ├── Verification Process │ ├ - Signature Parsing │ ├ - Norm Computation │ └ - Validity Check └── Integration Layers ├ - Java Native Interface (JNI) ├ - Pure Java Implementation └ - Cloud KMS Integration

Core Implementation

1. Maven Dependencies

<properties> <bouncycastle.version>1.78</bouncycastle.version> <falcon.version>1.2.0</falcon.version> <pqc-java.version>1.0.0</pqc-java.version> </properties> <dependencies> <!-- Bouncy Castle for cryptographic primitives --> <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> <!-- Falcon Java Implementation --> <dependency> <groupId>com.github.falcon-signature</groupId> <artifactId>falcon-java</artifactId> <version>${falcon.version}</version> </dependency> <!-- PQC Java Library --> <dependency> <groupId>org.pqc</groupId> <artifactId>pqc-java</artifactId> <version>${pqc-java.version}</version> </dependency> <!-- JNI bridge for native implementation --> <dependency> <groupId>net.java.dev.jna</groupId> <artifactId>jna</artifactId> <version>5.13.0</version> </dependency> <!-- Apache Commons for utilities --> <dependency> <groupId>commons-codec</groupId> <artifactId>commons-codec</artifactId> <version>1.16.0</version> </dependency> <!-- Google Tink for hybrid cryptography --> <dependency> <groupId>com.google.crypto.tink</groupId> <artifactId>tink</artifactId> <version>1.12.0</version> </dependency> <!-- Protocol Buffers for serialization --> <dependency> <groupId>com.google.protobuf</groupId> <artifactId>protobuf-java</artifactId> <version>3.25.1</version> </dependency> <!-- Testing --> <dependency> <groupId>org.junit.jupiter</groupId> <artifactId>junit-jupiter</artifactId> <version>5.10.1</version> <scope>test</scope> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <version>3.11.0</version> <configuration> <source>17</source> <target>17</target> </configuration> </plugin> <!-- Native library compilation --> <plugin> <groupId>org.codehaus.mojo</groupId> <artifactId>native-maven-plugin</artifactId> <version>1.0.0</version> <executions> <execution> <id>compile-native</id> <phase>compile</phase> <goals> <goal>javah</goal> </goals> </execution> </executions> </plugin> </plugins> </build>

2. Falcon Key Generation Service

package com.falcon.signature; import org.bouncycastle.crypto.digests.SHA256Digest; import org.bouncycastle.crypto.digests.SHA512Digest; import org.bouncycastle.util.encoders.Hex; import org.pqc.jcajce.spec.FalconParameterSpec; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.stereotype.Service; import javax.crypto.SecretKey; import java.security.*; import java.security.spec.PKCS8EncodedKeySpec; import java.security.spec.X509EncodedKeySpec; import java.util.*; import java.util.concurrent.ConcurrentHashMap; @Service public class FalconKeyGenerationService { private static final Logger logger = LoggerFactory.getLogger(FalconKeyGenerationService.class); // Falcon parameter sets (NIST security levels) public enum FalconParameter { FALCON_512(1, 512, 128), // NIST Level 1 (128-bit security) FALCON_1024(5, 1024, 256); // NIST Level 5 (256-bit security) final int nistLevel; final int n; // Polynomial degree final int securityStrength; // Bits FalconParameter(int nistLevel, int n, int securityStrength) { this.nistLevel = nistLevel; this.n = n; this.securityStrength = securityStrength; } public int getNistLevel() { return nistLevel; } public int getN() { return n; } public int getSecurityStrength() { return securityStrength; } } // Cache for key pairs private final Map<String, FalconKeyPair> keyCache = new ConcurrentHashMap<>(); private final SecureRandom secureRandom = new SecureRandom(); /** * Generate Falcon key pair */ public FalconKeyPair generateKeyPair(FalconParameter parameter) throws FalconException { try { long startTime = System.nanoTime(); // Initialize Falcon key pair generator KeyPairGenerator keyGen = KeyPairGenerator.getInstance("Falcon", "PQC"); keyGen.initialize(getParameterSpec(parameter), secureRandom); // Generate key pair KeyPair keyPair = keyGen.generateKeyPair(); // Extract keys byte[] publicKey = keyPair.getPublic().getEncoded(); byte[] privateKey = keyPair.getPrivate().getEncoded(); // Create Falcon key pair FalconKeyPair falconKeyPair = new FalconKeyPair( publicKey, privateKey, parameter, System.currentTimeMillis() ); long duration = System.nanoTime() - startTime; logger.info("Generated Falcon-{} key pair in {} ms", parameter.n, duration / 1_000_000); return falconKeyPair; } catch (Exception e) { throw new FalconException("Failed to generate Falcon key pair", e); } } /** * Generate key pair with seed for deterministic generation */ public FalconKeyPair generateDeterministicKeyPair(FalconParameter parameter, byte[] seed) throws FalconException { try { // Create deterministic random from seed SecureRandom deterministicRandom = SecureRandom.getInstance("SHA1PRNG"); deterministicRandom.setSeed(seed); KeyPairGenerator keyGen = KeyPairGenerator.getInstance("Falcon", "PQC"); keyGen.initialize(getParameterSpec(parameter), deterministicRandom); KeyPair keyPair = keyGen.generateKeyPair(); return new FalconKeyPair( keyPair.getPublic().getEncoded(), keyPair.getPrivate().getEncoded(), parameter, System.currentTimeMillis() ); } catch (Exception e) { throw new FalconException("Failed to generate deterministic key pair", e); } } /** * Load public key from bytes */ public FalconPublicKey loadPublicKey(byte[] publicKeyBytes, FalconParameter parameter) throws FalconException { try { KeyFactory keyFactory = KeyFactory.getInstance("Falcon", "PQC"); X509EncodedKeySpec keySpec = new X509EncodedKeySpec(publicKeyBytes); PublicKey publicKey = keyFactory.generatePublic(keySpec); return new FalconPublicKey(publicKey, parameter); } catch (Exception e) { throw new FalconException("Failed to load public key", e); } } /** * Load private key from bytes */ public FalconPrivateKey loadPrivateKey(byte[] privateKeyBytes, FalconParameter parameter) throws FalconException { try { KeyFactory keyFactory = KeyFactory.getInstance("Falcon", "PQC"); PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(privateKeyBytes); PrivateKey privateKey = keyFactory.generatePrivate(keySpec); return new FalconPrivateKey(privateKey, parameter); } catch (Exception e) { throw new FalconException("Failed to load private key", e); } } /** * Generate key pair from password */ public FalconKeyPair generateKeyPairFromPassword(FalconParameter parameter, char[] password, byte[] salt) throws FalconException { try { // Derive seed from password using PBKDF2 byte[] seed = deriveSeedFromPassword(password, salt, parameter.securityStrength / 8); // Generate key pair deterministically return generateDeterministicKeyPair(parameter, seed); } catch (Exception e) { throw new FalconException("Failed to generate key pair from password", e); } } /** * Export key pair in PKCS#12 format */ public byte[] exportToPKCS12(FalconKeyPair keyPair, String alias, char[] password) throws FalconException { try { // Create PKCS12 keystore KeyStore pkcs12 = KeyStore.getInstance("PKCS12"); pkcs12.load(null, null); // Convert to JCE keys PrivateKey privateKey = loadPrivateKey(keyPair.getPrivateKey(), keyPair.getParameter()).getPrivateKey(); PublicKey publicKey = loadPublicKey(keyPair.getPublicKey(), keyPair.getParameter()).getPublicKey(); // Create certificate chain (self-signed) X509Certificate[] chain = createSelfSignedCertificate(keyPair); // Store private key pkcs12.setKeyEntry(alias, privateKey, password, chain); // Export keystore ByteArrayOutputStream baos = new ByteArrayOutputStream(); pkcs12.store(baos, password); return baos.toByteArray(); } catch (Exception e) { throw new FalconException("Failed to export to PKCS12", e); } } /** * Get key metadata */ public KeyMetadata getKeyMetadata(byte[] publicKey) throws FalconException { try { // Parse public key to determine parameters FalconPublicKey falconKey = loadPublicKey(publicKey, FalconParameter.FALCON_512); KeyMetadata metadata = new KeyMetadata(); metadata.setAlgorithm("Falcon"); metadata.setParameter(falconKey.getParameter()); metadata.setPublicKeySize(publicKey.length); metadata.setCreationTime(falconKey.getCreationTime()); metadata.setKeyHash(calculateKeyHash(publicKey)); return metadata; } catch (Exception e) { throw new FalconException("Failed to get key metadata", e); } } /** * Rotate key pair (generate new and re-sign) */ public KeyRotationResult rotateKey(FalconKeyPair oldKeyPair, List<byte[]> signedMessages) throws FalconException { try { // Generate new key pair FalconKeyPair newKeyPair = generateKeyPair(oldKeyPair.getParameter()); // Re-sign messages with new key FalconSigningService signingService = new FalconSigningService(); List<byte[]> newSignatures = new ArrayList<>(); for (byte[] message : signedMessages) { byte[] signature = signingService.sign(message, newKeyPair.getPrivateKey()); newSignatures.add(signature); } return new KeyRotationResult(oldKeyPair, newKeyPair, newSignatures); } catch (Exception e) { throw new FalconException("Key rotation failed", e); } } private AlgorithmParameterSpec getParameterSpec(FalconParameter parameter) { switch (parameter) { case FALCON_512: return new FalconParameterSpec(512); case FALCON_1024: return new FalconParameterSpec(1024); default: throw new IllegalArgumentException("Unsupported parameter: " + parameter); } } private byte[] deriveSeedFromPassword(char[] password, byte[] salt, int keyLength) throws NoSuchAlgorithmException, InvalidKeySpecException { PBEKeySpec spec = new PBEKeySpec(password, salt, 100000, keyLength * 8); SecretKeyFactory factory = SecretKeyFactory.getInstance("PBKDF2WithHmacSHA256"); SecretKey key = factory.generateSecret(spec); return key.getEncoded(); } private X509Certificate[] createSelfSignedCertificate(FalconKeyPair keyPair) throws Exception { // Generate self-signed certificate // Implementation using Bouncy Castle X509v3CertificateBuilder // Returns certificate chain return new X509Certificate[0]; // Placeholder } private String calculateKeyHash(byte[] publicKey) throws NoSuchAlgorithmException { MessageDigest digest = MessageDigest.getInstance("SHA-256"); byte[] hash = digest.digest(publicKey); return Hex.toHexString(hash); } // Data classes public static class FalconKeyPair { private final byte[] publicKey; private final byte[] privateKey; private final FalconParameter parameter; private final long creationTime; public FalconKeyPair(byte[] publicKey, byte[] privateKey, FalconParameter parameter, long creationTime) { this.publicKey = publicKey; this.privateKey = privateKey; this.parameter = parameter; this.creationTime = creationTime; } public byte[] getPublicKey() { return publicKey; } public byte[] getPrivateKey() { return privateKey; } public FalconParameter getParameter() { return parameter; } public long getCreationTime() { return creationTime; } public int getPublicKeySize() { return publicKey.length; } public int getPrivateKeySize() { return privateKey.length; } } public static class FalconPublicKey { private final PublicKey publicKey; private final FalconParameter parameter; private final long creationTime; public FalconPublicKey(PublicKey publicKey, FalconParameter parameter) { this.publicKey = publicKey; this.parameter = parameter; this.creationTime = System.currentTimeMillis(); } // getters } public static class FalconPrivateKey { private final PrivateKey privateKey; private final FalconParameter parameter; private final long creationTime; public FalconPrivateKey(PrivateKey privateKey, FalconParameter parameter) { this.privateKey = privateKey; this.parameter = parameter; this.creationTime = System.currentTimeMillis(); } // getters } public static class KeyMetadata { private String algorithm; private FalconParameter parameter; private int publicKeySize; private long creationTime; private String keyHash; // getters and setters } public static class KeyRotationResult { private final FalconKeyPair oldKeyPair; private final FalconKeyPair newKeyPair; private final List<byte[]> newSignatures; public KeyRotationResult(FalconKeyPair oldKeyPair, FalconKeyPair newKeyPair, List<byte[]> newSignatures) { this.oldKeyPair = oldKeyPair; this.newKeyPair = newKeyPair; this.newSignatures = newSignatures; } // getters } public static class FalconException extends Exception { public FalconException(String message) { super(message); } public FalconException(String message, Throwable cause) { super(message, cause); } } }

3. Falcon Signing Service

package com.falcon.signature; import org.bouncycastle.crypto.digests.SHA256Digest; import org.bouncycastle.crypto.digests.SHA512Digest; import org.bouncycastle.util.encoders.Hex; import org.springframework.stereotype.Service; import java.nio.ByteBuffer; import java.nio.charset.StandardCharsets; import java.security.*; import java.util.*; import java.util.concurrent.*; @Service public class FalconSigningService { private static final Logger logger = LoggerFactory.getLogger(FalconSigningService.class); // Signature format version private static final byte SIGNATURE_VERSION = 0x01; // Supported hash algorithms public enum HashAlgorithm { SHA256(32), SHA512(64), SHAKE128(32), SHAKE256(64); final int outputLength; HashAlgorithm(int outputLength) { this.outputLength = outputLength; } public int getOutputLength() { return outputLength; } } // Thread-local for performance private final ThreadLocal<MessageDigest> digestCache = new ThreadLocal<>(); private final ExecutorService signingExecutor = Executors.newFixedThreadPool( Runtime.getRuntime().availableProcessors() ); /** * Sign message with Falcon private key */ public byte[] sign(byte[] message, byte[] privateKey) throws FalconException { try { long startTime = System.nanoTime(); // Load private key PrivateKey key = loadPrivateKey(privateKey); // Initialize signature Signature falconSig = Signature.getInstance("Falcon", "PQC"); falconSig.initSign(key); // Hash message (Falcon handles hashing internally) falconSig.update(message); // Generate signature byte[] signature = falconSig.sign(); // Add version header byte[] versionedSignature = addVersionHeader(signature); long duration = System.nanoTime() - startTime; logger.debug("Signed {} bytes in {} ms", message.length, duration / 1_000_000); return versionedSignature; } catch (Exception e) { throw new FalconException("Signing failed", e); } } /** * Sign message with explicit hash algorithm */ public byte[] signWithHash(byte[] message, byte[] privateKey, HashAlgorithm hashAlg) throws FalconException { try { // Hash message first byte[] messageHash = hashMessage(message, hashAlg); // Sign the hash PrivateKey key = loadPrivateKey(privateKey); Signature falconSig = Signature.getInstance("Falcon", "PQC"); falconSig.initSign(key); falconSig.update(messageHash); byte[] signature = falconSig.sign(); // Add metadata (hash algorithm) return addMetadata(signature, hashAlg, messageHash.length); } catch (Exception e) { throw new FalconException("Signing with hash failed", e); } } /** * Verify signature with public key */ public boolean verify(byte[] message, byte[] signature, byte[] publicKey) throws FalconException { try { // Remove version header byte[] rawSignature = removeVersionHeader(signature); // Load public key PublicKey key = loadPublicKey(publicKey); // Initialize verification Signature falconSig = Signature.getInstance("Falcon", "PQC"); falconSig.initVerify(key); falconSig.update(message); // Verify boolean verified = falconSig.verify(rawSignature); logger.debug("Signature verification: {}", verified); return verified; } catch (Exception e) { throw new FalconException("Verification failed", e); } } /** * Batch sign multiple messages */ public List<byte[]> batchSign(List<byte[]> messages, byte[] privateKey) throws FalconException { List<CompletableFuture<byte[]>> futures = new ArrayList<>(); for (byte[] message : messages) { CompletableFuture<byte[]> future = CompletableFuture.supplyAsync(() -> { try { return sign(message, privateKey); } catch (FalconException e) { throw new RuntimeException(e); } }, signingExecutor); futures.add(future); } try { List<byte[]> signatures = new ArrayList<>(); for (CompletableFuture<byte[]> future : futures) { signatures.add(future.get(30, TimeUnit.SECONDS)); } return signatures; } catch (Exception e) { throw new FalconException("Batch signing failed", e); } } /** * Sign streaming data */ public byte[] signStream(InputStream dataStream, byte[] privateKey, int bufferSize) throws FalconException, IOException { try { PrivateKey key = loadPrivateKey(privateKey); Signature falconSig = Signature.getInstance("Falcon", "PQC"); falconSig.initSign(key); byte[] buffer = new byte[bufferSize]; int bytesRead; while ((bytesRead = dataStream.read(buffer)) != -1) { falconSig.update(buffer, 0, bytesRead); } return falconSig.sign(); } catch (Exception e) { throw new FalconException("Stream signing failed", e); } } /** * Sign with context string (for domain separation) */ public byte[] signWithContext(byte[] message, byte[] privateKey, String context) throws FalconException { try { // Create context-aware message byte[] contextBytes = context.getBytes(StandardCharsets.UTF_8); byte[] messageWithContext = ByteBuffer.allocate(4 + contextBytes.length + message.length) .putInt(contextBytes.length) .put(contextBytes) .put(message) .array(); return sign(messageWithContext, privateKey); } catch (Exception e) { throw new FalconException("Context-aware signing failed", e); } } /** * Extract signature metadata */ public SignatureMetadata extractMetadata(byte[] signature) { SignatureMetadata metadata = new SignatureMetadata(); // Parse version metadata.setVersion(signature[0]); // Parse hash algorithm if present if (signature.length > 1 && (signature[1] & 0x80) != 0) { int hashAlgCode = signature[1] & 0x7F; metadata.setHashAlgorithm(HashAlgorithm.values()[hashAlgCode]); // Get hash length metadata.setHashLength(signature[2]); // Raw signature starts at position 3 metadata.setRawSignatureOffset(3); } else { metadata.setRawSignatureOffset(1); } metadata.setSignatureSize(signature.length); metadata.setRawSignatureSize(signature.length - metadata.getRawSignatureOffset()); return metadata; } /** * Verify signature and return verification time */ public VerificationResult verifyWithTiming(byte[] message, byte[] signature, byte[] publicKey) throws FalconException { long startTime = System.nanoTime(); boolean verified = verify(message, signature, publicKey); long duration = System.nanoTime() - startTime; return new VerificationResult(verified, duration); } private PrivateKey loadPrivateKey(byte[] privateKeyBytes) throws Exception { KeyFactory keyFactory = KeyFactory.getInstance("Falcon", "PQC"); PKCS8EncodedKeySpec keySpec = new PKCS8EncodedKeySpec(privateKeyBytes); return keyFactory.generatePrivate(keySpec); } private PublicKey loadPublicKey(byte[] publicKeyBytes) throws Exception { KeyFactory keyFactory = KeyFactory.getInstance("Falcon", "PQC"); X509EncodedKeySpec keySpec = new X509EncodedKeySpec(publicKeyBytes); return keyFactory.generatePublic(keySpec); } private byte[] hashMessage(byte[] message, HashAlgorithm hashAlg) throws NoSuchAlgorithmException { MessageDigest digest; switch (hashAlg) { case SHA256: digest = MessageDigest.getInstance("SHA-256"); break; case SHA512: digest = MessageDigest.getInstance("SHA-512"); break; case SHAKE128: case SHAKE256: // Use Bouncy Castle for SHAKE digest = MessageDigest.getInstance(hashAlg.name(), "BC"); break; default: throw new IllegalArgumentException("Unsupported hash: " + hashAlg); } return digest.digest(message); } private byte[] addVersionHeader(byte[] signature) { byte[] versioned = new byte[signature.length + 1]; versioned[0] = SIGNATURE_VERSION; System.arraycopy(signature, 0, versioned, 1, signature.length); return versioned; } private byte[] removeVersionHeader(byte[] versionedSignature) { if (versionedSignature[0] != SIGNATURE_VERSION) { throw new IllegalArgumentException("Invalid signature version"); } return Arrays.copyOfRange(versionedSignature, 1, versionedSignature.length); } private byte[] addMetadata(byte[] signature, HashAlgorithm hashAlg, int hashLength) { byte[] withMetadata = new byte[signature.length + 3]; withMetadata[0] = SIGNATURE_VERSION; withMetadata[1] = (byte) (0x80 | hashAlg.ordinal()); withMetadata[2] = (byte) hashLength; System.arraycopy(signature, 0, withMetadata, 3, signature.length); return withMetadata; } // Data classes public static class SignatureMetadata { private byte version; private HashAlgorithm hashAlgorithm; private int hashLength; private int rawSignatureOffset; private int signatureSize; private int rawSignatureSize; // getters and setters } public static class VerificationResult { private final boolean verified; private final long verificationTimeNanos; public VerificationResult(boolean verified, long verificationTimeNanos) { this.verified = verified; this.verificationTimeNanos = verificationTimeNanos; } // getters } public static class FalconException extends Exception { public FalconException(String message) { super(message); } public FalconException(String message, Throwable cause) { super(message, cause); } } }

4. Falcon Key Management Service

package com.falcon.signature; import com.google.crypto.tink.*; import com.google.crypto.tink.aead.AeadConfig; import org.springframework.stereotype.Service; import javax.crypto.SecretKey; import javax.crypto.spec.SecretKeySpec; import java.security.*; import java.util.*; import java.util.concurrent.ConcurrentHashMap; @Service public class FalconKeyManagementService { static { try { AeadConfig.register(); } catch (GeneralSecurityException e) { throw new RuntimeException("Failed to initialize Tink", e); } } private final Map<String, KeyEntry> keyStore = new ConcurrentHashMap<>(); private final Map<String, KeyPolicy> keyPolicies = new ConcurrentHashMap<>(); private final FalconKeyGenerationService keyGenService; private final SecureRandom secureRandom = new SecureRandom(); public FalconKeyManagementService(FalconKeyGenerationService keyGenService) { this.keyGenService = keyGenService; } /** * Store key with metadata */ public String storeKey(String keyId, byte[] privateKey, byte[] publicKey, KeyMetadata metadata) throws KeyManagementException { KeyEntry entry = new KeyEntry( keyId, privateKey, publicKey, metadata, System.currentTimeMillis(), KeyStatus.ACTIVE ); keyStore.put(keyId, entry); logger.info("Stored key: {}", keyId); return keyId; } /** * Generate and store new key */ public String generateAndStoreKey(String keyId, FalconKeyGenerationService.FalconParameter parameter, KeyPolicy policy) throws KeyManagementException { try { // Generate key pair FalconKeyGenerationService.FalconKeyPair keyPair = keyGenService.generateKeyPair(parameter); // Create metadata KeyMetadata metadata = new KeyMetadata(); metadata.setKeyId(keyId); metadata.setParameter(parameter); metadata.setCreationTime(System.currentTimeMillis()); metadata.setAlgorithm("Falcon"); metadata.setPublicKeySize(keyPair.getPublicKey().length); // Store key storeKey(keyId, keyPair.getPrivateKey(), keyPair.getPublicKey(), metadata); // Store policy if (policy != null) { keyPolicies.put(keyId, policy); } return keyId; } catch (Exception e) { throw new KeyManagementException("Failed to generate and store key", e); } } /** * Get key for signing */ public SigningKey getSigningKey(String keyId) throws KeyManagementException { KeyEntry entry = keyStore.get(keyId); if (entry == null) { throw new KeyManagementException("Key not found: " + keyId); } if (entry.getStatus() != KeyStatus.ACTIVE) { throw new KeyManagementException("Key is not active: " + keyId); } // Check policy KeyPolicy policy = keyPolicies.get(keyId); if (policy != null && !policy.isAllowedForSigning()) { throw new KeyManagementException("Key not allowed for signing"); } return new SigningKey(keyId, entry.getPrivateKey(), entry.getMetadata()); } /** * Get key for verification */ public VerificationKey getVerificationKey(String keyId) throws KeyManagementException { KeyEntry entry = keyStore.get(keyId); if (entry == null) { throw new KeyManagementException("Key not found: " + keyId); } if (entry.getStatus() == KeyStatus.REVOKED) { throw new KeyManagementException("Key is revoked: " + keyId); } return new VerificationKey(keyId, entry.getPublicKey(), entry.getMetadata()); } /** * Rotate key */ public KeyRotationResult rotateKey(String keyId) throws KeyManagementException { KeyEntry oldEntry = keyStore.get(keyId); if (oldEntry == null) { throw new KeyManagementException("Key not found: " + keyId); } try { // Generate new key String newKeyId = keyId + "_" + System.currentTimeMillis(); FalconKeyGenerationService.FalconKeyPair newKeyPair = keyGenService.generateKeyPair(oldEntry.getMetadata().getParameter()); // Create metadata for new key KeyMetadata newMetadata = new KeyMetadata(); newMetadata.setKeyId(newKeyId); newMetadata.setParameter(oldEntry.getMetadata().getParameter()); newMetadata.setCreationTime(System.currentTimeMillis()); newMetadata.setAlgorithm("Falcon"); newMetadata.setPublicKeySize(newKeyPair.getPublicKey().length); // Store new key storeKey(newKeyId, newKeyPair.getPrivateKey(), newKeyPair.getPublicKey(), newMetadata); // Mark old key as rotated oldEntry.setStatus(KeyStatus.ROTATED); // Copy policy to new key KeyPolicy policy = keyPolicies.get(keyId); if (policy != null) { keyPolicies.put(newKeyId, policy); } return new KeyRotationResult(keyId, newKeyId); } catch (Exception e) { throw new KeyManagementException("Key rotation failed", e); } } /** * Revoke key */ public void revokeKey(String keyId, RevocationReason reason) throws KeyManagementException { KeyEntry entry = keyStore.get(keyId); if (entry == null) { throw new KeyManagementException("Key not found: " + keyId); } entry.setStatus(KeyStatus.REVOKED); entry.setRevocationReason(reason); entry.setRevocationTime(System.currentTimeMillis()); logger.warn("Key revoked: {} - {}", keyId, reason); } /** * Backup key with encryption */ public byte[] backupKey(String keyId, byte[] encryptionKey) throws KeyManagementException { KeyEntry entry = keyStore.get(keyId); if (entry == null) { throw new KeyManagementException("Key not found: " + keyId); } try { // Create backup structure KeyBackup backup = new KeyBackup( entry.getPrivateKey(), entry.getPublicKey(), entry.getMetadata(), entry.getCreationTime(), entry.getStatus() ); // Serialize byte[] serialized = serializeBackup(backup); // Encrypt Aead aead = createAead(encryptionKey); byte[] encrypted = aead.encrypt(serialized, ("key_backup_" + keyId).getBytes()); return encrypted; } catch (Exception e) { throw new KeyManagementException("Key backup failed", e); } } /** * Restore key from backup */ public String restoreKey(byte[] encryptedBackup, byte[] encryptionKey) throws KeyManagementException { try { // Decrypt Aead aead = createAead(encryptionKey); byte[] serialized = aead.decrypt(encryptedBackup, "key_backup_".getBytes()); // Deserialize KeyBackup backup = deserializeBackup(serialized); // Restore key String keyId = backup.getMetadata().getKeyId() + "_restored"; storeKey(keyId, backup.getPrivateKey(), backup.getPublicKey(), backup.getMetadata()); return keyId; } catch (Exception e) { throw new KeyManagementException("Key restoration failed", e); } } /** * List all keys */ public List<KeyInfo> listKeys(KeyFilter filter) { List<KeyInfo> keys = new ArrayList<>(); for (Map.Entry<String, KeyEntry> entry : keyStore.entrySet()) { if (filter == null || filter.matches(entry.getValue())) { keys.add(new KeyInfo( entry.getKey(), entry.getValue().getMetadata(), entry.getValue().getStatus(), entry.getValue().getCreationTime() )); } } return keys; } /** * Set key policy */ public void setKeyPolicy(String keyId, KeyPolicy policy) { keyPolicies.put(keyId, policy); logger.info("Policy set for key: {}", keyId); } /** * Get key policy */ public KeyPolicy getKeyPolicy(String keyId) { return keyPolicies.get(keyId); } private Aead createAead(byte[] keyBytes) throws GeneralSecurityException { KeysetHandle keysetHandle = KeysetHandle.generateNew( KeyTemplates.get("AES256_GCM") ); return keysetHandle.getPrimitive(Aead.class); } private byte[] serializeBackup(KeyBackup backup) { // Implement serialization (e.g., using Protocol Buffers) return new byte[0]; } private KeyBackup deserializeBackup(byte[] serialized) { // Implement deserialization return null; } // Data classes public enum KeyStatus { ACTIVE, ROTATED, REVOKED, EXPIRED } public enum RevocationReason { COMPROMISED, SUPERSEDED, CESSATION_OF_OPERATION, AFFILIATION_CHANGED } public static class KeyEntry { private final String keyId; private final byte[] privateKey; private final byte[] publicKey; private final KeyMetadata metadata; private final long creationTime; private KeyStatus status; private RevocationReason revocationReason; private long revocationTime; // constructor and getters/setters } public static class KeyMetadata { private String keyId; private FalconKeyGenerationService.FalconParameter parameter; private long creationTime; private String algorithm; private int publicKeySize; private Map<String, String> attributes; // getters and setters } public static class KeyPolicy { private boolean allowedForSigning = true; private boolean allowedForVerification = true; private int maxSignatures = -1; private long expirationTime = -1; private List<String> allowedApplications; private boolean requireAuditLogging = true; // getters and setters } public static class SigningKey { private final String keyId; private final byte[] privateKey; private final KeyMetadata metadata; // constructor and getters } public static class VerificationKey { private final String keyId; private final byte[] publicKey; private final KeyMetadata metadata; // constructor and getters } public static class KeyBackup { private final byte[] privateKey; private final byte[] publicKey; private final KeyMetadata metadata; private final long backupTime; private final KeyStatus originalStatus; // constructor and getters } public static class KeyInfo { private final String keyId; private final KeyMetadata metadata; private final KeyStatus status; private final long creationTime; // constructor and getters } public interface KeyFilter { boolean matches(KeyEntry entry); } public static class KeyManagementException extends Exception { public KeyManagementException(String message) { super(message); } public KeyManagementException(String message, Throwable cause) { super(message, cause); } } }

5. Falcon Native Bridge (JNI)

// falcon_jni.c #include <jni.h> #include <falcon.h> #include <stdio.h> // Native method implementations JNIEXPORT jbyteArray JNICALL Java_com_falcon_signature_FalconNativeBridge_generateKeyPairNative( JNIEnv *env, jobject thiz, jint logn) { falcon_keypair_t *keypair; uint8_t *public_key; uint8_t *private_key; size_t public_key_len; size_t private_key_len; // Generate Falcon key pair int result = falcon_keypair_generate(&keypair, logn); if (result != FALCON_SUCCESS) { return NULL; } // Export keys falcon_keypair_get_public_key(keypair, &public_key, &public_key_len); falcon_keypair_get_private_key(keypair, &private_key, &private_key_len); // Combine keys for return jbyteArray result_array = (*env)->NewByteArray(env, public_key_len + private_key_len); jbyte *buffer = (*env)->GetByteArrayElements(env, result_array, NULL); memcpy(buffer, public_key, public_key_len); memcpy(buffer + public_key_len, private_key, private_key_len); (*env)->ReleaseByteArrayElements(env, result_array, buffer, 0); // Cleanup falcon_keypair_destroy(keypair); free(public_key); free(private_key); return result_array; } JNIEXPORT jbyteArray JNICALL Java_com_falcon_signature_FalconNativeBridge_signNative( JNIEnv *env, jobject thiz, jbyteArray message, jbyteArray privateKey) { // Get message bytes jbyte *message_bytes = (*env)->GetByteArrayElements(env, message, NULL); jsize message_len = (*env)->GetArrayLength(env, message); // Get private key bytes jbyte *key_bytes = (*env)->GetByteArrayElements(env, privateKey, NULL); jsize key_len = (*env)->GetArrayLength(env, privateKey); // Load private key falcon_private_key_t *priv_key; falcon_private_key_import(&priv_key, (uint8_t*)key_bytes, key_len); // Sign message uint8_t *signature; size_t signature_len; int result = falcon_sign(priv_key, (uint8_t*)message_bytes, message_len, &signature, &signature_len); // Release elements (*env)->ReleaseByteArrayElements(env, message, message_bytes, 0); (*env)->ReleaseByteArrayElements(env, privateKey, key_bytes, 0); if (result != FALCON_SUCCESS) { falcon_private_key_destroy(priv_key); return NULL; } // Create result array jbyteArray result_array = (*env)->NewByteArray(env, signature_len); (*env)->SetByteArrayRegion(env, result_array, 0, signature_len, (jbyte*)signature); // Cleanup falcon_private_key_destroy(priv_key); free(signature); return result_array; } JNIEXPORT jboolean JNICALL Java_com_falcon_signature_FalconNativeBridge_verifyNative( JNIEnv *env, jobject thiz, jbyteArray message, jbyteArray signature, jbyteArray publicKey) { // Get message bytes jbyte *message_bytes = (*env)->GetByteArrayElements(env, message, NULL); jsize message_len = (*env)->GetArrayLength(env, message); // Get signature bytes jbyte *sig_bytes = (*env)->GetByteArrayElements(env, signature, NULL); jsize sig_len = (*env)->GetArrayLength(env, signature); // Get public key bytes jbyte *key_bytes = (*env)->GetByteArrayElements(env, publicKey, NULL); jsize key_len = (*env)->GetArrayLength(env, publicKey); // Load public key falcon_public_key_t *pub_key; falcon_public_key_import(&pub_key, (uint8_t*)key_bytes, key_len); // Verify signature int result = falcon_verify(pub_key, (uint8_t*)message_bytes, message_len, (uint8_t*)sig_bytes, sig_len); // Release elements (*env)->ReleaseByteArrayElements(env, message, message_bytes, 0); (*env)->ReleaseByteArrayElements(env, signature, sig_bytes, 0); (*env)->ReleaseByteArrayElements(env, publicKey, key_bytes, 0); // Cleanup falcon_public_key_destroy(pub_key); return result == FALCON_SUCCESS ? JNI_TRUE : JNI_FALSE; }

6. Falcon Native Bridge Java Wrapper

package com.falcon.signature; import com.sun.jna.Library; import com.sun.jna.Native; import com.sun.jna.Platform; import com.sun.jna.Pointer; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.stereotype.Component; import javax.annotation.PostConstruct; import java.io.*; import java.nio.file.*; @Component public class FalconNativeBridge { private static final Logger logger = LoggerFactory.getLogger(FalconNativeBridge.class); // Load native library static { try { // Extract and load native library extractAndLoadLibrary(); } catch (IOException e) { logger.error("Failed to load Falcon native library", e); throw new RuntimeException("Native library loading failed", e); } } private native byte[] generateKeyPairNative(int logn); private native byte[] signNative(byte[] message, byte[] privateKey); private native boolean verifyNative(byte[] message, byte[] signature, byte[] publicKey); /** * Generate Falcon key pair using native implementation */ public FalconKeyGenerationService.FalconKeyPair generateKeyPair( FalconKeyGenerationService.FalconParameter parameter) throws FalconException { try { int logn = getLognForParameter(parameter); byte[] keyPairBytes = generateKeyPairNative(logn); // Split into public and private keys int keySize = getKeySizeForParameter(parameter); byte[] publicKey = new byte[keySize]; byte[] privateKey = new byte[keyPairBytes.length - keySize]; System.arraycopy(keyPairBytes, 0, publicKey, 0, keySize); System.arraycopy(keyPairBytes, keySize, privateKey, 0, privateKey.length); return new FalconKeyGenerationService.FalconKeyPair( publicKey, privateKey, parameter, System.currentTimeMillis() ); } catch (Exception e) { throw new FalconException("Native key generation failed", e); } } /** * Sign using native implementation */ public byte[] sign(byte[] message, byte[] privateKey) throws FalconException { try { return signNative(message, privateKey); } catch (Exception e) { throw new FalconException("Native signing failed", e); } } /** * Verify using native implementation */ public boolean verify(byte[] message, byte[] signature, byte[] publicKey) throws FalconException { try { return verifyNative(message, signature, publicKey); } catch (Exception e) { throw new FalconException("Native verification failed", e); } } /** * Benchmark native performance */ public NativeBenchmark benchmarkNative(int iterations) throws FalconException { NativeBenchmark benchmark = new NativeBenchmark(); try { // Key generation benchmark long start = System.nanoTime(); for (int i = 0; i < iterations; i++) { generateKeyPair(FalconKeyGenerationService.FalconParameter.FALCON_512); } long keyGenTime = System.nanoTime() - start; benchmark.setKeyGenerationAvgNanos(keyGenTime / iterations); // Signing benchmark byte[] testMessage = "Benchmark message".getBytes(); FalconKeyGenerationService.FalconKeyPair keyPair = generateKeyPair(FalconKeyGenerationService.FalconParameter.FALCON_512); start = System.nanoTime(); for (int i = 0; i < iterations; i++) { sign(testMessage, keyPair.getPrivateKey()); } long signTime = System.nanoTime() - start; benchmark.setSigningAvgNanos(signTime / iterations); // Verification benchmark byte[] signature = sign(testMessage, keyPair.getPrivateKey()); start = System.nanoTime(); for (int i = 0; i < iterations; i++) { verify(testMessage, signature, keyPair.getPublicKey()); } long verifyTime = System.nanoTime() - start; benchmark.setVerificationAvgNanos(verifyTime / iterations); } catch (Exception e) { throw new FalconException("Benchmark failed", e); } return benchmark; } private static void extractAndLoadLibrary() throws IOException { String libName = System.mapLibraryName("falcon_jni"); String osName = System.getProperty("os.name").toLowerCase(); String osArch = System.getProperty("os.arch"); // Determine resource path based on OS and architecture String resourcePath = String.format("/native/%s/%s/%s", osName.contains("win") ? "windows" : osName.contains("mac") ? "darwin" : "linux", osArch, libName ); // Extract library to temp directory try (InputStream is = FalconNativeBridge.class.getResourceAsStream(resourcePath)) { if (is == null) { throw new IOException("Native library not found: " + resourcePath); } Path tempLib = Files.createTempFile("libfalcon_jni", libName.substring(libName.lastIndexOf('.'))); Files.copy(is, tempLib, StandardCopyOption.REPLACE_EXISTING); // Load library System.load(tempLib.toAbsolutePath().toString()); logger.info("Loaded Falcon native library from: {}", tempLib); // Schedule cleanup on exit tempLib.toFile().deleteOnExit(); } } private int getLognForParameter(FalconKeyGenerationService.FalconParameter parameter) { switch (parameter) { case FALCON_512: return 9; // 2^9 = 512 case FALCON_1024: return 10; // 2^10 = 1024 default: throw new IllegalArgumentException("Unsupported parameter: " + parameter); } } private int getKeySizeForParameter(FalconKeyGenerationService.FalconParameter parameter) { switch (parameter) { case FALCON_512: return 897; // Falcon-512 public key size case FALCON_1024: return 1793; // Falcon-1024 public key size default: throw new IllegalArgumentException("Unsupported parameter: " + parameter); } } public static class NativeBenchmark { private long keyGenerationAvgNanos; private long signingAvgNanos; private long verificationAvgNanos; // getters and setters } public static class FalconException extends Exception { public FalconException(String message) { super(message); } public FalconException(String message, Throwable cause) { super(message, cause); } } }

7. Falcon Hybrid Encryption Service

package com.falcon.signature; import com.google.crypto.tink.*; import com.google.crypto.tink.aead.AeadConfig; import org.springframework.stereotype.Service; import javax.crypto.*; import javax.crypto.spec.*; import java.security.*; import java.util.Arrays; @Service public class FalconHybridService { static { try { AeadConfig.register(); } catch (GeneralSecurityException e) { throw new RuntimeException("Failed to initialize Tink", e); } } private final FalconKeyGenerationService keyGenService; private final FalconSigningService signingService; public FalconHybridService(FalconKeyGenerationService keyGenService, FalconSigningService signingService) { this.keyGenService = keyGenService; this.signingService = signingService; } /** * Sign-then-Encrypt hybrid operation */ public HybridCiphertext signThenEncrypt(byte[] plaintext, byte[] signerPrivateKey, byte[] recipientPublicKey) throws HybridException { try { // Step 1: Sign the plaintext byte[] signature = signingService.sign(plaintext, signerPrivateKey); // Step 2: Generate symmetric key SecretKey symmetricKey = generateSymmetricKey(); byte[] iv = generateIV(); // Step 3: Encrypt plaintext with symmetric key byte[] ciphertext = encryptSymmetric(plaintext, symmetricKey, iv); // Step 4: Encrypt symmetric key with recipient's public key byte[] encryptedKey = encryptKeyWithFalcon(symmetricKey, recipientPublicKey); // Step 5: Combine all parts return new HybridCiphertext( encryptedKey, iv, ciphertext, signature ); } catch (Exception e) { throw new HybridException("Sign-then-encrypt failed", e); } } /** * Decrypt-then-Verify hybrid operation */ public byte[] decryptThenVerify(HybridCiphertext ciphertext, byte[] recipientPrivateKey, byte[] signerPublicKey) throws HybridException { try { // Step 1: Decrypt symmetric key SecretKey symmetricKey = decryptKeyWithFalcon( ciphertext.getEncryptedKey(), recipientPrivateKey ); // Step 2: Decrypt ciphertext byte[] plaintext = decryptSymmetric( ciphertext.getCiphertext(), symmetricKey, ciphertext.getIv() ); // Step 3: Verify signature boolean verified = signingService.verify( plaintext, ciphertext.getSignature(), signerPublicKey ); if (!verified) { throw new HybridException("Signature verification failed"); } return plaintext; } catch (Exception e) { throw new HybridException("Decrypt-then-verify failed", e); } } /** * Signcryption (combined sign and encrypt) */ public SigncryptedData signcrypt(byte[] plaintext, byte[] senderPrivateKey, byte[] recipientPublicKey) throws HybridException { try { // Generate ephemeral key pair for key exchange FalconKeyGenerationService.FalconKeyPair ephemeralKey = keyGenService.generateKeyPair(FalconKeyGenerationService.FalconParameter.FALCON_512); // Derive shared secret byte[] sharedSecret = deriveSharedSecret( ephemeralKey.getPrivateKey(), recipientPublicKey ); // Generate encryption key from shared secret SecretKey encryptionKey = deriveEncryptionKey(sharedSecret); byte[] iv = generateIV(); // Encrypt plaintext byte[] ciphertext = encryptSymmetric(plaintext, encryptionKey, iv); // Sign the ciphertext + ephemeral public key byte[] dataToSign = concatenate(ciphertext, ephemeralKey.getPublicKey()); byte[] signature = signingService.sign(dataToSign, senderPrivateKey); return new SigncryptedData( ephemeralKey.getPublicKey(), iv, ciphertext, signature ); } catch (Exception e) { throw new HybridException("Signcryption failed", e); } } /** * Unsigncrypt (verify and decrypt) */ public byte[] unsigncrypt(SigncryptedData signcryptedData, byte[] recipientPrivateKey, byte[] senderPublicKey) throws HybridException { try { // Derive shared secret using recipient's private key and sender's ephemeral key byte[] sharedSecret = deriveSharedSecret( recipientPrivateKey, signcryptedData.getEphemeralPublicKey() ); // Derive decryption key SecretKey decryptionKey = deriveEncryptionKey(sharedSecret); // Verify signature byte[] dataToVerify = concatenate( signcryptedData.getCiphertext(), signcryptedData.getEphemeralPublicKey() ); boolean verified = signingService.verify( dataToVerify, signcryptedData.getSignature(), senderPublicKey ); if (!verified) { throw new HybridException("Signature verification failed"); } // Decrypt return decryptSymmetric( signcryptedData.getCiphertext(), decryptionKey, signcryptedData.getIv() ); } catch (Exception e) { throw new HybridException("Unsigncryption failed", e); } } private SecretKey generateSymmetricKey() throws NoSuchAlgorithmException { KeyGenerator keyGen = KeyGenerator.getInstance("AES"); keyGen.init(256); return keyGen.generateKey(); } private byte[] generateIV() { byte[] iv = new byte[12]; new SecureRandom().nextBytes(iv); return iv; } private byte[] encryptSymmetric(byte[] plaintext, SecretKey key, byte[] iv) throws Exception { Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding"); GCMParameterSpec spec = new GCMParameterSpec(128, iv); cipher.init(Cipher.ENCRYPT_MODE, key, spec); return cipher.doFinal(plaintext); } private byte[] decryptSymmetric(byte[] ciphertext, SecretKey key, byte[] iv) throws Exception { Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding"); GCMParameterSpec spec = new GCMParameterSpec(128, iv); cipher.init(Cipher.DECRYPT_MODE, key, spec); return cipher.doFinal(ciphertext); } private byte[] encryptKeyWithFalcon(SecretKey key, byte[] recipientPublicKey) throws FalconSigningService.FalconException { // Encrypt symmetric key using Falcon-based key encapsulation // This is simplified - actual implementation would use proper KEM byte[] keyBytes = key.getEncoded(); return signingService.sign(keyBytes, recipientPublicKey); } private SecretKey decryptKeyWithFalcon(byte[] encryptedKey, byte[] recipientPrivateKey) throws FalconSigningService.FalconException, NoSuchAlgorithmException { // Decrypt symmetric key byte[] keyBytes = signingService.verifyAndExtract(encryptedKey, recipientPrivateKey); return new SecretKeySpec(keyBytes, "AES"); } private byte[] deriveSharedSecret(byte[] privateKey, byte[] publicKey) { // Derive shared secret using Falcon-based key agreement // Implementation would use lattice-based key exchange return new byte[32]; // Placeholder } private SecretKey deriveEncryptionKey(byte[] sharedSecret) { byte[] keyBytes = Arrays.copyOf(sharedSecret, 32); return new SecretKeySpec(keyBytes, "AES"); } private byte[] concatenate(byte[] a, byte[] b) { byte[] result = new byte[a.length + b.length]; System.arraycopy(a, 0, result, 0, a.length); System.arraycopy(b, 0, result, a.length, b.length); return result; } // Data classes public static class HybridCiphertext { private final byte[] encryptedKey; private final byte[] iv; private final byte[] ciphertext; private final byte[] signature; public HybridCiphertext(byte[] encryptedKey, byte[] iv, byte[] ciphertext, byte[] signature) { this.encryptedKey = encryptedKey; this.iv = iv; this.ciphertext = ciphertext; this.signature = signature; } // getters } public static class SigncryptedData { private final byte[] ephemeralPublicKey; private final byte[] iv; private final byte[] ciphertext; private final byte[] signature; // constructor and getters } public static class HybridException extends Exception { public HybridException(String message) { super(message); } public HybridException(String message, Throwable cause) { super(message, cause); } } }

8. Falcon REST API

package com.falcon.rest; import com.falcon.signature.*; import org.springframework.http.*; import org.springframework.web.bind.annotation.*; import org.springframework.web.multipart.MultipartFile; import java.util.*; import java.util.concurrent.CompletableFuture; @RestController @RequestMapping("/api/falcon") public class FalconController { private final FalconKeyGenerationService keyGenService; private final FalconSigningService signingService; private final FalconKeyManagementService keyMgmtService; private final FalconNativeBridge nativeBridge; public FalconController(FalconKeyGenerationService keyGenService, FalconSigningService signingService, FalconKeyManagementService keyMgmtService, FalconNativeBridge nativeBridge) { this.keyGenService = keyGenService; this.signingService = signingService; this.keyMgmtService = keyMgmtService; this.nativeBridge = nativeBridge; } @PostMapping("/keys/generate") public ResponseEntity<KeyResponse> generateKeys( @RequestParam(defaultValue = "FALCON_512") FalconKeyGenerationService.FalconParameter parameter) { try { FalconKeyGenerationService.FalconKeyPair keyPair = keyGenService.generateKeyPair(parameter); // Store key String keyId = keyMgmtService.generateAndStoreKey( UUID.randomUUID().toString(), parameter, null ); return ResponseEntity.ok(new KeyResponse( keyId, Base64.getEncoder().encodeToString(keyPair.getPublicKey()), Base64.getEncoder().encodeToString(keyPair.getPrivateKey()), parameter )); } catch (FalconKeyGenerationService.FalconException | FalconKeyManagementService.KeyManagementException e) { return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR) .body(new KeyResponse("Key generation failed: " + e.getMessage())); } } @PostMapping("/sign") public ResponseEntity<SignatureResponse> sign( @RequestHeader("X-Key-Id") String keyId, @RequestBody SignRequest request) { try { // Get signing key FalconKeyManagementService.SigningKey signingKey = keyMgmtService.getSigningKey(keyId); // Sign message byte[] signature = signingService.sign( request.getMessage().getBytes(), signingKey.getPrivateKey() ); return ResponseEntity.ok(new SignatureResponse( Base64.getEncoder().encodeToString(signature), request.getMessage().length(), signature.length )); } catch (Exception e) { return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR) .body(new SignatureResponse("Signing failed: " + e.getMessage())); } } @PostMapping("/verify") public ResponseEntity<VerifyResponse> verify( @RequestBody VerifyRequest request) { try { // Get verification key FalconKeyManagementService.VerificationKey verificationKey = keyMgmtService.getVerificationKey(request.getKeyId()); // Verify signature boolean verified = signingService.verify( request.getMessage().getBytes(), Base64.getDecoder().decode(request.getSignature()), verificationKey.getPublicKey() ); return ResponseEntity.ok(new VerifyResponse( verified, verified ? "Signature valid" : "Signature invalid" )); } catch (Exception e) { return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR) .body(new VerifyResponse(false, "Verification failed: " + e.getMessage())); } } @PostMapping("/sign/file") public ResponseEntity<FileSignatureResponse> signFile( @RequestHeader("X-Key-Id") String keyId, @RequestParam("file") MultipartFile file) { try { byte[] fileBytes = file.getBytes(); // Get signing key FalconKeyManagementService.SigningKey signingKey = keyMgmtService.getSigningKey(keyId); // Sign file byte[] signature = signingService.sign(fileBytes, signingKey.getPrivateKey()); // Generate file hash String fileHash = calculateFileHash(fileBytes); return ResponseEntity.ok(new FileSignatureResponse( file.getOriginalFilename(), file.getSize(), Base64.getEncoder().encodeToString(signature), fileHash )); } catch (Exception e) { return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR) .body(new FileSignatureResponse("File signing failed: " + e.getMessage())); } } @PostMapping("/verify/file") public ResponseEntity<VerifyResponse> verifyFile( @RequestParam("file") MultipartFile file, @RequestParam("signature") String signatureBase64, @RequestParam("keyId") String keyId) { try { byte[] fileBytes = file.getBytes(); byte[] signature = Base64.getDecoder().decode(signatureBase64); // Get verification key FalconKeyManagementService.VerificationKey verificationKey = keyMgmtService.getVerificationKey(keyId); // Verify signature boolean verified = signingService.verify( fileBytes, signature, verificationKey.getPublicKey() ); return ResponseEntity.ok(new VerifyResponse( verified, verified ? "File signature valid" : "File signature invalid" )); } catch (Exception e) { return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR) .body(new VerifyResponse(false, "File verification failed: " + e.getMessage())); } } @PostMapping("/keys/rotate") public ResponseEntity<RotateResponse> rotateKey( @RequestParam("keyId") String keyId) { try { FalconKeyManagementService.KeyRotationResult result = keyMgmtService.rotateKey(keyId); return ResponseEntity.ok(new RotateResponse( result.getOldKeyId(), result.getNewKeyId(), "Key rotated successfully" )); } catch (FalconKeyManagementService.KeyManagementException e) { return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR) .body(new RotateResponse(keyId, null, "Rotation failed: " + e.getMessage())); } } @PostMapping("/keys/revoke") public ResponseEntity<RevokeResponse> revokeKey( @RequestParam("keyId") String keyId, @RequestParam("reason") FalconKeyManagementService.RevocationReason reason) { try { keyMgmtService.revokeKey(keyId, reason); return ResponseEntity.ok(new RevokeResponse( keyId, reason, "Key revoked successfully" )); } catch (FalconKeyManagementService.KeyManagementException e) { return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR) .body(new RevokeResponse(keyId, reason, "Revocation failed: " + e.getMessage())); } } @GetMapping("/keys") public ResponseEntity<List<FalconKeyManagementService.KeyInfo>> listKeys( @RequestParam(required = false) FalconKeyManagementService.KeyStatus status) { List<FalconKeyManagementService.KeyInfo> keys = keyMgmtService.listKeys( entry -> status == null || entry.getStatus() == status ); return ResponseEntity.ok(keys); } @PostMapping("/batch/sign") public CompletableFuture<ResponseEntity<BatchSignResponse>> batchSign( @RequestHeader("X-Key-Id") String keyId, @RequestBody BatchSignRequest request) { return CompletableFuture.supplyAsync(() -> { try { FalconKeyManagementService.SigningKey signingKey = keyMgmtService.getSigningKey(keyId); List<byte[]> messages = request.getMessages().stream() .map(String::getBytes) .toList(); List<byte[]> signatures = signingService.batchSign( messages, signingKey.getPrivateKey() ); List<String> signatureBase64 = signatures.stream() .map(sig -> Base64.getEncoder().encodeToString(sig)) .toList(); return ResponseEntity.ok(new BatchSignResponse( signatureBase64, messages.size() )); } catch (Exception e) { return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR) .body(new BatchSignResponse("Batch signing failed: " + e.getMessage())); } }); } @GetMapping("/benchmark") public ResponseEntity<BenchmarkResponse> benchmark( @RequestParam(defaultValue = "100") int iterations) { try { FalconNativeBridge.NativeBenchmark benchmark = nativeBridge.benchmarkNative(iterations); return ResponseEntity.ok(new BenchmarkResponse( iterations, benchmark.getKeyGenerationAvgNanos(), benchmark.getSigningAvgNanos(), benchmark.getVerificationAvgNanos() )); } catch (FalconNativeBridge.FalconException e) { return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR) .body(new BenchmarkResponse("Benchmark failed: " + e.getMessage())); } } private String calculateFileHash(byte[] fileBytes) throws NoSuchAlgorithmException { MessageDigest digest = MessageDigest.getInstance("SHA-256"); byte[] hash = digest.digest(fileBytes); return Base64.getEncoder().encodeToString(hash); } // Request/Response classes public static class KeyResponse { private String keyId; private String publicKey; private String privateKey; private String parameter; private String error; public KeyResponse(String keyId, String publicKey, String privateKey, FalconKeyGenerationService.FalconParameter parameter) { this.keyId = keyId; this.publicKey = publicKey; this.privateKey = privateKey; this.parameter = parameter.name(); } public KeyResponse(String error) { this.error = error; } // getters } public static class SignRequest { private String message; // getter and setter } public static class SignatureResponse { private String signature; private int messageSize; private int signatureSize; private String error; public SignatureResponse(String signature, int messageSize, int signatureSize) { this.signature = signature; this.messageSize = messageSize; this.signatureSize = signatureSize; } public SignatureResponse(String error) { this.error = error; } // getters } public static class VerifyRequest { private String keyId; private String message; private String signature; // getters and setters } public static class VerifyResponse { private boolean verified; private String message; public VerifyResponse(boolean verified, String message) { this.verified = verified; this.message = message; } // getters } }

9. Testing and Validation

package com.falcon.test; import com.falcon.signature.*; import org.junit.jupiter.api.*; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.boot.test.context.SpringBootTest; import java.security.SecureRandom; import java.util.*; import static org.junit.jupiter.api.Assertions.*; @SpringBootTest public class FalconSignatureTests { @Autowired private FalconKeyGenerationService keyGenService; @Autowired private FalconSigningService signingService; @Autowired private FalconKeyManagementService keyMgmtService; @Autowired private FalconNativeBridge nativeBridge; private FalconKeyGenerationService.FalconKeyPair testKeyPair; @BeforeEach void setUp() throws Exception { testKeyPair = keyGenService.generateKeyPair( FalconKeyGenerationService.FalconParameter.FALCON_512 ); } @Test void testKeyGeneration() { assertNotNull(testKeyPair); assertNotNull(testKeyPair.getPublicKey()); assertNotNull(testKeyPair.getPrivateKey()); assertEquals(FalconKeyGenerationService.FalconParameter.FALCON_512, testKeyPair.getParameter()); } @Test void testSignAndVerify() throws Exception { byte[] message = "Test message".getBytes(); // Sign byte[] signature = signingService.sign(message, testKeyPair.getPrivateKey()); assertNotNull(signature); // Verify boolean verified = signingService.verify( message, signature, testKeyPair.getPublicKey() ); assertTrue(verified); } @Test void testInvalidSignature() throws Exception { byte[] message = "Test message".getBytes(); byte[] wrongMessage = "Wrong message".getBytes(); byte[] signature = signingService.sign(message, testKeyPair.getPrivateKey()); boolean verified = signingService.verify( wrongMessage, signature, testKeyPair.getPublicKey() ); assertFalse(verified); } @Test void testDifferentParameters() throws Exception { FalconKeyGenerationService.FalconKeyPair keyPair1024 = keyGenService.generateKeyPair( FalconKeyGenerationService.FalconParameter.FALCON_1024 ); assertTrue(keyPair1024.getPublicKeySize() > testKeyPair.getPublicKeySize()); byte[] message = "Test message".getBytes(); byte[] signature = signingService.sign(message, keyPair1024.getPrivateKey()); boolean verified = signingService.verify(message, signature, keyPair1024.getPublicKey()); assertTrue(verified); } @Test void testDeterministicGeneration() throws Exception { byte[] seed = new byte[32]; new SecureRandom().nextBytes(seed); FalconKeyGenerationService.FalconKeyPair keyPair1 = keyGenService.generateDeterministicKeyPair( FalconKeyGenerationService.FalconParameter.FALCON_512, seed ); FalconKeyGenerationService.FalconKeyPair keyPair2 = keyGenService.generateDeterministicKeyPair( FalconKeyGenerationService.FalconParameter.FALCON_512, seed ); assertArrayEquals(keyPair1.getPublicKey(), keyPair2.getPublicKey()); assertArrayEquals(keyPair1.getPrivateKey(), keyPair2.getPrivateKey()); } @Test void testKeyManagement() throws Exception { // Generate and store key String keyId = keyMgmtService.generateAndStoreKey( "test-key-1", FalconKeyGenerationService.FalconParameter.FALCON_512, null ); // Retrieve key FalconKeyManagementService.SigningKey signingKey = keyMgmtService.getSigningKey(keyId); assertNotNull(signingKey); // Use key byte[] message = "Test".getBytes(); byte[] signature = signingService.sign(message, signingKey.getPrivateKey()); assertNotNull(signature); // Rotate key FalconKeyManagementService.KeyRotationResult rotation = keyMgmtService.rotateKey(keyId); assertNotNull(rotation.getNewKeyId()); // Revoke old key keyMgmtService.revokeKey(keyId, FalconKeyManagementService.RevocationReason.SUPERSEDED); // Verify old key is revoked assertThrows(FalconKeyManagementService.KeyManagementException.class, () -> { keyMgmtService.getSigningKey(keyId); }); } @Test void testBatchSigning() throws Exception { List<byte[]> messages = Arrays.asList( "Message 1".getBytes(), "Message 2".getBytes(), "Message 3".getBytes() ); List<byte[]> signatures = signingService.batchSign( messages, testKeyPair.getPrivateKey() ); assertEquals(messages.size(), signatures.size()); // Verify each for (int i = 0; i < messages.size(); i++) { boolean verified = signingService.verify( messages.get(i), signatures.get(i), testKeyPair.getPublicKey() ); assertTrue(verified); } } @Test void testNativeImplementation() throws Exception { // Generate key pair using native FalconKeyGenerationService.FalconKeyPair nativeKeyPair = nativeBridge.generateKeyPair( FalconKeyGenerationService.FalconParameter.FALCON_512 ); assertNotNull(nativeKeyPair); // Sign using native byte[] message = "Native test".getBytes(); byte[] signature = nativeBridge.sign(message, nativeKeyPair.getPrivateKey()); // Verify using native boolean verified = nativeBridge.verify( message, signature, nativeKeyPair.getPublicKey() ); assertTrue(verified); } @Test void testPerformance() throws Exception { int iterations = 1000; byte[] message = "Performance test".getBytes(); // Measure signing long start = System.nanoTime(); for (int i = 0; i < iterations; i++) { signingService.sign(message, testKeyPair.getPrivateKey()); } long signTime = System.nanoTime() - start; // Measure verification byte[] signature = signingService.sign(message, testKeyPair.getPrivateKey()); start = System.nanoTime(); for (int i = 0; i < iterations; i++) { signingService.verify(message, signature, testKeyPair.getPublicKey()); } long verifyTime = System.nanoTime() - start; System.out.printf("Signing: %d ns/op%n", signTime / iterations); System.out.printf("Verification: %d ns/op%n", verifyTime / iterations); } }

10. Spring Boot Configuration

package com.falcon.config; import org.springframework.boot.context.properties.ConfigurationProperties; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import org.springframework.scheduling.annotation.EnableScheduling; import java.security.Security; @Configuration @EnableScheduling @ConfigurationProperties(prefix = "falcon") public class FalconConfig { static { // Register Bouncy Castle provider Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider()); // Register PQC provider try { Class.forName("org.pqc.jcajce.provider.BouncyCastlePQCProvider"); Security.addProvider( (java.security.Provider) Class.forName( "org.pqc.jcajce.provider.BouncyCastlePQCProvider" ).newInstance() ); } catch (Exception e) { throw new RuntimeException("Failed to register PQC provider", e); } } private String defaultParameter = "FALCON_512"; private int keyCacheSize = 1000; private long keyRotationPeriod = 30L; // days private boolean enableNative = true; @Bean public FalconKeyGenerationService keyGenerationService() { return new FalconKeyGenerationService(); } @Bean public FalconSigningService signingService() { return new FalconSigningService(); } @Bean public FalconKeyManagementService keyManagementService( FalconKeyGenerationService keyGenService) { return new FalconKeyManagementService(keyGenService); } @Bean public FalconNativeBridge nativeBridge() { if (enableNative) { return new FalconNativeBridge(); } return null; } @Bean public FalconHealthIndicator healthIndicator( FalconKeyManagementService keyMgmtService) { return new FalconHealthIndicator(keyMgmtService); } // Scheduled key rotation @Scheduled(cron = "0 0 2 * * SUN") // Weekly at 2 AM Sunday public void rotateKeys() { // Find keys nearing expiration and rotate them List<FalconKeyManagementService.KeyInfo> keys = keyManagementService().listKeys(entry -> { // Find keys older than rotation period long age = System.currentTimeMillis() - entry.getCreationTime(); return age > (keyRotationPeriod * 24 * 60 * 60 * 1000); }); for (FalconKeyManagementService.KeyInfo keyInfo : keys) { try { keyManagementService().rotateKey(keyInfo.getKeyId()); logger.info("Rotated key: {}", keyInfo.getKeyId()); } catch (Exception e) { logger.error("Failed to rotate key: {}", keyInfo.getKeyId(), e); } } } // Getters and setters for configuration } @Component public class FalconHealthIndicator implements HealthIndicator { private final FalconKeyManagementService keyMgmtService; public FalconHealthIndicator(FalconKeyManagementService keyMgmtService) { this.keyMgmtService = keyMgmtService; } @Override public Health health() { try { List<FalconKeyManagementService.KeyInfo> keys = keyMgmtService.listKeys(null); long activeKeys = keys.stream() .filter(k -> k.getStatus() == FalconKeyManagementService.KeyStatus.ACTIVE) .count(); long expiredKeys = keys.stream() .filter(k -> k.getStatus() == FalconKeyManagementService.KeyStatus.EXPIRED) .count(); return Health.up() .withDetail("total_keys", keys.size()) .withDetail("active_keys", activeKeys) .withDetail("expired_keys", expiredKeys) .withDetail("default_parameter", "FALCON_512") .build(); } catch (Exception e) { return Health.down() .withException(e) .build(); } } }

Best Practices

1. Key Security

// Always use secure key storage public class SecureKeyStorage { public void storePrivateKey(byte[] privateKey, String keyId) { // Encrypt before storage byte[] encrypted = encryptKey(privateKey); // Store in HSM or secure key vault keyVault.store(keyId, encrypted); // Zeroize memory Arrays.fill(privateKey, (byte) 0); } }

2. Constant-Time Verification

// Implement constant-time comparison to avoid timing attacks public boolean constantTimeEquals(byte[] a, byte[] b) { if (a.length != b.length) { return false; } int result = 0; for (int i = 0; i < a.length; i++) { result |= a[i] ^ b[i]; } return result == 0; }

3. Memory Management

// Use SecureString for sensitive data public class SecureString implements AutoCloseable { private final byte[] data; public SecureString(String value) { this.data = value.getBytes(StandardCharsets.UTF_8); } @Override public void close() { Arrays.fill(data, (byte) 0); } }

4. Hybrid Deployment

// Fallback mechanism for compatibility public class FalconFallbackStrategy { public byte[] signWithFallback(byte[] message, byte[] privateKey) { try { // Try native first for performance return nativeBridge.sign(message, privateKey); } catch (Exception e) { logger.warn("Native signing failed, falling back to Java", e); // Fall back to Java implementation return javaSigningService.sign(message, privateKey); } } }

Conclusion

This comprehensive Falcon signature implementation provides:

Post-quantum security with NIST-standardized Falcon
Multiple security levels (FALCON-512 for NIST Level 1, FALCON-1024 for NIST Level 5)
High performance with native JNI implementation
Comprehensive key management with rotation and revocation
Hybrid cryptography combining Falcon with symmetric encryption
Batch signing for high-throughput scenarios
RESTful API for easy integration
Thorough testing and validation

Key benefits:

Quantum-resistant signatures for long-term security
Compact signatures (Falcon-512: 666 bytes, Falcon-1024: 1280 bytes)
Fast verification suitable for high-volume applications
NIST standardization ensures long-term viability
Hardware acceleration support through native implementation

This setup ensures your applications are prepared for the post-quantum era while maintaining high performance and compatibility with existing systems.

Advanced Java Programming Concepts and Projects (Related to Java Programming)

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HashMap Basics in Java:
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The This Keyword in Java:
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