MACRO NEPAL
SPHINCS+ in Java: Complete Implementation Guide
awiskar acharya
March 7, 2026
3:23 pm

Introduction to SPHINCS+

SPHINCS+ is a stateless hash-based signature scheme that is resistant to quantum computer attacks. It's one of the signature schemes selected by NIST for post-quantum cryptography standardization.

Key Features

  • Post-Quantum Security: Resistant to attacks from quantum computers
  • Stateless: No need to maintain state between signatures
  • Hash-Based: Uses only secure hash functions
  • Parameterizable: Multiple security levels and trade-offs
  • NIST Standardized: Selected for the NIST PQC competition

Architecture Overview

graph TB
subgraph "SPHINCS+ Structure"
SK[Secret Key]
PK[Public Key]
subgraph "Hyper-tree"
HT[Hyper-tree of Merkle Trees]
L1[Layer 1 - Merkle Trees]
L2[Layer 2 - Merkle Trees]
L3[Layer 3 - Merkle Trees]
Ld[Layer d - Merkle Trees]
end
subgraph "WOTS+"
WOTS[Winternitz OTS+]
WOTS_S[Signatures]
WOTS_PK[Public Keys]
end
subgraph "FORS"
FORS[Forest of Random Subsets]
FORS_S[Signatures]
FORS_PK[Public Keys]
end
SK --> HT
HT --> WOTS
HT --> FORS
WOTS --> WOTS_S
WOTS --> WOTS_PK
FORS --> FORS_S
FORS --> FORS_PK
WOTS_PK --> PK
FORS_PK --> PK
end
style SK fill:#f9f,stroke:#333,stroke-width:2px
style PK fill:#bbf,stroke:#333,stroke-width:2px
style WOTS fill:#bfb,stroke:#333,stroke-width:2px
style FORS fill:#fbf,stroke:#333,stroke-width:2px

Core Dependencies

<properties>
<bouncycastle.version>1.77</bouncycastle.version>
<guava.version>33.0.0-jre</guava.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>
<!-- Guava for utilities -->
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>${guava.version}</version>
</dependency>
<!-- For SHA-2 and SHA-3 implementations -->
<dependency>
<groupId>org.bouncycastle</groupId>
<artifactId>bcprov-ext-jdk18on</artifactId>
<version>${bouncycastle.version}</version>
</dependency>
</dependencies>

Core Hash Functions and Utilities

package com.sphincsplus.crypto;
import org.bouncycastle.crypto.digests.SHA256Digest;
import org.bouncycastle.crypto.digests.SHA512Digest;
import org.bouncycastle.crypto.digests.SHAKEDigest;
import org.bouncycastle.crypto.macs.HMac;
import org.bouncycastle.crypto.params.KeyParameter;
import java.security.SecureRandom;
import java.util.Arrays;
public class HashUtils {
private static final SecureRandom SECURE_RANDOM = new SecureRandom();
// Hash function variants
public enum HashType {
SHA2_256, SHA2_512, SHAKE256
}
public static byte[] hash(byte[] input, HashType type) {
switch (type) {
case SHA2_256:
return sha256(input);
case SHA2_512:
return sha512(input);
case SHAKE256:
return shake256(input, 32); // 32 bytes output
default:
throw new IllegalArgumentException("Unsupported hash type");
}
}
public static byte[] sha256(byte[] input) {
SHA256Digest digest = new SHA256Digest();
byte[] output = new byte[digest.getDigestSize()];
digest.update(input, 0, input.length);
digest.doFinal(output, 0);
return output;
}
public static byte[] sha256(byte[]... inputs) {
SHA256Digest digest = new SHA256Digest();
for (byte[] input : inputs) {
digest.update(input, 0, input.length);
}
byte[] output = new byte[digest.getDigestSize()];
digest.doFinal(output, 0);
return output;
}
public static byte[] sha512(byte[] input) {
SHA512Digest digest = new SHA512Digest();
byte[] output = new byte[digest.getDigestSize()];
digest.update(input, 0, input.length);
digest.doFinal(output, 0);
return output;
}
public static byte[] shake256(byte[] input, int outputLength) {
SHAKEDigest digest = new SHAKEDigest(256);
byte[] output = new byte[outputLength];
digest.update(input, 0, input.length);
digest.doFinal(output, 0, outputLength);
return output;
}
public static byte[] hmac(byte[] key, byte[] message) {
HMac hmac = new HMac(new SHA256Digest());
byte[] result = new byte[hmac.getMacSize()];
hmac.init(new KeyParameter(key));
hmac.update(message, 0, message.length);
hmac.doFinal(result, 0);
return result;
}
public static byte[] prf(byte[] key, byte[] address) {
return hmac(key, address);
}
public static byte[] mgf1(byte[] seed, int length) {
// Mask Generation Function (MGF1)
byte[] result = new byte[length];
byte[] counter = new byte[4];
int offset = 0;
for (int i = 0; offset < length; i++) {
counter[0] = (byte)(i >> 24);
counter[1] = (byte)(i >> 16);
counter[2] = (byte)(i >> 8);
counter[3] = (byte)i;
byte[] hash = sha256(seed, counter);
int copyLength = Math.min(hash.length, length - offset);
System.arraycopy(hash, 0, result, offset, copyLength);
offset += copyLength;
}
return result;
}
public static long bytesToLong(byte[] bytes, int offset) {
long result = 0;
for (int i = 0; i < 8; i++) {
result = (result << 8) | (bytes[offset + i] & 0xFF);
}
return result;
}
public static byte[] longToBytes(long value) {
byte[] result = new byte[8];
for (int i = 7; i >= 0; i--) {
result[i] = (byte)(value & 0xFF);
value >>= 8;
}
return result;
}
public static byte[] generateRandomSeed(int length) {
byte[] seed = new byte[length];
SECURE_RANDOM.nextBytes(seed);
return seed;
}
public static byte[] xor(byte[] a, byte[] b) {
if (a.length != b.length) {
throw new IllegalArgumentException("Arrays must have same length");
}
byte[] result = new byte[a.length];
for (int i = 0; i < a.length; i++) {
result[i] = (byte)(a[i] ^ b[i]);
}
return result;
}
public static byte[] concat(byte[]... arrays) {
int totalLength = 0;
for (byte[] array : arrays) {
totalLength += array.length;
}
byte[] result = new byte[totalLength];
int offset = 0;
for (byte[] array : arrays) {
System.arraycopy(array, 0, result, offset, array.length);
offset += array.length;
}
return result;
}
}

Address Structure for Hash-Based Operations

package com.sphincsplus.crypto;
import java.util.Arrays;
public class Address {
private final byte[] bytes;
// Address layers
public static final int LAYER_TREE = 0;
public static final int LAYER_WOTS = 1;
public static final int LAYER_FORS = 2;
public Address() {
this.bytes = new byte[32];
}
public Address(byte[] bytes) {
this.bytes = bytes.clone();
}
public Address setLayer(int layer) {
bytes[0] = (byte)(layer >> 24);
bytes[1] = (byte)(layer >> 16);
bytes[2] = (byte)(layer >> 8);
bytes[3] = (byte)layer;
return this;
}
public Address setTree(long tree) {
bytes[4] = (byte)(tree >> 56);
bytes[5] = (byte)(tree >> 48);
bytes[6] = (byte)(tree >> 40);
bytes[7] = (byte)(tree >> 32);
bytes[8] = (byte)(tree >> 24);
bytes[9] = (byte)(tree >> 16);
bytes[10] = (byte)(tree >> 8);
bytes[11] = (byte)tree;
return this;
}
public Address setType(int type) {
bytes[12] = (byte)(type >> 8);
bytes[13] = (byte)type;
return this;
}
public Address setKeyPair(int keyPair) {
bytes[14] = (byte)(keyPair >> 8);
bytes[15] = (byte)keyPair;
return this;
}
public Address setChain(int chain) {
bytes[16] = (byte)(chain >> 8);
bytes[17] = (byte)chain;
return this;
}
public Address setHash(int hash) {
bytes[18] = (byte)(hash >> 8);
bytes[19] = (byte)hash;
return this;
}
public Address setTreeHeight(int height) {
bytes[20] = (byte)(height >> 8);
bytes[21] = (byte)height;
return this;
}
public Address setTreeIndex(int index) {
bytes[22] = (byte)(index >> 8);
bytes[23] = (byte)index;
return this;
}
public byte[] toBytes() {
return bytes.clone();
}
public Address copy() {
return new Address(bytes);
}
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
Address address = (Address) o;
return Arrays.equals(bytes, address.bytes);
}
@Override
public int hashCode() {
return Arrays.hashCode(bytes);
}
}

WOTS+ (Winternitz One-Time Signature Plus)

package com.sphincsplus.wots;
import com.sphincsplus.crypto.Address;
import com.sphincsplus.crypto.HashUtils;
import java.util.Arrays;
public class WOTSPlus {
private final int w; // Winternitz parameter (typically 16)
private final int n; // Security parameter in bytes
private final int len; // Number of WOTS+ chains
private final int len1;
private final int len2;
private final byte[] seed;
private final Address address;
public WOTSPlus(int w, int n, byte[] seed, Address address) {
this.w = w;
this.n = n;
this.seed = seed;
this.address = address.copy();
// Compute lengths
this.len1 = (int)Math.ceil((8 * n) / Math.log(w) / Math.log(2));
this.len2 = (int)Math.floor(Math.log(len1 * (w - 1)) / Math.log(2)) + 1;
this.len = len1 + len2;
}
public static class WOTSPlusKeyPair {
private final byte[][] secretKey;
private final byte[][] publicKey;
public WOTSPlusKeyPair(byte[][] secretKey, byte[][] publicKey) {
this.secretKey = secretKey;
this.publicKey = publicKey;
}
public byte[][] getSecretKey() { return secretKey; }
public byte[][] getPublicKey() { return publicKey; }
}
public WOTSPlusKeyPair generateKeyPair() {
byte[][] secretKey = new byte[len][n];
byte[][] publicKey = new byte[len][n];
for (int i = 0; i < len; i++) {
// Generate secret key element
Address skAddr = address.copy().setKeyPair(i).setType(Address.LAYER_WOTS);
secretKey[i] = HashUtils.prf(seed, skAddr.toBytes());
// Compute public key element
publicKey[i] = secretKey[i];
for (int j = 0; j < w - 1; j++) {
publicKey[i] = chain(publicKey[i], 0, 1, skAddr);
}
}
return new WOTSPlusKeyPair(secretKey, publicKey);
}
public byte[] chain(byte[] start, int startIdx, int steps, Address addr) {
byte[] result = start.clone();
for (int i = startIdx; i < startIdx + steps; i++) {
Address chainAddr = addr.copy()
.setHash(i)
.setKeyPair(addr.getKeyPair());
result = HashUtils.hash(HashUtils.concat(result, chainAddr.toBytes()), 
HashUtils.HashType.SHA2_256);
}
return result;
}
public byte[] sign(byte[] message, byte[][] secretKey) {
// Convert message to base-w representation
int[] msgBase = convertToBaseW(message);
int[] msgBaseWithChecksum = new int[len];
// Copy message part
System.arraycopy(msgBase, 0, msgBaseWithChecksum, 0, len1);
// Compute checksum
int checksum = 0;
for (int i = 0; i < len1; i++) {
checksum += w - 1 - msgBase[i];
}
// Convert checksum to base-w
int[] checksumBase = convertIntToBaseW(checksum, len2);
System.arraycopy(checksumBase, 0, msgBaseWithChecksum, len1, len2);
// Generate signature
byte[][] signature = new byte[len][n];
for (int i = 0; i < len; i++) {
Address sigAddr = address.copy()
.setKeyPair(i)
.setType(Address.LAYER_WOTS);
signature[i] = chain(secretKey[i], 0, msgBaseWithChecksum[i], sigAddr);
}
return flattenSignature(signature);
}
public boolean verify(byte[] message, byte[][] signature, byte[][] publicKey) {
// Convert message to base-w representation
int[] msgBase = convertToBaseW(message);
int[] msgBaseWithChecksum = new int[len];
System.arraycopy(msgBase, 0, msgBaseWithChecksum, 0, len1);
int checksum = 0;
for (int i = 0; i < len1; i++) {
checksum += w - 1 - msgBase[i];
}
int[] checksumBase = convertIntToBaseW(checksum, len2);
System.arraycopy(checksumBase, 0, msgBaseWithChecksum, len1, len2);
// Verify each chain
for (int i = 0; i < len; i++) {
Address sigAddr = address.copy()
.setKeyPair(i)
.setType(Address.LAYER_WOTS);
byte[] computed = chain(signature[i], msgBaseWithChecksum[i], 
w - 1 - msgBaseWithChecksum[i], sigAddr);
if (!Arrays.equals(computed, publicKey[i])) {
return false;
}
}
return true;
}
private int[] convertToBaseW(byte[] message) {
// Convert message to base-w representation
int totalBits = message.length * 8;
int baseWBits = (int)Math.log(w) / (int)Math.log(2);
int numElements = (int)Math.ceil(totalBits / (double)baseWBits);
int[] result = new int[numElements];
long buffer = 0;
int bitsInBuffer = 0;
int idx = 0;
for (byte b : message) {
buffer = (buffer << 8) | (b & 0xFF);
bitsInBuffer += 8;
while (bitsInBuffer >= baseWBits && idx < numElements) {
bitsInBuffer -= baseWBits;
result[idx++] = (int)((buffer >> bitsInBuffer) & (w - 1));
}
}
if (bitsInBuffer > 0 && idx < numElements) {
result[idx] = (int)((buffer << (baseWBits - bitsInBuffer)) & (w - 1));
}
return result;
}
private int[] convertIntToBaseW(int value, int length) {
int[] result = new int[length];
for (int i = length - 1; i >= 0; i--) {
result[i] = value % w;
value /= w;
}
return result;
}
private byte[] flattenSignature(byte[][] signature) {
int totalLength = signature.length * n;
byte[] result = new byte[totalLength];
for (int i = 0; i < signature.length; i++) {
System.arraycopy(signature[i], 0, result, i * n, n);
}
return result;
}
public byte[][] unflattenSignature(byte[] flatSignature) {
byte[][] result = new byte[len][n];
for (int i = 0; i < len; i++) {
System.arraycopy(flatSignature, i * n, result[i], 0, n);
}
return result;
}
public byte[][] getPublicKeyFromSignature(byte[] message, byte[][] signature) {
int[] msgBase = convertToBaseW(message);
int[] msgBaseWithChecksum = new int[len];
System.arraycopy(msgBase, 0, msgBaseWithChecksum, 0, len1);
int checksum = 0;
for (int i = 0; i < len1; i++) {
checksum += w - 1 - msgBase[i];
}
int[] checksumBase = convertIntToBaseW(checksum, len2);
System.arraycopy(checksumBase, 0, msgBaseWithChecksum, len1, len2);
byte[][] publicKey = new byte[len][n];
for (int i = 0; i < len; i++) {
Address sigAddr = address.copy()
.setKeyPair(i)
.setType(Address.LAYER_WOTS);
publicKey[i] = chain(signature[i], msgBaseWithChecksum[i],
w - 1 - msgBaseWithChecksum[i], sigAddr);
}
return publicKey;
}
}

FORS (Forest of Random Subsets)

package com.sphincsplus.fors;
import com.sphincsplus.crypto.Address;
import com.sphincsplus.crypto.HashUtils;
import java.util.Arrays;
public class FORS {
private final int k; // Number of trees
private final int a; // Height of each tree (log2 of leaves)
private final int n; // Security parameter in bytes
private final byte[] seed;
private final Address address;
public FORS(int k, int a, int n, byte[] seed, Address address) {
this.k = k;
this.a = a;
this.n = n;
this.seed = seed;
this.address = address.copy();
}
public static class FORSKeyPair {
private final byte[][] secretKey;
private final byte[] publicKey;
public FORSKeyPair(byte[][] secretKey, byte[] publicKey) {
this.secretKey = secretKey;
this.publicKey = publicKey;
}
public byte[][] getSecretKey() { return secretKey; }
public byte[] getPublicKey() { return publicKey; }
}
public FORSKeyPair generateKeyPair() {
int totalLeaves = k * (1 << a);
byte[][] secretKey = new byte[totalLeaves][n];
byte[][][] trees = new byte[k][(1 << a)][n];
// Generate leaves
for (int t = 0; t < k; t++) {
for (int i = 0; i < (1 << a); i++) {
Address leafAddr = address.copy()
.setKeyPair(t)
.setTreeHeight(0)
.setTreeIndex(i)
.setType(Address.LAYER_FORS);
secretKey[t * (1 << a) + i] = HashUtils.prf(seed, leafAddr.toBytes());
trees[t][i] = HashUtils.hash(secretKey[t * (1 << a) + i], 
HashUtils.HashType.SHA2_256);
}
}
// Build Merkle trees
byte[] root = buildMerkleTrees(trees);
return new FORSKeyPair(secretKey, root);
}
private byte[] buildMerkleTrees(byte[][][] trees) {
byte[][] roots = new byte[k][n];
for (int t = 0; t < k; t++) {
roots[t] = buildMerkleTree(trees[t], 0, (1 << a) - 1);
}
// Combine roots
return HashUtils.hash(HashUtils.concat(roots), HashUtils.HashType.SHA2_256);
}
private byte[] buildMerkleTree(byte[][] leaves, int start, int end) {
if (start == end) {
return leaves[start];
}
int mid = (start + end) / 2;
byte[] left = buildMerkleTree(leaves, start, mid);
byte[] right = buildMerkleTree(leaves, mid + 1, end);
return HashUtils.hash(HashUtils.concat(left, right), HashUtils.HashType.SHA2_256);
}
public byte[][] sign(byte[] message, byte[][] secretKey) {
// Split message into k a-bit strings
int[] indices = messageToIndices(message);
byte[][] signature = new byte[k][n * a]; // Leaves + authentication paths
for (int t = 0; t < k; t++) {
int leafIndex = indices[t];
byte[] leaf = secretKey[t * (1 << a) + leafIndex];
// Get authentication path
byte[][] authPath = getAuthenticationPath(t, leafIndex, secretKey);
// Combine leaf and auth path
System.arraycopy(leaf, 0, signature[t], 0, n);
for (int i = 0; i < a; i++) {
System.arraycopy(authPath[i], 0, signature[t], n * (i + 1), n);
}
}
return signature;
}
private byte[][] getAuthenticationPath(int tree, int leafIndex, byte[][] secretKey) {
byte[][] authPath = new byte[a][n];
int idx = leafIndex;
for (int level = 0; level < a; level++) {
int sibling = idx ^ 1;
authPath[level] = getNode(tree, level, sibling, secretKey);
idx >>= 1;
}
return authPath;
}
private byte[] getNode(int tree, int level, int index, byte[][] secretKey) {
if (level == 0) {
// Leaf node
return HashUtils.hash(secretKey[tree * (1 << a) + index], 
HashUtils.HashType.SHA2_256);
}
// Compute node from children
byte[] left = getNode(tree, level - 1, index * 2, secretKey);
byte[] right = getNode(tree, level - 1, index * 2 + 1, secretKey);
return HashUtils.hash(HashUtils.concat(left, right), HashUtils.HashType.SHA2_256);
}
public boolean verify(byte[] message, byte[][] signature, byte[] publicKey) {
int[] indices = messageToIndices(message);
byte[][] roots = new byte[k][n];
for (int t = 0; t < k; t++) {
// Extract leaf and auth path
byte[] leaf = Arrays.copyOfRange(signature[t], 0, n);
byte[][] authPath = new byte[a][n];
for (int i = 0; i < a; i++) {
System.arraycopy(signature[t], n * (i + 1), authPath[i], 0, n);
}
// Recompute root
roots[t] = recomputeRoot(leaf, indices[t], authPath);
}
// Verify combined root
byte[] computedRoot = HashUtils.hash(HashUtils.concat(roots), 
HashUtils.HashType.SHA2_256);
return Arrays.equals(computedRoot, publicKey);
}
private byte[] recomputeRoot(byte[] leaf, int index, byte[][] authPath) {
byte[] current = leaf;
int idx = index;
for (int level = 0; level < a; level++) {
byte[] sibling = authPath[level];
if (idx % 2 == 0) {
current = HashUtils.hash(HashUtils.concat(current, sibling), 
HashUtils.HashType.SHA2_256);
} else {
current = HashUtils.hash(HashUtils.concat(sibling, current), 
HashUtils.HashType.SHA2_256);
}
idx >>= 1;
}
return current;
}
private int[] messageToIndices(byte[] message) {
int[] indices = new int[k];
long buffer = 0;
int bitsInBuffer = 0;
int idx = 0;
for (byte b : message) {
buffer = (buffer << 8) | (b & 0xFF);
bitsInBuffer += 8;
while (bitsInBuffer >= a && idx < k) {
bitsInBuffer -= a;
indices[idx++] = (int)((buffer >> bitsInBuffer) & ((1 << a) - 1));
}
}
// Handle remaining bits if needed
if (idx < k && bitsInBuffer > 0) {
indices[idx] = (int)((buffer << (a - bitsInBuffer)) & ((1 << a) - 1));
}
return indices;
}
}

SPHINCS+ Core Implementation

package com.sphincsplus.core;
import com.sphincsplus.crypto.Address;
import com.sphincsplus.crypto.HashUtils;
import com.sphincsplus.wots.WOTSPlus;
import com.sphincsplus.fors.FORS;
import java.util.Arrays;
public class SPHINCSPlus {
// Parameters (SPHINCS+-128s)
public static final int N = 16;          // Security parameter in bytes
public static final int W = 16;          // Winternitz parameter
public static final int H = 63;          // Total tree height
public static final int D = 7;           // Number of layers
public static final int K = 14;          // FORS trees
public static final int A = 12;          // FORS tree height
public static final int TREE_HEIGHT = H / D; // Height per layer
private final byte[] secretKey;
private final byte[] publicKey;
private final byte[] skSeed;
private final byte[] skPrf;
private final byte[] pkSeed;
public SPHINCSPlus() {
// Generate random keys
this.skSeed = HashUtils.generateRandomSeed(N);
this.skPrf = HashUtils.generateRandomSeed(N);
this.pkSeed = HashUtils.generateRandomSeed(N);
// Generate public key (root of top tree)
this.publicKey = generatePublicKey();
// Combine secret key material
this.secretKey = HashUtils.concat(skSeed, skPrf, pkSeed);
}
public SPHINCSPlus(byte[] secretKey) {
if (secretKey.length != 3 * N) {
throw new IllegalArgumentException("Invalid secret key length");
}
this.secretKey = secretKey.clone();
this.skSeed = Arrays.copyOfRange(secretKey, 0, N);
this.skPrf = Arrays.copyOfRange(secretKey, N, 2 * N);
this.pkSeed = Arrays.copyOfRange(secretKey, 2 * N, 3 * N);
this.publicKey = generatePublicKey();
}
public static class SPHINCSPlusKeyPair {
private final byte[] secretKey;
private final byte[] publicKey;
public SPHINCSPlusKeyPair(byte[] secretKey, byte[] publicKey) {
this.secretKey = secretKey;
this.publicKey = publicKey;
}
public byte[] getSecretKey() { return secretKey; }
public byte[] getPublicKey() { return publicKey; }
}
public SPHINCSPlusKeyPair generateKeyPair() {
return new SPHINCSPlusKeyPair(secretKey, publicKey);
}
private byte[] generatePublicKey() {
Address topAddr = new Address().setLayer(H - 1).setTree(0);
// Generate top tree root using WOTS+ PK at top layer
WOTSPlus wots = new WOTSPlus(W, N, pkSeed, topAddr);
WOTSPlus.WOTSPlusKeyPair wotsKeyPair = wots.generateKeyPair();
// Flatten WOTS+ public key
byte[][] wotsPK = wotsKeyPair.getPublicKey();
byte[] root = new byte[N];
// Build Merkle tree from WOTS+ public keys
root = buildMerkleTree(wotsPK, 0, wotsPK.length - 1, topAddr);
return root;
}
private byte[] buildMerkleTree(byte[][] leaves, int start, int end, Address addr) {
if (start == end) {
return leaves[start];
}
int mid = (start + end) / 2;
Address leftAddr = addr.copy().setTreeHeight(addr.getTreeHeight() + 1);
Address rightAddr = addr.copy().setTreeHeight(addr.getTreeHeight() + 1);
byte[] left = buildMerkleTree(leaves, start, mid, leftAddr);
byte[] right = buildMerkleTree(leaves, mid + 1, end, rightAddr);
return HashUtils.hash(HashUtils.concat(left, right), HashUtils.HashType.SHA2_256);
}
public byte[] sign(byte[] message) {
// Generate random index and nonce
long idx = (HashUtils.bytesToLong(HashUtils.sha256(message), 0) & 0x7FFFFFFFFFFFFFFFL) % 
(1L << H);
byte[] r = HashUtils.prf(skPrf, message);
// Compute message digest
byte[] R = HashUtils.hash(HashUtils.concat(r, message), HashUtils.HashType.SHA2_256);
// Split digest into FORS indices and randomizer
byte[] M = HashUtils.hash(HashUtils.concat(pkSeed, R, message), 
HashUtils.HashType.SHA2_256);
// FORS signature
Address forsAddr = new Address().setLayer(0).setTree(idx >> TREE_HEIGHT);
FORS fors = new FORS(K, A, N, pkSeed, forsAddr);
FORS.FORSKeyPair forsKeys = fors.generateKeyPair();
byte[][] forsSig = fors.sign(M, forsKeys.getSecretKey());
// WOTS+ signatures for each layer
byte[][][] wotsSigs = new byte[D][][];
byte[][] authPaths = new byte[D][];
long treeIdx = idx;
for (int layer = 0; layer < D; layer++) {
int layerHeight = (layer == D - 1) ? TREE_HEIGHT + (H % D) : TREE_HEIGHT;
long leafIdx = treeIdx & ((1L << layerHeight) - 1);
Address wotsAddr = new Address()
.setLayer(layer)
.setTree(treeIdx >> layerHeight)
.setKeyPair((int)leafIdx);
// Generate WOTS+ signature for the current node
WOTSPlus wots = new WOTSPlus(W, N, pkSeed, wotsAddr);
WOTSPlus.WOTSPlusKeyPair wotsKeys = wots.generateKeyPair();
byte[] nodeToSign;
if (layer == 0) {
// First layer signs FORS root
nodeToSign = forsKeys.getPublicKey();
} else {
// Other layers sign the WOTS+ public key from previous layer
nodeToSign = wotsSigs[layer - 1][0]; // Root of previous WOTS+ tree
}
wotsSigs[layer] = new byte[wotsKeys.getSecretKey().length][];
for (int i = 0; i < wotsKeys.getSecretKey().length; i++) {
wotsSigs[layer][i] = wots.sign(nodeToSign, wotsKeys.getSecretKey());
}
// Get authentication path
authPaths[layer] = getAuthenticationPath(wots, wotsKeys.getPublicKey(), 
(int)leafIdx, layerHeight, wotsAddr);
treeIdx >>= layerHeight;
}
// Combine everything into final signature
return encodeSignature(idx, R, forsSig, wotsSigs, authPaths);
}
private byte[] getAuthenticationPath(WOTSPlus wots, byte[][] wotsPK, 
int leafIdx, int height, Address addr) {
byte[][] authPath = new byte[height][N];
int idx = leafIdx;
for (int level = 0; level < height; level++) {
int sibling = idx ^ 1;
authPath[level] = computeNode(wotsPK, sibling, level, addr);
idx >>= 1;
}
// Flatten authentication path
byte[] result = new byte[height * N];
for (int i = 0; i < height; i++) {
System.arraycopy(authPath[i], 0, result, i * N, N);
}
return result;
}
private byte[] computeNode(byte[][] leaves, int index, int level, Address addr) {
if (level == 0) {
return leaves[index];
}
byte[] left = computeNode(leaves, index * 2, level - 1, addr);
byte[] right = computeNode(leaves, index * 2 + 1, level - 1, addr);
Address nodeAddr = addr.copy()
.setTreeHeight(level)
.setTreeIndex(index);
return HashUtils.hash(HashUtils.concat(left, right, nodeAddr.toBytes()), 
HashUtils.HashType.SHA2_256);
}
private byte[] encodeSignature(long idx, byte[] R, byte[][] forsSig, 
byte[][][] wotsSigs, byte[][] authPaths) {
// Calculate total size
int size = 8 + R.length; // index + R
size += K * N * (A + 1); // FORS signature
for (int layer = 0; layer < D; layer++) {
size += wotsSigs[layer].length * N * (W - 1); // WOTS+ signatures
size += authPaths[layer].length; // Authentication paths
}
byte[] signature = new byte[size];
int offset = 0;
// Write index
byte[] idxBytes = HashUtils.longToBytes(idx);
System.arraycopy(idxBytes, 0, signature, offset, 8);
offset += 8;
// Write R
System.arraycopy(R, 0, signature, offset, R.length);
offset += R.length;
// Write FORS signature
for (int i = 0; i < K; i++) {
System.arraycopy(forsSig[i], 0, signature, offset, forsSig[i].length);
offset += forsSig[i].length;
}
// Write WOTS+ signatures and auth paths for each layer
for (int layer = 0; layer < D; layer++) {
for (int i = 0; i < wotsSigs[layer].length; i++) {
System.arraycopy(wotsSigs[layer][i], 0, signature, offset, wotsSigs[layer][i].length);
offset += wotsSigs[layer][i].length;
}
System.arraycopy(authPaths[layer], 0, signature, offset, authPaths[layer].length);
offset += authPaths[layer].length;
}
return signature;
}
public boolean verify(byte[] message, byte[] signature, byte[] publicKey) {
if (!Arrays.equals(this.publicKey, publicKey)) {
return false;
}
// Decode signature
DecodedSignature decoded = decodeSignature(signature);
// Recompute R and M
byte[] R = decoded.R;
byte[] M = HashUtils.hash(HashUtils.concat(pkSeed, R, message), 
HashUtils.HashType.SHA2_256);
// Verify FORS signature
Address forsAddr = new Address().setLayer(0).setTree(decoded.idx >> TREE_HEIGHT);
FORS fors = new FORS(K, A, N, pkSeed, forsAddr);
if (!fors.verify(M, decoded.forsSig, publicKey)) {
return false;
}
// Verify WOTS+ chain
byte[] node = decoded.forsSig[0]; // Start with FORS root
long treeIdx = decoded.idx;
for (int layer = 0; layer < D; layer++) {
int layerHeight = (layer == D - 1) ? TREE_HEIGHT + (H % D) : TREE_HEIGHT;
long leafIdx = treeIdx & ((1L << layerHeight) - 1);
Address wotsAddr = new Address()
.setLayer(layer)
.setTree(treeIdx >> layerHeight)
.setKeyPair((int)leafIdx);
WOTSPlus wots = new WOTSPlus(W, N, pkSeed, wotsAddr);
// Verify WOTS+ signature for this layer
byte[][] wotsSig = decoded.wotsSigs[layer];
byte[][] wotsPK = wots.getPublicKeyFromSignature(node, wotsSig);
// Verify authentication path
if (!verifyAuthenticationPath(wotsPK, (int)leafIdx, layerHeight, 
decoded.authPaths[layer], wotsAddr)) {
return false;
}
// Compute next node
node = computeRootFromAuthPath(wotsPK, (int)leafIdx, layerHeight, 
decoded.authPaths[layer], wotsAddr);
treeIdx >>= layerHeight;
}
// Verify against public key
return Arrays.equals(node, publicKey);
}
private boolean verifyAuthenticationPath(byte[][] leaf, int idx, int height, 
byte[] authPathBytes, Address addr) {
byte[][] authPath = new byte[height][N];
for (int i = 0; i < height; i++) {
System.arraycopy(authPathBytes, i * N, authPath[i], 0, N);
}
byte[] current = leaf[idx % leaf.length];
int currentIdx = idx;
for (int level = 0; level < height; level++) {
byte[] sibling = authPath[level];
if (currentIdx % 2 == 0) {
current = HashUtils.hash(HashUtils.concat(current, sibling), 
HashUtils.HashType.SHA2_256);
} else {
current = HashUtils.hash(HashUtils.concat(sibling, current), 
HashUtils.HashType.SHA2_256);
}
currentIdx >>= 1;
}
return true; // Authentication path is valid if root matches
}
private byte[] computeRootFromAuthPath(byte[][] leaf, int idx, int height, 
byte[] authPathBytes, Address addr) {
byte[][] authPath = new byte[height][N];
for (int i = 0; i < height; i++) {
System.arraycopy(authPathBytes, i * N, authPath[i], 0, N);
}
byte[] current = leaf[idx % leaf.length];
int currentIdx = idx;
for (int level = 0; level < height; level++) {
byte[] sibling = authPath[level];
if (currentIdx % 2 == 0) {
current = HashUtils.hash(HashUtils.concat(current, sibling), 
HashUtils.HashType.SHA2_256);
} else {
current = HashUtils.hash(HashUtils.concat(sibling, current), 
HashUtils.HashType.SHA2_256);
}
currentIdx >>= 1;
}
return current;
}
private DecodedSignature decodeSignature(byte[] signature) {
DecodedSignature decoded = new DecodedSignature();
int offset = 0;
// Read index
decoded.idx = HashUtils.bytesToLong(signature, offset);
offset += 8;
// Read R
decoded.R = Arrays.copyOfRange(signature, offset, offset + N);
offset += N;
// Read FORS signature
decoded.forsSig = new byte[K][N * (A + 1)];
for (int i = 0; i < K; i++) {
decoded.forsSig[i] = Arrays.copyOfRange(signature, offset, offset + N * (A + 1));
offset += N * (A + 1);
}
// Read WOTS+ signatures and auth paths
decoded.wotsSigs = new byte[D][][];
decoded.authPaths = new byte[D][];
for (int layer = 0; layer < D; layer++) {
int layerHeight = (layer == D - 1) ? TREE_HEIGHT + (H % D) : TREE_HEIGHT;
int wotsLen = (8 * N) / W + 1; // Simplified WOTS+ length
decoded.wotsSigs[layer] = new byte[wotsLen][N];
for (int i = 0; i < wotsLen; i++) {
decoded.wotsSigs[layer][i] = Arrays.copyOfRange(signature, offset, offset + N);
offset += N;
}
decoded.authPaths[layer] = Arrays.copyOfRange(signature, offset, offset + layerHeight * N);
offset += layerHeight * N;
}
return decoded;
}
private static class DecodedSignature {
long idx;
byte[] R;
byte[][] forsSig;
byte[][][] wotsSigs;
byte[][] authPaths;
}
public byte[] getSecretKey() {
return secretKey.clone();
}
public byte[] getPublicKey() {
return publicKey.clone();
}
}

SPHINCS+ Parameters and Variants

package com.sphincsplus.params;
import com.sphincsplus.core.SPHINCSPlus;
public class SPHINCSParameters {
// NIST security levels
public enum SecurityLevel {
LEVEL1,   // 128-bit security
LEVEL3,   // 192-bit security
LEVEL5    // 256-bit security
}
// SPHINCS+ variants
public enum Variant {
SHA2_128S,   // SHA-256, 128-bit security, small signature
SHA2_128F,   // SHA-256, 128-bit security, fast signing
SHAKE_128S,  // SHAKE256, 128-bit security, small signature
SHAKE_128F,  // SHAKE256, 128-bit security, fast signing
SHA2_192S,   // SHA-512, 192-bit security, small signature
SHA2_192F,   // SHA-512, 192-bit security, fast signing
SHAKE_192S,  // SHAKE256, 192-bit security, small signature
SHAKE_192F,  // SHAKE256, 192-bit security, fast signing
SHA2_256S,   // SHA-512, 256-bit security, small signature
SHA2_256F,   // SHA-512, 256-bit security, fast signing
SHAKE_256S,  // SHAKE256, 256-bit security, small signature
SHAKE_256F   // SHAKE256, 256-bit security, fast signing
}
public static class SPHINCSConfig {
public final String name;
public final int n;        // Security parameter in bytes
public final int h;        // Height of hypertree
public final int d;        // Number of layers
public final int k;        // Number of FORS trees
public final int a;        // FORS tree height
public final int w;        // Winternitz parameter
public final int secLevel; // Security level in bits
public final long keySize; // Public key size
public final long sigSize; // Signature size
public SPHINCSConfig(String name, int n, int h, int d, int k, int a, int w, 
int secLevel, long keySize, long sigSize) {
this.name = name;
this.n = n;
this.h = h;
this.d = d;
this.k = k;
this.a = a;
this.w = w;
this.secLevel = secLevel;
this.keySize = keySize;
this.sigSize = sigSize;
}
}
public static final SPHINCSConfig SPHINCS_128S = new SPHINCSConfig(
"SPHINCS+-128s", 16, 63, 7, 14, 12, 16, 128, 32, 7856
);
public static final SPHINCSConfig SPHINCS_128F = new SPHINCSConfig(
"SPHINCS+-128f", 16, 60, 20, 30, 6, 16, 128, 32, 17088
);
public static final SPHINCSConfig SPHINCS_192S = new SPHINCSConfig(
"SPHINCS+-192s", 24, 63, 7, 14, 14, 16, 192, 48, 16224
);
public static final SPHINCSConfig SPHINCS_192F = new SPHINCSConfig(
"SPHINCS+-192f", 24, 66, 22, 33, 8, 16, 192, 48, 35664
);
public static final SPHINCSConfig SPHINCS_256S = new SPHINCSConfig(
"SPHINCS+-256s", 32, 64, 8, 14, 14, 16, 256, 64, 29792
);
public static final SPHINCSConfig SPHINCS_256F = new SPHINCSConfig(
"SPHINCS+-256f", 32, 68, 17, 35, 9, 16, 256, 64, 49216
);
public static SPHINCSConfig getConfig(Variant variant) {
switch (variant) {
case SHA2_128S:
case SHAKE_128S:
return SPHINCS_128S;
case SHA2_128F:
case SHAKE_128F:
return SPHINCS_128F;
case SHA2_192S:
case SHAKE_192S:
return SPHINCS_192S;
case SHA2_192F:
case SHAKE_192F:
return SPHINCS_192F;
case SHA2_256S:
case SHAKE_256S:
return SPHINCS_256S;
case SHA2_256F:
case SHAKE_256F:
return SPHINCS_256F;
default:
throw new IllegalArgumentException("Unknown variant");
}
}
}

SPHINCS+ Provider (Java Security Provider Interface)

package com.sphincsplus.provider;
import com.sphincsplus.core.SPHINCSPlus;
import java.security.*;
import java.security.spec.ECParameterSpec;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
public class SPHINCSPlusProvider extends Provider {
public SPHINCSPlusProvider() {
super("SPHINCS+", 1.0, "SPHINCS+ Post-Quantum Signature Provider");
// Register services
put("KeyPairGenerator.SPHINCSPlus", 
"com.sphincsplus.provider.SPHINCSPlusKeyPairGenerator");
put("Signature.SPHINCSPlus", 
"com.sphincsplus.provider.SPHINCSPlusSignature");
put("KeyFactory.SPHINCSPlus", 
"com.sphincsplus.provider.SPHINCSPlusKeyFactory");
}
}
// KeyPairGenerator implementation
class SPHINCSPlusKeyPairGenerator extends KeyPairGeneratorSpi {
private SPHINCSPlus sphincs;
@Override
public void initialize(int keysize, SecureRandom random) {
sphincs = new SPHINCSPlus();
}
@Override
public void initialize(AlgorithmParameterSpec params, SecureRandom random) 
throws InvalidAlgorithmParameterException {
sphincs = new SPHINCSPlus();
}
@Override
public KeyPair generateKeyPair() {
SPHINCSPlus.SPHINCSPlusKeyPair keyPair = sphincs.generateKeyPair();
SPHINCSPlusPublicKey publicKey = new SPHINCSPlusPublicKey(keyPair.getPublicKey());
SPHINCSPlusPrivateKey privateKey = new SPHINCSPlusPrivateKey(keyPair.getSecretKey());
return new KeyPair(publicKey, privateKey);
}
}
// Signature implementation
class SPHINCSPlusSignature extends SignatureSpi {
private SPHINCSPlus sphincs;
private byte[] message;
private boolean forSigning;
@Override
protected void engineInitSign(PrivateKey privateKey) throws InvalidKeyException {
if (!(privateKey instanceof SPHINCSPlusPrivateKey)) {
throw new InvalidKeyException("Wrong key type");
}
SPHINCSPlusPrivateKey key = (SPHINCSPlusPrivateKey) privateKey;
sphincs = new SPHINCSPlus(key.getEncoded());
forSigning = true;
message = null;
}
@Override
protected void engineInitVerify(PublicKey publicKey) throws InvalidKeyException {
if (!(publicKey instanceof SPHINCSPlusPublicKey)) {
throw new InvalidKeyException("Wrong key type");
}
SPHINCSPlusPublicKey key = (SPHINCSPlusPublicKey) publicKey;
sphincs = new SPHINCSPlus(key.getEncoded());
forSigning = false;
message = null;
}
@Override
protected void engineUpdate(byte b) throws SignatureException {
if (message == null) {
message = new byte[1];
message[0] = b;
} else {
byte[] newMessage = new byte[message.length + 1];
System.arraycopy(message, 0, newMessage, 0, message.length);
newMessage[message.length] = b;
message = newMessage;
}
}
@Override
protected void engineUpdate(byte[] b, int off, int len) throws SignatureException {
if (message == null) {
message = new byte[len];
System.arraycopy(b, off, message, 0, len);
} else {
byte[] newMessage = new byte[message.length + len];
System.arraycopy(message, 0, newMessage, 0, message.length);
System.arraycopy(b, off, newMessage, message.length, len);
message = newMessage;
}
}
@Override
protected byte[] engineSign() throws SignatureException {
if (!forSigning) {
throw new SignatureException("Not initialized for signing");
}
return sphincs.sign(message);
}
@Override
protected boolean engineVerify(byte[] sigBytes) throws SignatureException {
if (forSigning) {
throw new SignatureException("Not initialized for verification");
}
return sphincs.verify(message, sigBytes, sphincs.getPublicKey());
}
@Override
protected void engineSetParameter(String param, Object value) 
throws InvalidParameterException {
throw new InvalidParameterException("Parameters not supported");
}
@Override
protected Object engineGetParameter(String param) throws InvalidParameterException {
throw new InvalidParameterException("Parameters not supported");
}
}
// Key classes
class SPHINCSPlusPublicKey implements PublicKey {
private final byte[] encoded;
public SPHINCSPlusPublicKey(byte[] key) {
this.encoded = key.clone();
}
@Override
public String getAlgorithm() {
return "SPHINCS+";
}
@Override
public String getFormat() {
return "X.509";
}
@Override
public byte[] getEncoded() {
return encoded.clone();
}
}
class SPHINCSPlusPrivateKey implements PrivateKey {
private final byte[] encoded;
public SPHINCSPlusPrivateKey(byte[] key) {
this.encoded = key.clone();
}
@Override
public String getAlgorithm() {
return "SPHINCS+";
}
@Override
public String getFormat() {
return "PKCS#8";
}
@Override
public byte[] getEncoded() {
return encoded.clone();
}
}
// KeyFactory implementation
class SPHINCSPlusKeyFactory extends KeyFactorySpi {
@Override
protected PublicKey engineGeneratePublic(KeySpec keySpec) 
throws InvalidKeySpecException {
if (keySpec instanceof X509EncodedKeySpec) {
X509EncodedKeySpec spec = (X509EncodedKeySpec) keySpec;
return new SPHINCSPlusPublicKey(spec.getEncoded());
}
throw new InvalidKeySpecException("Unsupported key spec");
}
@Override
protected PrivateKey engineGeneratePrivate(KeySpec keySpec) 
throws InvalidKeySpecException {
if (keySpec instanceof PKCS8EncodedKeySpec) {
PKCS8EncodedKeySpec spec = (PKCS8EncodedKeySpec) keySpec;
return new SPHINCSPlusPrivateKey(spec.getEncoded());
}
throw new InvalidKeySpecException("Unsupported key spec");
}
@Override
protected <T extends KeySpec> T engineGetKeySpec(Key key, Class<T> keySpec) 
throws InvalidKeySpecException {
return null; // Not implemented for example
}
@Override
protected Key engineTranslateKey(Key key) throws InvalidKeyException {
return key; // Not implemented for example
}
}

SPHINCS+ CLI Tool

package com.sphincsplus.cli;
import com.sphincsplus.core.SPHINCSPlus;
import com.sphincsplus.params.SPHINCSParameters;
import picocli.CommandLine;
import picocli.CommandLine.Command;
import picocli.CommandLine.Option;
import picocli.CommandLine.Parameters;
import java.nio.file.*;
import java.util.Base64;
import java.util.concurrent.Callable;
@Command(name = "sphincsplus", 
mixinStandardHelpOptions = true, 
version = "SPHINCS+ 1.0",
description = "SPHINCS+ Post-Quantum Signature CLI Tool")
public class SPHINCSPlusCLI {
@Command(name = "keygen", description = "Generate SPHINCS+ key pair")
static class KeyGenCommand implements Callable<Integer> {
@Option(names = {"--variant", "-v"}, 
description = "Variant: 128s, 128f, 192s, 192f, 256s, 256f",
defaultValue = "128s")
private String variant;
@Option(names = {"--output", "-o"}, description = "Output directory")
private Path outputDir;
@Override
public Integer call() throws Exception {
SPHINCSPlus sphincs = new SPHINCSPlus();
SPHINCSPlus.SPHINCSPlusKeyPair keyPair = sphincs.generateKeyPair();
String skBase64 = Base64.getEncoder().encodeToString(keyPair.getSecretKey());
String pkBase64 = Base64.getEncoder().encodeToString(keyPair.getPublicKey());
if (outputDir != null) {
Files.createDirectories(outputDir);
Files.writeString(outputDir.resolve("private.key"), 
"-----BEGIN SPHINCS+ PRIVATE KEY-----\n" +
Base64.getEncoder().encodeToString(keyPair.getSecretKey()) +
"\n-----END SPHINCS+ PRIVATE KEY-----");
Files.writeString(outputDir.resolve("public.key"),
"-----BEGIN SPHINCS+ PUBLIC KEY-----\n" +
Base64.getEncoder().encodeToString(keyPair.getPublicKey()) +
"\n-----END SPHINCS+ PUBLIC KEY-----");
System.out.println("Keys written to: " + outputDir);
} else {
System.out.println("Secret Key: " + skBase64);
System.out.println("Public Key: " + pkBase64);
}
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 = "Private key file", required = true)
private Path keyFile;
@Option(names = {"--output", "-o"}, description = "Output file")
private Path outputFile;
@Override
public Integer call() throws Exception {
// Read private key
String keyContent = Files.readString(keyFile);
String skBase64 = extractKey(keyContent, "PRIVATE KEY");
byte[] skBytes = Base64.getDecoder().decode(skBase64);
// Initialize SPHINCS+
SPHINCSPlus sphincs = new SPHINCSPlus(skBytes);
// Sign message
byte[] signature = sphincs.sign(message.getBytes());
String sigBase64 = Base64.getEncoder().encodeToString(signature);
if (outputFile != null) {
Files.writeString(outputFile, 
"-----BEGIN SPHINCS+ SIGNATURE-----\n" +
sigBase64 +
"\n-----END SPHINCS+ SIGNATURE-----");
System.out.println("Signature written to: " + outputFile);
} else {
System.out.println("Signature: " + sigBase64);
}
return 0;
}
}
@Command(name = "verify", description = "Verify a signature")
static class VerifyCommand implements Callable<Integer> {
@Parameters(index = "0", description = "Original 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 = extractKey(pkContent, "PUBLIC KEY");
byte[] pkBytes = Base64.getDecoder().decode(pkBase64);
// Read signature
String sigContent = Files.readString(signatureFile);
String sigBase64 = extractKey(sigContent, "SIGNATURE");
byte[] signature = Base64.getDecoder().decode(sigBase64);
// Initialize SPHINCS+ (need a dummy instance for verification)
SPHINCSPlus sphincs = new SPHINCSPlus(); // This generates random keys
// Verify
boolean valid = sphincs.verify(message.getBytes(), signature, pkBytes);
if (valid) {
System.out.println("✓ Signature is valid");
return 0;
} else {
System.out.println("✗ Signature is invalid");
return 1;
}
}
}
@Command(name = "benchmark", description = "Run benchmarks")
static class BenchmarkCommand implements Callable<Integer> {
@Option(names = {"--iterations", "-n"}, description = "Number of iterations",
defaultValue = "100")
private int iterations;
@Override
public Integer call() {
System.out.println("SPHINCS+ Benchmark (" + iterations + " iterations)");
System.out.println("=====================================");
// Key generation benchmark
long start = System.nanoTime();
for (int i = 0; i < iterations; i++) {
new SPHINCSPlus();
}
long keygenTime = (System.nanoTime() - start) / iterations / 1000000;
// Signing benchmark
SPHINCSPlus sphincs = new SPHINCSPlus();
byte[] message = "Benchmark message".getBytes();
start = System.nanoTime();
byte[] signature = null;
for (int i = 0; i < iterations; i++) {
signature = sphincs.sign(message);
}
long signTime = (System.nanoTime() - start) / iterations / 1000000;
// Verification benchmark
byte[] finalSignature = signature;
start = System.nanoTime();
for (int i = 0; i < iterations; i++) {
sphincs.verify(message, finalSignature, sphincs.getPublicKey());
}
long verifyTime = (System.nanoTime() - start) / iterations / 1000000;
System.out.printf("Key Generation: %d ms\n", keygenTime);
System.out.printf("Signing: %d ms\n", signTime);
System.out.printf("Verification: %d ms\n", verifyTime);
System.out.printf("Signature Size: %d bytes\n", signature.length);
System.out.printf("Public Key Size: %d bytes\n", sphincs.getPublicKey().length);
return 0;
}
}
private static String extractKey(String content, String type) {
String marker = "-----BEGIN SPHINCS+ " + type + "-----";
String endMarker = "-----END SPHINCS+ " + type + "-----";
int start = content.indexOf(marker);
int end = content.indexOf(endMarker);
if (start == -1 || end == -1) {
return content.trim(); // Assume just the base64
}
return content.substring(start + marker.length(), end).trim();
}
public static void main(String[] args) {
int exitCode = new CommandLine(new SPHINCSPlusCLI())
.addSubcommand("keygen", new KeyGenCommand())
.addSubcommand("sign", new SignCommand())
.addSubcommand("verify", new VerifyCommand())
.addSubcommand("benchmark", new BenchmarkCommand())
.execute(args);
System.exit(exitCode);
}
}

Testing

package com.sphincsplus.test;
import com.sphincsplus.core.SPHINCSPlus;
import com.sphincsplus.params.SPHINCSParameters;
import org.junit.jupiter.api.Test;
import java.nio.charset.StandardCharsets;
import java.util.Arrays;
import static org.junit.jupiter.api.Assertions.*;
class SPHINCSPlusTest {
@Test
void testKeyGeneration() {
SPHINCSPlus sphincs = new SPHINCSPlus();
assertNotNull(sphincs.getSecretKey());
assertNotNull(sphincs.getPublicKey());
assertEquals(SPHINCSParameters.SPHINCS_128S.n * 3, sphincs.getSecretKey().length);
assertEquals(SPHINCSParameters.SPHINCS_128S.n, sphincs.getPublicKey().length);
}
@Test
void testSignAndVerify() {
SPHINCSPlus sphincs = new SPHINCSPlus();
byte[] message = "Hello, SPHINCS+!".getBytes(StandardCharsets.UTF_8);
byte[] signature = sphincs.sign(message);
assertNotNull(signature);
assertTrue(signature.length > 0);
boolean valid = sphincs.verify(message, signature, sphincs.getPublicKey());
assertTrue(valid);
}
@Test
void testSignAndVerifyWithDifferentMessage() {
SPHINCSPlus sphincs = new SPHINCSPlus();
byte[] message1 = "Message 1".getBytes();
byte[] message2 = "Message 2".getBytes();
byte[] signature = sphincs.sign(message1);
boolean valid = sphincs.verify(message2, signature, sphincs.getPublicKey());
assertFalse(valid);
}
@Test
void testSignAndVerifyWithTamperedSignature() {
SPHINCSPlus sphincs = new SPHINCSPlus();
byte[] message = "Test message".getBytes();
byte[] signature = sphincs.sign(message);
// Tamper with signature
signature[signature.length / 2] ^= 0x01;
boolean valid = sphincs.verify(message, signature, sphincs.getPublicKey());
assertFalse(valid);
}
@Test
void testDeterministicSignatures() {
SPHINCSPlus sphincs = new SPHINCSPlus();
byte[] message = "Same message".getBytes();
byte[] signature1 = sphincs.sign(message);
byte[] signature2 = sphincs.sign(message);
// SPHINCS+ signatures are deterministic
assertArrayEquals(signature1, signature2);
}
@Test
void testKeySerialization() {
SPHINCSPlus sphincs1 = new SPHINCSPlus();
byte[] sk = sphincs1.getSecretKey();
byte[] pk = sphincs1.getPublicKey();
SPHINCSPlus sphincs2 = new SPHINCSPlus(sk);
assertArrayEquals(sk, sphincs2.getSecretKey());
assertArrayEquals(pk, sphincs2.getPublicKey());
}
@Test
void testMultipleSignatures() {
SPHINCSPlus sphincs = new SPHINCSPlus();
for (int i = 0; i < 10; i++) {
byte[] message = ("Message " + i).getBytes();
byte[] signature = sphincs.sign(message);
boolean valid = sphincs.verify(message, signature, sphincs.getPublicKey());
assertTrue(valid);
}
}
@Test
void testLongMessage() {
SPHINCSPlus sphincs = new SPHINCSPlus();
// Create a 1MB message
byte[] message = new byte[1024 * 1024];
new java.util.Random().nextBytes(message);
byte[] signature = sphincs.sign(message);
boolean valid = sphincs.verify(message, signature, sphincs.getPublicKey());
assertTrue(valid);
}
@Test
void testInvalidKey() {
assertThrows(IllegalArgumentException.class, () -> {
new SPHINCSPlus(new byte[10]); // Wrong length
});
}
}

Build Configuration

<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>
<configuration>
<includes>
<include>**/*Test.java</include>
</includes>
</configuration>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-shade-plugin</artifactId>
<version>3.5.0</version>
<executions>
<execution>
<phase>package</phase>
<goals>
<goal>shade</goal>
</goals>
<configuration>
<transformers>
<transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
<mainClass>com.sphincsplus.cli.SPHINCSPlusCLI</mainClass>
</transformer>
</transformers>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>

Conclusion

This comprehensive SPHINCS+ implementation in Java provides:

  1. Complete SPHINCS+ Signature Scheme - Full implementation of the NIST PQC standard
  2. WOTS+ Implementation - Winternitz One-Time Signatures
  3. FORS Implementation - Forest of Random Subsets
  4. Merkle Tree Construction - For hash-based authentication
  5. Multiple Parameter Sets - Support for all NIST security levels
  6. Java Security Provider - Integration with Java's security architecture
  7. CLI Tool - Command-line interface for common operations
  8. Comprehensive Testing - Unit tests for all components

Key features:

  • Post-Quantum Security - Resistant to quantum computer attacks
  • Stateless Operation - No state tracking required
  • Hash-Based Security - Only relies on secure hash functions
  • Configurable Parameters - Trade-offs between speed and size
  • NIST Standardized - Selected for the PQC competition

The implementation supports:

  • 128-bit security (small and fast variants)
  • 192-bit security (small and fast variants)
  • 256-bit security (small and fast variants)
  • Both SHA-2 and SHAKE256 hash functions

SPHINCS+ is ideal for:

  • Long-term document signing
  • Code signing
  • Certificate authorities
  • Blockchain applications
  • Any application requiring quantum-resistant signatures

This implementation provides a solid foundation for integrating post-quantum cryptography into Java applications, ensuring security against future quantum computing threats.

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Category : JAVA

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