Quantum-Safe Cryptography: Preparing for Post-Quantum Security

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# Python implementation using quantum-safe algorithms
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives.asymmetric import padding
import kyber  # Quantum-safe key encapsulation
import dilithium  # Quantum-safe digital signatures

class QuantumSafeCrypto:
    def __init__(self):
        # Initialize Kyber for key encapsulation
        self.kyber_keypair = kyber.generate_keypair()
        # Initialize Dilithium for digital signatures
        self.dilithium_keypair = dilithium.generate_keypair()
    
    def secure_key_exchange(self, peer_public_key):
        """Quantum-safe key exchange using Kyber"""
        # Encapsulate shared secret
        ciphertext, shared_secret = kyber.encapsulate(peer_public_key)
        return ciphertext, shared_secret
    
    def quantum_safe_sign(self, message):
        """Create quantum-resistant digital signature"""
        signature = dilithium.sign(
            self.dilithium_keypair.private_key, 
            message.encode('utf-8')
        )
        return signature
    
    def verify_quantum_signature(self, message, signature, public_key):
        """Verify quantum-resistant signature"""
        try:
            dilithium.verify(public_key, message.encode('utf-8'), signature)
            return True
        except dilithium.InvalidSignature:
            return False

# Hybrid implementation for transition period
class HybridCryptography:
    def __init__(self):
        self.classical_crypto = self._init_classical()
        self.quantum_safe_crypto = QuantumSafeCrypto()
    
    def hybrid_encrypt(self, data, recipient_keys):
        """Encrypt using both classical and quantum-safe algorithms"""
        # Classical encryption
        classical_result = self.classical_crypto.encrypt(data)
        
        # Quantum-safe encryption
        quantum_result = self.quantum_safe_crypto.encrypt(data)
        
        # Combine both for maximum security during transition
        return {
            'classical': classical_result,
            'quantum_safe': quantum_result,
            'algorithm_metadata': {
                'classical_algorithm': 'RSA-4096',
                'quantum_algorithm': 'Kyber-1024'
            }
        }

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// Vulnerable Ethereum smart contract example
pragma solidity ^0.8.0;

contract VulnerableWallet {
    mapping(address => uint256) public balances;
    
    // VULNERABLE: Uses ECDSA for signature verification
    function withdraw(uint256 amount, bytes memory signature) public {
        bytes32 messageHash = keccak256(abi.encodePacked(msg.sender, amount));
        address signer = recoverSigner(messageHash, signature);
        
        require(signer == msg.sender, "Invalid signature");
        require(balances[msg.sender] >= amount, "Insufficient balance");
        
        balances[msg.sender] -= amount;
        payable(msg.sender).transfer(amount);
    }
    
    // This function becomes vulnerable to quantum attacks
    function recoverSigner(bytes32 hash, bytes memory signature) 
        internal pure returns (address) {
        // ECDSA recovery - quantum vulnerable
        return ECDSA.recover(hash, signature);
    }
}

// Quantum-safe alternative implementation
contract QuantumSafeWallet {
    mapping(address => uint256) public balances;
    mapping(address => bytes) public quantumPublicKeys;
    
    // Use post-quantum signature verification
    function withdrawQuantumSafe(
        uint256 amount, 
        bytes memory dilithiumSignature,
        bytes memory publicKey
    ) public {
        bytes32 messageHash = keccak256(abi.encodePacked(msg.sender, amount));
        
        // Verify using quantum-resistant Dilithium signature
        require(
            verifyDilithiumSignature(messageHash, dilithiumSignature, publicKey),
            "Invalid quantum-safe signature"
        );
        
        balances[msg.sender] -= amount;
        payable(msg.sender).transfer(amount);
    }
}

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# Quantum-safe cryptocurrency wallet implementation
import hashlib
from typing import Tuple, Dict
import dilithium  # Post-quantum signature scheme
import kyber     # Post-quantum key encapsulation

class QuantumSafeWallet:
    def __init__(self):
        # Generate quantum-safe key pairs
        self.dilithium_keypair = dilithium.generate_keypair()
        self.kyber_keypair = kyber.generate_keypair()
        self.balance = 0
        self.transaction_history = []
    
    def create_quantum_safe_transaction(self, recipient_address: str, 
                                      amount: float, 
                                      fee: float = 0.001) -> Dict:
        """Create a quantum-resistant transaction"""
        transaction = {
            'sender': self.get_quantum_address(),
            'recipient': recipient_address,
            'amount': amount,
            'fee': fee,
            'timestamp': int(time.time()),
            'nonce': self.get_nonce()
        }
        
        # Create transaction hash
        tx_hash = hashlib.sha256(
            json.dumps(transaction, sort_keys=True).encode()
        ).digest()
        
        # Sign with quantum-safe Dilithium
        signature = dilithium.sign(
            self.dilithium_keypair.private_key, 
            tx_hash
        )
        
        transaction['signature'] = signature.hex()
        transaction['public_key'] = self.dilithium_keypair.public_key.hex()
        
        return transaction
    
    def verify_quantum_transaction(self, transaction: Dict) -> bool:
        """Verify quantum-safe transaction signature"""
        # Recreate transaction hash
        tx_copy = transaction.copy()
        signature = bytes.fromhex(tx_copy.pop('signature'))
        public_key = bytes.fromhex(tx_copy.pop('public_key'))
        
        tx_hash = hashlib.sha256(
            json.dumps(tx_copy, sort_keys=True).encode()
        ).digest()
        
        try:
            dilithium.verify(public_key, tx_hash, signature)
            return True
        except dilithium.InvalidSignature:
            return False
    
    def get_quantum_address(self) -> str:
        """Generate quantum-safe wallet address"""
        # Use post-quantum public key for address generation
        public_key_hash = hashlib.sha256(
            self.dilithium_keypair.public_key
        ).digest()
        
        # Add quantum-safe address prefix
        return f"qs_{public_key_hash[:20].hex()}"

# Blockchain network quantum upgrade implementation
class QuantumSafeBlockchain:
    def __init__(self):
        self.blocks = []
        self.pending_transactions = []
        self.difficulty = 4
        self.quantum_safe_enabled = True
    
    def add_quantum_safe_block(self, transactions: list) -> bool:
        """Add block with quantum-safe verification"""
        if not self.quantum_safe_enabled:
            raise Exception("Quantum-safe mode required for new blocks")
        
        # Verify all transactions use quantum-safe signatures
        for tx in transactions:
            if not self.verify_quantum_transaction(tx):
                return False
        
        # Create quantum-safe block
        previous_hash = self.get_latest_block_hash()
        block = {
            'index': len(self.blocks),
            'timestamp': int(time.time()),
            'transactions': transactions,
            'previous_hash': previous_hash,
            'quantum_safe': True
        }
        
        # Mine block with quantum-resistant proof of work
        block['hash'] = self.mine_quantum_safe_block(block)
        self.blocks.append(block)
        return True
    
    def mine_quantum_safe_block(self, block: Dict) -> str:
        """Quantum-resistant proof of work mining"""
        nonce = 0
        target = "0" * self.difficulty
        
        while True:
            block['nonce'] = nonce
            # Use SHA-3 for quantum resistance
            block_string = json.dumps(block, sort_keys=True)
            hash_result = hashlib.sha3_256(block_string.encode()).hexdigest()
            
            if hash_result[:self.difficulty] == target:
                return hash_result
            
            nonce += 1

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// Upgradeable quantum-safe DeFi protocol
pragma solidity ^0.8.0;

import "@openzeppelin/contracts-upgradeable/proxy/utils/Initializable.sol";
import "./QuantumSafeLib.sol";

contract QuantumSafeDeFiProtocol is Initializable {
    using QuantumSafeLib for bytes;
    
    mapping(address => uint256) public liquidity;
    mapping(bytes32 => bool) public usedQuantumNonces;
    
    // Migration state tracking
    bool public quantumMigrationActive;
    uint256 public migrationDeadline;
    
    event QuantumMigrationStarted(uint256 deadline);
    event UserMigratedToQuantumSafe(address indexed user, bytes32 newQuantumAddress);
    
    function initiateQuantumMigration() external onlyOwner {
        quantumMigrationActive = true;
        migrationDeadline = block.timestamp + 180 days; // 6 months to migrate
        emit QuantumMigrationStarted(migrationDeadline);
    }
    
    function migrateToQuantumSafe(
        bytes memory dilithiumPublicKey,
        bytes memory migrationSignature,
        bytes memory classicalSignature
    ) external {
        require(quantumMigrationActive, "Migration not active");
        require(block.timestamp < migrationDeadline, "Migration deadline passed");
        
        // Verify classical signature for current ownership
        bytes32 messageHash = keccak256(
            abi.encodePacked(msg.sender, dilithiumPublicKey, block.timestamp)
        );
        address signer = ECDSA.recover(messageHash, classicalSignature);
        require(signer == msg.sender, "Invalid classical signature");
        
        // Verify quantum-safe signature
        require(
            QuantumSafeLib.verifyDilithium(
                dilithiumPublicKey, 
                messageHash, 
                migrationSignature
            ),
            "Invalid quantum signature"
        );
        
        // Create quantum-safe address mapping
        bytes32 quantumAddress = keccak256(dilithiumPublicKey);
        
        // Transfer user's assets to quantum-safe control
        uint256 userBalance = liquidity[msg.sender];
        liquidity[msg.sender] = 0;
        
        // Store in quantum-safe mapping
        quantumLiquidity[quantumAddress] = userBalance;
        quantumKeys[quantumAddress] = dilithiumPublicKey;
        
        emit UserMigratedToQuantumSafe(msg.sender, quantumAddress);
    }
    
    // New quantum-safe functions
    mapping(bytes32 => uint256) public quantumLiquidity;
    mapping(bytes32 => bytes) public quantumKeys;
    
    function quantumSafeWithdraw(
        uint256 amount,
        bytes memory dilithiumSignature,
        bytes32 nonce
    ) external {
        require(!usedQuantumNonces[nonce], "Nonce already used");
        
        bytes32 quantumAddress = keccak256(msg.data);
        require(quantumLiquidity[quantumAddress] >= amount, "Insufficient balance");
        
        // Verify quantum-safe signature
        bytes32 messageHash = keccak256(
            abi.encodePacked(quantumAddress, amount, nonce)
        );
        
        require(
            QuantumSafeLib.verifyDilithium(
                quantumKeys[quantumAddress],
                messageHash,
                dilithiumSignature
            ),
            "Invalid quantum signature"
        );
        
        usedQuantumNonces[nonce] = true;
        quantumLiquidity[quantumAddress] -= amount;
        
        // Transfer funds
        payable(msg.sender).transfer(amount);
    }
}

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// Cross-chain quantum-safe bridge implementation
class QuantumSafeBridge {
    constructor(networks) {
        this.networks = networks;
        this.quantumSafeValidators = new Map();
        this.hybridMode = true; // Support both classical and quantum-safe
    }
    
    async initializeBridge() {
        // Set up quantum-safe validator network
        for (const network of this.networks) {
            const validators = await this.deployQuantumSafeValidators(network);
            this.quantumSafeValidators.set(network.chainId, validators);
        }
    }
    
    async createQuantumSafeCrossChainTransaction(
        sourceChain, 
        targetChain, 
        amount, 
        recipient,
        quantumSignature
    ) {
        // Verify quantum-safe signature on source chain
        const sourceValidator = this.quantumSafeValidators.get(sourceChain);
        const isValidSignature = await sourceValidator.verifyDilithiumSignature(
            quantumSignature.publicKey,
            quantumSignature.message,
            quantumSignature.signature
        );
        
        if (!isValidSignature) {
            throw new Error('Invalid quantum-safe signature');
        }
        
        // Lock funds on source chain with quantum-safe contract
        const lockTx = await sourceValidator.lockFunds(
            amount,
            recipient,
            targetChain,
            quantumSignature
        );
        
        // Generate quantum-safe proof for target chain
        const quantumProof = await this.generateQuantumSafeProof(
            lockTx,
            sourceChain,
            targetChain
        );
        
        // Mint on target chain
        const targetValidator = this.quantumSafeValidators.get(targetChain);
        return await targetValidator.mintWithQuantumProof(
            amount,
            recipient,
            quantumProof
        );
    }
    
    async generateQuantumSafeProof(lockTx, sourceChain, targetChain) {
        // Create quantum-resistant merkle proof
        const merkleTree = new QuantumSafeMerkleTree();
        merkleTree.addTransaction(lockTx);
        
        // Use multiple quantum-safe signature schemes for redundancy
        const dilithiumSignature = await this.signWithDilithium(merkleTree.root);
        const falconSignature = await this.signWithFalcon(merkleTree.root);
        const sphincsSignature = await this.signWithSphincs(merkleTree.root);
        
        return {
            merkleRoot: merkleTree.root,
            proof: merkleTree.getProof(lockTx.hash),
            signatures: {
                dilithium: dilithiumSignature,
                falcon: falconSignature,
                sphincs: sphincsSignature
            },
            sourceChain,
            targetChain,
            timestamp: Date.now()
        };
    }
}

## Major Cryptocurrency Projects and Quantum Readiness

### Bitcoin Quantum Vulnerability Timeline

Bitcoin's transition to quantum-safe cryptography presents unique challenges due to its decentralized governance and consensus requirements:

**Phase 1 (2025-2027): Preparation and Soft Fork Implementation**
- BIP proposal for quantum-safe address formats
- Introduction of hybrid P2QS (Pay-to-Quantum-Safe) scripts
- Wallet software updates supporting quantum-safe key generation

**Phase 2 (2027-2030): Network-Wide Migration**
- Mandatory quantum-safe signatures for new transactions
- Legacy address deprecation warnings
- Mining pool quantum-safe infrastructure upgrades

**Phase 3 (2030+): Full Quantum Security**
- Complete phase-out of ECDSA signatures
- Quantum-safe consensus mechanisms
- Emergency quantum incident response protocols

```python
# Bitcoin quantum-safe transaction implementation
import hashlib
import struct
from typing import List, Tuple

class QuantumSafeBitcoinTransaction:
    def __init__(self):
        self.version = 2  # Enhanced version for quantum-safe support
        self.inputs = []
        self.outputs = []
        self.locktime = 0
        self.quantum_safe_flag = True
    
    def add_quantum_safe_input(self, prev_tx_hash: bytes, 
                              output_index: int,
                              dilithium_signature: bytes,
                              dilithium_pubkey: bytes) -> None:
        """Add quantum-safe input to transaction"""
        script_sig = self.create_quantum_safe_script_sig(
            dilithium_signature, 
            dilithium_pubkey
        )
        
        tx_input = {
            'prev_tx_hash': prev_tx_hash,
            'output_index': output_index,
            'script_sig': script_sig,
            'sequence': 0xFFFFFFFF,
            'quantum_safe': True
        }
        
        self.inputs.append(tx_input)
    
    def create_quantum_safe_script_sig(self, signature: bytes, 
                                     pubkey: bytes) -> bytes:
        """Create quantum-resistant script signature"""
        # OP_PUSHDATA for Dilithium signature (larger than ECDSA)
        script = bytearray()
        
        # Push signature length and data
        sig_len = len(signature)
        if sig_len <= 75:
            script.append(sig_len)
        else:
            script.append(0x4c)  # OP_PUSHDATA1
            script.append(sig_len)
        script.extend(signature)
        
        # Push public key length and data
        pubkey_len = len(pubkey)
        if pubkey_len <= 75:
            script.append(pubkey_len)
        else:
            script.append(0x4c)  # OP_PUSHDATA1
            script.append(pubkey_len)
        script.extend(pubkey)
        
        # Add quantum-safe verification opcode (future Bitcoin upgrade)
        script.append(0xba)  # OP_CHECKSIG_QUANTUM (hypothetical opcode)
        
        return bytes(script)
    
    def serialize_quantum_safe(self) -> bytes:
        """Serialize quantum-safe transaction"""
        result = bytearray()
        
        # Version (4 bytes)
        result.extend(struct.pack('<I', self.version))
        
        # Quantum-safe flag (1 byte)
        result.append(0x01 if self.quantum_safe_flag else 0x00)
        
        # Input count
        result.extend(self.encode_varint(len(self.inputs)))
        
        # Serialize inputs
        for tx_input in self.inputs:
            result.extend(tx_input['prev_tx_hash'])
            result.extend(struct.pack('<I', tx_input['output_index']))
            
            script_sig = tx_input['script_sig']
            result.extend(self.encode_varint(len(script_sig)))
            result.extend(script_sig)
            
            result.extend(struct.pack('<I', tx_input['sequence']))
        
        # Output count and outputs
        result.extend(self.encode_varint(len(self.outputs)))
        for output in self.outputs:
            result.extend(struct.pack('<Q', output['value']))
            script_pubkey = output['script_pubkey']
            result.extend(self.encode_varint(len(script_pubkey)))
            result.extend(script_pubkey)
        
        # Locktime
        result.extend(struct.pack('<I', self.locktime))
        
        return bytes(result)

# Ethereum quantum-safe upgrade implementation
class EthereumQuantumSafeUpgrade:
    def __init__(self):
        self.eip_number = 7560  # Hypothetical EIP for quantum-safe Ethereum
        self.activation_block = 20000000  # Future block number
        self.migration_period_blocks = 2102400  # ~1 year at 15s blocks
    
    def create_quantum_safe_account(self, dilithium_pubkey: bytes) -> str:
        """Create quantum-safe Ethereum account"""
        # Use Keccak-256 hash of Dilithium public key
        pubkey_hash = self.keccak256(dilithium_pubkey)
        
        # Take last 20 bytes for address, add quantum-safe prefix
        address_bytes = pubkey_hash[-20:]
        
        # Add checksum using EIP-55 standard
        address_hex = address_bytes.hex()
        checksum_hash = self.keccak256(address_hex.encode()).hex()
        
        checksummed_address = ""
        for i, char in enumerate(address_hex):
            if char.isdigit():
                checksummed_address += char
            else:
                # Uppercase if corresponding hash character is >= 8
                if int(checksum_hash[i], 16) >= 8:
                    checksummed_address += char.upper()
                else:
                    checksummed_address += char.lower()
        
        return f"0x{checksummed_address}"
    
    def create_quantum_safe_transaction(self, 
                                      nonce: int,
                                      gas_price: int,
                                      gas_limit: int,
                                      to_address: str,
                                      value: int,
                                      data: bytes,
                                      dilithium_private_key: bytes) -> dict:
        """Create quantum-safe Ethereum transaction"""
        # Create transaction object
        tx_data = {
            'nonce': nonce,
            'gasPrice': gas_price,
            'gas': gas_limit,
            'to': to_address,
            'value': value,
            'data': data,
            'quantumSafe': True,
            'signatureAlgorithm': 'dilithium'
        }
        
        # Serialize transaction for signing
        serialized_tx = self.serialize_transaction(tx_data)
        tx_hash = self.keccak256(serialized_tx)
        
        # Sign with Dilithium
        signature = dilithium.sign(dilithium_private_key, tx_hash)
        
        # Add quantum-safe signature fields
        tx_data['dilithiumSignature'] = signature.hex()
        tx_data['recoveryMethod'] = 'dilithium_verify'
        
        return tx_data

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// Quantum-safe optimistic rollup implementation
pragma solidity ^0.8.0;

contract QuantumSafeOptimisticRollup {
    struct QuantumSafeState {
        bytes32 stateRoot;
        uint256 blockNumber;
        bytes dilithiumSignature;
        bytes validatorPublicKey;
        bool quantumVerified;
    }
    
    mapping(uint256 => QuantumSafeState) public stateRoots;
    mapping(address => bytes) public validatorQuantumKeys;
    
    uint256 public constant CHALLENGE_PERIOD = 7 days;
    uint256 public constant QUANTUM_VERIFICATION_REWARD = 1 ether;
    
    event QuantumSafeStateSubmitted(
        uint256 indexed blockNumber,
        bytes32 stateRoot,
        address validator
    );
    
    event QuantumChallengeInitiated(
        uint256 indexed blockNumber,
        address challenger,
        string reason
    );
    
    function submitQuantumSafeState(
        bytes32 newStateRoot,
        bytes memory stateTransitionProof,
        bytes memory dilithiumSignature
    ) external {
        require(
            validatorQuantumKeys[msg.sender].length > 0,
            "Validator not registered with quantum-safe key"
        );
        
        // Verify state transition proof with quantum-safe cryptography
        require(
            verifyQuantumSafeStateTransition(
                stateRoots[block.number - 1].stateRoot,
                newStateRoot,
                stateTransitionProof,
                dilithiumSignature,
                validatorQuantumKeys[msg.sender]
            ),
            "Invalid quantum-safe state transition"
        );
        
        stateRoots[block.number] = QuantumSafeState({
            stateRoot: newStateRoot,
            blockNumber: block.number,
            dilithiumSignature: dilithiumSignature,
            validatorPublicKey: validatorQuantumKeys[msg.sender],
            quantumVerified: true
        });
        
        emit QuantumSafeStateSubmitted(block.number, newStateRoot, msg.sender);
    }
    
    function challengeQuantumSafety(
        uint256 blockNumber,
        bytes memory fraudProof,
        string memory challengeReason
    ) external payable {
        require(msg.value >= 1 ether, "Insufficient challenge bond");
        require(
            block.timestamp <= stateRoots[blockNumber].blockNumber + CHALLENGE_PERIOD,
            "Challenge period expired"
        );
        
        // Verify fraud proof using quantum-safe verification
        bool isFraud = verifyQuantumSafeFraudProof(
            stateRoots[blockNumber],
            fraudProof
        );
        
        if (isFraud) {
            // Slash validator and reward challenger
            _slashValidator(stateRoots[blockNumber].validatorPublicKey);
            payable(msg.sender).transfer(QUANTUM_VERIFICATION_REWARD);
            
            // Revert to previous valid state
            delete stateRoots[blockNumber];
        } else {
            // Challenge failed, forfeit bond
            // Bond goes to validator as compensation
        }
        
        emit QuantumChallengeInitiated(blockNumber, msg.sender, challengeReason);
    }
    
    function verifyQuantumSafeStateTransition(
        bytes32 previousRoot,
        bytes32 newRoot,
        bytes memory proof,
        bytes memory signature,
        bytes memory publicKey
    ) internal pure returns (bool) {
        // Implement quantum-safe state transition verification
        bytes32 transitionHash = keccak256(
            abi.encodePacked(previousRoot, newRoot, proof)
        );
        
        // Use Dilithium signature verification
        return QuantumSafeLib.verifyDilithium(
            publicKey,
            transitionHash,
            signature
        );
    }
}

// Zero-knowledge proof quantum-safe rollup
contract QuantumSafeZKRollup {
    using QuantumSafeLib for bytes;
    
    struct QuantumZKProof {
        bytes32 publicInputsHash;
        bytes quantumSafeProof;  // Post-quantum ZK proof
        bytes dilithiumSignature;
        uint256 timestamp;
    }
    
    mapping(uint256 => QuantumZKProof) public zkProofs;
    bytes32 public quantumSafeCircuitHash;
    
    event QuantumZKProofSubmitted(
        uint256 indexed batchNumber,
        bytes32 publicInputsHash,
        address prover
    );
    
    function submitQuantumZKProof(
        uint256 batchNumber,
        bytes32 publicInputsHash,
        bytes memory quantumSafeProof,
        bytes memory dilithiumSignature
    ) external {
        // Verify quantum-safe ZK proof
        require(
            verifyQuantumSafeZKProof(
                quantumSafeCircuitHash,
                publicInputsHash,
                quantumSafeProof
            ),
            "Invalid quantum-safe ZK proof"
        );
        
        // Verify prover signature
        bytes32 commitmentHash = keccak256(
            abi.encodePacked(
                batchNumber,
                publicInputsHash,
                quantumSafeProof
            )
        );
        
        require(
            QuantumSafeLib.verifyDilithium(
                getProverQuantumKey(msg.sender),
                commitmentHash,
                dilithiumSignature
            ),
            "Invalid prover signature"
        );
        
        zkProofs[batchNumber] = QuantumZKProof({
            publicInputsHash: publicInputsHash,
            quantumSafeProof: quantumSafeProof,
            dilithiumSignature: dilithiumSignature,
            timestamp: block.timestamp
        });
        
        emit QuantumZKProofSubmitted(batchNumber, publicInputsHash, msg.sender);
    }
    
    function verifyQuantumSafeZKProof(
        bytes32 circuitHash,
        bytes32 publicInputs,
        bytes memory proof
    ) internal pure returns (bool) {
        // Implement post-quantum zero-knowledge proof verification
        // This would use a quantum-resistant ZK-SNARK/STARK system
        // such as STARK, Bulletproofs, or other post-quantum schemes
        
        // Placeholder for actual quantum-safe ZK verification
        bytes32 proofHash = keccak256(
            abi.encodePacked(circuitHash, publicInputs, proof)
        );
        
        // In real implementation, this would call a quantum-safe
        // proof verification library
        return proofHash != bytes32(0);
    }
}

## Cryptocurrency Exchange and Custody Quantum Security

Centralized exchanges and custody providers face immediate quantum threats to their hot and cold wallet systems:

### Exchange Security Implementation

```python
# Quantum-safe cryptocurrency exchange architecture
import asyncio
import json
from typing import Dict, List
from dataclasses import dataclass

@dataclass
class QuantumSafeOrder:
    order_id: str
    user_id: str
    symbol: str
    side: str  # buy/sell
    quantity: float
    price: float
    dilithium_signature: bytes
    timestamp: int

class QuantumSafeExchange:
    def __init__(self):
        self.hot_wallets = {}  # Quantum-safe hot wallets
        self.cold_storage = QuantumSafeColdStorage()
        self.order_book = {}
        self.user_balances = {}
        self.quantum_safe_enabled = True
    
    async def initialize_quantum_safe_wallets(self):
        """Initialize quantum-resistant wallet infrastructure"""
        supported_assets = ['BTC', 'ETH', 'USDC', 'USDT']
        
        for asset in supported_assets:
            # Generate quantum-safe keypairs for each asset
            wallet = QuantumSafeWallet(asset)
            await wallet.initialize_quantum_keys()
            self.hot_wallets[asset] = wallet
            
        # Initialize cold storage with air-gapped quantum-safe keys
        await self.cold_storage.setup_quantum_safe_storage()
    
    async def process_quantum_safe_order(self, order_data: Dict) -> bool:
        """Process order with quantum-safe verification"""
        # Verify user's quantum-safe signature
        user_quantum_key = self.get_user_quantum_key(order_data['user_id'])
        
        if not self.verify_order_signature(order_data, user_quantum_key):
            raise ValueError("Invalid quantum-safe order signature")
        
        order = QuantumSafeOrder(**order_data)
        
        # Verify sufficient balance
        if not self.check_balance(order.user_id, order.symbol, order.quantity):
            return False
        
        # Execute trade with quantum-safe settlement
        await self.execute_quantum_safe_trade(order)
        
        # Update balances with quantum-safe transaction logging
        await self.update_balances_quantum_safe(order)
        
        return True
    
    async def quantum_safe_withdrawal(self, 
                                   user_id: str,
                                   asset: str,
                                   amount: float,
                                   destination_address: str,
                                   dilithium_signature: bytes) -> str:
        """Process withdrawal with quantum-safe security"""
        # Verify withdrawal signature
        user_key = self.get_user_quantum_key(user_id)
        withdrawal_hash = self.create_withdrawal_hash(
            user_id, asset, amount, destination_address
        )
        
        if not dilithium.verify(user_key, withdrawal_hash, dilithium_signature):
            raise ValueError("Invalid withdrawal signature")
        
        # Multi-signature quantum-safe approval
        approval_signatures = await self.collect_quantum_safe_approvals(
            withdrawal_hash
        )
        
        if len(approval_signatures) < self.required_approvals:
            raise ValueError("Insufficient quantum-safe approvals")
        
        # Execute withdrawal from hot wallet
        hot_wallet = self.hot_wallets[asset]
        tx_hash = await hot_wallet.send_quantum_safe_transaction(
            destination_address,
            amount
        )
        
        # Log withdrawal with quantum-safe audit trail
        await self.log_quantum_safe_withdrawal(
            user_id, asset, amount, tx_hash, approval_signatures
        )
        
        return tx_hash

class QuantumSafeColdStorage:
    def __init__(self):
        self.storage_devices = []
        self.threshold_scheme = QuantumSafeSecretSharing()
        self.air_gap_enabled = True
    
    async def setup_quantum_safe_storage(self):
        """Initialize air-gapped quantum-safe cold storage"""
        # Generate master quantum-safe keypairs
        master_keys = {}
        supported_assets = ['BTC', 'ETH', 'USDC', 'USDT']
        
        for asset in supported_assets:
            # Generate Dilithium keypair for each asset
            private_key, public_key = dilithium.generate_keypair()
            
            # Split private key using quantum-safe secret sharing
            key_shares = self.threshold_scheme.split_secret(
                private_key,
                threshold=3,
                total_shares=5
            )
            
            # Distribute shares across air-gapped devices
            for i, share in enumerate(key_shares):
                device = self.get_storage_device(i)
                await device.store_quantum_safe_share(asset, share)
            
            master_keys[asset] = {
                'public_key': public_key,
                'threshold': 3,
                'total_shares': 5
            }
        
        # Store public keys for verification
        self.master_public_keys = master_keys
    
    async def sign_quantum_safe_transaction(self, 
                                          asset: str,
                                          transaction_data: bytes) -> bytes:
        """Sign transaction using threshold quantum-safe signatures"""
        # Collect required number of key shares
        required_shares = self.master_public_keys[asset]['threshold']
        collected_shares = []
        
        for i in range(required_shares):
            device = self.get_storage_device(i)
            share = await device.retrieve_quantum_safe_share(asset)
            collected_shares.append(share)
        
        # Reconstruct private key
        private_key = self.threshold_scheme.reconstruct_secret(
            collected_shares
        )
        
        # Sign transaction with Dilithium
        signature = dilithium.sign(private_key, transaction_data)
        
        # Securely erase reconstructed private key
        self.secure_erase(private_key)
        
        return signature

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#!/bin/bash
# Cryptographic algorithm discovery script
echo "=== Cryptographic Algorithm Audit ==="

# Check SSL/TLS configurations
echo "Checking SSL/TLS configurations..."
openssl s_client -connect localhost:443 -cipher 'ALL' 2>/dev/null | \
    grep -E "Cipher|Protocol"

# Scan for RSA key usage
echo "Scanning for RSA keys..."
find /etc -name "*.pem" -o -name "*.key" -o -name "*.crt" 2>/dev/null | \
    xargs -I {} sh -c 'echo "File: {}"; openssl rsa -in {} -text -noout 2>/dev/null | head -3'

# Check for ECC usage
echo "Checking for ECC configurations..."
grep -r "ECDSA\|ECDHE\|secp256r1\|prime256v1" /etc/ 2>/dev/null

# Database encryption analysis
echo "Analyzing database encryption..."
mysql -e "SHOW VARIABLES LIKE '%ssl%';" 2>/dev/null || echo "MySQL not available"
psql -c "SHOW ssl;" 2>/dev/null || echo "PostgreSQL not available"

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# Kubernetes deployment with quantum-safe TLS
apiVersion: v1
kind: Secret
metadata:
  name: quantum-safe-tls
  namespace: production
type: kubernetes.io/tls
data:
  # Hybrid certificate combining RSA and post-quantum algorithms
  tls.crt: <BASE64_ENCODED_HYBRID_CERT>
  tls.key: <BASE64_ENCODED_HYBRID_KEY>
---
apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: quantum-safe-ingress
  annotations:
    nginx.ingress.kubernetes.io/ssl-protocols: "TLSv1.3"
    nginx.ingress.kubernetes.io/ssl-ciphers: "TLS_AES_256_GCM_SHA384:KYBER_1024"
    nginx.ingress.kubernetes.io/configuration-snippet: |
      ssl_ecdh_curve X25519:Kyber1024;
spec:
  tls:
  - hosts:
    - secure.example.com
    secretName: quantum-safe-tls
  rules:
  - host: secure.example.com
    http:
      paths:
      - path: /
        pathType: Prefix
        backend:
          service:
            name: quantum-safe-service
            port:
              number: 443

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# Terraform configuration for quantum-safe infrastructure
resource "aws_kms_key" "quantum_safe_key" {
  description = "Quantum-safe encryption key"
  key_usage   = "ENCRYPT_DECRYPT"
  
  # Use quantum-safe key spec when available
  key_spec = "SYMMETRIC_DEFAULT"  # Will migrate to quantum-safe spec
  
  tags = {
    QuantumSafe = "true"
    MigrationPhase = "complete"
  }
}

resource "aws_s3_bucket_server_side_encryption_configuration" "quantum_safe" {
  bucket = aws_s3_bucket.secure_data.id

  rule {
    apply_server_side_encryption_by_default {
      kms_master_key_id = aws_kms_key.quantum_safe_key.arn
      sse_algorithm     = "aws:kms"
    }
    
    # Enable quantum-safe encryption when available
    bucket_key_enabled = true
  }
}

# RDS with quantum-safe encryption
resource "aws_db_instance" "quantum_safe_db" {
  identifier = "quantum-safe-database"
  
  # Use quantum-safe encryption
  storage_encrypted = true
  kms_key_id       = aws_kms_key.quantum_safe_key.arn
  
  # Configure quantum-safe TLS
  ca_cert_identifier = "rds-ca-quantum-safe-2025"
}

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// Optimized Kyber implementation with AVX2
#include <immintrin.h>
#include "kyber.h"

class OptimizedKyber {
private:
    // Use SIMD instructions for polynomial operations
    void ntt_avx2(int16_t* poly) {
        __m256i coeffs = _mm256_loadu_si256((__m256i*)poly);
        // Optimized Number Theoretic Transform
        coeffs = _mm256_mullo_epi16(coeffs, _mm256_set1_epi16(KYBER_Q));
        _mm256_storeu_si256((__m256i*)poly, coeffs);
    }
    
public:
    // Hardware-accelerated key generation
    KeyPair generate_keypair_optimized() {
        // Leverage hardware random number generation
        if (__builtin_cpu_supports("rdrnd")) {
            return generate_with_rdrnd();
        }
        return generate_standard();
    }
    
    // Batch signature verification
    bool verify_batch(const std::vector<Message>& messages,
                     const std::vector<Signature>& signatures,
                     const PublicKey& public_key) {
        // Optimize for multiple signature verification
        return batch_verify_optimized(messages, signatures, public_key);
    }
};

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{
  "quantum_safe_compliance": {
    "nist_compliance": {
      "algorithms_approved": ["Kyber", "Dilithium", "FALCON", "SPHINCS+"],
      "key_sizes": {
        "kyber": "1024",
        "dilithium": "3",
        "falcon": "512"
      },
      "transition_deadline": "2025-12-31"
    },
    "audit_requirements": {
      "cryptographic_inventory": "quarterly",
      "vulnerability_assessment": "monthly",
      "penetration_testing": "annually"
    },
    "documentation": {
      "cryptographic_standards": "mandatory",
      "migration_plan": "required",
      "incident_response": "quantum_specific"
    }
  }
}