@finite-logic/blind-query/src/BlindProxy.js

FINITE LOGIC: BlindProxy - Homomorphic Encryprtion Core for Private Data Aggregation (Free Tier).

// NOTE: Full Homomorphic Encryption (FHE) is mathematically complex and
// not practical for a single file demo. This code demonstrates the *concept*
// of an Additive Homomorphic scheme (like Paillier) for aggregation.
const crypto = require('crypto');

// A simple (non-cryptographically secure) function to simulate a one-way encryption
// In a real HE system, the ciphertext would allow arithmetic operations.
function simpleEncrypt(value, key) {
    const cipher = crypto.createCipher('aes-256-cbc', key);
    let encrypted = cipher.update(String(value), 'utf8', 'hex');
    encrypted += cipher.final('hex');
    return encrypted;
}

// The core conceptual function that works on the "encrypted" state.
// Additive HE allows C(A) + C(B) = C(A+B).
// Here, we simulate by simply concatenating, but in a real HE,
// this operation would be complex mathematical manipulation of the ciphertext.
function homomorphicAdd(ciphertextA, ciphertextB) {
    // In a real HE scheme, this would be a complex math operation on the ciphertext.
    // Conceptually, for addition: we'll simulate the result by tracking the total.
    return {
        _type: 'HomomorphicSum',
        // In this demo, we store the *value* of the encrypted data (not secure)
        // to show that the operation results in the correct aggregated state.
        // In a real HE, we'd only store the manipulated ciphertext.
        _aggregate: ciphertextA._aggregate + ciphertextB._aggregate 
    };
}

class BlindQueryProxy {
    constructor(secretKey) {
        this.secretKey = secretKey || 'a_strong_secret_key_for_demo';
    }

    /**
     * Simulates encrypting a value (the data owner side).
     */
    encryptData(value) {
        // This is where a real Paillier or BFV scheme would operate.
        const ciphertext = simpleEncrypt(value, this.secretKey); 
        return { ciphertext, _aggregate: value }; // We include _aggregate for the demo's homomorphicAdd
    }

    /**
     * Executes a conceptual homomorphic operation on ciphertexts (the server side).
     * The server never sees the real value.
     */
    runAggregateQuery(encryptedDataList) {
        if (!encryptedDataList || encryptedDataList.length === 0) return null;

        // Start with the first element's aggregate state
        let currentSum = encryptedDataList[0];

        // Perform the homomorphic addition for all subsequent elements
        for (let i = 1; i < encryptedDataList.length; i++) {
            currentSum = homomorphicAdd(currentSum, encryptedDataList[i]);
        }

        console.log(`[BlindQuery] Homomorphic operation complete on ${encryptedDataList.length} items.`);
        return currentSum; // Returns the final encrypted result
    }

    /**
     * Decrypts the final aggregate result (only the data owner can do this).
     * NOTE: This requires implementing a full HE decryption, which is omitted here.
     * We just expose the demo aggregate value.
     */
    decryptAggregate(encryptedResult) {
        // In a real scenario, this would be the final, private decryption step.
        return encryptedResult._aggregate; 
    }
}

// --- Demonstration ---
const proxy = new BlindQueryProxy('MyMasterKey');

const dataPoints = [10, 25, 40];
const encryptedPoints = dataPoints.map(p => proxy.encryptData(p));

console.log('--- BlindQuery Engine: Homomorphic Demo ---');
console.log(`Original Data Sum: ${dataPoints.reduce((a, b) => a + b, 0)}`);
console.log(`Encrypted Data Sample (Ciphertext): ${encryptedPoints[0].ciphertext.substring(0, 15)}...`);

// The server runs the query on the encrypted data:
const encryptedResult = proxy.runAggregateQuery(encryptedPoints);

// The data owner decrypts the result
const finalSum = proxy.decryptAggregate(encryptedResult);
console.log(`Final Decrypted Sum: ${finalSum}`);

module.exports = { BlindQueryProxy };