Cloud KMS — Key Management Service

import { KMSClient, GenerateDataKeyCommand, DecryptCommand, EncryptCommand } from "@aws-sdk/client-kms"; import { createCipheriv, createDecipheriv, randomBytes } from "crypto"; const kms = new KMSClient({ region: "ap-southeast-1" }); const KEY_ID = "arn:aws:kms:ap-southeast-1:123456789:key/abc-def"; // ─── ENCRYPT DATA (envelope encryption) ─────────────────────── async function encryptData(plaintext: Buffer): Promise<{ ciphertext: Buffer; encryptedDEK: Buffer }> { // 1. Ask KMS to generate a data key const { Plaintext: dek, CiphertextBlob: encryptedDEK } = await kms.send( new GenerateDataKeyCommand({ KeyId: KEY_ID, KeySpec: "AES_256" }) ); try { // 2. Encrypt locally with the plaintext DEK (never leaves your process) const iv = randomBytes(12); // 96-bit IV for GCM const cipher = createCipheriv("aes-256-gcm", dek!, iv); const encrypted = Buffer.concat([cipher.update(plaintext), cipher.final()]); const authTag = cipher.getAuthTag(); // integrity check // Ciphertext format: [IV (12)] + [AuthTag (16)] + [EncryptedData] const ciphertext = Buffer.concat([iv, authTag, encrypted]); return { ciphertext, encryptedDEK: Buffer.from(encryptedDEK!) }; } finally { // 3. Zero out plaintext DEK from memory immediately dek?.fill(0); } } // ─── DECRYPT DATA ───────────────────────────────────────────── async function decryptData(ciphertext: Buffer, encryptedDEK: Buffer): Promise<Buffer> { // 1. Ask KMS to decrypt the data key (one call per batch) const { Plaintext: dek } = await kms.send( new DecryptCommand({ CiphertextBlob: encryptedDEK }) ); try { // 2. Decrypt locally const iv = ciphertext.subarray(0, 12); const authTag = ciphertext.subarray(12, 28); const encrypted = ciphertext.subarray(28); const decipher = createDecipheriv("aes-256-gcm", dek!, iv); decipher.setAuthTag(authTag); // verify integrity return Buffer.concat([decipher.update(encrypted), decipher.final()]); } finally { dek?.fill(0); // always zero out DEK } }

// One DEK per user — revoking access to one user's CMK-scope // doesn't expose other users' data // Schema CREATE TABLE users ( id UUID PRIMARY KEY, email TEXT, -- plaintext for lookups ssn_cipher BYTEA, -- AES-256-GCM(ssn) dek_cipher BYTEA, -- KMS_CMK(DEK) — store with row iv BYTEA -- 12-byte GCM IV ); // Insert encrypted row async function insertUser(email: string, ssn: string) { const { ciphertext, encryptedDEK } = await encryptData(Buffer.from(ssn)); await db.query( `INSERT INTO users (email, ssn_cipher, dek_cipher) VALUES ($1, $2, $3)`, [email, ciphertext, encryptedDEK] ); } // Read and decrypt async function getSSN(userId: string): Promise<string> { const row = await db.query(`SELECT ssn_cipher, dek_cipher FROM users WHERE id=$1`, [userId]); const plaintext = await decryptData(row.ssn_cipher, row.dek_cipher); return plaintext.toString(); }