YepAPI/skills

Data Encryption

Rules

• TLS everywhere: redirect HTTP to HTTPS, set HSTS headers, never allow unencrypted connections
• Encrypt PII columns at the application level with AES-256-GCM before storing in the database
• Hash emails with SHA-256 for lookup, encrypt with AES-256-GCM for display — enables search without exposing data
• Passwords: bcrypt or argon2id only — never SHA, MD5, or reversible encryption
• Encrypt database backups and store encryption keys separately from the data
• Use crypto.subtle for browser-side encryption, node:crypto for server-side
• Store encryption keys in a secrets manager, never in code or alongside encrypted data

// AES-256-GCM encrypt/decrypt in Node.js
import { createCipheriv, createDecipheriv, randomBytes } from "node:crypto";

const ENCRYPTION_KEY = Buffer.from(process.env.ENCRYPTION_KEY!, "hex"); // 32 bytes

function encrypt(plaintext: string): string {
  const iv = randomBytes(12);
  const cipher = createCipheriv("aes-256-gcm", ENCRYPTION_KEY, iv);
  const encrypted = Buffer.concat([cipher.update(plaintext, "utf8"), cipher.final()]);
  const tag = cipher.getAuthTag();
  return Buffer.concat([iv, tag, encrypted]).toString("base64");
}

function decrypt(ciphertext: string): string {
  const buf = Buffer.from(ciphertext, "base64");
  const iv = buf.subarray(0, 12);
  const tag = buf.subarray(12, 28);
  const encrypted = buf.subarray(28);
  const decipher = createDecipheriv("aes-256-gcm", ENCRYPTION_KEY, iv);
  decipher.setAuthTag(tag);
  return decipher.update(encrypted) + decipher.final("utf8");
}

Avoid

• Storing PII in plaintext — one database breach exposes everything
• Using ECB mode or AES without authentication (CBC without HMAC) — use GCM
• MD5 or SHA for password hashing — they are not password hashing algorithms
• Hardcoding encryption keys in source code — use environment variables or a KMS
• Sending sensitive data over HTTP, even internally — use TLS for all connections