Encryption at rest for sensitive data

Storing SSNs, health records, or payment card data as plaintext in a database means a SQL injection, a misconfigured backup, or a rogue employee with SELECT privileges can access the raw values immediately. CWE-311 (Missing Encryption of Sensitive Data) and OWASP A02 (Cryptographic Failures) classify this as a high-severity failure. NIST 800-53 SC-28 mandates encryption of information at rest for sensitive categories. Infrastructure-level disk encryption (RDS encryption, full-disk) does not protect against application-layer attacks or insider queries — field-level AES-256-GCM encryption is the only control that survives a database dump.

Encrypt sensitive fields before writing them to the database using AES-256-GCM with a randomly generated IV per record:

import crypto from 'crypto'

const KEY = Buffer.from(process.env.ENCRYPTION_KEY!, 'hex')  // 32-byte hex key

function encrypt(text: string): string {
  const iv = crypto.randomBytes(16)
  const cipher = crypto.createCipheriv('aes-256-gcm', KEY, iv)
  const enc = Buffer.concat([cipher.update(text, 'utf8'), cipher.final()])
  const tag = cipher.getAuthTag()
  return `${iv.toString('hex')}:${tag.toString('hex')}:${enc.toString('hex')}`
}

Store ENCRYPTION_KEY in AWS Secrets Manager or HashiCorp Vault — not in a .env file alongside the data it protects. Fields eligible for a HIPAA or PCI skip (e.g., Stripe-tokenized cards) need documented evidence of third-party handling.