Field-Level Encryption for REST APIs: Protect Sensitive Data Beyond HTTPS
Your database isn’t safe. Your API isn’t either. The only way to be sure no one can read your sensitive data is to encrypt it before it leaves the client—and never send the raw values anywhere. Field-level encryption for REST APIs does exactly that.
Most REST APIs depend on HTTPS. That’s not enough. HTTPS secures data in transit, but once it hits your backend, it’s in plaintext. Anyone with database access, admin rights, or a leaked dump gets the whole thing. With field-level encryption, each sensitive field—like a credit card number, SSN, or private message—is encrypted at the application layer, before the API request is sent. The backend stores only cipher text. Decryption happens only where you decide it should, often on the client or in a secure enclave.
Implementing field-level encryption in a REST API is simple in concept but requires strict discipline:
- Choose a Strong, Modern Cipher
Stick to AES-256-GCM or ChaCha20-Poly1305. Avoid outdated algorithms. Make sure you generate a unique IV for each encrypted field. - Manage Keys Securely
Keys should never be hardcoded or stored alongside your data. Use a dedicated KMS (Key Management Service) or an HSM (Hardware Security Module). Rotate your keys regularly and keep a policy for key revocation. - Encrypt Only What’s Necessary
Don’t over-encrypt; it adds complexity. Identify fields with regulatory or business-critical sensitivity and wrap those in encryption. - Handle Metadata Carefully
Even with encryption, metadata leaks can reveal patterns. Don’t index encrypted values. Don’t store unhashed identifiers next to encrypted fields. - Test Every Step
Encrypt. Send. Decrypt. Validate. Build automated tests to ensure you never store plaintext by mistake.
For performance, encrypt on the client side before making a POST or PUT request. This avoids adding CPU load to your API servers and keeps sensitive values invisible to logs, caches, and middleware. If you need search or filtering on sensitive values, integrate deterministic encryption for equality checks—but be aware of its trade-offs.
The main challenge isn’t just writing the crypto. It’s wiring it into your full request lifecycle in a way that no path exists for unencrypted data to slip in. It’s making sure your logging, debugging, and monitoring pipelines aren’t silently dumping private values. It’s ensuring key rotation doesn’t make existing data unusable.
If your REST API handles user PII, financial records, medical details, or any regulated data, field-level encryption isn’t optional. It’s the difference between a security incident being catastrophic or meaningless.
You can build it from scratch. Or you can see it working in minutes. With hoop.dev you can set up, test, and watch field-level encryption in a live REST API right now. No delays, no weeks of setup. What you encrypt in the client stays safe, even if everything else is compromised.
Do it now. Your database doesn’t need to know your secrets.