What is the difference between encryption at rest and encryption in transit
· Category: Cybersecurity
Short answer
Encryption at rest protects data stored on disk — if someone steals the hard drive, they can't read the data without the key. Encryption in transit protects data while it's being sent over a network — if someone intercepts the traffic, they can't read it. You need both for complete security. For how transit encryption works, see how does HTTPS encryption work.
Key differences
| Factor | Encryption at rest | Encryption in transit |
|---|---|---|
| Protects against | Physical theft, disk disposal, insider access | Eavesdropping, MITM attacks |
| Protocol | AES-256, often managed by cloud KMS | TLS 1.3 (successor to SSL) |
| When applied | When data is written to storage | When data is sent over network |
| Key management | Server-side or client-side encryption keys | Certificates and key exchange |
| Performance impact | Minimal (hardware acceleration) | Small TLS handshake overhead |
How they work together
- User submits data over HTTPS (encryption in transit)
- Server receives and decrypts the TLS layer
- Server encrypts data with AES-256 before writing to disk (encryption at rest)
- When reading data, server decrypts the storage layer, re-encrypts via TLS, sends to user
If you skip either: without transit encryption, network eavesdroppers can read data. Without at-rest encryption, someone with physical disk access can read data.
Tips
- Cloud providers offer at-rest encryption by default (AWS S3, Azure Blob, GCP Cloud Storage)
- Always enforce HTTPS — never allow HTTP connections. For understanding certificate setup, see how to set up SSL/TLS certificates for a web server