Encryption for data at rest and in transit ensures that sensitive information remains secure while stored or transmitted. For data at rest—such as files in databases, disks, or backups—encryption converts readable data (plaintext) into scrambled data (ciphertext) using algorithms and keys. A common approach is AES-256, a symmetric encryption standard, where the same key encrypts and decrypts data. For example, a database might encrypt credit card numbers using AES-256 in CBC mode, with keys managed by a hardware security module (HSM) or cloud-based key management service (KMS). This prevents unauthorized access if storage media is physically stolen or breached.
For data in transit—like API calls, emails, or network traffic—encryption protects information as it moves between systems. Transport Layer Security (TLS) is widely used here. TLS combines asymmetric encryption (e.g., RSA or ECC) for initial key exchange with symmetric encryption (e.g., AES) for the actual data transfer. For instance, when a user submits a login form, the browser and server first perform a TLS handshake: the server sends a certificate with its public key, the client verifies it, and both agree on a session key. All subsequent data is encrypted with AES using that key. This prevents eavesdropping or tampering during transmission. Tools like Let’s Encrypt provide free certificates to enable HTTPS (HTTP over TLS) for websites.
Key management and protocol choices are critical for both scenarios. For data at rest, developers must ensure encryption keys are stored separately from the encrypted data and rotated periodically. Cloud services like AWS KMS or Azure Key Vault automate this. For data in transit, TLS configurations must use modern protocols (e.g., TLS 1.3) and avoid deprecated ones like SSLv3. Compliance standards like GDPR or HIPAA often mandate encryption for both states. Developers should also validate certificates and enforce strict cipher suites to prevent vulnerabilities. Combining encryption at rest and in transit creates layered security, addressing threats like unauthorized access, data leaks, or man-in-the-middle attacks.