Encryption at Rest - Securing Data on Disk

About 2 min read

Encryption at rest is a technique that protects data stored in storage by encrypting it. Even if data stored on a hard disk, SSD, or cloud storage is physically stolen or accessed without authorization, its contents cannot be read as long as it is encrypted. As of 2025, major cloud services (AWS, Azure, GCP) enable encryption at rest by default, and it is a standard measure for corporate compliance requirements. It is a concept that pairs with encryption in transit.

Real-World Use Cases

"An employee's laptop was stolen while on a business trip, but because full-disk encryption with BitLocker was enabled, we judged the risk of a data breach to be extremely low. Without encryption, it would have triggered a reporting obligation as a leak of customer information."

Methods of Encryption at Rest

Full-disk encryption (FDE) encrypts the entire disk, with BitLocker (Windows) and FileVault (macOS) being representative examples. File-level encryption encrypts individual files or folders. Database encryption protects data within a database using methods such as TDE (Transparent Data Encryption). In cloud environments, server-side encryption using AWS KMS or Azure Key Vault is standard.data encryption books on Amazon provide a detailed look at this topic.

The Difference from Encryption in Transit

Whereas encryption at rest protects data on storage, encryption in transit (such as SSL/TLS) protects data flowing over the network. For example, a password sent over HTTPS is encrypted during transmission, but when it is stored in the server's database it remains in plaintext unless encryption at rest is in place. Complete data protection requires both. The basics of encryption explains the relationship between the two in detail.

Relation to Passwords

Decrypting encrypted storage requires a password or an encryption key. Using a sufficiently long random password as the disk encryption passphrase achieves strong protection even against physical theft. Managing the encryption key is also important, because losing the key makes the data inaccessible. Laptops are said to be lost or stolen by the millions each year, so full-disk encryption is an essential measure together with cloud storage security.key management books (Amazon) are also a helpful reference.