Encryption at Rest
Encryption at rest is the practice of encrypting data while it is stored on a physical medium such as a hard drive, database, or cloud storage, protecting it from unauthorized access if the storage is compromised.
Encryption at rest ensures that sensitive data remains protected even when storage media is physically stolen, improperly decommissioned, or accessed by unauthorized individuals. Without encryption at rest, anyone with physical or logical access to the storage device can read the data directly.
There are several approaches to implementing encryption at rest. Full-disk encryption (FDE) encrypts the entire storage volume, protecting all data including temporary files and swap space. File-level or column-level encryption provides more granular control, encrypting specific files or database columns while leaving others in plaintext. Application-level encryption encrypts data before it reaches the storage layer, providing the strongest protection because the application controls the keys.
Key management is the most critical aspect of encryption at rest. Encryption keys must be stored separately from the encrypted data, rotated regularly, and protected with strict access controls. Cloud providers offer managed key management services (AWS KMS, Azure Key Vault, Google Cloud KMS) that simplify this process. Hardware Security Modules (HSMs) provide the highest level of key protection by storing keys in tamper-resistant hardware. Organizations should implement encryption at rest for all sensitive data including databases, backups, logs, and temporary files. Compliance frameworks such as PCI DSS, HIPAA, and GDPR either require or strongly recommend encryption at rest for regulated data.