Encryption at rest is a critical security mechanism in AWS that protects your data when it is stored on physical storage media. This means your data remains encrypted while sitting on disk, in databases, or in any persistent storage, ensuring confidentiality even if the underlying hardware is compr…Encryption at rest is a critical security mechanism in AWS that protects your data when it is stored on physical storage media. This means your data remains encrypted while sitting on disk, in databases, or in any persistent storage, ensuring confidentiality even if the underlying hardware is compromised.<br><br>AWS provides encryption at rest across numerous services including S3, EBS, RDS, DynamoDB, Redshift, and many others. There are two primary approaches to implementing encryption at rest:<br><br>**Server-Side Encryption (SSE):** AWS manages the encryption process automatically. When data is written, AWS encrypts it before storing, and decrypts it when you access it. This is transparent to applications and requires minimal configuration.<br><br>**Client-Side Encryption:** You encrypt data before sending it to AWS. This gives you complete control over encryption keys and processes, but requires more implementation effort.<br><br>AWS Key Management Service (KMS) plays a central role in encryption at rest. KMS allows you to create, manage, and control cryptographic keys. You can use AWS managed keys, which AWS creates and manages for specific services, or Customer Managed Keys (CMKs) for greater control over key policies and rotation.<br><br>For S3, you have multiple SSE options: SSE-S3 uses Amazon-managed keys, SSE-KMS integrates with KMS for audit trails and key management, and SSE-C lets you provide your own encryption keys.<br><br>EBS volumes support encryption using KMS keys, encrypting data at rest, data in transit between the volume and instance, and all snapshots created from the volume.<br><br>RDS supports encryption for database instances, automated backups, read replicas, and snapshots using KMS integration.<br><br>Key benefits include compliance with regulatory requirements like HIPAA and PCI-DSS, protection against physical theft, and defense-in-depth security strategy. Encryption at rest is considered a fundamental security best practice for protecting sensitive information in cloud environments.
Encryption at Rest - AWS Developer Associate Guide
What is Encryption at Rest?
Encryption at rest refers to the protection of data when it is stored on a physical medium such as hard drives, SSDs, or any persistent storage. This means that data is encrypted before being written to disk and decrypted when read by authorized users or applications.
Why is Encryption at Rest Important?
• Data Protection: Protects sensitive information from unauthorized access if storage media is compromised, stolen, or improperly disposed of • Compliance Requirements: Many regulations (HIPAA, PCI-DSS, GDPR) mandate encryption of sensitive data at rest • Defense in Depth: Adds an additional layer of security beyond network and access controls • Data Sovereignty: Helps organizations maintain control over their data even when stored in cloud environments
How Encryption at Rest Works in AWS
Key Management: AWS uses AWS Key Management Service (KMS) as the primary service for managing encryption keys. Keys can be: • AWS Managed Keys: Automatically created and managed by AWS services • Customer Managed Keys (CMK): Created and controlled by you with full key policy control • Customer Provided Keys: You generate and manage keys outside AWS (SSE-C for S3)
Common AWS Services with Encryption at Rest:
• S3: SSE-S3, SSE-KMS, SSE-C options available; can enable default encryption on buckets • EBS: AES-256 encryption; can be enabled at volume creation or set as account default • RDS: Uses AES-256; must be enabled at database creation time • DynamoDB: Encryption enabled by default using AWS owned keys or customer managed KMS keys • EFS: Supports encryption using KMS keys • Redshift: Supports KMS and HSM for key management
Encryption Process: 1. A data encryption key (DEK) is generated 2. The DEK encrypts your data 3. The DEK itself is encrypted by a master key (envelope encryption) 4. Both encrypted data and encrypted DEK are stored together 5. During decryption, the master key decrypts the DEK, which then decrypts the data
Exam Tips: Answering Questions on Encryption at Rest
Key Concepts to Remember:
• Default Encryption: Know which services have encryption enabled by default (DynamoDB, S3 bucket default encryption) versus those requiring explicit enablement • Timing Matters: RDS encryption must be enabled at creation; you cannot encrypt an existing unencrypted RDS instance - you must create an encrypted snapshot and restore from it • EBS Snapshots: Snapshots of encrypted volumes are automatically encrypted; snapshots of unencrypted volumes are unencrypted • Cross-Region Copies: When copying encrypted snapshots across regions, you need to specify a KMS key in the destination region • S3 Encryption Options: Understand the differences between SSE-S3 (Amazon manages keys), SSE-KMS (you control key policies), and SSE-C (you provide and manage keys)
Common Question Patterns:
• Questions about compliance typically point toward SSE-KMS for audit trails via CloudTrail • Questions mentioning 'minimal operational overhead' often suggest SSE-S3 or AWS managed keys • Questions requiring separation of key management from AWS point toward SSE-C or CloudHSM • If a question asks about encrypting an existing unencrypted resource, look for answers involving snapshots, copies, or migration steps
Remember These Facts:
• KMS keys are region-specific • Envelope encryption is used to encrypt data keys with master keys • AWS managed keys rotate automatically every year • Customer managed keys can have automatic rotation enabled (annually) or be rotated manually • CloudTrail logs all KMS API calls for auditing purposes