Automatic key rotation is a security feature provided by AWS Key Management Service (KMS) that helps maintain the security of your encryption keys by periodically creating new cryptographic material for your customer master keys (CMKs). When enabled, AWS KMS generates new backing key material for y…Automatic key rotation is a security feature provided by AWS Key Management Service (KMS) that helps maintain the security of your encryption keys by periodically creating new cryptographic material for your customer master keys (CMKs). When enabled, AWS KMS generates new backing key material for your CMK every year (365 days). This process is transparent and does not affect the functionality of your applications or require any changes to your code. The key ID, key ARN, region, policies, and permissions associated with the CMK remain unchanged during rotation. AWS KMS retains all previous versions of the backing key material, ensuring that any data encrypted with older key versions can still be decrypted. When you encrypt new data, KMS uses the current (newest) backing key material, while decryption operations automatically use the appropriate key version that was used during encryption. This feature is only available for symmetric CMKs that are created by AWS KMS. Asymmetric CMKs and CMKs with imported key material do not support automatic rotation. For CMKs in custom key stores backed by AWS CloudHSM clusters, automatic rotation is also not available. To enable automatic key rotation, you can use the AWS Management Console, AWS CLI, or AWS SDKs. The EnableKeyRotation API call activates this feature, while DisableKeyRotation turns it off. You can check the rotation status using GetKeyRotationStatus. Automatic key rotation provides several benefits including reduced risk of key compromise over time, compliance with security policies requiring periodic key rotation, and simplified key management since AWS handles the rotation process. There are no additional charges for enabling automatic key rotation. However, if your compliance requirements demand more frequent rotation or you need to rotate asymmetric keys, you must implement manual key rotation by creating new CMKs and updating your applications to use them.
Automatic Key Rotation in AWS KMS
What is Automatic Key Rotation?
Automatic key rotation is a security feature in AWS Key Management Service (KMS) that automatically generates new cryptographic material for your Customer Master Keys (CMKs) on a regular schedule. When enabled, AWS KMS creates new backing key material for your CMK every year (365 days), while preserving all previous versions of the key material to decrypt data encrypted with older versions.
Why is Automatic Key Rotation Important?
Key rotation is a fundamental security best practice for several reasons:
• Reduces risk of key compromise: If cryptographic material is exposed, the impact is limited to data encrypted with that specific version • Compliance requirements: Many regulatory frameworks (PCI-DSS, HIPAA, SOC 2) mandate regular key rotation • Limits data exposure: Minimizes the amount of data encrypted under a single key version • Defense in depth: Adds an additional layer of security to your encryption strategy
How Automatic Key Rotation Works
1. Key Material Generation: AWS KMS generates new cryptographic backing material annually
2. Key ID Preservation: The CMK's key ID, ARN, alias, and permissions remain unchanged
3. Transparent Decryption: AWS KMS retains all previous key material versions and automatically uses the appropriate version to decrypt older ciphertext
4. New Encryptions: All new encryption operations use the latest key material version
Key Limitations and Considerations:
• Automatic rotation is only available for symmetric CMKs with AWS KMS-generated key material • Not available for: Asymmetric CMKs, CMKs in custom key stores, CMKs with imported key material, or AWS managed keys • Rotation period is fixed at one year and cannot be customized • You can perform manual rotation if you need more frequent rotation
Enabling Automatic Key Rotation:
Via AWS Console: Navigate to KMS → Customer managed keys → Select key → Key rotation tab → Enable
Via AWS CLI: aws kms enable-key-rotation --key-id [key-id]
Manual Rotation Alternative:
For keys that do not support automatic rotation (imported keys, asymmetric keys), you must perform manual rotation by: 1. Creating a new CMK 2. Updating your key alias to point to the new CMK 3. Keeping the old CMK available for decrypting historical data
Exam Tips: Answering Questions on Automatic Key Rotation
• Remember the rotation period: Automatic rotation occurs every 365 days - this is not configurable
• Know what supports automatic rotation: Only symmetric CMKs with KMS-generated key material support automatic rotation
• Imported key material: CMKs with imported key material require manual rotation
• Key ID stays the same: After rotation, applications continue working with the same key ID and alias
• Old data accessibility: Rotated keys can still decrypt data encrypted with previous key material versions
• AWS managed keys: These rotate automatically every three years and you cannot manage this rotation
• Cost considerations: Automatic rotation does not incur additional charges beyond standard CMK storage
• Compliance scenarios: If a question mentions PCI-DSS or regulatory compliance with encryption, automatic key rotation is likely part of the answer
• Asymmetric keys: If asked about rotating asymmetric keys, remember that manual rotation is the only option