AWS KMS Automatic Key Rotation | Deep Dive.

twtech deep into AWS KMS Automatic Key Rotation, one of the key lifecycle management and security best practices in AWS cryptography.

Focus:

• The Concept: Key Rotation
• Types of Key Rotation in AWS KMS,
• How Automatic Key Rotation Works,
• Visual Workflow: Key Rotation Flow,
• Key Rotation vs. Re-Encryption,
• Key Metadata and Tracking,
• Automatic Key Rotation – Limitations,
• Benefits of Automatic Key Rotation,
• Manual Rotation Alternative (Custom Schedule),
• Diagram: AWS KMS Automatic Key Rotation Architecture

1. The Concept: Key Rotation

•        Key rotation is the process of replacing an old cryptographic key with a new one while maintaining continuity of encryption and access to previously encrypted data.
•        In AWS KMS, key rotation ensures long-term data protection by limiting how long any one encryption key is used.

 2. Types of Key Rotation in AWS KMS

Rotation Type	Description	Applies To
Automatic Key Rotation	AWS KMS automatically generates new key material every 365 days for a Customer Managed Key (CMK).	Customer-managed symmetric KMS keys
Manual Rotation	twtech manually create a new key and update its   applications or aliases to use it.	Symmetric or asymmetric CMKs
AWS Managed Keys Rotation	AWS automatically rotates keys used by AWS services (e.g., aws/s3, aws/rds).	AWS-managed service keys

 3. How Automatic Key Rotation Works

Automatic key rotation only applies to Customer Managed Symmetric Keys (CMKs).

Here’s the workflow:

1.     twtechou enables automatic rotation on your KMS key.

2.     Every 365 days, KMS:

o   Generates a new cryptographic backing key (key material).

o   Keeps all old versions (key material) associated with the same logical key.

3.     Each version of the key has its own unique key ID under the same CMK.

4.     KMS uses:

o   The latest key version for new encryptions.

o   The older key versions for decrypting data encrypted earlier.

5.     The CMK ARN (Amazon Resource Name) remains the same, so no application changes are required.

 4. Visual Workflow: Key Rotation Flow

NB:
All older versions remain available for decryption, ensuring backward compatibility with existing data.

 5. Key Rotation vs. Re-Encryption

Concept	Description
Key Rotation		KMS automatically generates new key material (for same CMK ID).
Re-Encryption		twtech explicitly re-encrypt data using a new CMK.
Combined		Best practice: Enable automatic rotation and periodically re-encrypt critical data.

 6. Key Metadata and Tracking

Each rotated key version shares:

•         The same CMK ARN and alias
•         Different key material IDs (underlying HSM key)
•         Logged actions in AWS CloudTrail for full traceability

# twtech can track key rotations using:

aws kms get-key-rotation-status --key-id <twtechkeyID>

#  Then, Enable rotation with:

aws kms enable-key-rotation --key-id <twtechkeyID>

 7. Automatic Key Rotation – Limitations

Limitation	Description
Applies only to symmetric CMKs	Asymmetric keys (RSA, ECC) do not support auto-rotation.
Rotation interval is fixed at 365 days	twtech can’t customize the frequency.
Only for Customer Managed Keys	AWS-managed keys already rotate automatically; you can’t configure them.
No re-encryption of existing data	Old data stays encrypted with old key versions.

 8. Benefits of Automatic Key Rotation

Benefit	Description
Compliance	Meets PCI DSS, HIPAA, and ISO 27001 key management best practices.
Reduced risk	Limits exposure if key material is compromised.
Seamless	No application code or configuration changes required.
Transparent decryption	Older versions still decrypt seamlessly.

 9. Manual Rotation Alternative (Custom Schedule)

If twtech want to rotate keys more frequently than 365 days,  it uses manual rotation:

1.     Create a new CMK.
2.      Update aliases to point to the new key.
3.      Optionally re-encrypt data with the new key.
4.      Disable or delete the old CMK after verification.

 10. Diagram: AWS KMS Automatic Key Rotation Architecture

Components:

•         Customer-managed KMS key (CMK)
•         AWS KMS internal HSM key versions
•         AWS services (S3, RDS, Lambda, etc.)
•         CloudTrail logging