AWS Key Management Service (KMS) is a managed service that enables you to create, control, and manage cryptographic keys used to protect your data across AWS services and applications. Understanding KMS key management is essential for the AWS Certified SysOps Administrator - Associate exam, particu…AWS Key Management Service (KMS) is a managed service that enables you to create, control, and manage cryptographic keys used to protect your data across AWS services and applications. Understanding KMS key management is essential for the AWS Certified SysOps Administrator - Associate exam, particularly in the Security and Compliance domain.
KMS supports two types of keys: AWS managed keys and customer managed keys (CMKs). AWS managed keys are created and managed by AWS services on your behalf, while CMKs provide full control over key policies, rotation, and lifecycle management.
Key policies are resource-based policies that define who can use and manage KMS keys. They work alongside IAM policies to provide fine-grained access control. Every KMS key must have a key policy, and you can combine it with grants for temporary, programmatic access delegation.
Automatic key rotation is a critical feature where AWS rotates the backing key material annually for customer managed keys when enabled. The key ID remains the same, ensuring seamless encryption and decryption of previously encrypted data. AWS managed keys rotate automatically every three years.
KMS integrates with AWS CloudTrail, logging all API calls for auditing and compliance purposes. This helps track key usage, access patterns, and potential security incidents. You can monitor key usage through CloudWatch metrics and set up alarms for unusual activity.
For multi-Region scenarios, KMS offers multi-Region keys that replicate across AWS Regions, enabling encrypted data to be decrypted in different Regions using related keys.
Key deletion in KMS includes a mandatory waiting period (7-30 days) to prevent accidental deletion. During this period, the key is disabled but can be recovered. You can also disable keys temporarily to prevent their use.
Best practices include implementing least privilege access, enabling key rotation, monitoring usage through CloudTrail, and using separate keys for different applications or data classifications.
AWS Key Management Service (KMS) is a critical component of AWS security infrastructure. As a SysOps Administrator, understanding KMS is essential because it enables you to create, manage, and control cryptographic keys used to protect your data across AWS services. Proper key management ensures data confidentiality, helps meet compliance requirements (such as PCI-DSS, HIPAA, and SOC), and provides audit trails for all key usage.
What is AWS KMS?
AWS KMS is a managed service that allows you to create and manage encryption keys and control their use across AWS services and applications. KMS integrates with most AWS services including S3, EBS, RDS, Redshift, Lambda, and many others.
Key Types in AWS KMS:
• AWS Managed Keys (aws/service-name) - Created, managed, and used on your behalf by AWS services. Free to store but usage charges apply.
• Customer Managed Keys (CMKs) - Keys you create, own, and manage. You have full control over key policies, rotation, and enabling/disabling.
• AWS Owned Keys - Keys that AWS owns and manages for use across multiple accounts. Not visible in your account.
• Custom Key Stores - KMS keys stored in AWS CloudHSM clusters you control.
How AWS KMS Works
Envelope Encryption: KMS uses envelope encryption where data is encrypted with a Data Encryption Key (DEK), and the DEK is then encrypted with a KMS key (master key). This approach allows efficient encryption of large amounts of data.
Key Policies and Access Control: • Key policies are resource-based policies attached to KMS keys • IAM policies can grant permissions to use keys • Grants provide temporary, granular permissions • Key policies must explicitly allow the root account or specific principals
Key Rotation: • AWS managed keys rotate automatically every year • Customer managed keys can have automatic rotation enabled (every year) • Manual rotation requires creating a new key and updating aliases • Imported key material requires manual rotation
Key States: • Enabled - Key can be used for cryptographic operations • Disabled - Key cannot be used but can be re-enabled • Pending Deletion - Waiting period (7-30 days) before permanent deletion • Pending Import - Waiting for key material to be imported
Important KMS Features for SysOps
• Multi-Region Keys - Replicate keys to multiple regions for disaster recovery and lower latency • Asymmetric Keys - Support for RSA and ECC key pairs for encryption and signing • Key Aliases - Friendly names that point to KMS keys, making key rotation easier • CloudTrail Integration - All KMS API calls are logged for auditing • Cross-Account Access - Keys can be shared across accounts using key policies
Common KMS Operations
• Encrypt - Encrypt data up to 4KB using a KMS key • Decrypt - Decrypt ciphertext that was encrypted with a KMS key • GenerateDataKey - Returns a plaintext and encrypted copy of a data key • ReEncrypt - Decrypt and re-encrypt data with a different key
Exam Tips: Answering Questions on AWS KMS Key Management
Key Concepts to Remember:
1. Deletion Wait Period - When deleting a CMK, there is a mandatory waiting period of 7-30 days. During this time, the key is in 'Pending Deletion' state and can be canceled.
2. Key Policy Requirements - Every KMS key must have exactly one key policy. The default key policy gives the root user full access and allows IAM policies to grant access.
3. Imported Key Material - When you import your own key material, automatic rotation is NOT supported. You must rotate manually. Imported keys can also be set to expire.
4. Cross-Region Considerations - KMS keys are regional. To use encrypted data in another region, use Multi-Region keys or re-encrypt with a key in the target region.
5. Service Integration - Know which services support KMS encryption: S3, EBS, RDS, EFS, Secrets Manager, Parameter Store, Lambda environment variables.
6. Troubleshooting Access Issues - If a user cannot use a KMS key, check: key policy, IAM policy, grants, and whether the key is enabled.
7. Cost Optimization - AWS managed keys do not incur monthly charges, only usage charges. Customer managed keys cost $1/month plus usage.
8. Compliance and Auditing - For compliance questions, remember that CloudTrail logs all KMS API calls, providing full audit trails.
9. Key Rotation Scenarios - Automatic rotation creates new backing key material but keeps the same key ID and ARN. Old data remains accessible.
10. CloudHSM vs KMS - CloudHSM provides dedicated hardware and full key control. Choose CloudHSM when you need FIPS 140-2 Level 3 compliance or must manage keys in dedicated hardware.
Common Exam Scenarios:
• When asked about encrypting data across regions, consider Multi-Region keys • For scenarios involving key compromise, think about disabling or scheduling deletion • Questions about sharing encrypted resources across accounts require key policy modifications • Performance issues with KMS often relate to API throttling - consider data key caching