1. Overview
When it comes to securing our sensitive data in the cloud, AWS offers two powerful solutions: AWS CloudHSM and AWS KMS. Although both services provide encryption capabilities, they differ in their approach and use cases.
In this article, we’ll explore the key features and differences between these two services to help us make an informed decision about which one best suits our needs.
2. Tenancy
With AWS CloudHSM, we get dedicated hardware security modules (HSMs) that are single-tenant. This means that each HSM instance is exclusively ours, and we don’t share it with any other AWS customers. This single-tenant model provides an extra layer of security and control, as we have complete ownership over the hardware.
Alternatively, AWS KMS is a multi-tenant service. Although the underlying HSMs are shared among multiple AWS customers, our keys are still logically isolated and secured.
3. Key Management
One of the main differences between the two services is the level of control we have over the keys.
With CloudHSM, we have full control over the key lifecycle, including generation, storage, and deletion. We can even export the keys if needed.
In contrast, AWS KMS simplifies key management by offering a fully managed service. It takes care of key creation while providing features of automatic key rotation and policy-based access control. However, with KMS, we can’t export the keys, as we have less control over the key lifecycle.
4. Availability
AWS KMS is a regional service where we create keys within a specific AWS region. However, it supports multi-region key replication for enhanced disaster recovery and high availability.
In contrast, AWS CloudHSM is provisioned within a VPC and can only interact with resources in the same VPC or those connected to it via VPC peering. CloudHSM can also be configured as a cluster, providing managed load balancing and key duplication across availability zones. To achieve high availability, fault tolerance, and durability, we should configure at least 2 HSMs in a cluster.
5. Integration with AWS Services
KMS offers seamless integration with a wide range of other AWS services, such as Amazon S3, Amazon EBS, DynamoDB, etc. This integration allows us to easily encrypt and decrypt data within these services using AWS-managed keys or our own customer master keys (CMKs) stored in KMS.
On the other hand, AWS CloudHSM provides integration support for Amazon Redshift and Oracle RDS. However, integrating CloudHSM with other AWS services requires more manual configuration and setup using the AWS SDKs or APIs. While this gives us more control over the integration process, it also means we’ll have to invest more time and effort into setting up and maintaining these integrations.
6. FIPS 140-2 Compliance
Previously, one of the key differences between AWS CloudHSM and AWS KMS was their compliance levels with the Federal Information Processing Standards (FIPS) 140-2, which is a set of security requirements for cryptographic modules. AWS CloudHSM has always been validated at FIPS 140-2 Level 3, while AWS KMS was validated at Level 2.
However, as of May 2023, AWS KMS has also achieved FIPS 140-2 Level 3 validation for its hardware security modules (HSMs).
Despite this update, it’s important to note that AWS CloudHSM is also compliant with additional industry-specific standards, which may be a deciding factor if we have strict compliance needs.
7. Cost
Cost is a significant factor when choosing between AWS CloudHSM and AWS KMS. CloudHSM is more expensive due to its dedicated hardware and high level of control. We pay an hourly fee that differs with regions for each HSM instance we provision.
In contrast, AWS KMS is more cost-effective for most use cases. As a fully managed service, we only pay for the keys we create and the number of API calls we make. KMS also offers a generous free tier, making it attractive for smaller projects and organizations.
8. Comparison Summary
To help us quickly compare the main differences between AWS CloudHSM and AWS KMS that we’ve discussed, here’s a summary table:
Feature
AWS CloudHSM
AWS KMS
Tenancy
Single-tenant (dedicated hardware)
Multi-tenant (shared hardware)
Key Management
Full control over key lifecycle, keys can be exported
Managed service, keys cannot be exported
Availability
Within a VPC, can be configured as a cluster
Regional service, supports multi-region key replication
Integration with AWS Services
Requires manual configuration using SDKs or APIs
Seamless integration with a wide range of AWS services
FIPS 140-2 Compliance
Level 3, compliant with additional industry-specific standards
Level 3 (as of May 2023)
Cost
More expensive, hourly fee for each HSM instance
Cost-effective, pay for keys and API calls
9. Conclusion
In this article, we compared the AWS CloudHSM and AWS KMS services and explored the key features and differences between them.
Both AWS CloudHSM and AWS KMS are powerful solutions for encrypting our data in the cloud. CloudHSM offers a high level of control, dedicated hardware, and better performance, making it suitable for organizations with strict compliance requirements.
On the other hand, KMS provides a fully managed, scalable, and integrated solution that’s easier to use and more cost-effective for most use cases.
Ultimately, the choice between the two depends on our specific security requirements, performance needs, and budget. By understanding the key differences between these services, we can make an informed decision and ensure that our data remains secure in the cloud.