AWS KMS vs. AWS CloudHSM: Choosing the Right Key Management Solution

Understanding AWS Key Management Services

Amazon Web Services (AWS) offers two primary cryptographic key management services: AWS Key Management Service (KMS) and AWS CloudHSM. Both services provide key storage backed by a hardware security module (HSM), but they cater to different operational requirements and use cases within the AWS ecosystem.

AWS KMS for General Use Cases

AWS KMS is presented as the default choice for most key management workloads. It is a fully managed service that integrates with all AWS services and is available across all AWS Regions. This makes it a convenient and scalable option for general encryption needs.

AWS CloudHSM for Specialized Requirements

AWS CloudHSM is designed for specialized use cases. It is recommended when organizations have strict requirements for dedicated HSM instances or need to support legacy applications that rely on traditional HSM interfaces. These interfaces include PKCS#11, Java Cryptographic Extension (JCE), OpenSSL Provider, and Key Storage Provider (KSP, which are necessary when applications communicate directly with an HSM rather than through a cloud API. CloudHSM also supports deprecated algorithms like 3DES and PKCS#1 v1.5 with RSA, and less common operations such as AES key wrapping and AES with CTR or CBC modes.

Shared Security Benefits

Both AWS KMS and AWS CloudHSM offer robust security features. They provide tamper-resistant, HSM-based key management with physical data center controls and secure administration and workloads using Transport Layer Security (TLS). Neither service allows AWS employees to access customer key material. Both services deliver equivalent security through Federal Information Processing Standard (FIPS) 140-3 Level 3 validated hardware and enforce strict cryptographic isolation of customer keys.