title: AWS KMS: What's the difference between CMK and key material?
body: <p>In the following documentation, AWS refers to a concept called <code>key material</code>.</p>
  <blockquote>
  <p>AWS KMS <a href="https://docs.aws.amazon.com/kms/latest/developerguide/custom-key-store-overview.html" rel="nofollow noreferrer">Documentation</a>: Using a custom key store</p>
  <p>AWS KMS supports custom key stores backed by AWS CloudHSM clusters. When you create an AWS KMS customer master key (CMK) in a custom key store, AWS KMS generates and stores non-extractable key material for the CMK in an AWS CloudHSM cluster that you own and manage.</p>
  </blockquote>
  <p>Take an asymmetric encryption key pair in KMS as an example, what is key material? what is CMK? what's the difference between CMK and key material?</p>