Creates a customer master key (CMK).
You can use a CMK to encrypt small amounts of data (4 KiB or less) directly, but CMKs are more commonly used to encrypt data encryption keys (DEKs), which are used to encrypt raw data. For more information about DEKs and the difference between CMKs and DEKs, see the following:
The GenerateDataKey operation AWS Key Management Service Concepts (http://docs.aws.amazon.com/kms/latest/developerguide/concepts.html)
in the AWS Key Management Service Developer Guide