You can now import asymmetric and HMAC keys into AWS Key Management Service (AWS KMS) and use them within supported KMS-integrated AWS services and your own applications. Importing your own key gives you direct control over the generation, lifecycle management, and durability of your keys. You can control the availability of your imported keys by setting an expiration period, or deleting and re-importing them at any time. You have greater control over the durability of your imported keys because you can maintain the original version of the keys elsewhere. These additional controls could help you meet your specific compliance requirements if you must generate and store copies of keys outside of AWS.
Source:: Amazon AWS