KMS uses the authentication credential to sign requests that it sends to the external key store proxy (XKS proxy) on your behalf.
You establish these credentials on your external key store proxy and report them to KMS.
Detailed information about the external key store proxy (XKS proxy).
Your external key store proxy translates KMS requests into a format that your external key manager can understand.
These fields appear in a "DescribeCustomKeyStores" response only when the CustomKeyStoreType is EXTERNAL_KEY_STORE.