HMAC (Hashed Message Authentication Code) is a scheme for digitally signing messages using any
digest scheme such as Md5 or SHA-256. It is described by
RFC (2104). It requires a shared secret key. It is
not a public-private key scheme like Oasis. It is one of the schemes
Amazon supports for digitally signing transactions to its API (Application Programming Interface)
to access the book database.
How to Compute a HMAC
Oracle’s Javadoc on javax.crypto.Mac class : available: