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: