+ "A cryptographic key is called **ephemeral**
+ if it is generated for each execution of a key establishment process.
+ In some cases ephemeral keys are used more than once, within a single session
+ (e.g., in broadcast applications)
+ where the sender generates only one ephemeral key pair per message
+ and the private key is combined separately with each recipient's public key.
+ Contrast with a **static** key." - wikipedia
+ ( http://en.wikipedia.org/wiki/Ephemeral_key )