Ephemeral Key may be 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.
Private ephemeral key agreement key: Private ephemeral key agreement keys are the private keys of asymmetric key pairs that are used only once to establish one or more keys (e.g., key wrapping keys, data encryption keys, or MAC keys) and, optionally, other keying material (e.g., Initialization Vectors).