  This paper presents an efficient fair document exchange protocol. The
exchange of the documents will be between two parties. The protocol is based on
the verifiable and recoverable encryption of a document's key. This verifiable
and recoverable encryption of the document's key will allow one party to verify
the encrypted key. It will also ensure this party that the Semi Trusted Third
Party will be able to recover the key if the other party misbehaves. The
protocol also incorporates the concept of enforcing the honesty of one party.
The proposed protocol consists of only three messages and is more efficient
than related protocols.
