DSA-based verifiable and recoverable encryption of signatures and its application in certified e-goods delivery

We present a new method for Verifiable and Recoverable Encryption of DSA signatures, and apply this cryptographic primitive in the design of a novel certified e-goods delivery (DSA-CEGD) protocol. The DSA-CEGD protocol has the following features: (1) ensures strong fairness, (2) ensures non-repudiation of origin and non-repudiation of receipt, (3) allows the receiver of an e-goods to verify, during the protocol execution, that the e-goods he is about to receive is the one he is signing the receipt for, (4) does not require the on-line involvement of a fully trusted third party (TTP), but rather an off-line and transparent semi-trusted third party (STTP), and (5) provides the confidentiality protection for the exchanged items from the STTP.