1. Even, S., and Yacobi, Y., Relations Among Public Key Signature Systems, TR#175, Computer Science Dept., Technion, Haifa, Israel, March 1980.
2. Even, S., A Protocol for Signing Contracts, TR#231, Computer Science Dept., Technion, Haifa, Israel, January 1982.
3. Merkle, R.C., Secure Communication Over Insecure Channel, Comm. ACM, Vol. 21, April 1978, pp. 294–299.
4. Blum, M., and Rabin, M.O., How to Send Certified Electronic Mail. In preparation.
5. Blum, M., How to Exchange (secret) Keys, Memo No. UCB/ERL M81/90, March 1982. To appear in CACM.