3111	 Secure Communications Over Insecure Channels	 According to traditional conceptions of cryptographic security it is necessary to transmit a key by secret means before encrypted messages can be sent securely. This paper shows that it is possible to select a key over open communications channels in such a fashion that communications security can be maintained. A method is described which forces any enemy to expend an amount of work which increases as the square of the work required of the two communicants to select the key. The method provides a logically new kind of protection against the passive eaves dropper. It suggests that further research on this topic will be highly rewarding both in a theoretical and a practical sense. Security cryptography cryptology communications security wiretap computer network security passive eavesdropping key distribution public key cryptosystem
