A cryptographic protocol for secure communications

Abstract

Abstract A cryptographic communication system. The system, which employs a novel combination of public and private key cryptography, allows two parties, who share only a relatively insecure password, to bootstrap a computationally secure cryptographic system over an insecure network. The system is secure against active and passive attacks, and has the property that the password is protected against off-line "dictionary" attacks. If Alice and Bob are two parties who share the password P one embodiment of the system involves the following steps: (1) Alice generates a random public key E, encrypts it with P and sends P(E) to Bob ; (2) Bob decrypts to get E, encrypts a random secret key R with E and sends E(R) to Alice; (3) Alice decrypts to get R, generates a random challenge C A and sends R(C A ) to Bob ; (4) Bob decrypts to get C A , generates a random challenge C B and sends R(C A , C B ) to Alice; (5) Alice decrypts to get (C A ,C B ), compares the first against the challenge and sends R(C B ) to Bob if they are equal ; (6) Bob decrypts and compares with the earlier challenge ; and (7) Alice and Bob can use R as a shared secret key to protect the session.

Inventors

• 👤 Steven Michael Bellovin
• 👤 Michael Merritt

Bibliographic Details