Cryptographic communication and file security using terminals

US4386234A · kind A · utility

Assignee

• International Business Machines Corporation · US

Inventors

• William F. Ehrsam · Hurley, US
• Robert C. Elander · Saugerties, US
• Stephen M. Matyas · Manassas, US
• Carl H. W. Meyer · Portage, US
• Robert L. Powers · Topsfield, US
• Paul N. Prentice · Hyde Park, US
• John L. Smith · Woodstock, US
• Walter L. Tuchman · Woodstock, US

Key dates

• Filing date: Dec 5, 1977
• Grant date: May 31, 1983
• Expiry date: Dec 5, 1997

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y04S40/20
• WIPO field: Digital communication
• WIPO sector: Electrical engineering

Abstract

A data security device which includes storage means for storing a master cipher key, cryptographic apparatus for performing cryptographic operations and control means for controlling the writing of a master cipher key into the storage means, controlling the transfer of the master cipher key to the cryptographic apparatus and controlling the cryptographic apparatus to perform cryptographic operations. When a new master cipher key is written into the storage means, the old master cipher key is automatically overwritten with an arbitrary value, after which the new master key may be written into the storage means. The cryptographic apparatus of the data security device includes storage means, a cipher key register and cipher means for performing a cipher function on data stored in the cryptographic apparatus storage means under control of a working cipher key stored in the cipher key register with the resulting ciphered data being stored in the cryptographic apparatus storage means. A load cipher key direct function can be performed whereby a working cipher key may be loaded directly into the cipher key register for use as a working cipher key in performing a cipher function. A deciphe…