Cryptographic process and enciphered product

US4682954A · kind A · utility

Inventor

• Richard Cook · Chicago, US

Key dates

• Filing date: Oct 24, 1960
• Grant date: Jul 28, 1987
• Expiry date: Oct 24, 1980

Classification

• Technology area (CPC G): Physics
• CPC primary: G09C5/00
• WIPO field: Control
• WIPO sector: Instruments

Abstract

1. A cryptographic process for enciphering a text sheet having pictorial intelligence thereon in the form of opaque and transparent areas comprising the steps of placing a key sheet having random alternate opaque and transparent areas in registered relation to said text, exposing a sheet of film to light passed through the key and text sheets to produce a negative having opaque areas where both the key and text sheets are transparent and transparent areas where either the key to text is opaque, placing said negative in registered relation to said text and to a second film, exposing said second film to light passed through the negative and the key to expose the second film in areas where both the key and negative are transparent, placing the text in registering relation to the negative and to said second film, exposing said second film to light passed through the negative and text to expose the second film in areas where both the text and negative are transparent, and developing the second film to produce an image which is of one character in areas where said second film has been exposed and another character in areas where said second film has not been exposed.