Enciphering/deciphering system

• US 4,369,434 A
• Filed: 12/11/1980
• Issued: 01/18/1983
• Est. Priority Date: 12/20/1979
• Status: Expired due to Term

• Current Assignee: Gretag Data Systems AG
• Original Assignee: Gretag AG (Peach Property Group AG)
• Inventors: Mueller, Kurt H.
• Primary Examiner(s): Miller, C. D.
• Application Number:
  US06/215,493
• Time in Patent Office: 768 Days
• Field of Search: 364/717, 178/22.05, 178/22.06, 178/22.07, 178/22.08, 178/22.09, 178/22.19, 179/1.5 E, 179/1.5 S, 340/347 DD
• US Class Current: 380/264
• CPC Class Codes: H04L 9/0662 with particular pseudorandom sequence generator
• CPC Class Codes: H04L 9/12 Transmitting and receiving encryption devices synchronised or initially set up in a particular manner

Abstract

The enciphering section of an enciphering/deciphering system includes a random number generator, a primary code memory and a multiplex unit in addition to the actual enciphering unit. The deciphering section includes a deciphering unit, a primary code memory and a demultiplex unit. At the beginning of each transmission, and after disturbances, the enciphering and deciphering sections are first synchronized by means of a synchronization sequence. Then a random address is produced by the random number generator for a primary code, and a randomly determined auxiliary code is also selected. The address and the auxiliary code are then transmitted and the primary and auxiliary codes are loaded into the enciphering and deciphering units. The randomly controlled, statistical selection of the primary code simplifies the code management and thus the operation of the system.

Claims

1. An enciphering/deciphering system comprising:

an enciphering section for transforming unscrambled data into a coded message and having an enciphering generator whose mode of operation is determined by at least one primary secret code, and a first memory with a number of different primary codes stored therein;

a deciphering section for transforming the coded message back into unscrambled data and having a deciphering generator and a second memory with the same primary codes stored therein;

means for selecting a primary code from said first memory upon a new initialization of the system, loading it into said enciphering generator, transmitting a storage address of the selected primary code to the deciphering section and, on the basis of the transmitted memory address, reading the primary code out of said second memory and loading it into said deciphering generator; and

means for producing a randomly determined output signal in the enciphering section, which with each new initialization of the system forms a random selection address for the primary code which is contained in said first and second memories and which is to be newly loaded upon the new initialization, for controlling said code selecting and loading means.

2. The system of claim 1, wherein the operation of the enciphering and the deciphering generators is controlled according to the selected primary code and by a second, random code, said enciphering section including a random number generator for producing said second code, wherein said random number generator comprises said means for producing a randomly determined output signal.

3. The system of claims 1 or 2, wherein said enciphering and deciphering sections each include incrementing means which, after transmission of a given amount of data, automatically effect systematic selection and loading of a new code from said first and second memories respectively into said enciphering or deciphering generators without transmission of the storage address of the newly selected primary code.

4. The system according to claims 1 or 2, wherein said enciphering and deciphering sections include means responsive to at least one of transmission resumption, transmission disturbances, direction change, and transmission or processing of a given maximum amount of data, for effecting a new initialization of the system after detection of at least one of these events.

5. The system of claims 1 or 2, wherein said enciphering section includes transformation means for coding the memory address for the primary code selected by the means for producing a randomly determined output signal, and said deciphering section includes a corresponding transformation means for decoding the storage address.