Remote keyless entry encryption algorithm

• US 5,881,153 A
• Filed: 12/16/1996
• Issued: 03/09/1999
• Est. Priority Date: 12/16/1996
• Status: Expired due to Fees

• Current Assignee: Lear Automotive Dearborn, Incorporated (Lear Corporation)
• Original Assignee: UT Automotive Dearborn, Inc.
• Inventors: Settles, Steven R., Feldman, Andrea M.
• Primary Examiner(s): Stamber, Eric W.
• Assistant Examiner(s): JACK, TODD M
• Application Number:
  US08/771,336
• Time in Patent Office: 813 Days
• Field of Search: 380/23, 380/9, 380/44, 380/46, 380/49, 340/825.31, 340/825.34
• US Class Current: 380/28
• CPC Class Codes: H04L 2209/046 of operations, operands or results of the operations
• CPC Class Codes: H04L 2209/26 Testing cryptographic entity, e.g. testing integrity of encryption key or encryption algorithm
• CPC Class Codes: H04L 2209/805 Lightweight hardware, e.g. radio-frequency identification [RFID] or sensor
• CPC Class Codes: H04L 2209/84 Vehicles
• CPC Class Codes: H04L 9/065 Encryption by serially and continuously modifying data stream elements, e.g. stream cipher systems, RC4, SEAL or A5/3

Abstract

The present invention teaches a method and system of encrypting a set of data having a test bit. The method comprises the step of generating a first and a second data string from the set of data. Once generated, the test bit is tested, and should it comprises a first value, the first data string is shifted in a first direction to transfer a carry over bit from a carry over register into the first data string while transferring a first bit of the first data string to said carry over register. This shifting step is followed by the step of shifting the second data string in a second direction to transfer a first bit of the second data string to the carry over register while transferring the carry over bit from the carry over register into the second data string. However, if the test bit comprises a second value, a first logic operation is executed on the first data string with a first number, and a second logic operation is executed on the second data string with a second number. Thereafter, the first data string is shifted in the second direction such that said carry over bit from said carry over register is transferred onto the first data string while the first bit of the first data string is transferred to the carry over register. Subsequently, the second data string is shifted in the first direction such that the carry over bit from the carry over register is transferred onto the second data string while the first bit of the second data string is transferred to the carry over register.

Claims

1. A method of encrypting a set of data having a test bit, the method comprising the steps of:

generating a first and a second data string from the set of data;

if the test bit comprises a first value,

shifting said first data string in a first direction to transfer a carry over bit from a carry over register into said first data string while transferring a first bit of said first data string to said carry over register; and

shifting said second data string in a second direction to transfer a first bit of said second data string to said carry over register while transferring said carry over bit from said carry over register into said second data string; and

if the test bit comprises a second value,

executing a first logic operation on said first data string with a first number;

executing a second logic operation on said second data string with a second number;

shifting said first data string modified by said first logic operation in said second direction such that said carry over bit from said carry over register is transferred onto said first data string while said first bit of said first data string is transferred to said carry over register; and

shifting said second data string modified by said second logic operation in said first direction such that said carry over bit from said carry over register is transferred onto said second data string while said first bit of said second data string is transferred to said carry over register.

2. The invention of claim 1, further comprising the steps of:

counting each time the test bit equals said first or second value; and

repeating said steps of shifting said first data string in a first direction and shifting said second data string in a second direction if the test bit comprises said first value, and executing said first logic operation on said first data string, executing said second logic operation on said second data string, shifting said first data string in said second direction, and shifting said second data string in said first direction if the test bit comprises said second value, until said number of times counted equal a preselected count number.

3. The invention of claim 1, wherein said step of generating a first and a second data string comprises the step of initializing at least one of said first and second data strings.

4. The invention of claim 1, wherein at least one of said first and second logic operations comprise at least one of an OR, AND, NOR, NAND, EX-OR logic functions.

5. The invention of claim 1, wherein at least one of said first and second logic operations are performed using a mask.

6. The invention of claim 1, wherein at least one of said first and second number comprise a number stored in memory.

7. A method of encrypting data transmitted by a transmitter and received by a receiver, the method comprising the steps of:

initializing a first and a second register creating a first and a second data string having a test bit;

if said test bit comprises a first value,

shifting said first data string in a first direction to transfer a carry over bit from a carry over register into said first data string while transferring a first bit of said first data string to said carry over register; and

shifting said second data string in a second direction to transfer a first bit of said second data string to said carry over register while transferring said carry over bit from said carry over register into said second data string;

if the test bit comprises a second value,

executing a first logic operation on said first data string with a first number stored in a first memory location;

executing a second logic operation on said second data string with a second number stored in a second memory location;

shifting said first data string modified by said first logic operation in said second direction such that said carry over bit from said carry over register is transferred onto said first data string while said first bit of said first data string is transferred to said carry over register; and

shifting said second data string modified by said second logic operation in said first direction such that said carry over bit from said carry over register is transferred onto said second data string while said first bit of said second data string is transferred to said carry over register;

decrementing a counter each time the test bit equals said first or second value; and

repeating said steps of shifting said first data string in a first direction and shifting said second data string in a second direction if the test bit comprises said first value, and executing said first logic operation on said first data string, executing said second logic operation on said second data string, shifting said first data string in said second direction, and shifting said second data string in said first direction if the test bit comprises said second value, until said counter equals a preset number.

8. The invention of claim 7, wherein said first direction is leftwards, and said second direction is rightwards.

9. The invention of claim 7, wherein said test bit is the right most bit of said second data string.

10. The invention of claim 7, wherein at least one of said first and second logic operations comprise at least one of an OR, AND, NOR, NAND, EX-OR logic functions.

11. The invention of claim 7, wherein at least one of said first and second logic operations are performed using a mask.

17. The invention of claim 10, wherein at least one of said first and second storage devices comprise a memory cell in electrically erasable programmable read only memory.

12. A system for encrypting data transmitted by a transmitter and received by a receiver, the system comprising:

a first and a second storage device for storing a first and a second data string having a test bit;

a carry over bit register for storing a carry over bit from said first and second storage devices;

memory for supplying a first and a second number;

a microcomputer for testing the value of said test bit, and

if said test bit comprises a second value,

for shifting said first data string in a first direction to transfer a carry over bit from a carry over register into said first data string while transferring a first bit of said first data string to said carry over register; and

for shifting said second data string in a second direction to transfer a first bit of said second data string to said carry over register while transferring said carry over bit from said carry over register into said second data string;

if said test bit comprises a second value,

for executing a first logic operation on said first data string with a first number stored in a first memory location;

for executing a second logic operation on said second data string with a second number stored in a second memory location;

for shifting said first data string modified by said first logic operation in said second direction such that said carry over bit from said carry over register is transferred onto said first data string while said first bit of said first data string is transferred to said carry over register; and

for shifting said second data string modified by said second logic operation in said first direction such that said carry over bit from said carry over register is transferred onto said second data string while said first bit of said second data string is transferred to said carry over register;

for decrementing a counter each time the test bit equals said first or second value; and

for repeating said shifting said first data string in a first direction and said shifting said second data string in a second direction if the test bit comprises said first value, and said executing said first logic operation on said first data string, said executing said second logic operation on said second data string, said shifting said first data string in said second direction, and said shifting said second data string in said first direction if the test bit comprises said second value, until said counter equals a preset number.

13. The invention of claim 12, wherein said first direction is leftwards, and said second direction is rightwards.

14. The invention of claim 12, wherein said test bit is the right most bit of said second data string.

15. The invention of claim 12, wherein at least one of said first and second logic operations comprise at least one of an OR, AND, NOR, NAND, EX-OR logic functions.

16. The invention of claim 12, wherein at least one of said first and second logic operations are performed using a mask.