Password protected device using incorrect passwords as seed values for pseudo-random number generator for outputting random data to thwart unauthorized accesses

• US 5,206,905 A
• Filed: 11/19/1990
• Issued: 04/27/1993
• Est. Priority Date: 05/15/1989
• Status: Expired due to Term

• Current Assignee: Maxim Integrated Products, Inc. (Analog Devices, Inc.)
• Original Assignee: Dallas Semiconductor Corporation (Analog Devices, Inc.)
• Inventors: Lee, Robert D., Curry, Stephen M., Curry, Scott J.
• Primary Examiner(s): Anderson, Lawrence E.
• Assistant Examiner(s): Ellis, Richard Lee
• Application Number:
  US07/615,606
• Time in Patent Office: 890 Days
• Field of Search: 395/425, 395/725, 380/3, 380/4, 380/23, 380/46, 331/78, 235/380, 235/381, 235/382, 235/382.5, 340/825.31, 340/825.34
• US Class Current: 705/55
• CPC Class Codes: G06F 21/73 by creating or determining hardware identification, e.g. serial numbers
• CPC Class Codes: G06F 21/79 in semiconductor storage media, e.g. directly-addressable memories
• CPC Class Codes: G06F 3/0383 Signal control means within the pointing device
• CPC Class Codes: G06F 3/04897 Special input arrangements or commands for improving display capability
• CPC Class Codes: G06K 19/047 the record carrier being shaped as a coin or a gambling token
• CPC Class Codes: G06K 19/0706 the battery being replaceable
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G06K 19/07735 the record carrier comprising means for protecting against electrostatic discharge
• CPC Class Codes: G06K 19/07743 External electrical contacts
• CPC Class Codes: G06K 7/0021 for reading/sensing record carriers having surface contacts
• CPC Class Codes: G06K 7/0086 the connector comprising a circuit for steering the operations of the card connector
• CPC Class Codes: G11C 5/00 Details of stores covered by group G11C11/00
• CPC Class Codes: G11C 5/066 Means for reducing external access-lines for a semiconductor memory clip, e.g. by multiplexing at least address and data signals
• CPC Class Codes: G11C 7/24 Memory cell safety or protection circuits, e.g. arrangements for preventing inadvertent reading or writing; Status cells; Test cells
• CPC Class Codes: G11C 8/20 Address safety or protection circuits, i.e. arrangements for preventing unauthorized or accidental access
• CPC Class Codes: H01L 23/58 Structural electrical arrangements for semiconductor devices not otherwise provided for , e.g. in combination with batteries H01L23/49593, H01L23/49596 take precedence
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 2924/3011 Impedance
• CPC Class Codes: H04B 1/403 using the same oscillator for generating both the transmitter frequency and the receiver local oscillator frequency
• CPC Class Codes: H05K 1/0393 : Flexible materials H05K1/038 takes precedence; specific organic compositions are classified in H05K1/0313 and subgroups
• CPC Class Codes: H05K 3/325 : by abutting or pinching, i.e. without alloying process; mechanical auxiliary parts therefor adaptations of leads inserted in holes for press-fit connections H05K3/308

Abstract

An electronic key which includes a pseudo-random number generator. If the correct password is received, the contents of a secure memory will be outputted by the electronic key. However, if an incorrect password is received, that password will be used as a seed value for the pseudo-random number generator, and the resulting value will be outputted.

Thus, if a copier exercises the key through all possible passwords, the incorrect passwords, as well as the correct password, will result in the same output data every time it is tried.

Claims

1. An electronic key device, comprising:

a memory;

a pseudo-random number generator, connected to receive a seed value and to output a number which is strictly dependent on said seed value, but which is a nonlinear and non-monotone function of said seed value;

external connections for receiving a password, and external connections for outputting data;

a digital comparator, connected to compare a received password with a stored value, and (1) to enable output of data from said memory when said password does match said stored value and (2) to enable output of data from said pseudo-random number generator when said password does not match said stored value;

said pseudo-random number generator being connected to receive said password and to use said password as said seed value such that a unique set of data is output from said pseudo-random number generator for each non-identical password.

2. The device of claim 1, wherein said password is at least 64 bits in length.

3. The device of claim 1, wherein said pseudo-random number generator is an infinite impulse response (IIR) filter having both feed-forward and feedback connections.

4. The devices of claim 1, wherein said pseudo-random number generator comprises:

a chain of plural multiple-input logic gates, each having a clock input, and at least one data input, and at least one data output;

a feedforward bus and a feedback bus;

wherein substantially each said gate is connected in either a first configuration or a second configuration, and (1) ones of said gates which are connected in said first configuration have said data input thereof connected directly to said output of the preceding one of said gates in said chain, (2) ones of said gates which are connected in said second configuration have said data input thereof connected directly to the output of a respective XOR gate which has one input thereof connected directly to said output of the preceding one of said gates in said chain, said XOR gate also having another input thereof which is connected either to said feedforward bus or to said feedback bus.