Method and apparatus for enhancing a randomly varying security characteristic

Abstract

A randomly varying modulated current is generated and used to drive a magnetic write head in an apparatus for enhancing a randomly varying magnetic security characteristic of a medium. The write head can be positioned adjacent a fluid magnetic slurry for the purpose of altering the location of the various magnetic particles therein in a random fashion. The slurry can then be hardened thermally or using ultraviolet dryers. A circuit which can generate the randomly variable current for the read head includes a modulator which receives a first randomly variable signal and a second, different randomly varying signal which modulates the first signal.

I claim: 
     
       1. An apparatus for creating an enhanced random magnetic characteristic in a fluid magnetic region carried on an underlying medium, the apparatus comprising: a signal modulator with a modulatable signal input, a modulation signal input and a modulated signal output;   a source of substantially random electrical signals coupled to said modulatable signal input;   a source of substantially random modulating signals coupled to said modulation input:   a magnetic write head coupled to said modulated signal output and located adjacent to the fluid magnetic region for altering the magnetic characteristics thereof.   
     
     
       2. An apparatus as in claim 1 with said source of random signals including circuitry for generating an electrical signal having white noise-like frequency characteristics at least for a predetermined frequency range. 
     
     
       3. An apparatus as in claim .Iadd.1 .Iaddend.with said modulator including circuitry for altering a frequency parameter of said substantially random, electrical signals. 
     
     
       4. An apparatus as in claim 1 with said source of modulating signals including a voltage controlled oscillator. 
     
     
       5. A method of generating an enhanced random, magnetic characteristic in a magnetic slurry supported on an underlying medium comprising: providing a magnetic slurry;   generating a first electrical signal having a random-like characteristic;   generating a second electrical signal having a different random-like characteristic;   modulating the first signal with the second signal and, in response thereto, producing a third signal; and   altering the magnetic characteristics of the slurry with the third signal.   
     
     
       6. A method as in claim 5 including hardening the slurry after its magnetic characteristics have been altered. 
     
     
       7. A method as in claim 5 including drying the slurry after its magnetic characteristics have been altered. 
     
     
       8. A method as in claim 5 with said second electrical signal generated with a randomly varying frequency. 
     
     
       9. A method as in claim 5 with said first electrical signal generated with a randomly varying amplitude. 
     
     
       10. A method as in claim 5 including in the altering step generating an electro-magnetic field responsive to the third signal, moving the slurry and applying the electro-magnetic field to the moving slurry. 
     
     
       11. A method as in claim 5 including applying radiant energy to the magnetic slurry to harden same. 
     
     
       12. A method of generating an enhanced random, security characteristic in a slurry magnetic medium comprising: providing an enhanceable slurry magnetic medium;   generating a first electrical signal having a random-like characteristic;   generating a modulating signal;   synchronizing the electrical signal with the modulating signal;   modulating the synchronized electric signal; and   altering the random characteristics of the slurry magnetic medium with the synchronized and modulated electrical signal and then hardening the medium.   
     
     
       13. An apparatus for creating an enhanced random characteristic in a slurry magnetic medium prior to hardening that medium, the apparatus comprising: a signal modulator with a signal input port, a modulation input port, and a modulated signal output port;   a source of substantially random electrical signals coupled to said modulator signal input port;   circuitry, coupled to said modulation input port and to said source, for synchronizing an electrical signal from said source with an input to said modulation input port; and   an output device coupled to said modulated signal output port and located adjacent to the slurry magnetic medium for altering the random characteristics thereof in response to said modulated signal output while the medium is still a slurry. .Iadd.   
     
     
       14.  A method for generating a permanent fixed magnetic security characteristic embedded in a magnetic medium disposed on a support medium comprising the steps of: providing a magnetic slurry having a generally uniform enhanceable magnetic characteristic on a moving support medium;   generating a series of electrical signals, each having a randomly-created characteristic;   sequentially altering the enhanceable magnetic characteristic of the magnetic slurry in response to said electrical signals to produce substantially altered regions of magnetic characteristics different from said enhanceable generally uniform magnetic characteristic; and   hardening the altered magnetic slurry to permanently fix said altered regions and the remaining regions of generally uniform magnetic characteristic. .Iaddend..Iadd.15. The method of claim 14, in which said step of providing comprises providing a support medium and depositing said magnetic slurry continuously on said moving support medium. .Iaddend..Iadd.16. Apparatus for generating a permanent fixed magnetic security characteristic embedded in a magnetic medium disposed on a support medium comprising;   means for depositing an enhanceable slurry having a generally uniform magnetic characteristic on a moving support medium in a fluid condition;   an electrical signal generator for providing a series of electrical signals, each having a randomly-created characteristic;   a magnetic write-head for creating electromagnetic signals for sequentially altering the enhanceable generally uniform magnetic characteristic of the magnetic slurry in response to said electrical signals to produce substantially altered regions of magnetic characteristics different from said generally uniform magnetic characteristic; and   means for hardening the altered magnetic slurry to permanently fix said altered regions and the remaining regions of generally uniform magnetic   
     
     
        characteristic. .Iaddend..Iadd.17.  Apparatus in accordance with claim 16, in which said depositing means comprise an extrusion means. .Iaddend..Iadd.18. Apparatus in accordance with claim 16 in which said hardening means comprises a dryer. .Iaddend..Iadd.19. Apparatus in accordance with claim 16 in which said signal generator comprises means for generating first and second electrical signals, means for modulating a first electrical signal with a second electrical signal thereby to produce said series of modulated electrical signals. .Iaddend.