04304990 is referenced by 138 patents and cites 5 patents.

A card-coding system and method preserves the security of the encoding process against duplication and counterfeiting of cards by securing the interactions under the control of the individual and then of the issuing institution. Multilevels of offset codes are generated in successive interactions so that attempted alteration, duplication, or counterfeiting of a coded card will be readily detectable using "off-line" card-checking apparatus. An "active" card is initially issued or authorized with an established credit balance, and its authenticity, balance, and proper use are continuously checked, debited and updated in each authorized transaction completed by the proper individual.

Title
Multilevel security apparatus and method
Application Number
102858
Publication Number
4304990
Application Date
February 4, 1980
Publication Date
December 8, 1981
Inventor
Martin M Atalla
Atherton
CA, US
Agent
A C Smith
Assignee
Atalla Technovations
CA, US
IPC
G06K 7/01
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