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Method of protecting computer software from unauthorized execution using multiple keys

  • US 5,222,133 A
  • Filed: 10/17/1991
  • Issued: 06/22/1993
  • Est. Priority Date: 10/17/1991
  • Status: Expired due to Term
First Claim
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1. A method of protecting computer software from unauthorized execution using multiple keys, one of which is stored in a hardware device to produce a control key which will allow the protected software to execute comprising the steps of:

  • storing a plurality of unique first keys in a plurality of hardware devices, each hardware device having its own unique first key,establishing a plurality of unique second keys, each having a predetermined relationship with one of each of said first keys forming a plurality of unique key pairs,storing an algorithm for processing said unique key pairs in software which is desired to be protected,supplying identical copies of said software to be protected together with said hardware devices, each having one of said first keys, one device with each of said copies,supplying said second key that forms said key pair with one of said first keys in said hardware device,inserting one of said hardware devices in an input/output port of said computer,loading said software to be protected containing said algorithm in said computer,loading a second key external to said software to be protected in said computer, andprocessing said first and second keys in said algorithm for deriving a control key, if present, for permitting the continued processing of the software being protected.

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