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Software protection system using a single-key cryptosystem, a hardware-based authorization system and a secure coprocessor

  • US 4,817,140 A
  • Filed: 11/05/1986
  • Issued: 03/28/1989
  • Est. Priority Date: 11/05/1986
  • Status: Expired due to Fees
First Claim
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1. A method of restricting use of software to an authorized computer comprising the steps of:

  • providing said software in a form in which at least a portion thereof is encrypted,providing an encrypted decryption key for decrypting said encrypted software portion,providing a physically secure coprocessor coupled to said computer, which coprocessor is capable of decrypting said software if it retains said decryption key,coupling a transfer token source to said physically secure coprocessor, which transfer token source stores a token whose presence is required to effect a step of retaining said encrypted decryption key,transferring said encrypted decryption key to said physically secure coprocessor along with said token from said transfer token source,wherein said transferring step includes the step of altering said transfer token source as said token is transferred to said physically secure coprocessor so that said transfer token source is incapable of again transferring said token.

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