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Method and apparatus for verification of classes of documents

  • US 5,426,700 A
  • Filed: 08/23/1993
  • Issued: 06/20/1995
  • Est. Priority Date: 08/23/1993
  • Status: Expired due to Term
First Claim
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1. A method for verifying a document belonging to a particular class of documents, said particular class being one of a plurality of classes of documents, each of said classes corresponding to a class encryption/decryption key pair CE,CD, said document incorporating encrypted information E comprising information M derived from said document and encrypted with an encryption E selected from an encryption/decryption key pair E, D and said document further incorporating an encrypted decryption key DE comprising decryption key D selected from said key pair E, D encrypted with encryption key CE;

  • selected from encryption decryption key pair CE,CD associated with said particular class, said method comprising the steps of;

    a) providing enabling information for enabling retrieval of a decryption key from any document in a selected group of said classes;

    b) determining if said document is in said selected group, and if so retrieving said decryption key D from said document;

    c) decrypting said encrypted information E to obtain decrypted information D and deriving said information M from said document; and

    d) comparing said decrypted encrypted information Di D with said information M to verify the information contained in said document as authentic and unchanged.

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