Method for the secure distribution of electronic files in a distributed environment
Patent 5638446 Issued on June 10, 1997. Estimated Expiration Date: 
August 28, 2015. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
August 28, 2015. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent ReferencesPublic key/signature cryptosystem with enhanced digital signature certification Method for secure time-stamping of digital documents Method of extending the validity of a cryptographic certificate Method for certifying public keys in a digital signature scheme Patent #: 5420927 InventorAssigneeApplicationNo. 520351 filed on 08/28/1995US Classes:705/51, Usage protection of distributed data files380/30, Public key713/176, Authentication by digital signature representation or digital watermark713/187COMPUTER PROGRAM MODIFICATION DETECTION BY CRYPTOGRAPHYExaminersPrimary: Tarcza, Thomas H.Assistant: White, Carmen D. Attorney, Agent or FirmInternational ClassesH04L 009/32H04L 009/30 AbstractA process for using a trusted third party to create an electronic certificate for an electronic file that can be used to establish the file and verify the identity of the creator of the file. The process is composed of two phases, a registration phase and an electronic file distribution phase. In the registration phase, a trusted third party receives information about an author, including the author's public key and affirmatively verifies the accuracy of this information. In the file distribution phase, an author sends to the trusted third party a signed message containing the hash of the file the author wants to distribute. The trusted third party creates an electronic certificate, signed by the trusted third party, containing the hash of the file sent by the author. A user desiring to receive the file, retrieves the file with the certificate an uses the certificate to verifies, first, that the certificate was created by the trusted third party, and, second, that the hash of the file in the certificate is the same as the hash that is computed from the retrieved file. If these two hash's match, then the user is assured that the file did originate with the author and is uncorrupted.Other References
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