EP0464562A2 Expired / Lapsed EP ⏱️ 0.0 years remaining

Method and apparatus for decryption of an information packet having a format subject to modification

Assignee: Digital Equipment Corp

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Filing: 1991-06-24

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Granted: —

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Expires: 2011-06-24

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Abstract

Abstract A technique to facilitate decryption processing of information packets transmitted over a communication network after encryption in accordance with a specific network protocol, the details of which may be subject to later change as standards are developed or modified. Programmable registers are used in the decryption process to hold information for identifying an incoming information packet as being subject to the specific protocol and requiring decryption, and identifying a starting location of a data field to be decrypted. Specifically one programmable register contains a first offset locating an identifier field in the packet, in which a cryptographic identifier will be found if the packet is one conforming to the protocol; another programmable register contains a cryptographic identifier value that will be found in the identifier field if decryption is to be performed, and a third programmable register contains a second offset to locate the beginning of a data field to be decrypted.

Inventors

👤 William R. Hawe
👤 Butler W. Lampson
👤 Amar Gupta

Bibliographic Details

Application Number —

Jurisdiction EP

Data Source google_patents

Last Synchronized 2026-11-04 14:23

CPC Classifications

H; H04; H04L; H04L63/00; H04L63/04; H04L63/0428; H04L63/0485; H04L63/12; H04L9/00; H04L9/40; H04L63/16; H04L63/162

Claims Analysis

Total Claims: 5

Claim 1

Independent Claim 116 words

Apparatus for in-line decryption of a received information packet having a format that is subject to modification, the apparatus characterized by: programmable register means containing information that enables identification of a received information packet as being of a particular protocol type required decryption, and other information that indicates the location of an encrypted data field in the packet; means for analyzing each incoming packet based on the information stored in the programmable register means, to identify packets of the particular protocol type requiring decryption; and means for decrypting data fields of incoming packets identified as being of the particular protocol type, beginning decryption at a location specified by the information stored in the programmable register means.

Claim 2

Dependent Claim 79 words

Apparatus as defined in claim 1, wherein: the programmable register means includes means for storing (i) an offset from a reference field indicative of the location in the packet of an identifier field that should contain a cryptographic identifier, (ii) an identifier value that should be found in the identifier field to indicate that the packet is of a particular protocol requiring decryption, and (iii) a second offset value indicative of the start of encrypted data in the packet.

Claim 3

Dependent Claim 84 words

Apparatus as defined in claim 1, wherein the programmable register means includes: a first register for storing an offset indicative of the location in the packet of an identifier field that should contain a cryptographic identifier; a second register for storing an identifier value that should be found in the identifier field to indicate that the packet is of a particular protocol requiring decryption; and a third register for storing a second offset value indicative of the start of encrypted data in the packet.

Claim 4

Independent Claim 115 words

A method for performing in-line decryption of a received information packet having a format that is subject to modification, the method comprising the steps of: storing in programmable register means information that enables identification of a received information packet as a particular protocol type requiring decryption, and other information that indicates the location of an encrypted data field in the packet; analyzing each incoming packet based on the information stored in the programmable register means, to identify packets of the particular protocol type requiring decryption; and decrypting data fields of incoming packets identified as being of the particular protocol type, beginning decryption at a location specified by the information stored in the programmable register means.

Claim 5

Dependent Claim 109 words

A method as defined in claim 4, wherein the analyzing step includes: locating a cryptographic identifier field in the received packet, by means of an identifier offset value stored in the programmable register means; comparing a value contained in the cryptographic identifier field of the packet with a cryptographic identifier value stored in the programmable register means, to determined whether the packet is of a particular protocol type requiring decryption; and if the comparing step results in a match, skipping a portion of the packet indicated by a second offset value stored in the programmable register means, to begin decryption of a data field from the correct starting location.

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