Patent EP0281224B1 successfully refreshed from Google Patents.
EP0281224B1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Secure messaging systems
Assignee: HP Inc
•
Filing: 1988-01-18
•
Granted: 1994-03-23
•
Expires: 2008-01-18
Abstract
No abstract record available.
Inventors
- 👤 Alan David Marshall
- 👤 Graeme John Proudler
- 👤 Christopher John Mitchell
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-31 19:24
CPC Classifications
H; H04; H04L; H04L9/00; H04L9/08; H04L9/0891; H04L9/0816; H04L9/0819; H04L9/0822; H04L9/083; H04L9/0833; H04L9/0836
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
156 words
A secure communication system comprising at least three terminals (10, 10A, 10B) and a key distribution centre KDC (12) in which the KDC on request by a first terminal (10A) provides the first terminal and a second terminal (10B) specified by the first terminal with key means (LMK) for use by these terminals (10A, 10B) in communicating with each other, the KDC providing the key means (LMK) to the first and second terminals (10A, 10B) under encryption by key transporting keys (CKD) each of which is shared by a single terminal (10A, 10B) and the KDC(12), characterised in that the key means are used by the two terminals (10A, 10B) to provide key transporting keys (LMK) each of which is used to transport a succession of data transporting keys (LDK) between the terminals (10A, 10B), each such data transporting key (LDK) being used in turn by the two terminals (10A, 10B) for passing data between them.
Claim 2
Dependent Claim
47 words
A secure communication system according to claim 1 characterised in that the key means (LMK) consist of two keys, one for encrypting messages from the first terminal (10A) to the second (10B) and the other for encrypting messages from the second terminal (10B) to the first (10A).
Claim 3
Dependent Claim
74 words
A secure communication system according to either previous claim characterised by, in each terminal (10A,10B), usage counting means (33) for counting the usage of each data transporting key (LDK), means (30) for changing such a key on its usage reaching a predetermined value, and means (30,37) for causing the changed key to be transported to the terminal at the other end of its associated link under encryption by the appropriate key transporting key (LMK).
Claim 4
Dependent Claim
37 words
A secure communication system according to any previous claim, characterised in that there is a hierarchy of key transporting keys (CDK;LMK) with the keys higher in the hierarchy being used for transporting keys lower in the hierarchy.
Claim 5
Dependent Claim
78 words
A secure communication system according to claim 4, characterised by, in each terminal (10), usage counting means (40) for counting the usage of each key transporting key below the highest in the hierarchy, means (30) for updating such a key on its usage reaching a predetermined value, and means (30, 37) for causing the updated key to be transported to the terminal at the other end of its associated link by the key above it in the hierarchy.
Claim 6
Dependent Claim
96 words
A secure communication system according to any previous claim, characterised by means enabling a link to be terminated by a terminal, comprising erasure means (30) in each terminal for erasing the keys therein associated with the link, a link termination signal in a terminal causing the erasure means in that terminal to be operated and sending a link termination message to the KDC, the KDC including means (19) for logging the message and sending a link termination message to the other terminal of the link which causes the erasure means in that terminal to be operated.
Claim 7
Dependent Claim
113 words
A secure communication system according to any previous claim, characterised in that the KDC, in response to a request by a user from his terminal (UA1) for a journey key (JK) and specifying which other terminal (UA2) he wants to use, issues him with a journey key (JK), and also sets up UA2 to respond to the journey key by sending the journey key (under encryption) to UA2, where it is stored in a journey key register (107) together with the address code of UA1 , and UA1 is set up to store all received messages and to respond to calls from UA2 but sending them to UA2 encrypted under the journey key.
Claim 8
Dependent Claim
119 words
A secure communication system according to any previous claim, characterised in that the KDC maintains a record or log of all messages received and sent by it, in the order in which they are acted upon; the state of KDC is periodically stored as a back-up (19); and, if there is a failure at the KDC, it is first backed up to the previously stored state, the log of all messages which have occurred since then is played back to the KDC, and any messages which involved the generation and sending out of keys are repeated, so sending out fresh keys to the UAs to replace those which were previously sent out but have become lost by the KDC.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
Maintenance schedule is calculated for granted US utility patents.