Patent EP0334503A2 successfully refreshed from Google Patents.
EP0334503A2
Expired / Lapsed
EP
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Data-processing apparatus and method
Assignee: Racal Guardata Financial Systems Ltd
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Filing: 1989-03-06
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Granted: —
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Expires: 2009-03-06
Abstract
Abstract An encryption apparatus has a keyboard 1 for the input of message data and a processor 2 for encrypting that data under a working key. The working key is not, however, permanently stored in the apparatus. Rather, the working key is derived by encrypting "precursive key data" stored in a memory 5 of the apparatus under a key represented by, or derived from, a password input via the keyboard, and is erased after each use. In this way, the secrecy of the working key is not dependent on maintaining the ultimate physical security of the apparatus against possible attempts to gain access to its memory, but rather on the secrecy of the password which is input to the apparatus only as and when it is necessary to derive the key for performing the encryption process.
Inventors
- 👤 Paul William Halliden
- 👤 Simon Anthony Blair Avarne
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-07 13:30
CPC Classifications
H; H04; H04L; H04L9/00; H04L9/08; H04L9/0861; H04L9/0863; H04L9/32; H04L9/3226
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
87 words
A cryptographic apparatus comprising: means (1) for the input of data to be encrypted; and processing means for encrypting that data in accordance with a cryptographic algorithm and an associated key; characterised by: memory means (5) storing precursive key data; means (1) for the input of a password; and processing means (4) for deriving the said key from said precursive key data and password (or derivatives thereof); whereby, in use, said key is not permanently stored but derived only when it is required for encrypting input data.
Claim 2
Dependent Claim
87 words
A cryptographic apparatus comprising: means (1) for the input of data to be encrypted; and processing means for encrypting that data in accordance with a cryptographic algorithm and an associated key; characterised by: memory means (5) storing precursive key data; means (1) for the input of a password; and processing means (4) for deriving the said key from said precursive key data and password (or derivatives thereof); whereby, in use, said key is not permanently stored but derived only when it is required for encrypting input data.
Claim 3
Dependent Claim
41 words
An apparatus according to claim 1 wherein the second-mentioned processing means (4) is adapted to derive the said key by encryption of the precursive key data or a derivative thereof under a key represented by said password or a derivative thereof.
Claim 4
Dependent Claim
45 words
An apparatus according to claim 1 or claim 2 including memory means (5) storing identity data for that apparatus and wherein the second-mentioned processing means (4) is adapted to derive the first-mentioned key from said precursive key data, identity data and password (or derivatives thereof).
Claim 5
Dependent Claim
81 words
A cryptographic method which comprises: inputting data to be encrypted in an apparatus; and encrypting that data in accordance with a cryptographic algorithm and an associated key; characterised by the steps of: storing precursive key data in the apparatus; inputting a password to said apparatus; and deriving said key in the apparatus from said precursive key data and password (or derivatives thereof); wherein said key is not permanently stored but derived only when it is required for encrypting said input data.
Claim 6
Dependent Claim
81 words
A cryptographic method which comprises: inputting data to be encrypted in an apparatus; and encrypting that data in accordance with a cryptographic algorithm and an associated key; characterised by the steps of: storing precursive key data in the apparatus; inputting a password to said apparatus; and deriving said key in the apparatus from said precursive key data and password (or derivatives thereof); wherein said key is not permanently stored but derived only when it is required for encrypting said input data.
Claim 7
Dependent Claim
33 words
A method according to claim 4 wherein said key is derived by encryption of the precursive key data or a derivative thereof under a key represented by said password or a derivative thereof.
Claim 8
Dependent Claim
36 words
A method according to claim 4 or claim 5 including the steps of storing identity data for that apparatus and deriving the first-mentioned key from said precursive key data, identity data and password (or derivatives thereof).
References Cited (Backward Citations)
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