EP0175487A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Software protection device
Assignee: BTG International Ltd
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Filing: 1985-08-20
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Granted: —
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Expires: 2005-08-20
Abstract
Abstract 57 In order to prevent the unauthorised copying of software, a software module is encrypted using the data encryption standard (DES) algorithm, and the key is encrypted using the public key of a public/private key algorithm. To use the module it is entered into a software protection device where the private key held in a RAM 11 is used by a processor 13 to decode the DES key using instructions held in a ROM 12. Further instructions held by this ROM are used by the processor 13 to decode the module. Once the process of decoding keys and software has started, the processor 13 runs through a sequence of predetermined instructions and cannot be interrupted (except by switching off). When the sequence is complete processor 13, or for example a host computer 30, is enabled to use the decoded software, but a switch/reset circuit 17 operates preventing access to the RAM 11 and the ROM 12 so preserving the secrecy of the private key and any decoded DES key which is now stored in the RAM 11.
Inventors
- 👤 Bernard John Chorley
- 👤 Graeme Iain Papworth Parkin
- 👤 Brian Anderson Wichmann
- 👤 Simon Mays Elsom
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-30 06:06
CPC Classifications
G; G06; G06F; G06F21/00; G06F21/10
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
185 words
Apparatus for use in protecting software comprising first and second storage means, and a processor for carrying out instructions held by the second storage means, characterised in that the first storage means is adapted to contain at least one decryption key, the second storage means contains instructions for decrypting another key using a key held in the first storage means and for decrypting encrypted software using the said other key, and switch means having first and second modes in which the first storage means are, and are not, in communication with the processor, respectively, the switch means being constructed to enter its first mode automatically under predetermined conditions and while in this first mode to cause the processor to execute a sequence of the instructions held in the second storage means which end with an instruction which causes the switch means to enter its second mode, the first and second storage means, the processor and the switch means being contained in a tamper resistant housing, and the apparatus including an interface constructed to allow the processor to communicate with other apparatus external to the housing.
Claim 2
Dependent Claim
185 words
Apparatus for use in protecting software comprising first and second storage means, and a processor for carrying out instructions held by the second storage means, characterised in that the first storage means is adapted to contain at least one decryption key, the second storage means contains instructions for decrypting another key using a key held in the first storage means and for decrypting encrypted software using the said other key, and switch means having first and second modes in which the first storage means are, and are not, in communication with the processor, respectively, the switch means being constructed to enter its first mode automatically under predetermined conditions and while in this first mode to cause the processor to execute a sequence of the instructions held in the second storage means which end with an instruction which causes the switch means to enter its second mode, the first and second storage means, the processor and the switch means being contained in a tamper resistant housing, and the apparatus including an interface constructed to allow the processor to communicate with other apparatus external to the housing.
Claim 3
Dependent Claim
32 words
Apparatus according to Claim 1 characterised in that said second storage means are, and are not, in communication with said processor in the first and second modes of said switch means respectively.
Claim 4
Dependent Claim
41 words
Apparatus according to Claim 1 or 2 characterised in that said tamper-resistant housing contains third storage means for storing decrypted software, and fourth storage means containing instructions to operate the procssor in the first and second modes of said switch means.
Claim 5
Dependent Claim
25 words
Apparatus according to any preceding claim characterised in that the first storage means are random access memory and second storage means are read only memory.
Claim 6
Dependent Claim
44 words
Apparatus according to any preceding claim characterised in that the tamper-resistant housing contains a clock and the processor is arranged to operate correctly only if the encrypted software supplied to the apparatus contains a date having a predetermined relationship with the current clock indication.
Claim 7
Dependent Claim
29 words
Apparatus according to any preceding claim characterised in that the apparatus is so constructed that it is independent of the operating system of any computer used with the apparatus.
Claim 8
Dependent Claim
116 words
Method for use in protecting software comprising the steps of passing encrypted software from a host computer to software protection apparatus, decrypting the encrypted software using a processor of the said apparatus and at least one decryption key contained by the said apparatus, and executing the decrypted software on the processor under the control of the host computer, characterised by previously storing at least one decryption key for carrying out the said decryption in first storage means of the said apparatus, previously storing instructions for carrying out the said decryption in second storage means, the first and second storage means being contained in a tamper-resistant housing, and automatically isolating the first storage means under predetermined conditions.
Claim 9
Dependent Claim
116 words
Method for use in protecting software comprising the steps of passing encrypted software from a host computer to software protection apparatus, decrypting the encrypted software using a processor of the said apparatus and at least one decryption key contained by the said apparatus, and executing the decrypted software on the processor under the control of the host computer, characterised by previously storing at least one decryption key for carrying out the said decryption in first storage means of the said apparatus, previously storing instructions for carrying out the said decryption in second storage means, the first and second storage means being contained in a tamper-resistant housing, and automatically isolating the first storage means under predetermined conditions.
Claim 10
Dependent Claim
43 words
Method according to Claim 7 characterised in that protected software comprises at least one plaintext module and at least one encrypted module, the encrypted module being decrypted and run inside the tamper-resistant housing and the plaintext module being run on the host computer.
Claim 11
Dependent Claim
23 words
Method according to Claim 7 or 8 characterised in that the encrypted software is independent of the operating system of the host computer.
Claim 12
Dependent Claim
26 words
Method according to any of Claims 7 to 9 characterised in that the automatic isolation is carried out once decryption of the encrypted software is completed.
Claim 13
Dependent Claim
27 words
Method according to Claim 10 characterised in that the second storage means are also automatically isolated from the processor once decryption of the encrypted software is completed.
Claim 14
Dependent Claim
84 words
Method according to any of Claims 7 to 11 characterised in that decryption of encrypted software comprises decryption of a DES key using an RSA key stored in the first storage means and an RSA algorithm stored in the second storage means: storing the decrypted DES key in the first storage means, decryption of encrypted software using the decrypted DES key and a DES algorithm stored in the second storage means, and passing the decrypted software to third storage means in the tamper-resistant housing.
References Cited (Backward Citations)
No citation records indexed.
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