Granted Patent B2

US 9,003,181 · App. 13/070,178 · Granted Apr 7, 2015

Abstract

Claims (119)

1. A method to be performed by a certificate authority as part of an implicit certificate scheme, the method comprising:

receiving a certificate request from a requestor, the certificate request comprising a public value [Q A ] of the requestor;

selecting particular information [V A ] from a finite set;

performing an iterative process of generating a point [B A ] on an elliptic curve and applying a known function [F] to the point [B A ], wherein the iterative process is repeated until applying the known function [F] to the point [B A ] results in the particular information [V A ];

encoding an implicit certificate [IC A ] using the point [B A ] as public-key reconstruction data [B A ]; and

calculating an implicit signature [s] that corresponds to the implicit certificate [IC A ],

wherein the iterative process comprises:

generating a private value [d CA ] of the certificate authority;

multiplying the private value [d CA ] of the certificate authority by a base point [G] to obtain a public value [Q CA ] of the certificate authority;

calculating the public-key reconstruction data [B A ] as a sum of the public value [Q A ] of the requestor and the public value [Q CA ] of the certificate authority; and

determining whether applying the known function [F] to the public-key reconstruction data [B A ] results in the particular information [V A ],

wherein the public value [Q A ] of the requestor, the base point [G], and the public value [Q CA ] of the certificate authority are on the elliptic curve.

2. The method as claimed in claim 1 , further comprising:

sending the implicit certificate [IC A ] and the implicit signature [s] to the requestor for use in calculating a reconstructed private key [k A ] which forms a key pair with a public key [K A ] that can be reconstructed from the public-key reconstruction data [B A ].

3. The method as claimed in claim 1 , further comprising:

making the implicit certificate [IC A ] available to a recipient for use in calculating a public key [K A ] from the public-key reconstruction data [B A ].

4. The method as claimed in claim 1 , wherein the particular information [V A ] is related to one or more of the requestor, the implicit certificate [IC A ], and a public key [K A ] that can be reconstructed from the public-key reconstruction data [B A ].

5. The method as claimed in claim 1 , wherein the particular information [V A ] comprises a validity period of the implicit certificate [IC A ] or a validity date of the implicit certificate [IC A ] or both.

6. The method as claimed in claim 1 , wherein in the event that applying the known function [F] to the public-key reconstruction data [B A ] does not result in the particular information [V A ], the iterative process further comprises:

generating a new private value [new d CA ] of the certificate authority;

multiplying the new private value [new d CA ] of the certificate authority by the base point [G] to obtain a new public value [new Q CA ] of the certificate authority;

calculating new public-key reconstruction data [new B A ] as a sum of the public value [Q A ] of the requestor and the new public value [new Q CA ] of the certificate authority; and

determining whether applying the known function [F] to the new public-key reconstruction data [new B A ] results in the particular information [V A ],

wherein the new public value [new Q CA ] of the certificate authority and the new public-key reconstruction data [new B A ] are on the elliptic curve.

7. The method as claimed in claim 1 , wherein in the event that applying the known function [F] to the public-key reconstruction data [B A ] does not result in the particular information [V A ], the iterative process further comprises:

calculating an incremented private value [d CA +c] of the certificate authority as a sum of the private value [d CA ] of the certificate authority and a constant integer [c];

calculating incremented public-key reconstruction data [B A +cG] as a sum of the public-key reconstruction data [B A ] and a product of the constant integer [c] and the base point [G], wherein the incremented public-key reconstruction data [B A +cG] is on the elliptic curve; and

determining whether applying the known function [F] to the incremented public-key reconstruction data [B A +cG] results in the particular information [V A ].

8. A method to be performed by a requestor as part of an implicit certificate scheme, the method comprising:

sending a certificate request to a certificate authority;

receiving from the certificate authority an implicit certificate [IC A ] from which public-key reconstruction data [B A ] is recoverable, wherein the public-key reconstruction data [B A ] is on an elliptic curve and can be used to calculate a reconstructed public key [K A ];

receiving from the certificate authority an implicit signature [s] that corresponds to the implicit certificate [IC A ];

recovering the public-key reconstruction data [B A ] from the implicit certificate [IC A ]; and

extracting information [V A ] from the public-key reconstruction data [B A ] by applying a known function [F] to the public-key reconstruction data [B A ], the known function [F] having been agreed upon by the requestor and by the certificate authority for use by the certificate authority in incorporating the information [V A ] into the public-key reconstruction data [B A ].

9. The method as claimed in claim 8 , wherein the extracted information [V A ] is related to one or more of the requestor, the reconstructed public key [K A ], and the implicit certificate [IC A ].

10. The method as claimed in claim 8 , wherein the extracted information [V A ] comprises a validity period of the implicit certificate [IC A ] or a validity date of the implicit certificate [IC A ] or both.

11. The method as claimed in claim 8 , further comprising:

generating a private value [d A ] of the requestor; and

calculating a public value [Q A ] of the requestor as a product of the private value [d A ] of the requestor and a base point [G] on the elliptic curve,

wherein the public value [Q A ] of the requestor is on the elliptic curve, and

wherein sending the certificate request comprises sending the public value [Q A ] of the requestor.

12. The method as claimed in claim 8 , the method further comprising:

checking whether the extracted information [V A ] complies with certificate policy management rules accessible by the requestor.

13. The method as claimed in claim 11 , the method further comprising:

calculating the reconstructed public key [K A ] from the implicit certificate [IC A ] and from a public key of the CA [K CA ], and

calculating a reconstructed private key [k A ] from the implicit certificate [IC A ], from the implicit signature [s], and from the private value [d A ] of the requestor,

wherein the reconstructed private key [k A ] forms a key pair with the reconstructed public key [K A ].

14. A method to be performed by a recipient as part of an implicit certificate scheme, the method comprising:

receiving an implicit certificate [IC A ];

recovering public-key reconstruction data [B A ] from the implicit certificate [IC A ], wherein the public-key reconstruction data [B A ] is on an elliptic curve and can be used to calculate a reconstructed public key [K A ]; and

extracting information [V A ] from the public-key reconstruction data [B A ] by applying a known function [F] to the public-key reconstruction data [B A ], the known function [F] having been agreed upon by the recipient and by the certificate authority for use by the certificate authority in incorporating the information [V A ] into the public-key reconstruction data [B A ].

15. The method as claimed in claim 14 , wherein the extracted information [V A ] is related to one or more of the implicit certificate [IC A ], a requestor of the implicit certificate [IC A ], and the reconstructed public key [K A ].

16. The method as claimed in claim 14 , wherein the extracted information [V A ] comprises a validity period of the implicit certificate [IC A ] or a validity date of the implicit certificate [IC A ] or both.

17. The method as claimed in claim 14 , the method further comprising:

calculating the reconstructed public key [K A ] from the implicit certificate [IC A ] and from a public key of a certificate authority [K CA ]; and

implicitly authenticating the reconstructed public key [K A ] by using the reconstructed public key [K A ] during communication with a requestor of the implicit certificate [IC A ].

18. The method as claimed in claim 14 , the method further comprising:

checking whether the extracted information [V A ] complies with certificate policy management rules accessible by the recipient.

19. A certificate authority device for use in an implicit certificate scheme, the device comprising:

a processor;

a communication interface able to receive a certificate request from a requestor device, the certificate request comprising a public value [Q A ] of the requestor device; and

a memory storing code which, when executed by the processor, results in:

selecting particular information [V A ] from a finite set;

performing an iterative process of generating a point [B A ] on an elliptic curve and applying a known function [F] to the point [B A ], wherein the iterative process is repeated until applying the known function [F] to the point [B A ] results in the particular information [V A ];

encoding an implicit certificate [IC A ] using the point [B A ] as public-key reconstruction data [B A ]; and

calculating an implicit signature [s] that corresponds to the implicit certificate [IC A ],

wherein the iterative process comprises:

generating a private value [d CA ] of the certificate authority device;

multiplying the private value [d CA ] of the certificate authority device by a base point [G] to obtain a public value [Q CA ] of the certificate authority device;

calculating the public-key reconstruction data [B A ] as a sum of the public value [Q A ] of the requestor device and the public value [Q CA ] of the certificate authority device; and

determining whether applying the known function [F] to the public-key reconstruction data [B A ] results in the particular information [V A ],

wherein the public value [Q A ] of the requestor device, the base point [G], and the public value [Q CA ] of the certificate authority device are on the elliptic curve.

20. The certificate authority device as claimed in claim 19 , wherein the code, when executed by the processor, further results in:

sending the implicit certificate [IC A ] and the implicit signature [s] to the requestor device via the communication interface so that the requestor device is able to calculate from the implicit certificate [IC A ] and from the implicit signature [s] a reconstructed private key [k A ] which forms a key pair with a public key [K A ] that can be reconstructed from the public-key reconstruction data [B A ].

21. The certificate authority device as claimed in claim 19 , wherein the code, when executed by the processor, further results in:

making the implicit certificate [IC A ] available to a recipient device for use in calculating a public key [K A ] from the public-key reconstruction data [B A ].

22. The certificate authority device as claimed in claim 19 , wherein the particular information [V A ] is related to one or more of the requestor device, the implicit certificate [IC A ], and a public key [K A ] that can be reconstructed from public-key reconstruction data [B A ].

23. The certificate authority device as claimed in claim 19 , wherein the particular information [V A ] comprises a validity period of the implicit certificate [IC A ] or a validity date of the implicit certificate [IC A ] or both.

24. The certificate authority device as claimed in claim 19 , wherein in the event that applying the known function [F] to the public-key reconstruction data [B A ] does not result in the particular information [V A ], the iterative process further comprises:

generating a new private value [new d CA ] of the certificate authority device;

multiplying the new private value [new d CA ] of the certificate authority device by the base point [G] to obtain a new public value [new Q CA ] of the certificate authority device;

calculating new public-key reconstruction data [new B A ] as a sum of the public value [Q A ] of the requestor device and the new public value [new Q CA ] of the certificate authority device; and

determining whether applying the known function [F] to the new public-key reconstruction data [new B A ] results in the particular information [V A ],

wherein the new public value [new Q CA ] of the certificate authority device and the new public-key reconstruction data [new B A ] are on the elliptic curve.

25. The certificate authority device as claimed in claim 19 , wherein in the event that applying the known function [F] to the public-key reconstruction data [B A ] does not result in the particular information [V A ], the iterative process further comprises:

calculating an incremented private value [d CA +c] of the certificate authority device as a sum of the private value [d CA ] of the certificate authority device and a constant integer [c];

calculating incremented public-key reconstruction data [B A +cG] as a sum of the public-key reconstruction data [B A ] and a product of the constant integer [c] and the base point [G], wherein the incremented public-key reconstruction data [B A +cG] is on the elliptic curve; and

determining whether applying the known function [F] to the incremented public-key reconstruction data [B A +cG] results in the particular information [V A ].

26. A system for use in an implicit certificate generation scheme, the system comprising:

a requestor device to generate a certificate request, the certificate request comprising a public value [Q A ] of the requestor device; and

a certificate authority device to receive the certificate request from the requestor, to select particular information [V A ] from a finite set, and, in response to receiving the certificate request, to perform an iterative process of generating a point [B A ] on an elliptic curve and applying a known function [F] to the point [B A ], wherein the iterative process is repeated until applying the known function [F] to the point [B A ] results in the particular information [V A ], to encode an implicit certificate [IC A ] using the point [B A ] as public-key reconstruction data, to calculate an implicit signature [s] that corresponds to the implicit certificate [IC A ], and to send the implicit certificate [IC A ] and the implicit signature [s] to the requestor device,

wherein the iterative process comprises:

generating a private value [d CA ] of the certificate authority device;

multiplying the private value [d CA ] of the certificate authority device by a base point [G] to obtain a public value [Q CA ] of the certificate authority device;

calculating the public-key reconstruction data [B A ] as a sum of the public value [Q A ] of the requestor device and the public value [Q CA ] of the certificate authority device; and

determining whether applying the known function [F] to the public-key reconstruction data [B A ] results in the particular information [V A ],

wherein the public value [Q A ] of the requestor device, the base point [G], and the public value [Q CA ] of the certificate authority device are on the elliptic curve.

27. The system as claimed in claim 26 , wherein the requestor device, in response to receiving implicit certificate [IC A ] and the implicit signature [s] from the CA device, is to recover the public-key reconstruction data [B A ] from the implicit certificate [IC A ] and is to extract the information [V A ] from the public-key reconstruction data [B A ] by applying the known function [F] to the public-key reconstruction data [B A ].

28. The system as claimed in claim 26 , wherein the particular information [V A ] is related to one or more of the requestor device, the implicit certificate [IC A ], and a public key [K A ] that can be reconstructed from public-key reconstruction data [B A ].

29. The system as claimed in claim 26 , wherein the particular information [V A ] comprises a validity period of the implicit certificate [IC A ] or a validity date of the implicit certificate [IC A ] or both.

30. A non-transitory computer readable medium storing code which, when executed by a processor of a certificate authority device, results in:

selecting particular information [V A ] from a finite set;

performing an iterative process of generating a point [B A ] on an elliptic curve and applying a known function [F] to the point [B A ], wherein the iterative process is repeated until applying the known function [F] to the point [B A ] results in the particular information [V A ];

encoding an implicit certificate [IC A ] using the point [B A ] as public-key reconstruction data [B A ]; and

calculating an implicit signature [s] that corresponds to the implicit certificate [IC A ],

wherein the iterative process comprises:

generating a private value [d CA ] of the certificate authority device;

multiplying the private value [d CA ] of the certificate authority device by a base point [G] to obtain a public value [Q CA ] of the certificate authority device;

calculating the public-key data [B A ] as a sum of a public value [Q A ] of a requestor device and the public value [Q CA ] of the certificate authority device, the public value [Q A ] of the requestor device having been received by the certificate authority device in a certificate request from the requestor device; and

determining whether applying the known function [F] to the public-key reconstruction data [B A ] results in the particular information [V A ],

wherein the public value [Q A ] of the requestor device, the base point [G], and the public value [Q CA ] of the certificate authority device are on the elliptic curve.

31. A non-transitory computer readable medium storing code which, when executed by a processor of a requestor device that has sent a certificate request to a certificate authority device, results in:

responsive to receiving from the certificate authority device an implicit certificate [IC A ] from which public-key reconstruction data [B A ] is recoverable, and an implicit signature [s] that corresponds to the implicit certificate [IC A ], wherein the public-key reconstruction data [B A ] is on an elliptic curve and can be used to calculate a reconstructed public key [K A ]:

recovering the public-key reconstruction data [B A ] from the implicit certificate [IC A ]; and

extracting information [V A ] from the public-key reconstruction data [B A ] by applying a known function [F] to the public-key reconstruction data [B A ], the known function [F] having been agreed upon by the requestor device and by the certificate authority device for use by the certificate authority device in incorporating the information [V A ] into the public-key reconstruction data [B A ].

32. A non-transitory computer readable medium storing code which, when executed by a processor of a recipient device, results in:

responsive to receiving an implicit certificate [IC A ]:

recovering public-key reconstruction data [B A ] from the implicit certificate [IC A ], wherein the public-key reconstruction data [B A ] is on an elliptic curve and can be used to calculate a reconstructed public key [K A ]; and

extracting information [V A ] from the public-key reconstruction data [B A ] by applying a known function [F] to the public-key reconstruction data [B A ], the known function [F] having been agreed upon by the recipient device and by a certificate authority device for use by the certificate authority device in incorporating the information [V A ] into the public-key reconstruction data [B A ].

Assignments (12)