Incorporating data into cryptographic components of an ECQV certificate

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 [ICA] from which public-key reconstruction data [BA] is recoverable, wherein the public-key reconstruction data [BA] is on an elliptic curve and can be used to calculate a reconstructed public key [KA];
• receiving from the certificate authority an implicit signature [s] that corresponds to the implicit certificate [ICA];
• recovering the public-key reconstruction data [BA] from the implicit certificate [ICA];
• and
• extracting information [VA] from the public-key reconstruction data [BA] by applying a known function [F] to the public-key reconstruction data [BA], 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 [VA] into the public-key reconstruction data [BA].

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

• receiving an implicit certificate [ICA];
• recovering public-key reconstruction data [BA] from the implicit certificate [ICA], wherein the public-key reconstruction data [BA] is on an elliptic curve and can be used to calculate a reconstructed public key [KA];
• and
• extracting information [VA] from the public-key reconstruction data [BA] by applying a known function [F] to the public-key reconstruction data [BA], 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 [VA] into the public-key reconstruction data [BA].

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 [QA] of the requestor device;
• and
• a memory storing code which, when executed by the processor, results in:
• selecting particular information [VA] from a finite set;
• performing an iterative process of generating a point [BA] on an elliptic curve and applying a known function [F] to the point [BA], wherein the iterative process is repeated until applying the known function [F] to the point [BA] results in the particular information [VA];
• encoding an implicit certificate [ICA] using the point [BA] as public-key reconstruction data [BA];
• and
• calculating an implicit signature [s] that corresponds to the implicit certificate [ICA],
• wherein the iterative process comprises:
• generating a private value [dCA] of the certificate authority device;
• multiplying the private value [dCA] of the certificate authority device by a base point [G] to obtain a public value [QCA] of the certificate authority device;
• calculating the public-key reconstruction data [BA] as a sum of the public value [QA] of the requestor device and the public value [QCA] of the certificate authority device;
• and
• determining whether applying the known function [F] to the public-key reconstruction data [BA] results in the particular information [VA],
• wherein the public value [QA] of the requestor device, the base point [G], and the public value [QCA] of the certificate authority device are on the elliptic curve.

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 [QA] of the requestor device;
• and
• a certificate authority device to receive the certificate request from the requestor, to select particular information [VA] from a finite set, and, in response to receiving the certificate request, to perform an iterative process of generating a point [BA] on an elliptic curve and applying a known function [F] to the point [BA], wherein the iterative process is repeated until applying the known function [F] to the point [BA] results in the particular information [VA], to encode an implicit certificate [ICA] using the point [BA] as public-key reconstruction data, to calculate an implicit signature [s] that corresponds to the implicit certificate [ICA], and to send the implicit certificate [ICA] and the implicit signature [s] to the requestor device,
• wherein the iterative process comprises:
• generating a private value [dCA] of the certificate authority device;
• multiplying the private value [dCA] of the certificate authority device by a base point [G] to obtain a public value [QCA] of the certificate authority device;
• calculating the public-key reconstruction data [BA] as a sum of the public value [QA] of the requestor device and the public value [QCA] of the certificate authority device;
• and
• determining whether applying the known function [F] to the public-key reconstruction data [BA] results in the particular information [VA],
• wherein the public value [QA] of the requestor device, the base point [G], and the public value [QCA] of the certificate authority device are on the elliptic curve.

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

• selecting particular information [VA] from a finite set;
• performing an iterative process of generating a point [BA] on an elliptic curve and applying a known function [F] to the point [BA], wherein the iterative process is repeated until applying the known function [F] to the point [BA] results in the particular information [VA];
• encoding an implicit certificate [ICA] using the point [BA] as public-key reconstruction data [BA];
• and
• calculating an implicit signature [s] that corresponds to the implicit certificate [ICA],
• wherein the iterative process comprises:
• generating a private value [dCA] of the certificate authority device;
• multiplying the private value [dCA] of the certificate authority device by a base point [G] to obtain a public value [QCA] of the certificate authority device;
• calculating the public-key data [BA] as a sum of a public value [QA] of a requestor device and the public value [QCA] of the certificate authority device, the public value [QA] 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 [BA] results in the particular information [VA],
• wherein the public value [QA] of the requestor device, the base point [G], and the public value [QCA] of the certificate authority device are on the elliptic curve.

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 [ICA] from which public-key reconstruction data [BA] is recoverable, and an implicit signature [s] that corresponds to the implicit certificate [ICA], wherein the public-key reconstruction data [BA] is on an elliptic curve and can be used to calculate a reconstructed public key [KA]:
• recovering the public-key reconstruction data [BA] from the implicit certificate [ICA];
• and
• extracting information [VA] from the public-key reconstruction data [BA] by applying a known function [F] to the public-key reconstruction data [BA], 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 [VA] into the public-key reconstruction data [BA].

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 [ICA]:
• recovering public-key reconstruction data [BA] from the implicit certificate [ICA], wherein the public-key reconstruction data [BA] is on an elliptic curve and can be used to calculate a reconstructed public key [KA];
• and
• extracting information [VA] from the public-key reconstruction data [BA] by applying a known function [F] to the public-key reconstruction data [BA], 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 [VA] into the public-key reconstruction data [BA].