Interim root-of-trust enrolment and device-bound public key registration

An electronic device according to any preceding claim,

• wherein the one or more memories have installed thereon a temporary enrolment trusted root certificate;
• and
• wherein the processor is further configured to, subsequent to receiving the temporary enrolment device certificate, verify the temporary enrolment device certificate using the temporary enrolment trusted root certificate;
• and
• wherein installing the temporary enrolment device certificate is in response to the verification.

A method for performance by an electronic device, the electronic device comprising:

• a security module having a physical unclonable function (PUF), the security module configured to establish an enrolment key pair (EPK, ESK) based on a first challenge and response to the PUF, the enrolment key pair comprising an enrolment public key (EPK) and an enrolment secret key (ESK);
• and
• one or more memories;
• wherein the method comprises:
• over a secure connection, transmitting a certificate signing request (CSR) to a server for a certificate certifying that the EPK is associated with a device identifier, the CSR comprising:
• the device identifier;
• and
• the EPK;
• wherein the CSR is signed using the ESK, and wherein the device identifier is based on a function of the EPK;
• over the secure connection, receiving a temporary enrolment device certificate certifying that the EPK is associated with the device identifier and including a validity period;
• and
• installing the temporary enrolment device certificate in memory.

A server configured to:

• receive a certificate signing request (CSR) comprising a device identifier and an enrolment public key (EPK) of an enrolment key pair established by an electronic device, the CSR for a certificate certifying that the EPK is associated with the device identifier, wherein the device identifier is based on a function of the EPK;
• cause the device identifier to be checked against a database of device identifiers for which the server may sign a certificate;
• cause a check of the device identifier to be performed to certify the device identifier is a function of the EPK;
• cause the EPK to be associated with the device identifier in the database;
• sign a temporary enrolment device certificate certifying that the EPK is associated with the device identifier and including a validity period;
• and
• initiate transmission of the signed temporary enrolment device certificate over a secure connection to the electronic device identified by the device identifier.

A server according to any of claims 13 to 22, the server further configured to:

• receive the temporary enrolment device certificate;
• receive a second CSR comprising the device identifier and a device public key (DPK) of a device key pair established by the electronic device, wherein the second CSR is for a certificate certifying that the DPK is associated with the device identifier;
• cause the device identifier of the second CSR to be checked against the database of device identifiers for which the server may sign a certificate;
• cause a check of the device identifier of the second CSR to be performed to verify that the device identifier of the second CSR matches the device identifier specified in the received temporary enrolment device certificate;
• sign a device certificate based on the CSR, wherein the device certificate is a descendant of a primary trusted root certificate known to the electronic device;
• initiate transmission of the device certificate over a second secure connection to the electronic device identified by the device identifier.

A method comprising, in a server:

• receiving a certificate signing request (CSR) comprising a device identifier and an enrolment public key (EPK) of an enrolment key pair established by an electronic device, the CSR for a certificate certifying that the EPK is associated with the device identifier, wherein the device identifier is based on a function of the EPK;
• causing the device identifier to be checked against a database of device identifiers for which the server may sign a certificate;
• causing a check of the device identifier to be performed to certify the device identifier is a function of the EPK;
• causing the EPK to be associated with the device identifier in the database;
• signing a temporary enrolment device certificate certifying that the EPK is associated with the device identifier and including a validity period;
• and
• initiating transmission of the signed temporary enrolment device certificate over a secure connection to the electronic device identified by the device identifier.

A system comprising:

• an electronic device comprising:
• a security module having a physical unclonable function (PUF), the security module configured to establish an enrolment key pair (EPK, ESK) based on a first challenge and response to the PUF, the enrolment key pair comprising an enrolment public key (EPK) and an enrolment secret key (ESK);
• one or more memories;
• and
• a processor configured to:
• over a secure connection, transmit a certificate signing request (CSR) to a server of one or more servers for a certificate certifying that the EPK is associated with a device identifier, the CSR comprising:
• the device identifier;
• and
• the EPK;
• wherein the CSR is signed using the ESK, and wherein the device identifier is based on a function of the EPK;
• over the secure connection, receive a temporary enrolment device certificate certifying that the EPK is associated with the device identifier and including a validity period;
• and
• in response to the verification, install the temporary enrolment device certificate in memory;
• and
• one or more servers configured to:
• receive over the secure connection from the electronic device the CSR comprising the device identifier and the EPK for a certificate certifying that the EPK is associated with the device identifier;
• check the device identifier against a database of device identifiers for which the one or more servers may sign a certificate;
• check the device identifier to certify the device identifier is a function of the EPK;
• associate the EPK with the device identifier in the database;
• sign the temporary enrolment device certificate certifying that the EPK is associated with the device identifier and including the validity period;
• and
• send the signed temporary enrolment device certificate over the secure connection to the electronic device.