Event attestation for an electronic device

1. A method for validating an electronic device, comprising:

receiving from the electronic device an audit log indicating a time of occurrence of one or more local events occurring at the electronic device;

receiving attestation information provided by the electronic device attesting that the electronic device has received a plurality of event attestations, each event attestation providing a cryptographically authenticated attestation to an occurrence of a respective event for the electronic device during a lifecycle of the electronic device; and

determining a validation result in dependence on the audit log and a comparison of the audit log with information indicating when a batch of electronic devices associated with a given event attestation were processed by a given manufacturer, wherein the validation result indicates whether the attestation information is valid.

2. The method of claim 1 , wherein the attestation information comprises said plurality of event attestations; or

the attestation information comprises at least one cryptographically authenticated attestation attesting that the electronic device has verified that the plurality of event attestations were received by the electronic device.

3. The method of claim 1 , wherein a same event attestation is used to attest to an occurrence of an event for a plurality of different electronic devices.

4. The method of claim 1 , comprising at least one of:

determining a count indicative of a number of other electronic devices that have already attested to receiving a particular event attestation, and determining the validation result in dependence on the count; and

maintaining a record of at least one revoked event attestation, and determining the validation result in dependence on whether a particular event attestation attested in the attestation information is one of said at least one revoked event attestation.

5. The method of claim 1 , wherein an event attestation attesting to an occurrence of a later event during the lifecycle of the electronic device includes event chain information dependent on information from at least one event attestation for attesting to an occurrence of at least one earlier event expected to occur before the later event during the lifecycle of the electronic device.

6. The method of claim 5 , comprising determining the validation result in dependence on whether the event chain information for the plurality of event attestations indicates that events occurred in a prohibited sequence.

7. The method of claim 1 , comprising receiving from the electronic device an audit log indicating a time of occurrence of one or more local events occurring at the electronic device, and determining the validation result in dependence on the audit log.

8. The method of claim 1 , wherein said one or more local events comprise at least one of:

installation of a given event attestation on the electronic device;

calling of a given program code function by the electronic device;

booting of the electronic device; and

updating of one or more attributes of the electronic device.

9. The method of claim 1 , wherein an event attestation is determined to be valid when that event attestation is validated using a cryptographic key associated with a manufacturer or adapter that is permitted to cause a respective event to be performed for the electronic device.

10. The method of claim 9 , wherein a same cryptographic key is used to validate event attestations for a plurality of electronic devices.

11. A non-transitory storage medium storing a computer program comprising instructions, which when executed by a data processing apparatus, cause the data processing apparatus to perform the following method for validating an electronic device:

receiving from the electronic device an audit log indicating a time of occurrence of one or more local events occurring at the electronic device;

receiving attestation information provided by the electronic device attesting that the electronic device has received a plurality of event attestations, each event attestation providing a cryptographically authenticated attestation to an occurrence of a respective event for the electronic device during a lifecycle of the electronic device; and

determining a validation result in dependence on the audit log and a comparison of the audit log with information indicating when a batch of electronic devices associated with a given event attestation were processed by a given manufacturer, wherein the validation result indicates whether the attestation information is valid.

12. A method for an electronic device, comprising:

generating a validation request comprising attestation information attesting that the electronic device has received a plurality of event attestations, each event attestation comprising a cryptographically authenticated attestation to an occurrence of a respective event for the electronic device during a lifecycle of the electronic device; and

transmitting the validation request to a validation apparatus,

wherein each event attestation is associated with a hash value corresponding to a result of a predetermined hash function applied to contents of the event attestation;

the method further comprises, in response to a new event attestation provided to the electronic device;

when the new event attestation is validated, discarding a stub portion of said contents of the new event attestation, and

when a mismatch is detected between the hash value of the new event attestation and a result of the predetermined hash function applied to the contents of the new event attestation, rejecting the new event attestation,

wherein the hash value is dependent on the stub portion.

13. The method according to claim 12 , wherein the new event attestation is associated with a signature derived from said hash value and said contents of the new event attestation excluding said stub portion; and

the attestation information comprises the signatures associated with the plurality of event attestations or an indication that the signatures associated with the plurality of event attestations have been validated.

14. A method for an electronic device, comprising:

generating a validation request comprising attestation information attesting that the electronic device has received a plurality of event attestations, each event attestation comprising a cryptographically authenticated attestation to an occurrence of a respective event for the electronic device during a lifecycle of the electronic device; and

transmitting the validation request to a validation apparatus,

wherein one of said event attestations comprises a conditional event attestation for attesting to an occurrence of a predetermined event in the lifecycle of the electronic device on condition that a predetermined condition is satisfied by the electronic device; and

the method comprises validating whether the predetermined condition is satisfied and preventing transmission of attestation information attesting that the conditional event attestation has been validly received when the predetermined condition is not satisfied.

15. The method for the electronic device according to claim 14 , wherein the predetermined condition comprises specific software being installed at a predetermined region of storage circuitry.

16. A non-transitory storage medium storing a computer program comprising instructions, which when executed by a data processing apparatus, cause the data processing apparatus to perform the following method for an electronic device:

generating a validation request comprising attestation information attesting that the electronic device has received a plurality of event attestations, each event attestation comprising a cryptographically authenticated attestation to an occurrence of a respective event for the electronic device during a lifecycle of the electronic device; and

transmitting the validation request to a validation apparatus, wherein one of said event attestations comprises a conditional event attestation for attesting to an occurrence of a predetermined event in the lifecycle of the electronic device on condition that a predetermined condition is satisfied by the electronic device; and

the method comprises validating whether the predetermined condition is satisfied and preventing transmission of attestation information attesting that the conditional event attestation has been validly received when the predetermined condition is not satisfied.