Attestation methods

An attestation method for verifying the integrity of an attester device by an attestation proxy (AP) which is a node of a distributed ledger (DL) network;

• the attestation method comprising the AP:
• sending a trusted platform module (TPM) quote request message directly to a virtual TPM (vTPM) uniquely associated with the attester device, to prompt the vTPM to:
• produce a set of platform configuration register (PCR) values based on measurements requested and received by the vTPM directly from the attester device,
• then send a TPM quote comprising the set of PCR values directly to the AP;
• the attestation method further comprising the AP:
• receiving the TPM quote;
• retrieving, from a local copy of the DL, a latest set of PCR values recorded for the attester device;
• comparing that set of PCR values retrieved from the local copy of the DL with the set of PCR values received in the TPM quote to generate a local attestation indicator, wherein the local attestation indicator is negative when the set of PCR values retrieved from the local copy of the DL does not match the set of PCR values received in the TPM quote;
• and
• producing an attestation result based on the local attestation indicator, wherein the attestation result is negative when the local attestation indicator is negative.