Implementation of a Blockchain-based Distributed PKI for IoT using Emercoin NVS and TPM 2.0

Internet-of-Things is constantly expanding and one of the most relevant challenge is to secure the communications that involve these particular devices. Public Key Infrastructure (PKI) mechanisms are not well suited for IoT devices, and many new solutions to this problem leverage on the Blockchain technology for moving the "trust-anchor" from centralized root Certification Authorities (CAs) to a public distributed ledger. Starting from one of these solutions (proposed in a 2018's paper by Elisa Bertino, Ankush Singla, Jongho Won and Greg Bollella) based on a Blockchain project called Emercoin NVS, the purpose of this work is to propose an implementation that extends the original design using the TPM 2.0 technology for the identification of the IoT devices. By using this Blockchain-based system, the certificates of the IoT devices within a network are securely stored on the Blockchain, and they can be retrieved (with simple HTTP requests, using the RPC configuration of the Emercoin Wallet) during the certificate verification step of the TLS handshake, in replacement of the standard certificate chains provided by the Certification Authorities. The registration of devices certificates on the Blockchain is performed by interacting with a special node of the network called Device Manager (DM), that runs the Emercoin Wallet and maintain a local copy of the ledger. In the original design, there are no security measures to prevent the registration of a certificate forged by a "lying" entity. Any device can in fact claim an arbitrary identity during the certificate registration protocol with the DM. Thanks to TPM 2.0 technology, the security level of the original solution was improved, by providing a strong protection against the identity theft. Finally, some experiments based on this implementation have been conducted for measuring the TLS handshake time using the Emercoin-based distributed approach, in order to compare it with the standard centralized one. Blockchain-based TLS handshake was slower that than the standard one, but also more secure if we take into account that the revocation status check is frequently skipped in standard communications (also for web-based communications), unless the OCSP Must-Staple is enabled.