Two-Party ECDSA Protocol for Smart-ID

Abstract

Smart-ID is a digital signature solution based on threshold cryptography where two parties (mobile device and server) collaborate in key generation and signing process. The current solution uses RSA-based two-party signature scheme suggested by Buldas et al. in 2017 paper. This thesis proposes a Smart-ID-like solution based on Two-Party ECDSA protocol suggested by Lindell Yehuda in his 2017 paper. The thesis finds that the suggested ECDSA solution is able to provide the same security features as the current RSA-based Smart-ID solution, but with improved efficiency – more efficient key exchange, smaller signature size and does not require scalable secure storage on the server side. The security proof of the suggested ECDSA solution is not provided. However, the thesis provides a brief security analysis of the solution and the intuition why the suggested solution might be secure. The prototype implementation of the solution is also provided.