The signing of electronic contracts and the certification of important documents are realized by utilizing blockchain, identity-based cryptography and electronic signature technology. Blockchain technology can realize the data distributed ledgers through the entire system nodes, the whole processes, and the entire transactions. Identity-based cryptography and electronic signature technology can achieve data integrity, privacy, and nonrepudiation. All data is shared by all participating nodes, the information in the cyberspace is more transparent, and the behavior is more traceable. A complete and compliant contract signing process and data certification is achieved.