An electronic certification system that can simplify a process for verification of reliability while improving reliability. The electronic certification system guarantees reliability of data using an audit trail registered in a blockchain, the data being provided to a second terminal such as a client by a first terminal such as a server, the first terminal includes audit trail registration for registering information and the data as the audit trail in the blockchain, the information relating at least one of the first terminal, an administrator of the first terminal, and a program configured to run on the first terminal and exchange the data with the second terminal, and an audit trail provider for transmitting the audit trail to the second terminal. The second terminal determines that the data is reliable if the audit trail provided by the audit trail provider has been registered in the blockchain.