Abstract: A method for providing a personal data storage service between a first user who is a data provider and a second user who is a data requester by using a smart contract based on a first layer and a privacy layer and a storage layer based on a second layer is provided. The method has an effect of generating encoded subject data made by encoding subject data by using a random key as an encryption key generated through a data provider terminal, to thereby prevent the personal storage service provider from decoding the subject data. Further, the method has another effect of saving the storage for use in PDS service, since there is no need to generate each of encoded encryption key and encoded subject data in line with each of data requester even if the number of data requesters increase by implementing using a proxy re-encryption technology.

Abstract: A method for transmitting specific data whose data format is unknown at a relay from a first blockchain network to a second blockchain network via the relay is provided. The method includes steps of: the relay (a) in response to detecting that a blockchain communication message for transmitting the specific data from the first blockchain network following a first data format to the second blockchain network following a second data format is generated, generating a relay message including the blockchain communication message and verification information; and (b) transmitting the relay message to the second blockchain network, thereby instructing the second blockchain network to (i) verify the relay message by using the verification information included in the relay message and (ii) convert the specific data included in the relay message into the second data format to generate converted specific data and then transmit the converted specific data to a receiving party.