A computer-implemented method comprising: generating, by a client (302, 420) associated with a target blockchain network (306, 410), a request for operating client data from the target blockchain network and cross-chain data of one or more blockchain networks (316, 318, 320) different from the target blockchain network, wherein the request for operating cross-chain data comprises one or more smart contract computational logics for operating the cross-chain data and wherein the client cannot read data from, and exchange data with, the one or more blockchain networks different from the target blockchain network; sending, from the client, the request for operating cross-chain data to a smart contract service provider (308, 430) comprising a trusted computation execution environment TEE, wherein the smart contract service provider is off the target blockchain network; receiving, by the smart contract service provider (308, 430), from the client (302, 420) associated with the target blockchain network (306, 410), the request for operating cross-chain data of one or more blockchain networks (316, 318, 320) different from the target blockchain network; fetching by the smart contract service provider (308, 430), client data from the target blockchain; sending, by the smart contract service provider to a data visiting service provider (312, 440), a request for the cross-chain data; receiving, by the smart contract service provider, the cross-chain data from the data visiting service provider; generating, by the TEE, a result using the client data and the cross-chain data, wherein the result is generated by the TEE executing the smart contract computational logics using the client data and the cross-chain data, independently of the target blockchain network; and returning, by the smart contract service provider, the result to the client. generating, by a client (302, 420) associated with a target blockchain network (306, 410), a request for operating client data from the target blockchain network and cross-chain data of one or more blockchain networks (316, 318, 320) different from the target blockchain network, wherein the request for operating cross-chain data comprises one or more smart contract computational logics for operating the cross-chain data and wherein the client cannot read data from, and exchange data with, the one or more blockchain networks different from the target blockchain network; sending, from the client, the request for operating cross-chain data to a smart contract service provider (308, 430) comprising a trusted computation execution environment TEE, wherein the smart contract service provider is off the target blockchain network; receiving, by the smart contract service provider (308, 430), from the client (302, 420) associated with the target blockchain network (306, 410), the request for operating cross-chain data of one or more blockchain networks (316, 318, 320) different from the target blockchain network; fetching by the smart contract service provider (308, 430), client data from the target blockchain; sending, by the smart contract service provider to a data visiting service provider (312, 440), a request for the cross-chain data; receiving, by the smart contract service provider, the cross-chain data from the data visiting service provider; generating, by the TEE, a result using the client data and the cross-chain data, wherein the result is generated by the TEE executing the smart contract computational logics using the client data and the cross-chain data, independently of the target blockchain network; and returning, by the smart contract service provider, the result to the client.