Abstract: Disclosed herein are methods, devices, and apparatuses, including computer programs stored on computer-readable media, for managing a cryptographic key. One of the methods includes: receiving a request for a signature on transaction data; allocating a key manager corresponding to the request; and obtaining, by the key manager, the signature on the transaction data and the cryptographic key, wherein the cryptographic key is a public key, and the signature on the transaction data is obtained based on a private key corresponding to the public key.

Abstract: Disclosed herein are methods, systems, and apparatus for processing blockchain-based guarantee information. One method includes receiving a cross-chain request for relaying a cyphertext of a digital document to a second blockchain network, the digital document specifies a guarantee from the guarantor and one or more predetermined conditions of executing the guarantee, wherein the guarantee is made by the guarantor to a beneficiary; storing the cross-chain request and the cyphertext to a first blockchain associated with the first blockchain network based on performing a consensus algorithm; receiving a message from a second computing device for relaying information between the first blockchain network and the second blockchain network, the message includes a confirmation that the guarantee is accepted by the beneficiary and stored on a second blockchain associated with the second blockchain network; and updating a status of the guarantee to indicate that the guarantee has been voided on the first blockchain.

Abstract: Disclosed herein are methods, devices, and apparatuses, including computer programs stored on computer-readable media, for managing a cryptographic key. One of the methods includes: receiving a request for a signature on transaction data; allocating a key manager corresponding to the request; and obtaining, by the key manager, the signature on the transaction data and the cryptographic key, wherein the cryptographic key is a public key, and the signature on the transaction data is obtained based on a private key corresponding to the public key.

Abstract: Disclosed herein are methods, systems, and apparatus, including computer programs encoded on computer storage media, for processing guarantee information. One of the methods includes receiving an application of a guarantee made by at least a guarantor to a beneficiary; generating a digital version of the guarantee based on the information included in the application; encrypting the digital version to generate cyphertext of the guarantee; generating one or more zero-knowledge proofs (ZKPs) related to one or more values associated with the guarantee; and sending the cyphertext and the one or more ZKPs to a blockchain network to store the cyphertext on a blockchain, wherein the cyphertext is stored on the blockchain through consensus of blockchain nodes of the blockchain network after the one or more ZKPs are successfully verified by the blockchain nodes.

Abstract: Disclosed herein are methods, systems, and apparatus for processing blockchain-based guarantee information. One method includes receiving a cross-chain request for relaying a cyphertext of a digital document to a second blockchain network, the digital document specifies a guarantee from the guarantor and one or more predetermined conditions of executing the guarantee, wherein the guarantee is made by the guarantor to a beneficiary; storing the cross-chain request and the cyphertext to a first blockchain associated with the first blockchain network based on performing a consensus algorithm; receiving a message from a second computing device for relaying information between the first blockchain network and the second blockchain network, the message includes a confirmation that the guarantee is accepted by the beneficiary and stored on a second blockchain associated with the second blockchain network; and updating a status of the guarantee to indicate that the guarantee has been voided on the first blockchain.