System and method for digital asset transfer

1. A computer-implemented method for digital asset buyback, comprising:

generating a blockchain transaction for issuing a digital asset to a first blockchain account associated with a blockchain, wherein the blockchain transaction for issuing the digital asset invokes a blockchain contract that is deployed on the blockchain and that corresponds to the digital asset;

sending the blockchain transaction for issuing the digital asset to a blockchain node for adding to the blockchain;

obtaining a request for buying back the digital asset from the first blockchain account, the request comprising an identifier of the first blockchain account and a quantity of the digital asset;

identifying the blockchain contract based on the request;

generating a blockchain transaction for transferring the quantity of the digital asset from the first blockchain account to a second blockchain account associated with digital asset buyback, wherein the blockchain contract comprises a restriction prohibiting transfer of the digital asset out of the second blockchain account; and

sending, to a blockchain node for adding to the blockchain, the blockchain transaction for transferring the quantity of the digital asset from the first blockchain account to the second blockchain account.

2. The method of claim 1 , wherein the blockchain transaction for transferring the quantity of the digital asset from the first blockchain account to the second blockchain account comprises:

an identifier associated with the blockchain contract;

an identifier associated with the first blockchain account;

an identifier associated with the second blockchain account; or

the quantity of the digital asset to be transferred.

3. The method of claim 1 , further comprising, before generating the blockchain transaction for transferring the quantity of the digital asset from the first blockchain account to the second blockchain account:

determining, based on the obtained request, one or more permissions associated with a sender of the request for buying back the digital asset; and

verifying that the one or more determined permissions associated with the sender satisfy one or more required permissions for transferring the digital asset from the first blockchain account to the second blockchain account.

4. The method of claim 1 , further comprising, before generating the blockchain transaction for transferring the quantity of the digital asset from the first blockchain account to the second blockchain account:

obtaining, from the blockchain, data associated with the first blockchain account;

determining, based on the obtained data, a quantity of the digital asset in the first blockchain account; and

verifying that the determined quantity of the digital asset in the first blockchain account is no less than the quantity of the digital asset in the request for buying back the digital asset.

5. The method of claim 1 , further comprising, before generating the blockchain transaction for transferring the quantity of the digital asset from the first blockchain account to the second blockchain account:

determining, based on the blockchain contract, one or more required permissions for buying back the digital asset; and

determining that an entity associated with the second blockchain account possesses the one or more required permissions.

6. The method of claim 1 , further comprising, before obtaining the request for buying back the digital asset:

obtaining a request for transferring the digital asset from a third blockchain account associated with the blockchain to the first blockchain account;

generating, based on the request for transferring the digital asset, a different blockchain transaction for transferring the digital asset from the third blockchain account to the first blockchain account, wherein the different blockchain transaction invokes the identified blockchain contract; and

sending the different blockchain transaction to a blockchain node for adding to the blockchain.

7. The method of claim 1 , further comprising:

obtaining one or more blocks of the blockchain;

extracting, from the obtained one or more blocks, one or more blockchain transactions invoking the blockchain contract; and

determining a transaction history associated with the digital asset based on the one or more extracted blockchain transactions.

8. The method of claim 1 , further comprising:

obtaining one or more blocks of the blockchain;

extracting, from the obtained one or more blocks, one or more blockchain transactions associated with the first blockchain account; and

determining a transaction history associated with the first blockchain account based on the one or more extracted blockchain transactions.

9. The method of claim 1 , further comprising, before generating the blockchain transaction for transferring the quantity of the digital asset from the first blockchain account to the second blockchain account:

querying for any restriction placed on the first blockchain account or the second blockchain account; and

verifying that transferring the quantity of the digital asset from the first blockchain account to the second blockchain account is not prohibited by any restriction placed on the first blockchain account or the second blockchain account.

10. The method of claim 1 , further comprising, before generating the blockchain transaction for transferring the quantity of the digital asset from the first blockchain account to the second blockchain account:

querying for any restriction placed on the digital asset; and

verifying that transferring the quantity of the digital asset from the first blockchain account to the second blockchain account is not prohibited by any restriction placed on the digital asset.

11. A non-transitory computer-readable storage medium for digital asset buyback, configured with instructions executable by one or more processors to cause the one or more processors to perform operations comprising:

generating a blockchain transaction for issuing a digital asset to a first blockchain account associated with a blockchain, wherein the blockchain transaction for issuing the digital asset invokes a blockchain contract that is deployed on the blockchain and that corresponds to the digital asset;

sending the blockchain transaction for issuing the digital asset to a blockchain node for adding to the blockchain;

obtaining a request for buying back the digital asset from the first blockchain account, the request comprising an identifier of the first blockchain account and a quantity of the digital asset;

identifying the blockchain contract based on the request;

generating a blockchain transaction for transferring the quantity of the digital asset from the first blockchain account to a second blockchain account associated with digital asset buyback, wherein the blockchain contract comprises a restriction prohibiting transfer of the digital asset out of the second blockchain account; and

sending, to a blockchain node for adding to the blockchain, the blockchain transaction for transferring the quantity of the digital asset from the first blockchain account to the second blockchain account.

12. The non-transitory computer-readable storage medium of claim 11 , wherein the blockchain transaction for transferring the quantity of the digital asset from the first blockchain account to the second blockchain account comprises:

an identifier associated with the blockchain contract;

an identifier associated with the first blockchain account;

an identifier associated with the second blockchain account; or

the quantity of the digital asset to be transferred.

13. The non-transitory computer-readable storage medium of claim 11 , wherein the operations further comprise, before generating the blockchain transaction for transferring the quantity of the digital asset from the first blockchain account to the second blockchain account:

determining, based on the obtained request, one or more permissions associated with a sender of the request for buying back the digital asset; and

verifying that the permissions associated with the sender satisfy one or more required permissions for transferring the digital asset from the first blockchain account to the second blockchain account.

14. The non-transitory computer-readable storage medium of claim 11 , wherein the operations further comprise, before generating the blockchain transaction for transferring the quantity of the digital asset from the first blockchain account to the second blockchain account:

obtaining, from the blockchain, data associated with the first blockchain account;

determining, based on the obtained data, a quantity of the digital asset in the first blockchain account; and

verifying that the determined quantity of the digital asset in the first blockchain account is no less than the quantity of the digital asset in the request for buying back the digital asset.

15. The non-transitory computer-readable storage medium of claim 11 , wherein the operations further comprise, before generating the blockchain transaction for transferring the quantity of the digital asset from the first blockchain account to the second blockchain account:

determining, based on the blockchain contract, one or more required permissions for buying back the digital asset; and

determining that an entity associated with the second blockchain account possesses the one or more required permissions.

16. The non-transitory computer-readable storage medium of claim 11 , wherein the operations further comprise, before obtaining the request for buying back the digital asset:

obtaining a request for transferring the digital asset from a third blockchain account associated with the blockchain to the first blockchain account;

generating, based on the request for transferring the digital asset, a different blockchain transaction for transferring the digital asset from the third blockchain account to the first blockchain account, wherein the different blockchain transaction invokes the identified blockchain contract; and

sending the different blockchain transaction to a blockchain node for adding to the blockchain.

17. The non-transitory computer-readable storage medium of claim 11 , wherein the operations further comprise:

obtaining one or more blocks of the blockchain;

extracting, from the obtained one or more blocks, one or more blockchain transactions invoking the blockchain contract; and

determining a transaction history associated with the digital asset based on the one or more extracted blockchain transactions.

18. A system for digital asset buyback, comprising a processor and a non-transitory computer-readable storage medium storing instructions executable by the processor to cause the system to:

generating a blockchain transaction for issuing a digital asset to a first blockchain account associated with a blockchain, wherein the blockchain transaction for issuing the digital asset invokes a blockchain contract that is deployed on the blockchain and that corresponds to the digital asset;

sending the blockchain transaction for issuing the digital asset to a blockchain node for adding to the blockchain;

obtaining a request for buying back the digital asset from the first blockchain account, the request comprising an identifier of the first blockchain account and a quantity of the digital asset;

identifying the blockchain contract based on the request;

generating a blockchain transaction for transferring the quantity of the digital asset from the first blockchain account to a second blockchain account associated with digital asset buyback, wherein the blockchain contract comprises a restriction prohibiting transfer of the digital asset out of the second blockchain account; and

sending, to a blockchain node for adding to the blockchain, the blockchain transaction for transferring the quantity of the digital asset from the first blockchain account to the second blockchain account.