Device for providing blockchain did-based multi cloud service and its operating method

1. A cloud DID agent comprising:

a memory; and

at least one processor, wherein

the at least one processor is configured to

receive an upload action request for a file from a mobile agent,

generate an encryption key corresponding to the file in response to the upload action request and encrypt the file based on the encryption key,

generate a plurality of chunks by dividing the encrypted file into a predetermined size,

generate a plurality of data blocks corresponding to each of the plurality of chunks,

execute an upload action by distributing and transmitting the plurality of data blocks to a plurality of external cloud servers so that the plurality of data blocks are distributed and stored in the plurality of external cloud servers,

generate an action block file for the plurality of actions including the upload action executed during a predetermined period,

transmit a first hash value of the action block file to a cloud agency,

acquire a second hash value of an agency block file including the first hash value when receiving a verification request for the action block file from the mobile agent,

access the agency block file based on the second hash value,

acquire a third hash value of the action block file from the agency block file,

compare the first hash value with the third hash value, and

transmit a response to the verification request to the mobile agent based on the comparison result.

2. The cloud DID agent of claim 1 , wherein

the at least one processor is configured to

receive a download action request for the file from the mobile agent,

download at least some of the plurality of data blocks corresponding to each chunk included in the plurality of chunks from the plurality of external cloud servers in response to the download action request and recover each chunk based on the at least some of the plurality of data blocks,

recover the encrypted file based on the plurality of recovered chunks,

decrypt the recovered encrypted file using the encryption key, and

transmit the decrypted file to the mobile agent.

3. The cloud DID agent of claim 2 , wherein

the memory stores a user DID, and

the at least one processor is configured to

verify a user electronic signature included in the upload action request and the download action request through a blockchain network based on the user DID.

4. The cloud DID agent of claim 1 , wherein

the at least one processor is configured to

generate a predetermined number of the plurality of data blocks by performing erasure coding on one chunk included in the plurality of chunks.

5. The cloud DID agent of claim 1 , wherein

the memory stores a user private key, and

the action block file includes

an address value of a previous action block file, information on the plurality of actions executed, a time stamp and an electronic signature generated based on the user private key.

6. The cloud DID agent of claim 5 , wherein

the information on the plurality of actions executed includes an action type of each of the plurality of actions executed and data related to each action of the plurality of actions executed,

the address value of a previous action block file is a hash value of the previous action block file.

7. The cloud DID agent of claim 5 , wherein

the at least one processor is configured to

store the first hash value of the action block file in a storage space of the cloud DID agent and transmits the first hash value to the cloud agency.

8. The cloud DID agent of claim 1 , wherein

the memory stores

third party authority information, a user public key, and a user private key,

the at least one processor is configured to

verify a third party electronic signature included in a download action request through a blockchain network when receiving the download action request for the file from another mobile agent,

retrieve the third party authority information stored in the memory,

generate, based on a user private key and a third party public key, an encryption key, wherein the third party public key is acquired based on a third party DID included in the download action request,

encrypt the file based on the encryption key, and

transmit the encrypted file and a user DID to the another mobile agent.

9. The cloud DID agent of claim 8 , wherein

the third party authority information includes

whether or not a file download authority corresponding to the third party DID is granted.

10. A method for providing a cloud service, the method comprising:

receiving, by a cloud DID agent, an upload action request for a file from a mobile agent;

generating, by the cloud DID agent, an encryption key corresponding to the file in response to the upload action request and encrypting the file based on the encryption key;

generating, by the cloud DID agent, a plurality of chunks by dividing the encrypted file into a predetermined size;

generating, by the cloud DID agent, a plurality of data blocks corresponding to each of the plurality of chunks; and

executing, by the cloud DID agent, an upload action by distributing and transmitting the plurality of data blocks to a plurality of external cloud servers, by the cloud DID agent, so that the plurality of data blocks are distributed and stored in the plurality of external cloud servers

generating, by the cloud DID agent, an action block file for the plurality of actions including the upload action executed during a predetermined period;

transmitting, by the cloud DID agent, a first hash value of the action block file to a cloud agency; and

generating, by a cloud agency, an agency block file including the first hash value, and transmitting a second hash value of the agency block file to a blockchain network.

11. The method of claim 10 , further comprising:

receiving, by the cloud DID agent, a verification request for the action block file from the mobile agent;

acquiring, by the cloud DID agent, the first hash value from the action block file stored in a storage space of the cloud DID agent;

acquiring, by the cloud DID agent, the second hash value of the agency block file generated during the predetermined period from the blockchain network;

accessing, by the cloud DID agent, the agency block file based on the second hash value, and acquiring a third hash value of the action block file from the agency block file; and

comparing, by the cloud DID agent, the first hash value with the third hash value, and transmitting a response to the verification request to the mobile agent based on the comparison result.

12. The method of claim 10 , further comprising:

performing, by the cloud DID agent, erasure coding on one chunk included in the plurality of chunks wherein the one chunk is recovered based on a second number of data blocks among a first number of plurality of data blocks, and a first number is greater than the second number,

wherein a third number of data blocks smaller than the second number is stored in one external cloud server included in the plurality of external cloud servers.