US 12,093,215 B2
Management server, document file management system, document file management method, and document file management program
Yoshikuni Nakamura, Miyazaki (JP)
Assigned to SKYCOM CORPORATION, Tokyo (JP)
Appl. No. 17/311,342
Filed by SKYCOM CORPORATION, Tokyo (JP)
PCT Filed Nov. 26, 2020, PCT No. PCT/JP2020/043984
§ 371(c)(1), (2) Date Jun. 6, 2021,
PCT Pub. No. WO2021/106995, PCT Pub. Date Jun. 3, 2021.
Claims priority of application No. 2019-214608 (JP), filed on Nov. 27, 2019.
Prior Publication US 2022/0283987 A1, Sep. 8, 2022
Int. Cl. G06F 16/11 (2019.01); G06F 16/13 (2019.01); G06F 16/93 (2019.01); H04L 9/00 (2022.01); H04L 9/32 (2006.01)
CPC G06F 16/122 (2019.01) [G06F 16/137 (2019.01); G06F 16/93 (2019.01); H04L 9/3236 (2013.01); H04L 9/50 (2022.05)] 22 Claims
OG exemplary drawing
 
1. A management server connected to an information terminal device and a blockchain network for storing a hash value, a file size, and a non-hashed document file ID each time a PDF file is registered via a network, the management server comprising:
a reception unit that receives, from the information terminal device, a PDF file for adding to an original document, an updated content of the original document as incremental update in the order of update;
a hash value calculation unit that calculates a hash value of the PDF file received by the reception unit;
a document file ID acquisition unit that checks whether a non-hashed document file ID exists on the PDF file received by the reception unit, wherein said document file ID acquisition unit acquires_the non-hashed document file ID and uses the non-hashed document file ID to identify the PDF file if the non-hashed document file ID is included in the PDF file received by the reception unit, and wherein said document file ID acquisition unit creates and includes a new non-hashed document file ID to the PDF file received by the reception unit and transmits a copy of the PDF file back to the information terminal device to replace the PDF file on the information terminal device if the non-hashed document file ID is not included in the PDF file received by the reception unit;
a hash value acquisition unit that uses the non-hashed document file ID from the document file ID acquisition unit to acquire from the blockchain network to which a block storing the hash value of the PDF file, the non-hashed document file ID, and a file size of the PDF file in association with each other is registered each time the PDF file is updated, a hash value and a file size stored in a latest block among blocks storing the non-hashed document file ID acquired by the document file ID acquisition unit;
a tampering determination unit that determines whether the PDF file received by the reception unit is tampered, by determining whether the hash value calculated by the hash value calculation unit matches the hash value acquired by the hash value acquisition unit and by determining whether a file size of the PDF file received by the reception unit matches the file size acquired by the hash value acquisition unit; and
a transmission unit that transmits a determination result obtained by the tampering determination unit to the information terminal device.