The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Feb. 13, 2024
Filed:
Oct. 15, 2019
Nippon Telegraph and Telephone Corporation, Tokyo, JP;
NIPPON TELEGRAPH AND TELEPHONE CORPORATION, Tokyo, JP;
Abstract
A server device includes a memory and a processor to execute saving an encrypted text of a message generated by encrypting the message with a message key generated from a shared key and a group identifier, by using a message key identifier as an identifier of the message key as a key; saving an encrypted text of the message key generated by encrypting the message key to be re-encryptable by using the shared key, by using the message key identifier as a key; and receiving, after update of the shared key, a re-encryption key from a communication terminal that has generated the re-encryption key by using the shared key and the updated shared key, using the re-encryption key to generate a re-encrypted encrypted text of the message key, and overwriting the encrypted text of the message key before re-encryption with the re-encrypted encrypted text of the message key.