receiving, from a user of the document sharing system via a user interface of the document sharing system, a request for sharing a page of a document and automatically performing a keyword check for the requested page, wherein the keyword check corresponds to a checking of a keyword that is any one of one or more words registered with the document sharing system before the keyword check is automatically performed;

providing, to the user via the user interface of the document sharing system, a result of the keyword check for the requested page;

generating a token for the keyword extracted from the requested page as the result of the keyword check, and performing a locking process for the requested page using the token; and

determining a target page among at least one requested page for sharing, and designating a sharing target with which the target page is to be shared;

determining a lock processing method according to an attribute of the keyword; and

identifying, to the user via the user interface of the document sharing system, an importance of the target page or the sharing target based on the determined lock processing method,

wherein the token corresponds to the extracted keyword,

wherein the token is an authentication token for granting access permission to or for the locking process for the requested page, and

wherein the authentication token is based on an open standard protocol for authentication.