Authentication of LINE Chat History Files by Information Hiding

Abstract

With the prevalence of smartphones, message exchanges via mobile chatting programs like LINE have become popular. The messages in the form of chat records in a LINE chat history, after being downloaded for legal uses, might be tampered with illicitly. A novel method for authenticating the chat history against such attacks is proposed. The signal used for authenticating each chat-record segment is created by concatenating the ID label of the segment and a digest yielded by hashing the segment content. The signal is then encoded by three types of spacing code, namely half space, full space, and tab, and embedded into the blank-space areas created by the tab codes in the chat records of the segment. Authentication of a history file is accomplished by extracting the authentication signals embedded in the file and comparing them with the original signals computed directly from the file. The embedded signals are invisible, arousing no suspicion from the hacker. The signals are fragile, because any modification of the records can be detected by the authentication process. Experiments for testing four types of tampering with text files of four languages have been conducted, yielding correct authentication results that show the feasibility of the proposed method.