Honey chatting: A novel instant messaging system robust to eavesdropping over communication

There have been many efforts to strengthen security of Instant Messaging (IM) system. One of the typical technologies is the conventional message encryption using a secret or private key. However, the key is fundamentally vulnerable to a brute-force attack, causing to acquire the original message. In this respect, a countermeasure was suggested as the way to generating plausible-looking but fake plaintexts, which is called Honey Encryption (HE). In this paper, we present a HE-based statistical scheme and design a Honey Chatting application, which is robust to eavesdropping. Besides, we verify the effectiveness of the Honey Chatting by comparing the entropy of decrypted messages through experiments.

1. Introduction

Nowadays we frequently use Instant Messaging (IM) system for communication. While it provides us convenience to interact with others, there exist some side effects like an invasion of privacy through eavesdropping. Thus, popular IM systems such as Telegram and Threema have strengthened their security by message encryption. It makes the message unreadable to anybody except the sender and the receiver. However, it is still weak in a brute-force attack because the security of cryptosystem depends on the key size which has potential vulnerability to be cracked. There are 2ⁿ possible keys with a n-bit key, so the attacker needs to try 2¹²⁸ operations for cracking 128-bit key. In the case of Password based encryption (PBE), the necessary number of operations for cracking the key are much less by the fact that user-chosen passwords are tend to be weak, which results in the small key space.