Software Puzzle: A Countermeasure to Resource-Inflated Denial-of-Service Attacks

Denial-of-service (DoS) and Distributed Denial of Service (DDoS) are dangerous to cyber-security, and client puzzle, which request a client to perform computationally very high operations before providing services from a server to client, is a well-known countermeasure to them. After all, an attacker can boost its capability of DoS/DDoS attacks with fast puzzle solving software and/or inbuilt graphics processing unit such like (GPU) hardware to extremely weaken the effectiveness of client puzzles. There are many system exist like Timelock puzzle, Client puzzle are used in this paper. In this paper, we study how to prohibit DoS/DDoS attackers from inflating their puzzle-solving capacities. To this end, we introduce a new client puzzle named as software puzzle. Unlike the existing client puzzle strategy, which publish their puzzle algorithms previously and generate software puzzle for each client request, a puzzle algorithm in the present software puzzle scheme is created only after threshold value of client request exceed which is accepted at the server side by using decision tree and the algorithm is generated such that 1) an attacker is not able to prepare an implementation to solve the puzzle previously and 2) the attacker needs extensive effort in translating a central processing unit puzzle software to its functionally equal GPU version such that the transformation cannot be done in real time.