Improving SSL Server Performance While Preventing DOS Attack Using Reverse SSL with Client Puzzle

Secure communication is an intrinsic requirement of today’s world of on-line transactions. SSL and its variant TLS are most widely acceptable protocol to create secure connection between the client/server communicating applications. Although SSL provides confidentiality, integrity of data and authentication of the communicating parties but imposes overhead on web server to perform costly cryptographic operations. Therefore it degrades the secure server performance compare to an insecure web server. Moreover an attacker can take dvantage of this overhead and can run automated scripts to generate bulk of requests, each request requires server to perform some costly computation therefore cause denial of service attack on server. So DOS makes highly desirable to improve performance of the SSL handshakes. This paper focuses on Reverse SSL approach with client puzzle to improve server performance.Reverse SSL is an extension of SSL that alleviate the performance cost at server by exchanging role of client and server. Reverse SSL combined the client puzzle to prevent DOS attack. The purpose of paper is to show how the Reverse SSL with client puzzle can be implemented using openssl library and how it improves server performance while preventing the DOS attack.