Inside SSL: accelerating secure transactions

Abstract

By defining a protocol that supplies Web clients and servers with cryptographic parameters, the Secure Sockets Layer protocol enables the safe exchange of sensitive data, a crucial aspect of any e-business. The protocol's sticking point is that encrypting and decrypting data requires a tremendous amount of CPU processing power. The burden is especially apparent on the server side, because multiple Web clients often connect to a single Web server. For e-commerce transactions, it's important to implement SSL in a way that doesn't overburden your Web server's CPU and slow down the entire operation. Although the original Web servers that supported SSL did so exclusively in software, SSL adapter cards soon became available to help off-load the server's CPU load and increase performance. Today, content switches with SSL accelerators can encrypt and decrypt data at the network edge, eliminating the need for a Web server's CPU to perform any SSL-related calculations. The article focuses on the relative merits of these newer implementations. A look at the original software-only approach and its drawbacks clarify the reasons that hardware acceleration for SSL became necessary.