Inside SSL: accelerating secure transactions

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.