Swift is a new, principled approach to building web applications that are secure by construction. Web applications are hard to build because code and data need to be partitioned to make them responsive. They are also hard to build because code and data need to be partitioned for security. Currently there are no good methods for deciding when it is secure to move code and data to the client side.

Because of the connection (and tension) between the problems of security and interactive performance, Swift addresses both at once, automatically partitioning application code while providing assurance that the resulting placement is secure and efficient.

In the Swift approach, application code is written in the Jif language, a Java-based language that includes information security policies. The source code is automatically partitioned into JavaScript code running in the browser, and Java code running on the server. For interactive performance, code and data are placed on the client side where possible. Security-critical code is placed on the server and user interface code is placed on the client. Code placement is constrained by high-level, declarative information flow policies that strongly enforce the confidentiality and integrity of server-side information. The Swift compiler may also choose to replicate code and data across the client and server, with benefits for both security and performance.

Example Swift applications

• Guess-a-number (see current release for source code)

Related publications