SSL splitting and barnraising : cooperative caching with authenticity guarantees

Abstract

SSL splitting is a cryptographic technique to guarantee that public data served by caching Web proxies is endorsed by the originating server. When a client makes a request, the trusted server generates a stream of authentication records and sends them to the untrusted proxy, which combines them with a stream of data records retrieved from its local cache. The combined stream is relayed to the client, a standard Web browser, which verifies the data's integrity. Since the combined stream simulates a normal Secure Sockets Layer (SSL) [7] connection, SSL splitting works with unmodified browsers; however, since it does not provide confidentiality, it is appropriate for applications that require only authentication. The server must be linked to a patched version of the industry-standard OpenSSL library; no other server modifications are necessary. In experiments replaying two-hour access.log traces taken from LCS Web sites over a DSL link, SSL splitting reduces bandwidth consumption of the server by between 25% and 90% depending on the warmth of the cache and the redundancy of the trace. Uncached requests forwarded through the proxy exhibit latencies within approximately 5% of those of an unmodified SSL server.