In many computer systems today, an attacker that breaks one system component can steal data from millions of users. In this talk, I will present three systems that can withstand component compromise. I will describe (1) a single sign-on system that protects user security and privacy from a compromised single sign-on server, (2) a secure-hardware-based backup service that protects user backups from compromised secure hardware devices, and (3) a web search engine that protects user queries from a compromised search engine. These systems provide strong security and privacy properties while taking into account practical constraints such as compatibility requirements, hardware limitations, and user expectations. Each splits user secrets across different system components, using new cryptographic tools to provide necessary functionality while protecting user data.