Architecting Secure Prompt Caching (tinfoil.sh)

Tinfoil has launched a secure prompt caching feature within its Inference API, primarily aimed at reducing compute costs for users by leveraging cached inputs from previous inference requests. This enhancement, particularly beneficial for long-context tasks like coding, allows Tinfoil to maintain efficiency while addressing potential privacy concerns. Caching can introduce timing side channels that attackers could exploit to infer information based on processing speeds; thus, Tinfoil has implemented sophisticated measures to mitigate these risks, including a unique cache salting approach that protects user data from cross-user attacks. The caching mechanism works by storing preprocessed conversation history, allowing repeated interactions to leverage previously computed tokens, thus speeding up inference times and minimizing API costs. Tinfoil's architecture facilitates client-keyed cache salting, ensuring that cache data remains isolated from the infrastructure operator and enhancing security. The router is also designed to optimize cache usage by directing requests to appropriate model replicas based on cache keys. This combination of privacy-preserving technologies positions Tinfoil to support a new generation of private applications, particularly in high-context environments like coding agents.