End-to-end encryption security guarantees crucially rely on the assumption that the user has the correct identity public key for the person they wish to communicate with. Traditionally, E2EE communication systems have required the user to perform cumbersome manual checks to verify these keys, e.g. by physically scanning QR codes, or by verbally reading a fingerprint. In practice, these verifications are rarely performed.
Key transparency, first introduced in CONIKS, allows much of this verification to be automated. Roughly, the communication service provider regularly publishes a commitment to the identity key directory; this commitment must be publicly and consistently visible to all users. Every key request is accompanied by a proof that the key is correct w.r.t. the committed directory. Finally, the user’s device regularly monitors the committed directory to ensure that the user’s key is correctly reflected.
This talk will present the motivation for key transparency and introduce the approach and intuition behind the constructions. It will then overview the state of the art, survey current deployments, and discuss some areas of active research.
Speaker
Melissa Chase is a principal researcher in the Cryptography group at Microsoft Research, Redmond. Her research focuses on defining, constructing, and analyzing cryptographic protocols and primitives, with an emphasis on privacy-motivated applications. She has been at Microsoft for more than 15 years; her work has also formed the basis for systems deployed at Signal and WhatsApp. She has worked in a variety of areas within cryptography and privacy, including anonymous credentials, electronic cash, attribute-based encryption, and most recently problems in identity, transparency, and end-to-end encryption.
