If you’re reading this after Matrix’s blog post, make sure you read the addendum to this one. Two years ago, I glanced at Matrix’s Olm library and immediately found several side-channel vulnerabilities. After dragging their feet for 90 days, they ended up not bothering to fix any of it. The Matrix.org security team also failed […]
Tag: ECDH
If you’re ever tasked with implementing a cryptography feature–whether a high-level protocol or a low-level primitive–you will have to take special care to ensure you’re not leaking secret information through side-channels. The descriptions of algorithms you learn in a classroom or textbook are not sufficient for real-world use. (Yes, that means your toy RSA implementation […]
Suppose you need to encrypt data between two peer-to-peer devices over an untrusted medium (i.e. the Internet), and you have an authenticated low-bandwidth channel that can be used to send and authenticate a few bytes (less than 100), but that channel isn’t itself encrypted (otherwise it’d be a chicken-and-egg problem). Aside: If it helps your […]
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Authenticated Key Exchanges
Authenticated Key Exchanges are an interesting and important building block in any protocol that aims to allow people to communicate privately over an untrusted medium (i.e. the Internet). What’s an AKE? At their core, Authenticated Key Exchanges (AKEs for short) combine two different classes of protocol. An authentication mechanism, such as a MAC or a […]