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Original, edited content. The "real" blog.filippo.io posts.

Using Ed25519 signing keys for encryption

@Benjojo12 and I are building an encryption tool that will support SSH keys as recipients. For Ed25519 keys that requires converting points between different elliptic curves. Let's see why and how.…

A Go implementation of Poly1305 that makes sense

Cryptography code could be understandable if only we commented it. This Poly1305 implementation is an attempt to prove it. It should be readable with just an idea of what MACs are for, a beginner level of Go, and high school math.…

The scrypt parameters

The recommended scrypt parameters in the Go docs were recently brought up for discussion given they haven't changed since 2009. Even if at this point I memorized the three numbers (N=16384, r=8, p=1) I only have a vague understanding of their meaning, so I took some time…

We need to talk about Session Tickets

More specifically, TLS 1.2 Session Tickets. Session Tickets, specified in RFC 5077, are a technique to resume TLS sessions by storing key material encrypted on the clients. In TLS 1.2 they speed up the handshake from two to one round-trips. Unfortunately, a combination of deployment realities and three…

A secure captive portal browser with automatic DNS detection

Captive portals are the worst. Flaky detection. The OS and browser try to detect these annoying network features but fail quite often, leaving you with broken connections. DID YOU KNOW that probe-based captive portal detection really doesn't work very well, with ~30% FP *and* ~30% FN rate in…