arya's cryptography

Cryptography is an intriguing field. You can understand how a cryptographic primitive works with a few hours of research. But understanding why it is secure usually requires a PhD or two. While designing my own cryptographic primitive sounds like an awesome idea, I don’t think I’m knowledgeable enough about number theory to make something reliable. For now, I’ll stick to understanding existing primitives and applying them in interesting (but hopefully secure) ways.

keeping secrets

on September 21, 2024; by arya dradjica

My online identity comprises a number of accounts spread across dozens of websites and systems. They have different means of identity (e.g. usernames and e-mail addresses) and different modes of authentication (2FA, PIN codes, SSH keys, and traditional passwords). I’ve been using the pass tool to store the passwords for these. It’s a simple tool that follows the UNIX philosophy, storing every password in a separate GPG-encrypted file. It’s easy to understand and work with, and it comes with a number of useful integrations. However, I’ve been concerned about the fact that it doesn’t protect usernames or e-mail addresses—if an attacker can observe the password store, they can locate my accounts.

playing with uniqueness

on August 31, 2024; by arya dradjica

Daniel J. Bernstein has created a vast number of high-quality cryptographic primitives that have been accepted as state of the art, especially in pre-quantum cryptography. I was reading about the Ed25519 signature scheme when I noticed something interesting.

Ed25519 relies on a per-signature secret nonce, which is deterministically derived from the signer’s key and the message being signed. The rationale for not using a randomly generated nonce is that any collision (the signing of two different messages with the same nonce) will immediately reveal the secret key and compromise the system. Rather than trying to avoid this property, I’d like to examine it as a feature: there is at most one message for every nonce.