Pascal Schärli

Hi, I'm Pascal! Cryptography Engineer at ELCASecurity, privacy enjoyer and tinkerer. Here I write about Cryptography and Security. For shorter and more frequent posts see:

In-depth posts about cryptography and security. Short security news, published more frequently.
Thumbnail for Filen's password onion made me cry

Filen's password onion made me cry

Filen hashes passwords with MD5(MD4(MD2(pwd))). This post shows several cryptographic weaknesses in their protocol and questions if it's even worth doing end-to-end encryption delivered through a webpage.

Thumbnail for Post-Quantum Crypto Won't Fix Your Architecture

Post-Quantum Crypto Won't Fix Your Architecture

Adding PQC to this product was like installing a vault door on a tent. The server could intercept your keys and an RCE let attackers run code on your desktop.

Thumbnail for Proton's crypto is not Transparent and not OPAQUE

Proton's crypto is not Transparent and not OPAQUE

Proton says privacy "isn't a promise, it's mathematically ensured." I found new ways they could read your data anyway.

Thumbnail for Quantum Apocalypse?

Quantum Apocalypse?

NIST finalized their first post quantum secure cryptographic algorithms in August 2024. This post provides a gentle introduction and an intuition on the actual impact.

Thumbnail for Breaking Military Grade Encryption to Animate my Name

Breaking Military Grade Encryption to Animate my Name

Getting into the weeds of my flashy website banner, that simulates a padding-oracle attack on AES-CBC.

Thumbnail for Sharekey Cryptography Review

Sharekey Cryptography Review

During my master thesis I reviewed the cryptography of the end-to-end encrypted Sharekey collaboration app. This post covers the most interesting issues I found.

2026-11-10 Electron, we have a problem Many Electron apps auto-update without verifying signatures. Many also still trust the compromised eMudhra certificates. Together, that lets an attacker on your network install malware on your machine. 2026-08-17 Signal adds Key Transparency Signal Messenger just added Key Transparency (KT) for automatic key verification. It's good but a bit timid. I'm comparing their KT with the one used by Proton, where I disclosed some weaknesses earlier this year. 2026-04-07 33 Months to Q-Day The Post-Quantum cryptography timeline of industry leaders just went from "we have a decade" to "we have 33 months." Both Google and Cloudflare are now targeting 2029 for full post-quantum security, including authentication, not just encryption. 2026-02-27 What Comes After X.509 X.509 certificates have run the web for three decades. Quantum computers might be what finally kills them. Google announces they don't have immediate plans to add support for post-quantum secure X.509 certificates in Chrome in favor of a newer standard. 2025-07-03 When Giants Use Toothpicks Fireblocks is a digital asset custody platform, protecting trillions of dollars. During a security review at work I found how they protect their 4096-bit RSA 'disaster recovery' keys for customers with 2 rounds of MD5. 2020-12-01 ETH Study Materials Welcome to my collection of ETH Zürich study materials. As a former tutor at ETH, I've created resources for two Computer Science courses in the Electrical Engineering and Mechanical Engineering bachelor programs.