July 22, 2026
Proof is in the pudding fight
Introduction to Formal Verification with Lean Part 1
Math nerds are obsessed, newbies are confused, and everyone wants Lean to be less painful
TLDR: The article introduces Lean through a beginner-friendly cryptography tutorial that teaches computers to check proofs instead of humans just hoping they’re right. Commenters were split between hype, confusion, and setup horror stories, with fans calling Lean the future and frustrated newcomers asking why it feels so hard to use.
A new tutorial is trying to make proof-checking software feel less scary by teaching readers how to use Lean, a language that can turn math-style reasoning into code and then check whether it’s actually correct. The hook is unexpectedly spicy: instead of staying in pure classroom land, it uses a famous secret-message method called the One-Time Pad as the fun example. In plain English, it’s a beginner-friendly attempt to show cryptography fans how to get a computer to verify a proof instead of just trusting scribbles on paper.
But the real show is in the comments, where the crowd instantly split into familiar internet tribes. One camp was all-in, calling Lean “super cool” and linking bonus reading like they’d just discovered the world’s nerdiest fan club. Another commenter went full future-gazer, arguing that tools which catch mistakes before a program even runs could become huge, especially when paired with AI. That’s the hype machine talking.
Then came the newbie panic. One person asked the brutally relatable question: how is this any different from just using assert in Python? Oof. Another admitted they bounced off Lean entirely because getting it installed and the extra pieces working was a nightmare. Even a recommendation for a Lean book came with a mini side plot: great author, but the reading experience was bad enough to kill the vibe. So yes, the tutorial is being praised as fun and useful — but the comment section’s verdict is clear: people love the idea of Lean, and also kind of want Lean to stop making them suffer.
Key Points
- •The article introduces formal verification as a method for machine-checking mathematical proofs and uses Lean as the tutorial’s focus.
- •The tutorial is aimed at cryptographic engineers and uses the One-Time Pad protocol as the main worked example for formal verification.
- •Lean is described as both a theorem prover and a pure functional programming language created in 2013 by Leonardo de Moura at Microsoft Research.
- •The tutorial draws its cryptographic definitions and proofs from Dan Boneh and Victor Shoup’s *A Graduate Course in Applied Cryptography*.
- •The material is written in Lean 4 and includes hands-on setup guidance, simple `#eval` examples, and core syntax concepts such as function application and first-class functions.