Archive - Arsen

How to hack a Bitcoin light client?

Three merkle proofs verify the structure. The fourth check is a substring search on a field the miner fills in by hand.

Sep 7 • Arsen

August 2026

How to get wrecked via Solana RPC.

An off-chain service asked the chain how an account was created. Anyone could change the answer for one lamport, and the whole backfill queue stalled.

Aug 31 • Arsen

How Correct Code Loses Money

Every function did exactly what it was written to do.

Aug 21 • Arsen

February 2026

Ignore 85% of the code if you want critical bugs

New codebase? The question must be: How do I find the 5% of code that can kill the protocol?

Feb 8 • Arsen

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