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There is a tempting idea in cryptographic design: take individual hash outputs and XOR them together. It is simple, fast, and incremental — if one input changes, you just XOR out the old hash and XOR in the new one. No need to recompute the whole thing. The problem is that XOR hashing is broken. […]

1. Introduction — The Hidden Thread Between Math and Privacy If you’re reading this, chances are you’ve used encryption today — probably without realizing it. Every time you send a message, check your email, or make a blockchain transaction, your data is protected by math. But not just any math — it’s protected by problems

1. Introduction In June 2025, ResupplyFi — a lending protocol integrated with the Convex and Yearn ecosystems — suffered a devastating exploit that drained approximately $9.8 million in under 90 minutes. The attacker leveraged a classic ERC-4626 “donation attack” combined with a flawed vault implementation to manipulate the exchange rate of vault shares, turning a

Deep Dive into Storage Collisions, Multicall Exploitation, and Proxy Vulnerabilities Introduction Ethernaut, created by OpenZeppelin, is more than just a collection of Solidity puzzles. It is a security playground designed to replicate real-world vulnerabilities often found in decentralized applications. Among these challenges, Puzzle Wallet stands out as one of the more advanced levels because it

Uniswap v2 and the Magic of Automated Market Makers In the fast-moving world of decentralized finance (DeFi), one innovation stands out as a true game changer: the Automated Market Maker (AMM). Instead of relying on centralized exchanges or human market makers, AMMs use algorithms and smart contracts to set prices, hold liquidity, and execute trades