/tags/pairing-groups/Recent content in Pairing Groups onHugo -- gohugo.ioTue, 08 Jul 2025 18:02:16 +0100/post/r3coin/Tue, 08 Jul 2025 18:02:16 +0100/post/r3coin/This challenge involves a blockchain-like system that uses a chameleon hash function for transaction integrity. The goal is to exploit the chameleon hash properties to forge a transaction “Selling|flag|x” that allows us to buy the flag. Mechanics The app lets up perform a set of actions to interact with the chain: Work: Gives us some money Buy Gift: Appends a “Buy” entry followed by a “Selling|gift|100” onto the chain Refund oldest: Turns the oldest “Buy” transaction into a “Work|x” entry by internally forging a satisfying hash.