Amazon this week filed a US patent for a Proof-of-Work system which uses cryptography to generate Merkle trees. The Bitcoin and Ethereum networks use such ‘hash trees’ to verify the content of large data structures.
A Merkle tree is a fundamental component of a blockchain, whereby each non-leaf node is a hash of its respective child nodes. In Amazon’s patent, the generation of a Merkle tree could fulfill a challenge, allowing access to a computing resource. From the abstract: