Onchecked

Onchecked relies on a smart contract and a web application to allow the attestation of two individuals "presence" by creating a cryptographic on-chain timestamp between them. This timestamp can only be created when two people co-sign it within a reasonable timeframe, ensuring they "saw" each other or were able to communicate with each other virtually.

The project relies in a smart contract that validates a blockhash co-signed by two individuals (wallets). If the blockhash matches one of the last 256 blocks, and the signature is valid for both wallets, then we emit an on-chain event showcasing a "proof-of-presence", i.e. that these wallets were able to agree on a signature in this timeframe. To craft the signatures, Onchecked uses a front-end to get the respective latest blocks, which are prompted to the users to sign upon request. Thanks to Covalent, we were able to quickly retrieve this on-chain events.

The Onchecked protocol was deployed to Polygon, Optimism, and Aurora's mainnet. For testing, we also used Mumbai's Polygon Testnet. These blockchains were crucial to test Onchecked, as the protocol relies in the block speed, so depending on which network it was used, the proof has different "liveness". E.g. in Aurora blocks are minted significally faster, so Onchecked's constrains (i.e. signature <256 blocks) are tighter than in Optimism.