NOTE: The memo program and clients are now maintained at solana-program/memo.
A simple program that validates a string of UTF-8 encoded characters and logs it in the transaction log. The program also verifies that any accounts provided are signers of the transaction, and if so, logs their addresses. It can be used to record a string on-chain, stored in the instruction data of a successful transaction, and optionally verify the originator.
Full documentation is available at https://spl.solana.com/memo
The repository README contains information about program audits.