Bitcoin is the first implementation of a concept called "cryptocurrency", first described in 1998 by Wei Dai in the cypherpunks mailing list, suggesting the idea of a new form of money that uses cryptography to control manufacture and transactions, instead of using centralized authority. The first Bitcoin specification and proof of concept were published in 2009 in a cryptographic mailing list by Satoshi Nakamoto. Satoshi left the project at the end of 2010 without telling much about him. Bitcoin is publicly publicized and developers from around the world can review the code or create their own modified version of Bitcoin software.