namecoin

Namecoin is a decentralized key/value registration and transfer system
based on Bitcoin technology (a decentralized cryptocurrency).
It can be used for multiple purposes, for example a secure and
censorship resistant replacement for DNS. Ownership of a name
is based on ownership of a coin, which is in turn based on public key
cryptography. The namecoin network reaches consensus every few minutes
as to which names have been reserved or updated.