Bytecoin is a privacy-focused peer-to-peer cryptocurrency implementation of CryptoNote.
Bytecoin is one of the first post-Bitcoin, privacy-focused cryptocurrencies that implements CryptoNote, also used by other privacy coins like Monero. The Bytecoin team believes Bitcoin's on-chain transactional privacy is insufficient for a widely used, peer-to-peer value transfer network.
Borrowing the CryptoNote white paper, Bytecoin implements one-time ring signatures which enable complete transactional unlinkability between network participants. Unlinkability is one of two primary transaction data privacy goals for Bytecoin, the other being untraceability. Bytecoin believes Bitcoin does not sufficiently, if at all, meet these privacy requirements, and they aim to build a protocol that does.