Anonymity of Cryptocurrencies Part II – Cryptonote & Darkcoin

Although total anonymity is not feasible at the moment, a lesser form of high security may be. Cryptonote-based currencies can use ring signatures, as opposed to group signatures which require a trusted party. Each transaction with Bitcoin has a public key tied to it which requires a small script to be produced to spend the output using that key.
Anonymity of Cryptocurrencies Part II – Cryptonote & Darkcoin