Ring Confidential Transactions (RingCT)

Ring Confidential Transactions, usually shortened to RingCT, is a privacy method used by Monero to hide how much is being sent in each transaction. It combines two older ideas: ring signatures, which hide which of several possible coins is being spent, and confidential transactions, which replace visible amounts with cryptographic commitments. Nodes can still check that the inputs and outputs of a transaction balance and that no amount is negative, so no coins are created from nothing, without learning the actual figures. RingCT was proposed in 2015 and activated on Monero in a January 2017 network upgrade, becoming mandatory for transactions later that year. A shorter proof system called Bulletproofs, adopted in 2018, later cut transaction sizes and fees sharply. RingCT is one reason Monero is classed as a privacy coin and has been delisted by some exchanges. Also see zero-knowledge proof.