Aleo is a Layer-1 blockchain built from the ground up for private applications, using zero-knowledge proofs to enable private and public state within smart contracts. Its design originates from the 2018 ZEXE research (decentralized private computation) and implements an optimized zk-SNARK scheme called Varuna (an iteration of Marlin) to prove transactions. Transactions on Aleo can have encrypted inputs/outputs, and only validity proofs (succinct zero-knowledge proofs) are posted on-chain, preserving confidentiality.