Mixnet

One type of mix network accepts as input a collection of ciphertexts, and outputs the corresponding plaintexts in a randomly permuted order. The main privacy property desired of such a mixnet is that the permutation matching inputs to outputs should be known only to the mixnet, and no one else. In particular, an adversary should be unable to guess which input ciphertext corresponds to an output plaintext any more effectively than by guessing at random.

Each server in the mixnet removes only one layer of encryption, so that only the last server knows a message's ultimate destination.

This issue of privacy in blockchain isn't new, and many ideas have been proposed, such as keeping the data off-chain and using zero-knowledge proofs (ZKPs) to prove we did the right computation (e.g., Aleo and Aztec) or using mixnets to anonymize transactions (e.g., Tornado Cash).