What is Mina Protocol Network
The first cryptocurrency ever developed using succinct blockchain technology, Mina Protocol (formerly Coda Protocol) offers payment functionality similar to Bitcoin, with a dramatically faster verification time of 200ms making it practical for lightweight clients and mobile devices to perform full verification of the system’s history. Mina’s goal is to design a decentralized payment system that offers efficient verification of system history from genesis without relying on any external advice. Specifically, they aim to provide a verification time constant in the number of transactions, called a succinct blockchain by including succinct proofs of state validity in each block. In particular, Mina uses an account-based model like Ethereum. Instead of the UTXO model like Bitcoin and others where the current state of the blockchain is a list of all account balances rather than a list of unspent coins. Each block contains a commitment to this state (in a Merkle tree) and not the entire state. So a full node doesn’t need to store the entire state but can verify account balances just as efficiently, with only the information in the latest block header. However, a prover in the system (roughly equivalent to a miner in Bitcoin) does need to store the full state since it is part of the witness when proving the validity of new blocks.
Mina’s Consensus Protocol
The consensus protocol of Mina is developed as the first provably-secure proof-of-stake (PoS) consensus protocol for succinct blockchains called “Ouroboros Samasika”. Note that an off-the-shelf consensus mechanism is not necessarily compatible with a succinct blockchain framework, since the way consensus is achieved when there are multiple contending chains could rely on arbitrary transaction history, forcing nodes to store the entire transaction history. In fact, this is a natural approach for consensus mechanisms, since the information needed to tell apart an honest chain from a dishonest one is likely to involve details at the point of the fork. Since it is possible for a party to learn about a fork long after it occurred, it may need to store the entire history to assist in the chain selection process. This is indeed the case in known PoS consensus mechanisms that rely on a trusted external party for bootstrapping. In the current implementation, a state proof size is just 864 bytes, and takes around 200ms to verify it. Making any device that can support this level of computation, like current smartphones, able to verify the current state of the system with no trusted party.
Mina for Payments
With Mina, no matter how much the usage grows, the blockchain always stays the same, about the size of a few tweets. This means participants can quickly sync and verify the network. Made possible due to SNARKs, a type of cryptographic zero-knowledge proof. Each time a Mina node produces a new block, it also generates a SNARK proof verifying that the block was valid. All nodes can then store the small proof, as opposed to the entire chain. By not having to worry about block size, the Mina protocol enables a blockchain that is decentralized at scale. Given Mina’s lightweight design and the off-chain nature of Mina’s zkApp smart contract computations, it’s easy to use the Mina proof system from other chains. There is currently work being done…
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