The Mina Protocol blockchain has a record: that of being the lightest blockchain. In fact, it weighs only 22 kB (kilobytes). If you have a full node for Bitcoin, you will need to download over 460 GB (gigabytes) for synchronization. In 2012 and 2013, when the Bitcoin network was still little used, it already weighed more than 1 gigabyte. Mina's full node is therefore within everyone's reach and no storage space or high speed internet connection is required.

It is also possible to download it on a smartphone. Mina is a fork of Cardano's Ouroboros so it is a proof of stake with delegation but modified with an unlimited number of block producers. The blockchain weighs so little, thanks to the use of zk proofs (in particular zk-SNARKS), this obviously leads to a huge decentralization because, as mentioned, expensive hardware features are not required. Zk proofs (zero knowledge) are certificates of validity for transactions and blocks: basically it is as if screenshots (photos) were taken that demonstrate the existence of data (transactions in this case). Obviously all of this needs proof of validity. All these zk proofs are also recursive: each certificate of authenticity has another certificate. You think that it is as if you photograph an object to prove that I have it and then at the photo, you take another photo. Basically there are:

-Snark producers: take snapshots (snarks) of transactions and send them to block producers. These people are encouraged to do this because they are paid through a rebate auction system: the block producer will choose who offers the least, therefore snark producers will tend to lower the price.
-Block producers (validators): they create blocks with transactions and send snapshots to verifiers (it is a snapshot of a snapshot). In reality these validators can also produce snarks by themselves, without buying them from snark producers but it is more tiring to do everything in first person. The incentives come from staking rewards. In this case the requirements are very high (you need to have a lot of Mina) and a client of about 100 MB (this is not a problem!). There are around 240 validators to date
-Verifiers: check the snapshots that come from block producers and add the transaction to the block, if it is not malicious

THE SCALABILITY AND SECURITY PROBLEM
One of the problems with this architecture is scalability: the blockchain supports 25-30 TPS, due to the complexity of producing zk proofs. A transaction is finalized after 15 confirmations. Each confirmation takes place after about 4 minutes so the finalization of the transaction takes about 1 hour (similar to Bitcoin). Another possible problem could be security if the blockchain crashes, in this case it would be necessary to access the archive node. As we said earlier, this blockchain is lightweight because it shows snapshots of information, without showing them directly. The archive nodes are located on the data center and contain all real transactions and not snapshots. In a nutshell, the chain is as if it had a "copy" of itself, useful for retrieving the data, should the need arise.

SNAPPS: DAPPS ON MINA, WITHOUT SMART CONTRACT
However, this technology, in addition to streamlining and voiding the weight of the blockchain, also guarantees privacy (everything is encrypted).
Through this protocol (which does not support smart contracts) it is still possible to create snApps, obtaining data from the web and demonstrating them on chain. That is to take data online and bring it on-chain, via sk (without showing it directly but having proof of possessing it). One of the use cases are privacy-based applications, i.e. implementation of digital identities (login data) that would ensure a good level of privacy, voting systems (protecting voters' choices) and any financial system that handles sensitive data. The operation of this blockchain is very complex: it is based on snapshots of snapshots and works similar to an oracle for snapps. As a curiosity, "World Mina Day" was celebrated on February 2, 2022

(2/2/2022, clear reference to Mina's 22 kB!)

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