POS Consensus Paradigm Shift? APOS? better than POS ?

Seabook Chen
Nov 6 · 6 min read

Recently I was invited to have a look at an upcoming block-chain project called Marco-Polo Chain or Marco-Polo Protocol (MAP). In their drafted white paper, they mentioned an improved POS consensus called Asset POS a.k.a APOS. In today’s article, we will have a deep dive into their APOS system and see whether this could be a trend in the future POS Consensus based block-chain system.


First, let’s have a quick cap about POS consensus. Differ to POW, which consume extreme amount of power to resolve a difficult mathematical problem. POS is based on Staking, yes, the key word here is staking. To simulate the stake-based Validator (in POS, we call them validator rather than miner) selection process, the Follow-the-Satoshi (FTS) algorithm has been adopted in many PoS based block-chain networks such as Cardano, Dash etc.

The probability Ρi that node i is selected to be the Validator in a network of N participants is

where Si is the stake of participant i. This means that the more stake a node holds, the higher chance it is selected to be the Validator. And the Validator get the coin rewards of course.

See the following picture for easy understanding.

Then on top of the common POS, EOS, a popular blockchain project, “invented” a DPOS consensus, Delegated POS system. So in EOS eco system, globally there are 21 Validators or Super Nodes (they call them selves). So every participants I mean you and me normal guys, who owns EOS tokens need to stake on those Candidates who are competing for 21 Super Nodes, this process called Election, much like choose a Member of Parliament in real social life. The most powerful or popular 21 Nodes become the Super Nodes and they take in turn to validate the blocks and of course they get huge EOS coins as reward.

I think this is more like an mining pool in the POW word, only those big players get big profits.


Now let’s talk about a new improved POS, APOS, Asset based Proof of Stake. This is a new concept from the white paper of MAP block-chain project. Before we dive into what’s APOS, I think we need to understand what’s the purpose of MAP project and what issues the MAP try to resolve.

MAP itself wants to create a new peer to peer cash system, much like Bitcoin, but in a multiple coin interchangeable fashion. So basically you can think of multiple crypto currency trade settlement in MAP main chain. A good analogy is if we do business trade between Canda and Australia, then the settlement currency should be local currency, however in the middle the USD will be the exchange currency and using SWIFT system to do the conversion.

Of course, the MAP also claim itself support Smart Contract and each Dapp will be in their own block-chain system. We will dig into this in future articles.


So naturally it makes sense if I can use BTC to stake, or if I have ETH, then I should use ETH to stake, or in the future in MAP ecosystem, they can create their own tokens. I want be able to use those tokens to stake. That is where the Asset comes into the picture, so in a nut shell, you can use any supported coins to stake in MAP blockchain system.

I thoroughly discussed with MAP leading block-chain architect designer, the APOS consensus is happening in following steps:

  • If you think you have the right block-chain resources (hardware, network speed, bandwidth) + enough staking, you can apply for Candidates. (this is a bit like EOS candidates)
  • Choose your own favorite coin to stake on those candidates, initially will support BTC and MAP (as native coin in MAP ecosystem).
  • 100+ number of candidates will be elected as Block Validators, the team hasn’t decided how many Validators in total will happen in the MAP ecosystem, but it’s confirmed they want MAP to be more decentralized.
  • Then if the elected Validators being dishonest, then a process called SLASHING will happen, basically the staking on those dishonesty nodes will be diminished, so the new candidates will be able to be elected as Validator. Also every 10–15 mins, there is a re-election happen.
  • The validators take round-robin like algorithm to produce blocks turn by turn and get rewarded in MAP coins.
  • Then I believe there is a smart contract built in to allocate the rewards to every coin stakers such as you and me (small investors or participants)

For easy understanding, please refer the following diagram:

In the diagram, every actor or normal Joe, can stake on their prefered Candidates by using MAP, BTC or ETH (Multi Assets), then the candidates get elected to Validator, The red-ish (stands for dishonesty node) Validator 100+ will be de-elected in the next cycle and the stakes on it will be decreased.


So what’s the advantages and concerns with APOS?

Some biggest advantages are:

  • More people can be involved, you dont have to force yourself to get MAP token, as long as you have other main stream tokens, you are part of MAP APOS ecosystem
  • It can protect your assets, very often, eg. EOS, you need to exchange your BTC or ETH to EOS before you can be part of EOS eco system, due to the extreme volatility in Crypto Market, your BTC / ETH to EOS maybe a very bad decision. In APOS system, you still get keep you original BTC and ETH, just staked somewhere, this is actually a good way to be a HODLER.

Some concerns or questions

  • How does MAP determine the Stake Rate? What’s the weight of BTC and ETH in staking system? This should be constantly balanced, does that mean the staking value is changing all the time? Who decide the staking weight system? Is it based on exchange rate?
  • How do you secure those tokens? I imagine the MAP token can be secured in a smart contract on MAP chain, but what about Bitcoins and ETH? Is it in a separate smart contract system? How does the interchangeability work?
  • How to make it easy to use and not get confused by end user? I imagine need a special wallet to do this? or a smart contract like what EOS did? It’s vastly complicated to switch between different coins with variations of prices and staking weight.

In summary, it’s definitely a nice way to use your cold storaged BTC or ETH to stake some of the latest blockchain projects and get some rewards, but how to make it fair, secure, transparent, easy-to-use still remain a question. I guess we shall wait and see.

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