Shulou(Shulou.com)06/02 Report--

PoS, or Proof of Stake, is translated as proof of interest.

No matter PoW or PoS, it can be understood as the question of "who is qualified to write blockchain".

PoW proves that he is qualified to write blockchain by arithmetic, while PoS proves that he is qualified to write blockchain by the age of currency he owns.

Advantages and disadvantages of PoW

PoW, whose advantage is reliable and widely used, is a public chain consensus algorithm that has been fully tested in practice.

But its disadvantages are also obvious:

1. It consumes too much extra power, that is, a lot of energy.

2. A large amount of capital is invested in mining machines, which leads to the centralization of computing power, with a security risk of 51%.

The proposal of PoS and counting coins

The first virtual coin based on PoS is the dot coin.

In view of the shortcomings of PoW, Sunny King proposed PoS in 2012 and released dot coin PPCoin based on the hybrid mechanism of PoW and PoS.

In the early stage, PoW mining and currency distribution were used to ensure fairness. In the later stage, the PoS mechanism is used to ensure network security, that is, it is more difficult to own 51% currency, so as to prevent 51% security.

The core concept of PoS is currency age, that is, the time it takes to hold money. For example, if you have 10 coins and hold them for 90 days, you will have a currency age of 900 yuan days.

In addition, the use of currency means the destruction of the age of the currency.

There is a special transaction in PoS called interest coin, in which the holder can consume the age of the currency to earn interest, as well as the priority to generate blocks for the network and PoS coins.

The PoS implementation principle of Dot Coin

The PoS proof formula for dot coins is as follows:

Proofhash

< 币龄x目标值 　　展开如下： 　　hash(nStakeModifier + txPrev.block.nTime + txPrev.offset + txPrev.nTime + txPrev.vout.n + nTime) < bnTarget x bnCoinDayWeight 　　其中proofhash，对应一组数据的哈希值，即hash(nStakeModifier + txPrev.block.nTime + txPrev.offset + txPrev.nTime + txPrev.vout.n + nTime)。 　　币龄即bnCoinDayWeight，即币天，即持有的币数乘以持有币的天数，此处天数最大值为90天。 　　目标值，即bnTarget，用于衡量PoS挖矿难度。目标值与难度成反比，目标值越大、难度越小；反之亦然。 　　由公式可见，持有的币天越大，挖到区块的机会越大。 　　peercoin-0.6.1ppc中PoS证明计算代码如下： bool CheckStakeKernelHash(unsigned int nBits, const CBlockHeader& blockFrom, unsigned int nTxPrevOffset, const CTransaction& txPrev, const COutPoint& prevout, unsigned int nTimeTx, uint256& hashProofOfStake, bool fPrintProofOfStake){ if (nTimeTx < txPrev.nTime) // Transaction timestamp violation return error("CheckStakeKernelHash() : nTime violation"); unsigned int nTimeBlockFrom = blockFrom.GetBlockTime(); if (nTimeBlockFrom + nStakeMinAge >

NTimeTx) / / Min age requirement return error ("CheckStakeKernelHash (): min age violation"); / / the target value uses nBits CBigNum bnTargetPerCoinDay; bnTargetPerCoinDay.SetCompact (nBits); int64 nValueIn = txPrev.vout.n] .nValue / / v0.3 protocol kernel hash weight starts from 0 at the 30-day min age / / this change increases active coins participating the hash and helps / / to secure the network when proof-of-stake difficulty is low int64 nTimeWeight = min ((int64) nTimeTx-txPrev.nTime, (int64) STAKE_MAX_AGE)-(IsProtocolV03 (nTimeTx)? NStakeMinAge: 0); / / calculate currency age, STAKE_MAX_AGE is 90 days CBigNum bnCoinDayWeight = CBigNum (nValueIn) * nTimeWeight / COIN / (24 * 60 * 60); / / Calculate hash CDataStream ss (SER_GETHASH, 0); / / weight correction factor uint64 nStakeModifier = 0; int nStakeModifierHeight = 0; int64 nStakeModifierTime = 0 If (IsProtocolV03 (nTimeTx)) / / v0.3 protocol {if (! GetKernelStakeModifier (blockFrom.GetHash (), nTimeTx, nStakeModifier, nStakeModifierHeight, nStakeModifierTime, fPrintProofOfStake)) return false; ss GetBlockTime ()-pindexPrevPrev- > GetBlockTime (); / / ppcoin: target change every block / / ppcoin: retarget with exponential moving toward target spacing CBigNum bnNew; bnNew.SetCompact (pindexPrev- > nBits) / / STAKE_TARGET_SPACING is 10 minutes, that is, 10 * 60 / / the target interval between the two blocks is 10 minutes int64 nTargetSpacing = fProofOfStake? STAKE_TARGET_SPACING: min (nTargetSpacingWorkMax, (int64) STAKE_TARGET_SPACING * (1 + pindexLast- > nHeight-pindexPrev- > nHeight)); / / nTargetTimespan is one week, that is, 7 * 24 * 60 * 60 / / nInterval is 1008, that is, when the block interval is 10 minutes, 1008 blocks are generated in a week int64 nInterval = nTargetTimespan / nTargetSpacing; / / calculate the current block target value bnNew * = (nInterval-1) * nTargetSpacing + nActualSpacing + nActualSpacing) BnNew / = (nInterval + 1) * nTargetSpacing); if (bnNew > bnProofOfWorkLimit) bnNew = bnProofOfWorkLimit; return bnNew.GetCompact ();} / / Code location src/kernel.cppPoS 2.0 and black currency

In order to further strengthen the security of PoS, rat4 (Pavel Vasin) proposed PoS 2.0 in 2014 and released black money.

The first 5000 blocks of black currency are pure PoW stage, the 5001 to 10000 blocks are PoW and PoS coexistence stage, and from 100001 block to later are pure PoS stage.

Black coin pioneered the rapid mining + low dividend issuance model, the issuance phase of the use of POW, through algorithm improvement in a short time can not produce a special GPU and AISC mining machine to solve the problem of unfair distribution.

Improvements of PoS2.0 over PoS:

1. Remove the currency age from the equation. The new system uses the following formula to calculate the proof of interest:

Proofhash

< 币数x目标值 　　点点币中，部分节点平时保持离线，只在积累了可观的币龄以后才连线获取利息，然后再次离线。 　　PoS 2.0中拿掉币龄，使得积攒币龄的方法不再有效，所有节点必须更多的保持在线，以进行权益累积。 　　越多的节点在线进行权益累积，系统遭遇51%***的可能性就越低。 　　2、为了防范预先计算***，权益修正因子每次均改变。 　　3、改变时间戳规则，以及哈希算法改用SHA256。 黑币的PoS实现原理 　　黑币的PoS证明计算公式为： 　　proofhash < 币数x目标值 　　展开如下： 　　hash(nStakeModifier + txPrev.block.nTime + txPrev.nTime + txPrev.vout.hash + txPrev.vout.n + nTime) < bnTarget * nWeight 　　其中proofhash，对应一组数据的哈希值，即hash(nStakeModifier + txPrev.block.nTime + txPrev.nTime + txPrev.vout.hash + txPrev.vout.n + nTime)。 　　币数即nWeight，目标值即bnTarget。 　　blackcoin-1.2.4中PoS证明计算代码如下： static bool CheckStakeKernelHashV2(CBlockIndex* pindexPrev, unsigned int nBits, unsigned int nTimeBlockFrom, const CTransaction& txPrev, const COutPoint& prevout, unsigned int nTimeTx, uint256& hashProofOfStake, uint256& targetProofOfStake, bool fPrintProofOfStake){ if (nTimeTx < txPrev.nTime) // Transaction timestamp violation return error("CheckStakeKernelHash() : nTime violation"); //目标值使用nBits CBigNum bnTarget; bnTarget.SetCompact(nBits); //计算币数x目标值 int64_t nValueIn = txPrev.vout[prevout.n].nValue; CBigNum bnWeight = CBigNum(nValueIn); bnTarget *= bnWeight; targetProofOfStake = bnTarget.getuint256(); //权重修正因子 uint64_t nStakeModifier = pindexPrev->

NStakeModifier; uint256 bnStakeModifierV2 = pindexPrev- > bnStakeModifierV2; int nStakeModifierHeight = pindexPrev- > nHeight; int64_t nStakeModifierTime = pindexPrev- > nTime; / / calculate hash value / / that is, calculate hash (nStakeModifier + txPrev.block.nTime + txPrev.nTime + txPrev.vout.hash + txPrev.vout.n + nTime) CDataStream ss (SER_GETHASH, 0); if (IsProtocolV3 (nTimeTx)) ss

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