[ANN] (QTUM) - A Scalable Smart Contract Platform w/ Proof of Stake

[dzimbeck]

hi zimbeck, not too much really care about your posting.

also if you want to argue, you can ask that skycoin dev.

also from your earlier post, i know you also get a lot of free bitbay and you pumped bitbay price.

Skycoin dev doesn't know anything about Bitbay hahaha wtf. I'm the dev they hired to work on it and we are all saying Patrick is a theif. He got paid, he left and dumped his Bay. Period. If you guys don't care, fine but that doesn't change who he is.

And no, I did not "pump" Bitbay that is retarded. I spent two years coding it and improving the decentralized markets and unbreakable contracts. I've got no time for that bullshit. My code is 50,000 lines. I've got better things to do. I won't even bother selling until maybe long after the peg is done.

Yes I did get free Bitbay and it's very lucky that I did because had I had to work the past 2 years for free without any vested interest after Dai and Bob tried to harm my rep, it would have been a lot more difficult. And just so you know I still would have done it. Actually I would have simply bought BitBay.

Also speaking of "free" Bitbay. I was the only one who didn't buy on BTER. Steven and Lin and Bob bought and gave themselves kickbacks and reimbursed themselves BTC that should have gone into the project. Once I saw them do that I explained it to investors within a couple weeks after a long, long amount of thought (realizing the blowback).

I realize the only people supporting this project are either fake, or don't care if Patrick/Steven stole Bitcoins. But he did and there is proof and it is obvious he and his friends got free Qtum too by faking volume. You guys might be chasing a pump but just be aware of who you are giving money to. Its been at least a few months since I've posted here but consider this a friendly reminder and a big warning to people who are new to this thread and don't know. Too bad this can't be translated to chinese? Someone should do that.

No point in arguing with him man, his mind is made up as he is set on protecting his little 900 qtum investment and is ignorant of anything else.  It's obvious to anyone with a brain that you're more knowledgeable in this space than he will ever be.  I bought some tokens in the qtum ICO on a whim, without looking too deep in the Bitbay thing.  Had I known, I probably would have reconsidered.  

Would you say that Dai created the Bitpay project originally with the intention to scam though? It seems to me that this was a case of an arrangement gone bad, and Dai grabbing whatever he could get his hands on (regardless of whether he was entitled to it) and running for the door when he realized that the building was on fire.  Pumping the ICO reimbursing himself is shady as hell, but with the lack of regulation in the crypto market was it legally wrong?  Technically ICO funds are supposed to be at the disposal of the founding team, and he is apart of that team.  In any case i'm not sure that Qtum was even pumped.  The speed at which they raised the funds looked shady at first, but when you consider that TKN ICOd after and raised the same amount of money in under 30 minutes, then they could have easily reached 15m without any pump.  I think it's more of a sign that we're entering a bubble and people are eager to throw $ around.

I feel for what happened to you man.  You got put in a crappy situation by some shitty individuals who took advantage of your good nature and talent.  It looks like you've put in an incredible amount of work as the solo developer and I hope your project pans out to be a great success.  It sucks though if Dai still holds 10% of all bay like you say then him profiting off your blood & sweat is definitely a double edge sword.  

Yes he did, he partnered with Bobsurplus secretly and they even used the "Bay west toilet paper logo" from day one to mock me and they used fake profiles to discredit and harm my rep. I got sent pdfs in secret(they had a mole in the group), was shown fake profiles that got hacked by some people proving the propaganda campaign. It was seriously a rabbit hole. To this day, it still kind of humbles me. Their modus operandi was similar to JTRIG. Man, to be honest I don't mean to bring up the past but its true(I don't live in the past, every once in a while I'm candid). I don't think buying into your ICO is illegal per se but the website they set up was wrong because they lied about the funds release schedule and mocked me knowing that when I said something the project would crash. So that would constitute as fraud but extremely hard to prosecute. To add insult to injury, Bob would come by every few months to make fun of the investors he stole from. So Dai is lower than dirt to me. I tried to pursuade him to help and he was very blahzay and eventually just ignored me even when I tried to be NICE when it was eating me inside. I'm certain Qtum was pumped. Knowing that last time Dai partnered with Chinese exchanges like BTER who stole funds from users on so many occasions(millions they still owe me almost 3 btc). Qtum funded in "90 minutes" what does that tell you? Lol... and that was while Gleb was bombarding this thread. No way they funded what they claimed unless his rich chinese friends wanted free coins or something. Same Modus Operandi with just bigger numbers.

We all think Dai sold his Bitbay because he admitted it on the slack when I confronted him saying it "wasn't worth anything". But it was worth something to investors who didn't want to be dumped on. It shows how much contempt this dude had for us(he certainly didn't tell me while he was dumping). If you ask Dai directly I doubt he will give you a straight answer that is cogent.


Ironically, I'm not saying Qtum won't be a success. They very well may put contracts in UTXO which is in fact a better way to do it. I've often chastised Ethereum for bloating up the blockchain and it is true in fact, I think I might have even talked to Dai about this idea in the past that it is cleaner to do it that way. You just pay a hash, send a payload and sandbox it. It's not actually that hard. Ethereum is over-engineered in my opinion and will have 10x the scaling issue as Bitcoin or even Qtum and to be honest Ethereum is much more greedy and potentially have back door deals that would shock us.

I'm not here to take away from anyone's efforts, I've got better things to do like CODE. But let investors never forget this guy did leave with investors funds that he didn't work for, dumped his coins etc. There is NO FREE LUNCH in life. God knows how many times some CEO bankrupts his own business keeps investors funds and never sees bars (possibly Trump for example? haha). White collar crime isn't taken seriously which is why everyone wants to destroy wall street. Sadly, if investors don't get smarter, the process will repeat itself. So take this text for what its worth. BitBay has made tremendous progress and of course the peg will finish.

But maybe the guy is right, investors don't care who this guy is, they just want to make money. Still, I would never invest regardless even if they crapped gold bars. But thats my personal opinion perhaps many investors simply don't care. The ones that do, will listen carefully.

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[sangwoo]

hi zimbeck, not too much really care about your posting.

also if you want to argue, you can ask that skycoin dev.

also from your earlier post, i know you also get a lot of free bitbay and you pumped bitbay price.

Skycoin dev doesn't know anything about Bitbay hahaha wtf. I'm the dev they hired to work on it and we are all saying Patrick is a theif. He got paid, he left and dumped his Bay. Period. If you guys don't care, fine but that doesn't change who he is.

And no, I did not "pump" Bitbay that is retarded. I spent two years coding it and improving the decentralized markets and unbreakable contracts. I've got no time for that bullshit. My code is 50,000 lines. I've got better things to do. I won't even bother selling until maybe long after the peg is done.

Yes I did get free Bitbay and it's very lucky that I did because had I had to work the past 2 years for free without any vested interest after Dai and Bob tried to harm my rep, it would have been a lot more difficult. And just so you know I still would have done it. Actually I would have simply bought BitBay.

Also speaking of "free" Bitbay. I was the only one who didn't buy on BTER. Steven and Lin and Bob bought and gave themselves kickbacks and reimbursed themselves BTC that should have gone into the project. Once I saw them do that I explained it to investors within a couple weeks after a long, long amount of thought (realizing the blowback).

I realize the only people supporting this project are either fake, or don't care if Patrick/Steven stole Bitcoins. But he did and there is proof and it is obvious he and his friends got free Qtum too by faking volume. You guys might be chasing a pump but just be aware of who you are giving money to. Its been at least a few months since I've posted here but consider this a friendly reminder and a big warning to people who are new to this thread and don't know. Too bad this can't be translated to chinese? Someone should do that.

No point in arguing with him man, his mind is made up as he is set on protecting his little 900 qtum investment and is ignorant of anything else.  It's obvious to anyone with a brain that you're more knowledgeable in this space than he will ever be.  I bought some tokens in the qtum ICO on a whim, without looking too deep in the Bitbay thing.  Had I known, I probably would have reconsidered.  

Would you say that Dai created the Bitpay project originally with the intention to scam though? It seems to me that this was a case of an arrangement gone bad, and Dai grabbing whatever he could get his hands on (regardless of whether he was entitled to it) and running for the door when he realized that the building was on fire.  Pumping the ICO reimbursing himself is shady as hell, but with the lack of regulation in the crypto market was it legally wrong?  Technically ICO funds are supposed to be at the disposal of the founding team, and he is apart of that team.  In any case i'm not sure that Qtum was even pumped.  The speed at which they raised the funds looked shady at first, but when you consider that TKN ICOd after and raised the same amount of money in under 30 minutes, then they could have easily reached 15m without any pump.  I think it's more of a sign that we're entering a bubble and people are eager to throw $ around.

I feel for what happened to you man.  You got put in a crappy situation by some shitty individuals who took advantage of your good nature and talent.  It looks like you've put in an incredible amount of work as the solo developer and I hope your project pans out to be a great success.  It sucks though if Dai still holds 10% of all bay like you say then him profiting off your blood & sweat is definitely a double edge sword.  

Yes he did, he partnered with Bobsurplus secretly and they even used the "Bay west toilet paper logo" from day one to mock me and they used fake profiles to discredit and harm my rep. I got sent pdfs in secret(they had a mole in the group), was shown fake profiles that got hacked by some people proving the propaganda campaign. It was seriously a rabbit hole. To this day, it still kind of humbles me. Their modus operandi was similar to JTRIG. Man, to be honest I don't mean to bring up the past but its true(I don't live in the past, every once in a while I'm candid). I don't think buying into your ICO is illegal per se but the website they set up was wrong because they lied about the funds release schedule and mocked me knowing that when I said something the project would crash. So that would constitute as fraud but extremely hard to prosecute. To add insult to injury, Bob would come by every few months to make fun of the investors he stole from. So Dai is lower than dirt to me. I tried to pursuade him to help and he was very blahzay and eventually just ignored me even when I tried to be NICE when it was eating me inside. I'm certain Qtum was pumped. Knowing that last time Dai partnered with Chinese exchanges like BTER who stole funds from users on so many occasions(millions they still owe me almost 3 btc). Qtum funded in "90 minutes" what does that tell you? Lol... and that was while Gleb was bombarding this thread. No way they funded what they claimed unless his rich chinese friends wanted free coins or something. Same Modus Operandi with just bigger numbers.

We all think Dai sold his Bitbay because he admitted it on the slack when I confronted him saying it "wasn't worth anything". But it was worth something to investors who didn't want to be dumped on. It shows how much contempt this dude had for us(he certainly didn't tell me while he was dumping). If you ask Dai directly I doubt he will give you a straight answer that is cogent.


Ironically, I'm not saying Qtum won't be a success. They very well may put contracts in UTXO which is in fact a better way to do it. I've often chastised Ethereum for bloating up the blockchain and it is true in fact, I think I might have even talked to Dai about this idea in the past that it is cleaner to do it that way. You just pay a hash, send a payload and sandbox it. It's not actually that hard. Ethereum is over-engineered in my opinion and will have 10x the scaling issue as Bitcoin or even Qtum and to be honest Ethereum is much more greedy and potentially have back door deals that would shock us.

I'm not here to take away from anyone's efforts, I've got better things to do like CODE. But let investors never forget this guy did leave with investors funds that he didn't work for, dumped his coins etc. There is NO FREE LUNCH in life. God knows how many times some CEO bankrupts his own business keeps investors funds and never sees bars (possibly Trump for example? haha). White collar crime isn't taken seriously which is why everyone wants to destroy wall street. Sadly, if investors don't get smarter, the process will repeat itself. So take this text for what its worth. BitBay has made tremendous progress and of course the peg will finish.

But maybe the guy is right, investors don't care who this guy is, they just want to make money. Still, I would never invest regardless even if they crapped gold bars. But thats my personal opinion perhaps many investors simply don't care. The ones that do, will listen carefully.

I know what you're talking about. It is the end that you want say? or what is you want? I think you don't have anything else to say here.

[dzimbeck]

I've got nothing else to say, thanks. Just direct any questions elsewhere because I don't check this thread. This is the first time in probably months.

[sangwoo]

I've got nothing else to say, thanks. Just direct any questions elsewhere because I don't check this thread. This is the first time in probably months.

yea, I think you have enough sent your thought to investors about the matters.
I understand your thoughts but I don't think he's representing all the team.
If it is not difficult, you'd better sue him
Each member of the team is an important people of the family like you.
And now It is an important time to prepare for the future. So do you, too.
If you have nothing to say, I wish you would stop it. Thank you.

[Qtum]

The mainnet will be released ahead of time?

the dev said: mainnet i think will be released in September?

The Main Network will be released in September, but the Test Network is due for June. What's important is stability testing of the test network, we're giving ourselves 3 months to make sure there's no issues.

[zigoter]

Looks like it's a good coin ....
I was very impressed after reading some of their articles. Waiting for more news. Good luck

[BTCspace]

Newsletter Update:

Qtum Development Updates


Changes made through this week to the core wallet:

Bugs fixed:

* [Wallet] Fixed a bug where sendtocontract and sendtoaddress did not track their inputs properly and could try to spend already spent inputs.
* [Consensus/EVM] Fixed a bug where the vin SigScript would sometimes be empty for an AAL created gas refund

Work completed:

* [Consensus/PoS] Added Coinbase and Coinstake rules for PoS
* [Wallet/PoS] Added internal block creation for PoS that properly handles new EVM block header fields
* [Testing/EVM] Added more automated tests for new EVM block header fields
* [Consensus/EVM] Changed the method used to validate AAL created transactions to ensure that their order in the block and exact values are all consensus-critical
* [Consensus/PoS] Added most of the PoSv3 base consensus rules from validation.cpp

Ongoing in-progress work:

* [Consensus/PoS] Working on adding the remaining PoSv3 consensus rules from net_processing.cpp
* [Consensus] Working on initial DGP framework implementation



Community







Xiaolong, Patrick, and John educated students at Fudan's MBA Blockchain Association event this past Wednesday. At this event, the Qtum team introduced students to Bitcoin, its history, and economic incentives.








In addition, Patrick and John lectured master's and undergraduate students earlier that Wednesday on blockchain technology and Qtum in an International Finance class at Fudan University.



Join the Qtum Forum



We launched the Qtum forum where we will publish official Qtum updates and engage with the community. The Dev Team will be taking part; so, you can ask questions about how you can get started developing on Qtum once the testnet is live.


https://forum.qtum.org/



Recent News:

https://www.theverge.com/2017/5/11/15622222/china-s-unique-and-successful-take-on-the-blockchain

"Another example of China’s unique take on the blockchain resulting in interesting technological vectors is the Qtum project. Qtum, pronounced "Quantum", is a turing-complete smart contract blockchain, combining its own version of the Ethereum Virtual Machine with a Bitcoin blockchain. The result is a blockchain stack, able to execute ethereum-like smart contracts in mobile environments such as Smartphones, Tablets and IoT devices, which the company’s leadership recognized as the most necessary feature for corporate and government blockchain adoption.

Furthermore, Qtum plans to incorporate a smart contract template hub in its service, which will make it easy to write financial applications which adhere to commercial rules and regulations and which utilize digital identities."

thank you for the updates.

looking forward to the testnet release.

hope the testnet will release in june!

then we can test the first UTXO based smart contact platform!

this will be big for sure.

First UTXO based smart contact platform
First POS smart contact platform.

[cybterpunk]

just want to know the classic proof of stake consensus has a lot of problem

how do you solve it in Qtum ?

thank you


"
POS Attack Vectors

 the main attack vectors to the consensus approaches analyzed later in this section are summarized. In general, Denial of Service (DoS) and Sybil attacks against these approaches (performed at the network and/or consensus protocol levels) are possible. A DoS attack is an explicit attempt to disrupt the normal operation of the blockchain network by sending lots of data to its nodes (for example, by sending many transactions of low value so the system cannot process normal transactions). In a Sybil attack the normal operation of the network is subverted by a malicious adversary that creates and controls a many misbehaving nodes (which could appear as belonging to different participants).

Miners' default behaviour in PoW consensus is to immediately announce to the network each new found block. In selfish mining attacks, a misbehaving miner attempts to waste computational resources of other miners, as follows. When the malicious miner finds a valid block he temporarily withholds it and continues mining on top of it, trying to find more blocks before the other miners even find one; and when another miner finds a valid block, the attacker announces the blocks he was withholding. Even if for some researches , this attack vector could be in practice very unlikely, as mentioned in section IV.D, there are cases where miners could be motivated to carry out a slight variant of this attack, where valid blocks are selectively discarded in order to modify the result of a stochastic procedure in which there is much at stake.

In a short-range attack the attacker, controlling certain percentage of the resources used to secure the system (e.g., computational resources or cryptocurrency stake) performs a transaction (e.g., to spend coins or to execute a step of a contract) and then tries to reverse it (e.g., to make a double-spending, that is, successfully spending some of the cryptocurrency coins more than once) as follows. After the attacker submits to the network the transaction he aims to revert, he starts mining a blockchain fork (from the previous block) in which that transaction is not included, without publishing it until that transaction has at least a certain number n of confirmations. If by then the attacker achieved to mine (mint) more than n blocks in his blockchain fork, he publishes it, and being this the longest chain it is accepted as the new valid blockchain by the network; therefore, the transaction in question is reversed.

In a long-range attack the attacker (controlling a certain percentage of the resources used to secure the system) starts mining a blockchain fork from many blocks back or even from the very first (genesis) block; aiming to obtain block rewards and/or to reverse a transaction. This attack would be possible in systems based on PoS consensus, given that although the attacker may only own a small percentage of all coins (at the point of the fork), in his blockchain fork he is able to move his coins freely, which allows him to solve the computational puzzle to mint blocks much more easily, and therefore, to rapidly build a longer blockchain.

A coin-age accumulation attack could be possible in approaches based on PoS where the coin-age is used to compute a measure of nodes' stakes, the total
consumed coin-age determines the valid blockchain, and the coin-age of an unspent transaction output (UTXO) is computed as its value multiplied by the number of blocks elapsed since it was created (e.g., Peercoin as will be seen later in this section). In this case, the attacker would split the coins he owns (a high enough percentage of all coins) into multiple UTXOs and wait until his stake becomes several times the average. Then, after that, the attacker would be able to mint several blocks in a row with a high probability, allowing him to fork the blockchain and reverse transactions (e.g., to make a double-spending).

In PoS consensus the solution to the puzzle necessary to mint a given block depends on the previous block's hash. Then, an attacker (with enough computation resources and stake) minting at height h of the blockchain could try to influence the hash of the current block (by selectively modifying its set of transactions) in a trial and error process until he is able to mint the block at height h+1. This is known as a pre-computation-attack and it could be done recursively in order to build several blocks in a row, to obtain the corresponding block rewards and/or perform a double-spend attack.


"

also Ethereum seems will not switch to fully POS until 2018 or 2019 ?

and their Casper is not ready yet,

why Qtum choose POS from the very beginning?

thank you!

[cybterpunk]

also what's the block reward of Qtum per block?

thank you

[Qtum]

also what's the block reward of Qtum per block?

thank you

The specifications may change a little, but the block target is 128 seconds for Proof-of-Stake 3.0, and the reward will be 4 coins. That should be about 2700 coins per day from staking.

[cybterpunk]

also what's the block reward of Qtum per block?

thank you

The specifications may change a little, but the block target is 128 seconds for Proof-of-Stake 3.0, and the reward will be 4 coins. That should be about 2700 coins per day from staking.

thank you for the answer,

also do we need minimum coins for stake?

[onetwo12]

Newsletter Update:

Qtum Development Updates


Changes made through this week to the core wallet:

Bugs fixed:

* [Wallet] Fixed a bug where sendtocontract and sendtoaddress did not track their inputs properly and could try to spend already spent inputs.
* [Consensus/EVM] Fixed a bug where the vin SigScript would sometimes be empty for an AAL created gas refund

Work completed:

* [Consensus/PoS] Added Coinbase and Coinstake rules for PoS
* [Wallet/PoS] Added internal block creation for PoS that properly handles new EVM block header fields
* [Testing/EVM] Added more automated tests for new EVM block header fields
* [Consensus/EVM] Changed the method used to validate AAL created transactions to ensure that their order in the block and exact values are all consensus-critical
* [Consensus/PoS] Added most of the PoSv3 base consensus rules from validation.cpp

Ongoing in-progress work:

* [Consensus/PoS] Working on adding the remaining PoSv3 consensus rules from net_processing.cpp
* [Consensus] Working on initial DGP framework implementation



Community







Xiaolong, Patrick, and John educated students at Fudan's MBA Blockchain Association event this past Wednesday. At this event, the Qtum team introduced students to Bitcoin, its history, and economic incentives.








In addition, Patrick and John lectured master's and undergraduate students earlier that Wednesday on blockchain technology and Qtum in an International Finance class at Fudan University.



Join the Qtum Forum



We launched the Qtum forum where we will publish official Qtum updates and engage with the community. The Dev Team will be taking part; so, you can ask questions about how you can get started developing on Qtum once the testnet is live.


https://forum.qtum.org/



Recent News:

https://www.theverge.com/2017/5/11/15622222/china-s-unique-and-successful-take-on-the-blockchain

"Another example of China’s unique take on the blockchain resulting in interesting technological vectors is the Qtum project. Qtum, pronounced "Quantum", is a turing-complete smart contract blockchain, combining its own version of the Ethereum Virtual Machine with a Bitcoin blockchain. The result is a blockchain stack, able to execute ethereum-like smart contracts in mobile environments such as Smartphones, Tablets and IoT devices, which the company’s leadership recognized as the most necessary feature for corporate and government blockchain adoption.

Furthermore, Qtum plans to incorporate a smart contract template hub in its service, which will make it easy to write financial applications which adhere to commercial rules and regulations and which utilize digital identities."

what's the DGP network?

Working on initial DGP framework implementation

any more information about this?

thank you

[valdemar99]

which currency will be accepted for Qtum ICO ?

Nothing has been confirmed yet.  In a couple of weeks the details of the Qtum ICO will be released.  Until then, anything we hear can always be changed by the time the ICO is launched. 

is any one here who can tell us the exact figure about it.

[Goruno]

It sounds interesting . This is quite big project to run in next month.
This is a contract platform combination between Etherum and bitcoin platform .

[Qtum]

which currency will be accepted for Qtum ICO ?

Nothing has been confirmed yet.  In a couple of weeks the details of the Qtum ICO will be released.  Until then, anything we hear can always be changed by the time the ICO is launched. 

is any one here who can tell us the exact figure about it.

This was from an older post asking about the Crowdsale price. We sold the majority of the tokens for approximately 30 cents, 51 million of them.

[onetwo12]

It sounds interesting . This is quite big project to run in next month.
This is a contract platform combination between Etherum and bitcoin platform .

yes

Qtum try to combine the best part of BTC and ETH

and it's POS network!

[cnupo]

when there will be a chance to buy some iou tokens ?

[Qtum]

when there will be a chance to buy some iou tokens ?

Do you mean for Qtum futures trading? We can't control this, but so far none of the exchanges have offered it.

[BTCspace]

just want to know the classic proof of stake consensus has a lot of problem

how do you solve it in Qtum ?

thank you


"
POS Attack Vectors

 the main attack vectors to the consensus approaches analyzed later in this section are summarized. In general, Denial of Service (DoS) and Sybil attacks against these approaches (performed at the network and/or consensus protocol levels) are possible. A DoS attack is an explicit attempt to disrupt the normal operation of the blockchain network by sending lots of data to its nodes (for example, by sending many transactions of low value so the system cannot process normal transactions). In a Sybil attack the normal operation of the network is subverted by a malicious adversary that creates and controls a many misbehaving nodes (which could appear as belonging to different participants).

Miners' default behaviour in PoW consensus is to immediately announce to the network each new found block. In selfish mining attacks, a misbehaving miner attempts to waste computational resources of other miners, as follows. When the malicious miner finds a valid block he temporarily withholds it and continues mining on top of it, trying to find more blocks before the other miners even find one; and when another miner finds a valid block, the attacker announces the blocks he was withholding. Even if for some researches , this attack vector could be in practice very unlikely, as mentioned in section IV.D, there are cases where miners could be motivated to carry out a slight variant of this attack, where valid blocks are selectively discarded in order to modify the result of a stochastic procedure in which there is much at stake.

In a short-range attack the attacker, controlling certain percentage of the resources used to secure the system (e.g., computational resources or cryptocurrency stake) performs a transaction (e.g., to spend coins or to execute a step of a contract) and then tries to reverse it (e.g., to make a double-spending, that is, successfully spending some of the cryptocurrency coins more than once) as follows. After the attacker submits to the network the transaction he aims to revert, he starts mining a blockchain fork (from the previous block) in which that transaction is not included, without publishing it until that transaction has at least a certain number n of confirmations. If by then the attacker achieved to mine (mint) more than n blocks in his blockchain fork, he publishes it, and being this the longest chain it is accepted as the new valid blockchain by the network; therefore, the transaction in question is reversed.

In a long-range attack the attacker (controlling a certain percentage of the resources used to secure the system) starts mining a blockchain fork from many blocks back or even from the very first (genesis) block; aiming to obtain block rewards and/or to reverse a transaction. This attack would be possible in systems based on PoS consensus, given that although the attacker may only own a small percentage of all coins (at the point of the fork), in his blockchain fork he is able to move his coins freely, which allows him to solve the computational puzzle to mint blocks much more easily, and therefore, to rapidly build a longer blockchain.

A coin-age accumulation attack could be possible in approaches based on PoS where the coin-age is used to compute a measure of nodes' stakes, the total
consumed coin-age determines the valid blockchain, and the coin-age of an unspent transaction output (UTXO) is computed as its value multiplied by the number of blocks elapsed since it was created (e.g., Peercoin as will be seen later in this section). In this case, the attacker would split the coins he owns (a high enough percentage of all coins) into multiple UTXOs and wait until his stake becomes several times the average. Then, after that, the attacker would be able to mint several blocks in a row with a high probability, allowing him to fork the blockchain and reverse transactions (e.g., to make a double-spending).

In PoS consensus the solution to the puzzle necessary to mint a given block depends on the previous block's hash. Then, an attacker (with enough computation resources and stake) minting at height h of the blockchain could try to influence the hash of the current block (by selectively modifying its set of transactions) in a trial and error process until he is able to mint the block at height h+1. This is known as a pre-computation-attack and it could be done recursively in order to build several blocks in a row, to obtain the corresponding block rewards and/or perform a double-spend attack.


"

also Ethereum seems will not switch to fully POS until 2018 or 2019 ?

and their Casper is not ready yet,

why Qtum choose POS from the very beginning?

thank you!

proof of stake still have some potential attack vectors.

[onetwo12]

when there will be a chance to buy some iou tokens ?

i think you can not buy this until mainnet release

mainnet will be released in September.