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  • (01. January 2010., 10:27:49)











Author Topic: Qtum - UTXO based POS Smart Contracts | TESTNET LIVE!  (Read 7272 times)

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vindyne8

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Qtum Press From Japan:



Crypto Currency Magazine






The Bridge





Qtum Press Update:
8btc.com goes in depth with article about the Qtum project:
http://news.8btc.com/the-qtum-leap-driving-smart-contracts-to-mainstream-business
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vindyne8

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vindyne8

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Qtum Foundation Update:




The Economy Whitepaper, which details how Qtum will govern the Singapore based Qtum Foundation.




A couple new articles for Qtum today



Qtum article by Finance Magnates
Major Bitcoin Investors Back New Blockchain Platform Qtum






Qtum article by International Business Times
Qtum is building bridges between Bitcoin, Ethereum, Hyperledger, R3 Corda
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vindyne8

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From the original Qtum blog post here

Qtum Crowdsale Update

The Qtum team has been working very hard to prepare for the upcoming crowdsale. Although the official date and other details are yet to be published (will come soon), we are so excited to announce that you will be able to participate in our crowdsale through any of the following channels.

1. Bizhongchou (bizhongchou.com)
2. Yunbi (yunbi.com)
3. Yuanbao (www.yuanbao.com)
4. ICO365 (www.ico365.com)
5. Qtum official crowdsale website (crowdsale.qtum.org) – coming soon

Get started with registering on these website so you will be able to participate once it kicks off!

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vindyne8

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Article from news.bitcoin.com here



Qtum’s Patrick Dai Talks Smart Contracts and Bitcoin Security, announce Roger Ver as an Angel Backer
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Qtum Technical Introduction and Demonstration





Qtum mobile wallet and Apple Watch demo video





Qtum iMessage demo video



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vindyne8

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Quote
Some of you may have received our newsletter earlier about the crowd-sale.  For those of you wondering, here is a list of the exchanges that will be available.  Please note that we will no longer be using an official crowd-sale website.

Qtum Crowd-sale Updates

We are so excited to announce that Qtum crowd-sale will start at 12 PM GMT, March 16th, 2017 and end at 12 PM GMT, April 15th, 2017 (30 days). Both BTC and ETH will be accepted. Other terms and details including pricing and discounts will be announced on March 9th.

In addition, due to the legal compliance consideration, we have decided that Qtum crowd-sale will be available on the following exchanges. Please note the list of exchanges is not final, we may modify it before Qtum Crowd-sale start date.

Bizhongchou (https://bizhongchou.com/)
Yunbi (https://yunbi.com/)
ICOAGE (http://icoage.com)
Allcoin (https://www.allcoin.com/)
ICO365 (http://www.ico365.com/)


In order to fully comply with Singapore’s anti-money laundering and counter-terrorism financing laws and regulations, the Qtum Foundation will practice ‘know your customer’ exercise in the Qtum crowd-sale. Hence, we decide not to use Qtum official crowd-sale website although it is ready to launch.
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vindyne8

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The Qtum Whitepaper Has Been Updated:

Please visit https://qtum.org/en/white-papers to download.





Account Abstraction Layer Overview

Building on bitcoins reliable and proven-to-deliver blockchain, Qtum stacks its Account Abstraction Layer, allowing the Bitcoin Core 0.13 blockchain to seamlessly interact with the Ethereum Virtual Machine (EVM). With this innovation it is now possible to execute smart contracts and run decentralized applications, simply and securely, in environments that were previously out of reach for Ethereum, combining the endless possibilities provided by smart contracts with the stability and maturity of the bitcoin ecosystem.

Until now, attempts to implement smart contract solutions on top of the bitcoin blockchain have had issues, been lackluster, or failed to break into the mainstream business market. This is primarily due to the fact that the bitcoin blockchain employs an Unspent Transaction Output (UTXO) scheme to associate coins with addresses, rather than the easier to understand, but otherwise problematic, account-based model used by Ethereum.

An account based model works pretty much the way one would imagine:  if Alice has 10 tokens, and sends 5 of them to Bob, who has zero tokens; 5 tokens are simply subtracted from Alice’s balance and added to Bob’s, who now owns 5 coins.  On a UTXO blockchain, however, Alice does not directly hold 10 tokens, but a series of outputs, which are collections of coins resulting from previous transactions.

In such a model, instead of owning 10 tokens, Alice would, for example, hold 3 outputs: (a) consisting of 6 coins, (b) consisting of 2 coins, and (c) consisting of another 2 coins. In this scenario Alice couldn’t simply send 5 coins to Bob, but instead she (or her wallet, for that matter) would have to pick the best-suited output and receive “change” in return (a process called coin picking). In our example this means that Alice would transfer output (a), consisting of 6 coins, and receive 1 coin back as “change”. This “change” is what is called the Unspent Transaction Output, or UTXO. After the transaction Alice would still hold 3 outputs, this time (a) consisting of 1, while (b) and (c) remain 2.

Employing such a seemingly complex bookkeeping scheme allows the Bitcoin blockchain to support Simple Payment Verifications or SPVs. The SPV protocol enables the support of light wallets, which are wallets that can interact with the Bitcoin network in a decentralized and trustless manner, without having to download the entire Bitcoin blockchain. This property is immensely useful for mobile applications or in any low bandwidth/storage environment.

Until now, Ethereum smart contracts couldn't execute in such environments exactly because Ethereum’s account based blockchain does not provide a SPV analog. To solve this, Qtum builds its decentralized application platform on the proven-to-deliver Bitcoin blockchain and introduces the Qtum Account Abstract Layer, which serves as a communication layer between the Bitcoin Core 0.13 protocol and the EVM.

To achieve this, Qtum has extended the Bitcoin 'Script' language, adding 3 ‘opcodes’ so that it functions as a vehicle to transport code to the EVM, while adding special processing conditions, executing these EVM-using transactions immediately when added to the blockchain - allowing the EVM to operate within a UTXO environment.

In order to relieve Qtum smart contracts from the need to perform coin picking for every transaction, Qtum comes coded with an automated, generic coin picking algorithm which allows contracts to ignore the UTXO mode of operation, while functioning normally, as if deployed in an account-based environment. This method is what enables Qtum to be compatible with pre-existing Ethereum smart contracts, allowing them to be executed on Qtum with little to no change to their code.

For more information about Qtum’s architecture in general, please read this post or review our  Technical Whitepaper.   

https://qtum.org/ethereum-contracts-on-utxo/

https://qtum.org/wp-content/uploads/2017/01/Qtum-technical-white-paper-draft-version.pdf

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