Qtum is a decentralized and open-source smart contracts platform and value transfer protocol. Qtum uses proof-of-stake consensus, meaning node operators are rewarded for validating transactions. It is a DGP governed blockchain where community participants can vote to change certain network parameters. Qtum is built on a bitcoin core fork, but the foundation has created its own hybrid blockchain with the help of several key tools. The coin uses bitcoin’s chain because of its simple and stable nature, allowing the foundation to build upon it more easily. As the QTUM project is a hybrid of Bitcoin and Ethereum, its team comprises of members from both Bitcoin and Ethereum community. They also have team members who formerly worked with Tencent, Alibaba, Nasdaq etc. Apart from that, they are backed by some notable VCs and prominent people from the Blockchain community such as Patrick Dai (Project Co-Founder), Neil Mahi (Chief Blockchain Architect/Co-Founder) and Jordan Earls (Lead Developer/Co-Founder). Qtum provides a Turing-complete blockchain stack and is able to execute smart contracts and decentralised applications like the Ethereum blockchain. Qtum builds on Bitcoin's UTXO transaction model and uses the Proof-of-Stake algorithm. It is backed by some highly prominent members of the blockchain community such as Anthony Di Iorio, Xu Star, Bo Shen, David Lee, Jehan Chu and Roger Ver. Qtum sold over 10 million dollars’ worth of its tokens after only 90 minutes, eventually raising a total value of $15.7 million before stopping the campaign early after only 5 days. They raised a total amount of 11,156.766 bitcoins (BTC) and 77,081.031 ether (ETH) in exchange for the 51 million Qtum tokens being distributed to the public. In Qtum’s whitepaper, 51% of the coins were distributed to the public via the crowdfunding campaign. Of the remaining 49%, 29% of the coins would be allocated as community incentives, and the remaining 20% would be distributed to the early backers and development team.
Nxt uses the blockchain to create an entire ecosystem of decentralized features, all of which require the Nxt currency. Instead of modifying the original Bitcoin source code, as many altcoins have done, Nxt developers wrote their own code in Java from scratch. While Nxt is a public blockchain, licenses for private blockchains based on its software are also available for purchase. The developers refer to Nxt as Blockchain 2.0, providing numerous applications beyond simply keeping a public ledger of transactions. Jelurida BV took over the originally anonymously developed Nxt and now own the IP rights. Kristina Kalcheva, co-founder and legal expert of Jelurida, focuses on how to “explore the different open source licensing models and their enforceability in practice.” Currently, the main developer is an anonymous Star Trek fan, going by the name Jean-Luc Picard. While there is still the active development of Nxt, the parent company Jelurida is also working on a Nxt 2.0, known as Ardor, designed specifically to deal with scalability. Ardor will use the same blockchain technology as Nxt, combined with the idea of ‘child chains.’ According to Travin Keith, Nxt foundation Web and Marketing manager, Ardor allows for a “manageable blockchain size, which solves the problem of scalability by separating transactions and data that do not affect security from those that do, and moving all of those that don’t affect security onto child chains.” The core infrastructure of Nxt is complex. This adds risks as compared to the more lean bitcoin, but makes it easier for external services to be built on top of the blockchain. A peer-peer exchange allowing decentralized trading of shares, crypto assets. Since the blockchain is an unalterable public ledger of transactions, the Asset Exchange provides a trading record for items other than Nxt. To do this, Nxt allows the designation or ''coloring'' of a particular coin, which builds a bridge from the virtual crypto-currency world to the physical world. The ''colored coin'' can represent property, stocks/bonds, commodities, or even concepts. Arbitrary Messages enable the sending of encrypted or plain text, which can also function to send and store up to 1000 bytes of data permanently, or 42 kilobytes of data for a limited amount of time. As a result, it can be used to build file-sharing services, decentralized applications, and higher-level Nxt services. Nxt had no mining phase, all initial units were released to 73 people through a one-time fundraiser via bitcoins, after the announcement of the NXT project in the bitcointalk-forums by BCnext. Combine this with a PoS approach, and you have a situation where the big guys run the table. At one point, the Nxt community had a very public spat with Bitcoin developer Jeff Garzik. Garzik took issue with the Nxt marketing approach, its anonymous developers, and their responses to constructive criticism. Nxt responded to some of these claims, of course, but it remains one of the more controversial moments in its history. Another key problem the Nxt network ran into (like so many others) was blockchain bloat. Nodes get weighed down by the onerous task of having to store every transaction on the Nxt blockchain. This was one reason (among others) why Ardor/Ignis came into existence.'