Nexus Advanced Contracts

Nexus Advanced Contracts

Enterprise adoption is instrumental to blockchain technology becoming mainstream, and Nexus Advanced Contracts are the next step in leading this progression. Existing Smart Contracts have experienced issues in relation to ease of use and scalability due to a Turing complete system. Addressing these issues, Nexus has produced what is in essence a ‘Register-based Virtual Machine’, set for release in January 2019 with the Tritium upgrade. Tritium will allow developers to access the technology of Advanced Contracts simply through an API set. Before an explanation of Advanced Contracts is given, some context will be provided as to how conventional Smart Contracts function.



Smart Contracts

Smart Contracts are self-executing. Their design is to enforce the terms and conditions of a contract through programmable logic, reducing the need for third party intermediaries such as brokers and banks. Smart Contracts are an additional layer of processing above the ledger layer, i.e what is known as ‘the blockchain’, and are comparable to small computer programs that hold a state of information. The calculations of the contract are carried out by the processing nodes of a blockchain, which change the state of the information. Given that the calculations or processing is carried out by distributed consensus, the state of a Smart Contract is immutable.

Bitcoin was the first cryptocurrency with built-in Smart Contract capabilities, which it calls ‘scripts’. Scripts are not Turing complete and contain byte code. Ethereum augmented these capabilities into its ‘Turing Complete Smart Contracts’, which are generic to developers’ needs. Ethereum gives developers more access to contract functionality on a blockchain through a custom programming language called Solidity, which is then compiled into assembly language that is run on the Ethereum Virtual Machine (EVM). The EVM is a ‘Stack-based Virtual Machine’ that processes each instruction in turn.

Though very capable, Ethereum has experienced some issues in regards to security, performance, and ease-of-use, predominantly because of its Turing complete design. Some notable cases include the $75m DAO hack on Ethereum, and the $286m Parity bug. Vulnerabilities existed due to the large complexity of a Turing complete system, and the resulting difficulty of resolving bugs in a protocol written in immutable code. The complexity of operations that support universal computation or Turing complete designs also limit scalability. A universal system has a higher degree of complexity, and can not therefore compete with technology that is designed for more specialized tasks. An example of this observation would be the comparison between a CPU (Central Processing Unit) with a ASIC (Application Specific Integrated Circuit) in the mining of cryptocurrency. A CPU can’t compete against a SHA256 miner, as its complexity and design is geared to support universal general computation, not specialized computation. A similar conclusion could be drawn when a comparison is made between the system design of Ethereum (universal), and Nexus (specialized).


Nexus Advanced Contracts

Nexus has developed a ‘Register-based Virtual Machine’, a specialized contracting engine with greater capabilities than the EVM. Unlike the the EVM, which is defined by only two distinct layers of processing and is dependent on a Turing complete system, the Nexus contract engine is facilitated through the seven individual layers of the Nexus Software Stack, each designated to carry out specialized processes.

The third layer of processing is called the Register Layer. Here, the states of individual pieces of information contained by Advanced Contracts are recorded in architectural components called registers. Registers are used by typical computer processors and provide easy access to memory storage of frequently used information or values. With respect to Nexus Advanced Contracts, each register is owned by a Signature Chain. Therefore, the ownership and write access of a register is validated by the second layer, the Ledger Layer. The fourth layer is the Operation Layer which defines the rules of the state changes to a register, called ‘operations’. The operations are carried out by validating nodes that change the state of the registers by distributed consensus. The design provides the required functionality of a contract engine, without the over complexity and complications of a Turing complete system.

The ownership of a register can be transferred providing many proof of ownership use cases. Examples of such include titles, deeds, digital certificates and records, agreements, or any other digital means of representing tangible assets or time-stamped events. A register can also be owned and governed by another register, creating a relationship between many users. Relations can be used as proofs on the Operation Layer to provide additional functionality. An example of this would be a register that holds metadata representing the ownership of an item, and it being owned by another ‘token register’. The token ownership signifies partial ownership of the item, which provides the possibility for further use cases such as royalty payments with split ownership.

Conditions or stipulations can also be coded into Advanced Contracts by validation scripts or Boolean logic. Validation scripts require a transaction to fulfill a certain set of conditions to execute, which allows a user to program in stipulations on the exchange of NXS, tokens or any other digital asset. This allows a user to void transaction orders, place time locks on funds, or exchange any digital asset without a central intermediary.

Advanced Contracts which will be accessible through an API set will be able to improve many existing processes, including digital ownership, tokenization of assets and enterprises, digital rights, royalty payments, supply chain management, escrow services, financial applications, legal documentation of digital signatures, and many more.



The standards of object registers, operation codes, and API methods will be defined through working group consensus, to ensure a consistent connection between developers and users. Nexus borrows a similar model to the Internet Engineering Task Force (IETF) that provides the working groups for all RFC (Request for Comments) standards. This is important to drive a vibrant ecosystem forward. Just as we have seen with the success of the internet, we hope to continue this success in the next era of global connection: blockchain, artificial intelligence, and satellite communication.

Read more:

Nexus API article

Nexus Signature Chains article


Parity Bug

The DAO Hack