This article was originally published on The Daily Chain, 17th June 2020.
This article and interview demystifies misconceptions about smart contracts, UTXO vs Account, Gas and Virtual Machines. We reveal the power of ErgoScript, and how crypto can in fact be “Bitcoin-like” and still possess limitless functionality.
On a personal note, may I add that I feel many projects sacrifice fundamental Bitcoin values in order to strive for what Ergo has already achieved.
1. A Brief History Of Smart Contracts
2. Contractual Money
3. UTXO vs Account
- PoW vs PoS
- Light Nodes
- Ergo Script
- Privacy Protocols
5. Alex Chepurnoy (kushti)
7. Conclusion, Thanks and Useful Links
1. A Brief History Of Smart Contracts
To understand Ergo, we must first consider Bitcoin as a programming language.
When people think of smart contracts they usually think of Ethereum. While ETH certainly deserves credit for popularizing smart contracts, the ideas and implementations predate it considerably.
The Cypherpunk movement, and in particular Nick Szabo, are the progenitors of the concepts which date back to the 1990’s.
Computers make possible the running of algorithms heretofore prohibitively costly, and networks the quicker transmission of larger and more sophsiticated messages. Furthermore, computer scientists and cryptographers have recently discovered many new and quite interesting algorithms. Combining these messages and algorithms makes possible a wide variety of new protocols.
New institutions, and new ways to formalize the relationships that make up these institutions, are now made possible by the digital revolution. I call these new contracts “smart”, because they are far more functional than their inanimate paper-based ancestors. No use of artificial intelligence is implied. A smart contract is a set of promises, specified in digital form, including protocols within which the parties perform on these promises.
Nick Szabo, 1996 
Satoshi Nakamoto was first to implement a programming language with Bitcoin Script. An early example of a smart contract is a Hash Time Locked Contract, or HTLC . In HTLCs an arbitrary amount of currency can be locked in an address until a specified block height. Lightning Network uses HTLC as part of its Layer 2 payment solution.
Nakamoto high-frequency transactions was an early foray into more complex programming in Bitcoin . Put simply, peers who need to communicate lots of transactions may do so off-chain before committing the final updated transaction on-chain.
Implemented in Bitcoin 0.1 were features such as transaction replacement, input sequence numbers (nSequence), and nLockTime that would allow two or more parties to repeatedly update the state of an unconfirmed transaction prior to it becoming confirmed. Bitcoin wiki, “Payment Channels” 
In fact, sending bitcoin can be considered the simplest of all programs.
A program written in Bitcoin Script is attached to every transaction output (i.e., amount received); this program protects the transaction by determining how the transaction output can be used as an input to (i.e., spent in) a future transaction. 
2. Contractual Money
Whether we talk about programs or scripts or smart contracts or dApps, we are essentially talking about the same thing — programming money. Ergo refers to this as “Contractual Money”.
Certain methods for programming money have certain limitations. For example, Bitcoin Script does not support “looping”, although another language could if it was “rich enough” .
The Ethereum solution to the looping problem, otherwise known as Gas, is described in an Ergo paper as an “ad-hoc” solution. Gas is not a prerequisite for a smart contract platform.
If the scripting language is rich enough, it enables writing of Turing-complete contracts while avoiding ad-hoc solutions for program halting like gas in Ethereum. While having significantly more versatility than Bitcoin script, Ergo script only contains operations, that allow estimation of script complexity before execution, which prevents various DoS attacks. However this instructions set is enough to easily write any possible program — ErgoScript was proven to be Turing complete 
Over the years much of the power in the Bitcoin Script language has been deprecated, largely in the interest of security.
We know much more today than Nakamoto did a decade ago about how to create a secure programming language for smart contracts, and the subject is very well-researched.
Huge advances in blockchain privacy protocols have also been developed since those early days; whether ring signatures, non-interactive zero-knowledge proofs, or CoinJoin.
Which brings us to Ergo.
We present Ergo, a new flexible blockchain protocol. Ergo is designed for developing decentralized applications with the main focus of providing an efficient, secure and easy way to implement financial contracts.
To achieve this goal, Ergo includes various technical and economic improvements to existing blockchain solutions. Every coin in Ergo is pro-tected by a program in ErgoScript, which is a powerful and protocol- friendly scripting language based on Σ-protocols. 
Ergo is “Bitcoin-like”, but brings with it the latest in blockchain technology and research. Ergo is not the only Bitcoin-like smart contract platform which uses the UTXO model in preference to Ethereum’s Account model — but it is perhaps the most advanced.
Research doesn’t stop at smart contracts, but extends to other areas including mining, decentralized governance, and privacy protocols.
To survive in the long-term, Ergo prefers well-tested solutions. If there isn’t already a well-tested solution for some problem, we perform our own research, and the number of peer-reviewed papers from the Ergo development team is already extensive.
The Ergo team do a lot of research and write a great many academic papers. Three whitepapers, and another ten “Foundational” papers are presented on the Ergo website.
3. UTXO vs Account
There exist misconceptions regarding the efficacy of using a Bitcoin-like UTXO in smart contracts versus an Ethereum Account model. The quote below from a comparison article of UTXO and Account written by a researcher on Medium articulates the misconception.
A UTXO model-based blockchain is weak in programmability, complex computation is almost impossible.
However this fallacy is obliterated when reading an Ergo paper on FlowCards by Alexander Slesarenko, which asserts that “Ergo’s transaction model has many advantages over the account based model.” 
ErgoScript is the smart contract language used by the Ergo blockchain. While it has concise syntax adopted from Scala/Kotlin, it still may seem confusing at first because conceptually ErgoScript is quite different compared to conventional languages which we all know and love. This is because Ergo is a UTXO based blockchain, whereas smart contracts are traditionally associated with account based systems like Ethereum. However, Ergo’s transaction model has many advantages over the account based model and with the right approach it can even be significantly easier to develop Ergo contracts than to write and debug Solidity code. 
Slesarenko continues by contrasting Ethereum’s imperative paradigm with Ergo’s declarative one. The nuance here becomes quite technical, and evidently Ergo is doing things differently from other UTXO smart contract platforms.
“AVL+ trees allow building efficient authenticated dictionaries that reduce the proof size and speed up verification by 1.4–2.5 times in comparison to prior solutions” 
The account model of Ethereum is imperative. This means that the typical task of sending coins from Alice to Bob requires changing the balances in storage as a series of operations. Ergo’s UTXO based programming model on the other hand is declarative. ErgoScript contracts specify conditions for a transaction to be accepted by the blockchain (not changes to be made in the storage state as result of the contract execution).
Rapid execution of smart contracts and throughput are often cited as reasons for adopting an Account model. So I asked in discord:
Ethereum has a much faster blocktime then Ergo, and in general the Account model seems more effective for rapid execution of contracts. How does a UTXO model like ERGO compete with an Account model for smart contract execution?
Robert Kornacki of Emurgo (more about them in the interview) provided a surprising reply, which again demonstrates the misconceptions in this area.
You can parallelize actions in their own UTXOs allowing for higher throughput for a given smart contact which allows you to do more actions per block. Check out the final two patterns in this piece we (Emurgo) released a few days back 
UTXO design (together with some new design patterns) allows for higher throughput on a per-block basis. So it’s actually (imo) better than account-based because there is not mutation in state, but more functional destruction/creation of boxes. 
In our opinion, the overwhelming majority of successful public blockchain use‐cases are related to financial applications. Ergo is extending Bitcoin’s way of writing contracts by attaching a protecting script (together with additional custom data) to every coin. Thus Ergo applications are defined in terms of guarding scripts built into boxes also containing data involved in execution.
Before speaking with the Founder and Lead Developer of Ergo I will present some of its main features.
Ergo uses Proof-of-Work because of all consensus mechanisms it is the most rigorously well-tested.
PoW was chosen for several reasons including that PoW protocols are widely studied, have high security guarantees, and are friendly to light clients.
However, due to the centralization of mining resources PoW usually causes Ergo has developed a solution to enforce solo mining in which a miner must hold the private key to the address of the mining node. While great for decentralization and network security it raises the barrier to entry.
Interestingly a collateralized smart contract currently in development presents a solution. Alex discusses this in the interview (see below).
The Problem with Proof-of-Stake
In Proof-of-Stake coins are inextricably linked to network security. For PoW this is not the case. This creates a whole new class of vulnerabilities PoW networks need not consider.
Proof of Stake (PoS) is a burgeoning Sybil resistance mechanism that aims to have a digital asset (“token”) serve as security collateral in crypto networks. However, PoS has so far eluded a comprehensive threat model that encompasses both Byzantine attacks from distributed systems and financial attacks that arise from the dual usage of the token as a means of payment and a Sybil resistance mechanism. In particular, the existence of derivatives markets makes malicious coordination among validators easier to execute than in Proof of Work systems. We demonstrate that it is also possible for on-chain lending smart contracts to cannibalize network security in PoS systems. When the yield provided by these contracts is more attractive than the inflation rate provided from staking, stakers will tend to remove their staked tokens and lend them out, thus reducing network security. 
b. Light Nodes
Running full nodes on any high traffic network is beyond the reach of average users. Waiting days to sync a blockchain is a traumatic user experience, and so the vast majority of people rely on “Light Nodes” when using blockchains like Bitcoin or Ethereum.
The problem is that the vast majority of Light Node wallets rely on trusted nodes operated by the wallet vendors. These systems therefor make a mockery of the trustless setups required by blockchain for security and full decentralizion.
Ergo has a solution to the problem of centralized light nodes made possible because Ergo is a PoW coin.
Ergo was designed to be maximally user-friendly in the sense of decentralization. One of the important properties of PoW is that it enables verification of the work done without downloading the full chain. Ergo blocks support NiPoPoW proofs, allowing light clients to synchronize with the network by downloading less than a megabyte of data.
Bitcoin has fragmented and bifurcated several times through forks arising from disputes in the community regarding how to scale the cryptocurrency. Changes to block size, for example, require controversial hard forks.
Voting systems have been designed in attempts of create decentralized mediation solutions to arrive at community consensus on how to invoke changes. These approaches, like one of the earliest attempts by DASH using Master Nodes, are vulnerable to manipulation by parties who control most coins, and thusly most votes.
Ergo fixes this problem in what could be described as an “action speaks louder than words” approach with on-chain miner voting.
A resilient network should adapt to changing environment without the intervention of trusted parties (such as a “core developer“ team). Ergo’s on-chain miner voting protocol allows gradual changes in a large number of parameters including maximum block size, storage fee factor and more.
For more fundamental changes Ergo is going to follow a soft-forkability approach — — if an overwhelming majority of the network accepts a new feature, it is activated, however, old nodes which do not upgrade continue to operate normally and just skip over this feature validation. Thus disruptive hard forks should not be required in Ergo.
As mentioned above Ergo believe that “if the scripting language is rich enough, it enables writing of Turing-complete contracts while avoiding ad-hoc solutions for program halting like gas in Ethereum.”
Complex as these ideas are the Ergo website does an admirable job of explaining Ergo Script. Knowing what we now do about Bitcoin Script and the Ethereum paradigm shift, readers may more fully appreciate the evolution in Ergo.
Ergo DApps and offchain protocols may be implemented in a truly decentralized way due to light clients, however, they also require a flexible and safe smart contract language. Ergo smart contracts are based on a Bitcoin-like UTXO model, where every output is protected by some script. If the scripting language is rich enough, it enables writing of Turing-complete contracts while avoiding ad-hoc solutions for program halting like gas in Ethereum.
While having significantly more versatility than Bitcoin script, Ergo script also contains operations, that allow accurate estimation of script complexity before execution, which prevents various DoS attacks and the “halting” problem. However, this instructions set is still sufficient enough to write any possible program — ErgoScript has been proven to be Turing complete. The cryptographic part of Ergo script is based on sigma protocols and naturally supports threshold m- of-n signatures, ring signatures and more. Keeping all this in mind, we expect ErgoScript and Ergo’s design to make it uniquely useful as Contractual Money with countless applications possible.
As a UTXO coin with a powerful scripting language, Ergo supports ring signatures and non-interactive zero knowledge proofs.
Ergo is not a privacy coin per se, but does support extremely powerful privacy tools, like an on-chain mixer which combines CoinJoin with zk-SNARK s to create a powerful new protocol called ZeroJoin .
Privacy enhancing techniques in blockchains generally fall into two categories. The first is hiding the amounts being transferred, such as in Confidential Trans- actions . The second is obscuring the input-output relationships such as in Ze- roCoin , CoinJoin . Some solutions such as MimbleWimble  and Zcash [5,6] combine both approaches.
In this work, we describe ZeroJoin, another privacy enhancing protocol based on the latter approach of obscuring the input-output relationships, while keeping the amounts public. This allows us to avoid expensive range proofs necessary for the first approach. Our protocol is motivated from ZeroCoin and CoinJoin in order to overcome some of their limitations, and can be thought of as a combination of the two. 
More generally the use of these protocols within smart contracts permits the creation of DApps which respect financial and legal privacy.
Ergo deals with the problem of what happens when all coins are mined, a problem which still hounds the Bitcoin community. It does so by leveraging a fee from coins which have not moved in over four years, to charge them for storage.
This idea is similar to regular cloud storage services, but it’s application to blockchain systems has several significant consequences. First, Ergo mining will always be stable, unlike Bitcoin and other PoW currencies, in which mining may become unstable after the emission period. Second, state size growth becomes controllable and predictable reducing hardware requirements for Ergo miners. Third, by collecting storage fees from outdated boxes, miners return lost coins to circulation preventing a steady decrease of circulating supply due to lost keys.
This is an avant-garde concept and Chepurnoy speaks to it in the interview that follows.
All the above scarcely scratches the surface of what ERGO brings, but will have to suffice as a basic introduction. For now is the time to meet its Founder.
5. Alex Chepurnoy (kushti)
Alex Chepurnoy has been active in blockchain development and smart contracts since 2011. He was a core developer for NXT, started smartcontract.com in 2014, and is an IOHK researcher with over 20 academic papers to his name.
Years ago, NXT was well ahead of the game and while Alex was tokenizing assets and designing decentralized exchanges Vitalik Buterin was still writing Bitcoin Magazine and waiting to drop out of university.
Charles Hoskinson, the Ethereum co-founder who later became involved with Cardano (ADA) and established IOHK in 2015, is very positive about Ergo.
Chepurnoy carries a cool swagger and curiously beatific smile. The Russian’s attire and hairstyle, seen below in this presentation from 2019, brings to mind (at least for me) a 1970’s chess Grandmaster.
In the following interview Alex Chepurnoy, aka kushti, talks to The Daily Chain about Ergo.
6. The Interview
Q. Hi Alex. Can you please give us a rundown of your contributions in the blockchain space?
I am in the space since 2011. From early 2013 I started to work on different services around Bitcoin and cryptocurrency trading (a wallet with auto-hedging, one of the first trading data aggregators launched at the same time as BitcoinWisdom and so on).
In April, 2014, I joined Nxt core development and concentrated on core development mostly since then. Also, I made couple of projects with Sergey Nazarov back in 2014 (cryptamail.com, secureae.com), and in late 2014 we (me, Sergey Nazarov, Steve Ellis, and Wesley) released initial version of smartcontract.com, which was pivoted into well-known these days ChainLink (but I left in late 2015, and Wesley left before me). I left Nxt core development in late 2015 as well.
Working on Nxt, I started utterly simple blockchain framework Scorex, which was later pivoted into modular blockchain framework. This project got attention from Charles Hoskinson, Cardano and Ethereum cofounder, around mid-Autumn, 2015. Then I joined IOHK around January’ 2016. I guess I was among first five employees maybe even! Initial Ergo Platform design was born in late 2016, and from mid-2017 I am on unpaid leave to be fully concentrated on Ergo Platform development.
Q. Could you please tell us more about your work with IOHK and how that correlates to your work on Ergo?
In IOHK we worked on Scorex and some research topics, such as efficient stateless clients, hybrid Proof-of-Work + Proof-of-Stake protocol (TwinsCoin), storage rent model, efficient mobile clients (with real SPV security by using NiPoPoW tech), and so on. Ergo Platform is partially based on papers published by us, but also we considered results made by others (in IOHK, e.g. NiPoPoW was developed mostly by Dionyzis Zindros and Prof. Kiayias, but only, a good idea which sounds along with others can come from anyone after all).
Q. What were you doing before Bitcoin? Could you please tell us a bit about your background and education?
I was in distributed systems development and also interested in peer-to-peer applications before Bitcoin. My interest in Bitcoin was initially purely technical, understanding and excitement about possible social impact came later. I was educated to do both system (close to bare metal) and application-level programming, also, have unfinished Ph.D. on formal verification of distributed systems. In regards with cryptography, I am mostly self-educated.
Q. Why did you start Ergo, and why did you name it Ergo?
Initial idea was to combine different good designs from papers which can sound even better by being combined. There were many good designs around existing only on paper back then. It turned out that the design is also could be considered as deep rework of Bitcoin going from the same first principles.
Ergo means “therefore” in Latin, but “work” in Greek. I prefer the second meaning, but both are fine. Initially the name was chosen to point to the fact that the design of the cryptocurrency is ERGOnomical. One of the early mottos was “Ergo is AAA class of Proof-of-Work blockchains”).
Q. Is it true to say that Ergo unlocks the potential of Bitcoin with powerful scripting? Please discuss.
Ergo is following Bitcoin transactional model with one-time coins (UTXOs) to be fully consumed by a spending transaction. But a script protecting one-time coin is totally different in Ergo. Still, the focus is on security and scalability, but programs in Ergo are much more powerful than in Bitcoin. We have examples of crowdfunding, oracles, decentralized exchange, stablecoins, auctions, and so on.
Another feature which is truly unique is support for efficient and composable zero-knowldge protocols known as “Generalized Schnorr Proofs” (or sigma-protocols). I will explain implications further.
Q. Is it fair to say that Ergo has learned from mistakes made in Bitcoin? Please discuss.
Ergo is based on many observations from Bitcoin. For example, storage rent to stabilize miners income in the long-term was inspired by widely discussed now possible instability of Bitcoin network when emission will be done. Bitcoin scripting is not friendly to analysis and tooling, we considered that during contractual layer design. Bitcoin is going to adopt Schnorr signatures while a simplest signature in Ergo was always about Schnorr. And so on. So it is fair to say that we’ve learned a lot from deeply studying Bitcoin.
Q. How would you compare the Ethereum paradigm of smart contracts with the Ergo paradigm of smart contracts? Please mention the advantages or disadvantages of both approaches.
Ergo’s language is not Turing-complete, but computations on the blockchain shown to be Turing-complete. Ergo applications likely more complex to develop, on other hand, they more friendly to light clients, and more friendly to privacy.
Q. “Ergo applications likely more complex to develop”. Could you elaborate and tell us if this a temporary situation?
Powerful contracts in the UTXO model is the very new thing, so design patterns still to be discovered. Likely the situation will be very different few years after. As summarized pretty well by Robert Kornacki here.
“Given that smart contract powered UTXO systems are nascent, there is a distinct lack of known design patterns which developers can rely on when building dApps. Looking at account-based models like Ethereum, encoding protocols in the UTXO model is as comparably different as writing imperative code is to functional.”
But for some applications already discovered, it turns out that Ergo solutions are very elegant, comparing with Ethereum. However, a developer need to get into a new transactional model to get an elegant solution.
Q. What smart contracts have been deployed on Ergo’s mainnet, and what user-friendly templates exist, if any?
Mixer is working, there are some oracles delivering data, initial testing stablecoin primitives deployed. Mining pools coming also based on collateral contracts. More to be announced soon!
Q. “The language supports a type of non-interactive zero-knowledge proofs called Σ-protocols and is flexible enough to allow for ring-signatures, multisignatures, multiple currencies, atomic swaps, self-replicating scripts, and long-term computation.” Please explain the significance of Sigma protocols, and ErgoScript as an evolution in smart contract programming.
By using Generalized Schnorr Proofs it is possible to do non-interactive mixing on application level, and non-interactive mixer is already working on Ergo Platform mainnet! Support for ring and threshold signatures (preserving zero-knowledge, unlike multi-signatures in Bitcoin) is coming into the reference protocol client.
Q. Regarding storage: If I have 1000 ERG and don’t touch them for 10 years, how many will be left?
998.7 at least, if ergs are protected with a single key. Storage rent is charged on per-byte basis, so if you do not spam the blockchain, then fees would be very tolerable I guess. Also, miners can change them, so I’m giving the answer in regards with the maximum possible fee coefficient value (currently it is 2 times lower).
Q. You say it helps solve the problem of declining PoW rewards, so why haven’t you opted for a tail emission?
Endless emission needs for endless growth in demand, to avoid inflation (decline in purchasing ability, which is about a decline in fiat-denominated pricing, if we consider Ergo as much more volatile asset). This could be no very realistic, so we were in favor of limited emission and solving the mining rewards stability problem with other means.
Q. Regarding the “Social Contract”:Charles Hoskinson called out Ethereum for breaking the “social contract” after bailing out TheDAO and violating “Code is Law”. Is Ergo’s Social Contract a response to this event?
I also was very critical to Ethereum bailout fork, and we both gave an interview on that. Ergo’s Social Contract is definitely a response, to this event and many other sad events we witnessed in the space.
Q. Please tell us about the ERGO Security Audit and why Jean Philippe Aumasson was selected to perform the audit?
Security is top-priority for Ergo, it is above fancy features. So it is required for all the code to be reviewed internally, which is a usual thing for all the good projects. In addition, the most critical parts of the code were reviewed by highly professional and known people in the space. In particular, sigma-protocols implementation was reviewed by Leo Reyzin, a Boston University Professor (he also designed and implemented some parts of the sigma protocols).
Later on, after mainnet launch, we invited Jean-Philippe to perform audit of the most critical parts of the code: Proof-of-Work implementation, wallet, serialization, and so on. Jean-Philippe is very well known in the infosec space, and done some audits for cryptocurrency clients before Ergo, for example, he made audits for Waves and Mantis client for Ethereum Classic. Hopefully we will have more audits in future!
Q. Can you briefly discuss the project’s funding and partnerships?
Ergo Platform development is funded via Dev Fund rewards released on each block during first 2.5 years of the mainnet existence. With current liquidity and pricing the funding is hard, nevertheless, the development is going well!
Partnerships is essential part of Ergo Platform promotion. Currently, there are three partnerships announced. Recently Ergo joined Blockchain Privacy, Security and Adoption Alliance (bpsaa.vision). Also, in May Ergo Foundation announced a partnership with privacy-friendly Cypra wallet (which is planning to support BTC, ERG, and some other cryptocurrencies, with atomic swaps support), cypra.io. Finally, Ergo just announced a partneship with Emurgo to jointly work on DeFi, also, Ergo will be added to Yoroi wallet; details are in the press-release.
Q “The cryptographic part of Ergo script is based on sigma protocols and naturally supports threshold m- of-n signatures, ring signatures and more.” The more includes zero knowledge proofs and ZeroJoin. Please discuss privacy protocols in Ergo
Currently, the most established privacy-enhancing application is a mixer which is called ZeroJoin and described in https://eprint.iacr.org/2020/560. Unlike mixers in Bitcoin, ZeroJoin is non-interactive, so a user is working with blockchain only in order to mix, without relying on custodial services or coordinators. This solves a lot of security issues. There are some implementations of ZeroJoin already
working in the mainnet!
However, more applications will be developed in future, I believe, such as privacy-preserved auctions or privacy-preserving DAOs (see, I believe that a blockchain of a healthy cryptocurrency is for financial applications!).
Q. Are there things Ergo can do that Ethereum cannot?
Privacy applications from above are usually to expensive in Ethereum to be realistic. Even a ring signature is too expensive! I guess more applications which are too expensive in Ethereum but realistic in Ergo will be discovered.
Q. Ethereum created “Accounts” (a non-UTXO model), “Gas” and a “Virtual Machine” to run smart contracts. Ergo has none of these and is “Bitcoin-like” and yet can do almost everything Ethereum can do. Can you explain in simple terms how this “magic” is achieved?
There was one problem which I formulated in 2017 and I think in context of public blockchains (aka cryptocurrencies) this is the most significant problem these days maybe. The problem is following: how to support 99% of useful Ethereum applications (so without considering CryptoKitties and Ponzi schemes) but with much more elegant tools than Ethereum provides, and an approach must be friendly to known scalability solutions also.
The general observations driven Ergo contractual development are: almost all the useful applications are financial applications; there is no need to store a lot of data on the blockchain, better to support short proofs of offchain-data authenticity; better to have in-built tokens than created via contracts; access to a state element (contract) within another contract should be read-only. Thus we got a lot of useful contract examples with very elegant tools, and likely Ergo supports 99% of useful Ethereum applications.
Q. Can you discuss Light clients and how Ergo is different in the way it handles these?
Ergo Platform protocol is superior in regards with light clients. For the first time in the space it has support for light full-nodes. There is a great video on tech behind that. Ergo also has superior support for ultra-efficient mobile clients with real SPV security by using NiPoPoW tech explained at https://nipopows.com/ .
“nanos gigantum humeris insidentes”
Ergo stands on the shoulders of giants, and evolves with respect to its past, its research in the present, and its clear vision for the future.
It has learned from mistakes made by Bitcoin and Ethereum and developed some of the most innovative and brilliant solutions and technologies ever created in the cryptocurrency and smart contract space.
Alex Chepurnoy and Robert Kornacki
 Smart Contracts: Building Blocks for Digital Markets, Nick Szabo (1996)
 Hash Time Locked Contracts — Bitcoin Wiki
 Payment Channels — Bitcoin Wiki
 ErgoScript, a Cryptocurrency Scripting Language Supporting, Noninteractive Zero-Knowledge Proofs, Ergo Developers (March 2019)
 Ergo: The Resilient Platform For Contractual Money, Ergo Developers (May 2019)
 Competitive equilibria between staking and on-chain lending, Tarun Chitra (2019)
 ZeroJoin: Combining ZeroCoin and CoinJoin, Alexander Chepurnoy, Amitabh Saxena
 FlowCards: A Declarative Framework for Development of Ergo dApps, Alexander Slesarenko (April 2020)
 High Level Design Patterns In Extended UTXO Systems, Robert Kornacki, (June 2020)
 CoinPool, exploring generic payment pools for Fun and Privacy, Antoine Riard and Gleb Naumenko (June 2020)