Blogs on Dedaub

How Smart Contracts Are Audited: The Methodology

Tue, 14 Jul 2026 09:00:00 +0000

Search “how are smart contracts audited,” and most of what you find is either a marketing checklist or a post-mortem of the latest hack. What is genuinely rare is a practitioner-grade account of how the work is actually done: what a senior auditor looks at first, how automated tooling and manual reasoning divide the labor, and what a rigorous review actually does with the source a project hands over. This article walks through that methodology as Dedaub practices it.

You Pay For What You Touch: Locality as Ethereum's Next Cost Model

Fri, 10 Apr 2026 13:05:21 +0000

This post is based on a talk given by Neville Grech at the Stateless Summit 2026, drawing on a 2021 study Dedaub conducted for the Ethereum Foundation on the impact of Vitalik Buterin’s Verkle tree gas metering proposal — the direct precursor of EIP-7864.

TL;DR

Real-world Ethereum contracts are written to fight today’s gas model — not to respect locality. Under EIP-7864, the unified binary tree replacing the 16-way Merkle-Patricia trie, access locality becomes a first-class cost dimension: you pay extra every time execution touches a code chunk or a storage slot that lives outside the small co-located region around the contract account. In a 2021 Dedaub study commissioned by the Ethereum Foundation, we measured a net ~26% gas cost increase on existing contracts under the precursor Verkle proposal, with ~96% of internal transactions worse off. That number sounds alarming. It is also a one-time, upper-bound repricing of contracts written with zero awareness of locality. Most of the gap is closable by compilers, standard libraries, and a handful of opt-in primitives. This post walks through the cost model, the systematic patterns that misbehave under it, and concrete optimization opportunities.

A Discussion on the Immunefi Firewall: Design, Use Cases, and Real-World DeFi Security

Thu, 15 Jan 2026 10:00:00 +0100

DeFi Needs Firewalls: From Program Analysis to Real-World Defense

A conversation between Mitchell Amador (CEO, Immunefi) and Yannis Smaragdakis (Co-founder, Dedaub)

Introduction

In this conversation, Dedaub co-founder Yannis Smaragdakis and Mitchell Amador (CEO of Immunefi) discuss the evolution of smart contract security, drawing on decades of program analysis research and hands-on experience securing real-world DeFi protocols.

Reentrancy in Aptos Move: Insights from 300+ Audits

Wed, 17 Sep 2025 14:15:28 +0200

Introduction to Move

The Move language is a next-generation smart contract programming language originally designed for the Libra (later Diem) blockchain, a project since discontinued. Today, Move powers platforms like Aptos and Sui. Its hallmark is a focus on safety and expressiveness, particularly regarding digital assets. It enforces strong resource semantics, making it difficult to accidentally lose or duplicate tokens, a significant advantage over traditional smart contract languages.

The Early Days: Move and (the Lack of) Reentrancy

In web3 security, reentrancy vulnerabilities are notorious for enabling high-profile exploits (such as the DAO hack on Ethereum). Reentrancy refers to the execution of a second call to a contract before the first invocation is completed. Move, by design, did not support reentrancy in its early versions.

ERC 20 on Ethereum: Growth Risks and Hidden Traps in 2025

Tue, 09 Sep 2025 16:12:10 +0200

Trends

New ERC-20 token creation on Ethereum YTD has increased by ~15% vs. 2024 (same period). At the same time, ERC-20 transfers on Ethereum YTD are up ~36% vs. 2024 (same period), with over 660M transfers expected by end-2025.

Bar chart comparing the number of ERC-20 tokens created on Ethereum between January 1 and September 3 over two years. In 2024, 160,807 tokens were created, shown as a purple bar. In 2025, 185,745 tokens were created, shown as a cyan bar.

CPIMP Attack: Far-Reaching EVM Vulnerability Mitigated | Dedaub

Tue, 15 Jul 2025 09:11:49 +0000

[by the Dedaub team]

A major attack on several prominent DeFi protocols over many blockchains was (largely) successfully mitigated last week. The threat was potentially affecting (at a minimum) tens of millions of overall value, and yet the attacker was waiting for even more before making their move!

The most technically-interesting aspects of the threat don’t have to do with the infection method, but with the attack’s clandestine nature: the attack contracts had been hiding in plain sight for weeks, infiltrating (in custom ways!) multiple protocols, while making sure that they remain entirely transparent to both regular protocol execution and to contract browsing on etherscan.

Dedaub at EthCC[8] | Smart Contract Security Before and After Deployment

Wed, 11 Jun 2025 10:01:00 +0000

Dedaub is heading to Cannes! As a WAGMI sponsor at EthCC[8], we’re bringing end-to-end smart contract security, combining rigorous auditing with continuous, custom-built monitoring. Security is a mindset. Auditing gets you to launch. Monitoring keeps you going.

Dedaub’s security technology stack enables our team to analyze onchain data to create a comprehensive security framework tailored to your project’s unique risk profile and operational logic.

EthCC[8] | Where to find us

📍 Palais des Festivals, Cannes | WAGMI Sponsor Zone

Web 3 Audit Methodology by Dedaub

Mon, 09 Jun 2025 09:52:02 +0000

Web3 Audit Methodology

Dedaub’s Security Audit teams comprise at least two senior security researchers, as well as any support they may need (e.g., cryptography expertise, financial modeling, testing) from the rest of our team. We carefully match the team’s expertise to your project’s specific nature and requirements. Our auditors conduct a meticulous, line-by-line review of every contract within the audit scope, ensuring that each researcher examines 100% of the code. There is no substitute for deep understanding of the code and forming a thorough mental model of its interactions and correctness assumptions.

Solidity Security Vulnerabilities: A 2026 Guide

Mon, 09 Jun 2025 09:00:00 +0000

Solidity Security Vulnerabilities

Solidity security vulnerabilities cause the majority of value lost in Web3. Because deployed contracts are immutable and hold assets directly, a single flaw can drain a protocol in one transaction. This guide covers the highest-impact classes of Solidity security vulnerabilities, from reentrancy to oracle manipulation, each with a real, audit-grade example and the detection and prevention practices that address it.

The vulnerability classes that matter

1. Reentrancy

Reentrancy occurs when an external call transfers control to an attacker contract before the caller updates its own state, allowing the attacker to re-enter the same function and repeat an action, such as a withdrawal. The July 2023 Curve incident showed this can even originate in the compiler: Vyper versions 0.2.15, 0.2.16, and 0.3.0 shipped a reentrancy lock that did not share a global slot across functions, enabling cross-function reentrancy. Attackers drained more than $61 million across affected pools, including Curve’s CRV/ETH, Alchemix’s alETH-ETH, JPEG’d’s pETH-ETH, and Metronome’s sETH-ETH, before whitehat hackers began recovering funds within days. Prevention: apply the checks-effects-interactions pattern, use a reentrancy guard, and never assume a lock modifier compiles to what you expect. And don’t lean on an AI agent to catch this for you when it writes the code. One study found reentrancy in 10 of 17 compilable contracts generated by Meta AI and in 9 of 19 generated by ChatGPT. It’ll write the order confidently wrong.

The $11M Cork Protocol Hack: Uniswap V4 Hook Vulnerability | Dedaub

Fri, 30 May 2025 12:56:17 +0000

On 28th of May 2025, Cork Protocol suffered an $11M exploit due multiple security weaknesses, culminating in a critical access control vulnerability in their Uniswap V4 hook implementation. The attacker exploited missing validation in the hook’s callback functions fooling the protocol into thinking that valuable tokens (Redemption Assets) were deposited by the attacker, thus crediting the attacker with a number of derivative tokens that could be exchanged back to other valuable tokens. The attacker also exploited a risk premium calculation, which compounded the attack. Among other things, this incident highlights the importance of proper access control in Uniswap V4 hooks and the risks of highly flexible open designs, which are very hard to secure.

$200M Cetus AMM Hack: Sui Overflow Vulnerability Explained | Dedaub

Fri, 23 May 2025 13:05:21 +0000

On May 22, 2025, the Cetus AMM on the Sui Network suffered a devastating hack resulting in over $200 million in losses. This incident represents one of the most significant DeFi exploits in recent history, caused by a subtle but critical flaw in “overflow” protection. This analysis dissects the technical details of the exploit and examines when this issue was introduced, fixed, and re-introduced.

Executive Summary

The attacker exploited a vulnerability that truncates the most significant bits in a liquidity calculation function of Cetus AMM. This calculation is invoked when a user opens an LP position. When opening such position, a user can open a large or small position by specifying a “liquidity” parameter (what fraction of the pool you would like to get in return), and supplying the corresponding amount of tokens. By manipulating the liquidity parameter to an extremely high value, they caused an overflow in the intermediate calculations that went undetected due to a flawed truncation check. This allowed them to add massive liquidity positions with just 1 unit of token input, subsequently draining pools collectively containing hundreds of millions of dollars worth of token.

Dedaub Partners with Immunefi to Bring Native Firewall Capabilities to Magnus

Mon, 05 May 2025 13:16:35 +0000

Dedaub Partners with Immunefi to Bring Native Firewall Capabilities to Magnus

Dedaub has joined forces with Immunefi to develop an onchain firewall for the Magnus platform. This partnership brings together two leading teams in web3 security with a shared mission to improve smart contract resilience by building a system that can detect and block malicious transactions before they execute onchain.

From Ethereum to Solana: How Developer Assumptions Can Introduce Critical Security Vulnerabilities

Fri, 25 Apr 2025 08:34:00 +0000

Ethereum Developers on Solana

Solana stands out as one of the most popular blockchains, known for its high throughput and scalability that position it as an attractive alternative to Ethereum. These benefits arise from Solana’s distinctive architecture, which is markedly different from Ethereum’s design. While these architectural differences underlie many of Solana’s strengths, they also introduce unique risks that may be unfamiliar to developers transitioning from Ethereum. In this article, we will explore some common errors that Ethereum developers might make when building Solana programs, given the vastly different security models of the two platforms.

Dedaub at ETHDenver 2025 | Showcasing Real-Time Security Monitoring

Tue, 18 Feb 2025 15:10:40 +0000

Dedaub is excited to sponsor ETHDenver once again! This year, we will showcase the Dedaub Security Suite‘s real-time monitoring capabilities. Our team is eager to discuss the latest Web3 vulnerabilities, audit best practices, and develop partnerships at ETHDenver 2025.

ETHDenver 2025 | Stop by Booth #513

Located near the Main Entrance | You Won’t Miss Us!

Visit us at Booth #513, just a few steps from the main entrance, where our team will gladly guide you through our advanced monitoring and alerting tools at ETHDenver 2025. Discover how they provide three lines of defense in a single monitoring solution to proactively identify rug pulls, anomalies, and protocol breaches before they escalate.

Dedaub Security Suite Updates Q4-24

Thu, 12 Dec 2024 10:15:00 +0000

FREE MONITORING for all!

The Dedaub Security Suite continues to evolve with features designed to simplify blockchain transaction monitoring and security analysis. These new capabilities address Web3 challenges and empower developers, security professionals, and organizations to work more effectively. Here’s an overview of what’s new.

Blockchain Transaction Monitoring Available to Free-Tier Users

We are excited to offer all registered users free access to Blockchain Transaction Monitoring queries.

With our free plan, users can set up monitoring bots or queries to track on-chain activities and trigger custom actions through webhooks. These tools allow users to flag unusual transactions or stay alert to specific on-chain events, empowering them to maintain vigilant oversight of their projects. Blockchain transaction monitoring is essential for this oversight.

Dedaub at DeFi Security Summit 2024

Wed, 23 Oct 2024 11:00:00 +0000

DSS 2024 | Dedaub is sponsoring the DeFi Security Summit 2024 in Bangkok, Nov 7-9! 🎉 We’re contributing to sessions on secure development and using LLMs for smart contract analysis. Follow @summit_defi for the latest updates.

Transient Storage in the wild: An impact study on EIP-1153

Tue, 22 Oct 2024 15:48:06 +0000

With the recent introduction of transient storage in Ethereum, the landscape of state management within the Ethereum Virtual Machine (EVM) has evolved once again. This latest development has prompted us at Dedaub to take a fresh look at how data is stored and accessed in the EVM ecosystem, as well as analyze how the new transient storage is used in real-world applications.

It’s important to note that even though transient storage has properly been integrated into the EVM, the transient modifier is still not yet available in Solidity. Therefore, all usage of transient storage is directly from the TSTORE and TLOAD opcodes using inline assembly, meaning usage is not that widespread yet, and could also be at a higher risk of vulnerability.

DEDAUB Supports Privacy4Web3 Hackathon

Mon, 30 Sep 2024 10:56:05 +0000

Privacy4Web3 Hackathon

The Privacy4Web3 Hackathon, supported by Oasis Network, is an excellent opportunity for developers to use privacy-centric technologies while innovating in Web3. This edition, also known as Hackathon Oasis Network, has a prize pool of $130,000, with contributions from industry players, including Dedaub.

Developers can utilize Oasis’ confidential EVM, Sapphire, and the newly launched Runtime Off-chain Logic (ROFL) framework. ROFL enables off-chain components to interact with the on-chain domain, expanding Sapphire’s capabilities and creating new possibilities for composability. Learn more

Bedrock vulnerability disclosure and actions

Thu, 26 Sep 2024 22:53:22 +0000

A few hours ago, the Dedaub team discovered a smart contract vulnerability in a number of uniBTC vault smart contracts in the Bedrock project. We disclosed the issue to the Bedrock account on Twitter and soon thereafter (after no response in 20 mins) to SEAL 911 for immediate investigation and action.

A SEAL 911 war room, under the guidance of @pcaversaccio, was created and we frantically tried for two hours to reach Bedrock developers. At that time, blackhats exploited the vulnerability for a $1.8m loss. However, given that this was an infinite-mint vulnerability on the uniBTC token, it is perhaps fair to assess that the damage was contained. Most of the potential losses were averted by pausing third party protocols exposed to the at-risk funds, including [Pendle](https://www.pendle.finance/ ) and [Corn](https://usecorn.com/ ). Notably, Pendle had over $30M of liquidity on the Corn network for the vulnerable asset. On Ethereum, the market cap of uniBTC was $75M, which an infinite mint renders worthless, and the asset was deployed in (at least) 8 networks.

Dedaub coordinated the Secureum RACE-32

Fri, 20 Sep 2024 08:27:14 +0000

Smart contracts are the underpinning of blockchain technology, and they present unique security challenges. To address this, platforms like Secureum have emerged, focusing on training researchers and developers to navigate and mitigate security risks, and we at Dedaub decided we wanted to partner Secureum in this mission.

Why we support the Secureum RACE

We decided to be part of the Secureum RACE because we believe hands-on challenges are the best way to learn. Security isn’t something you can fully grasp from reading papers or attending lectures-you need to get your hands dirty, confront real-world vulnerabilities, and think like an attacker.

Dedaub Named Member of ZKsync Security Council

Fri, 13 Sep 2024 11:29:15 +0000

We’re thrilled to announce that Dedaub is now a member of the ZKsync Security Council. We’re grateful for the community’s recognition of our efforts to play an active role in securing and maintaining the integrity of the Web3 space.

What is the ZKsync Security Council?

The ZKsync Security Council is a governance body tasked with safeguarding the security of the ZKsync protocol (ZKsync ERA, ZK Chains, and other components of ZKsync). Comprised of at least nine technical experts, the council has the authority to perform both standard and emergency actions to address security threats. Members are Signers of a multisig wallet, giving them the power to execute critical decisions that protect the protocol. Read more.

Strengthening Legal Protections for White Hat Hackers

Thu, 12 Sep 2024 11:38:06 +0000

White Hat Hackers in the Crosshair

**Update (Mar/11/2025): Legal pardon given to the white-hats by parliamentary vote. ** As a white hat hacker and educator, I’ve seen first hand how legal frameworks can fail to protect those who devote their lives to secure software systems.

A case that strikes close to home is a case involving a couple of my University students, who were arrested and were now summoned in court for responsibly disclosing a vulnerability, in Malta. A copy of the leaked vulnerability disclosure email is available here. Two of the students, Michael Debono and Giorgio Grigolo, were subsequently hired by Dedaub. We also extended financial aid to cover part of their legal fees. The arrests occurred after they found and exposed a security flaw in Malta’s largest student application and suggested a bug bounty. This incident shows how the law can treat these good-faith efforts no differently from malicious hacking.

Dedaub at SPLASH 2024

Mon, 09 Sep 2024 15:27:34 +0000

Dedaub at SPLASH 2024

Dedaub is proud to sponsor the SPLASH 2024 conference, helping unite top thinkers in software, programming languages, and systems. We support the community’s advancement of computer science, extending beyond our Web3 security work.

The Doctoral Symposium, where mid-stage doctoral students receive vital research guidance, aligns with our academic roots. Led by university professors, our team is a powerhouse of expertise, with most members holding PhDs. We believe advanced knowledge is vital to delivering exceptional solutions and are excited to foster future tech leaders.

Rho Markets Incident

Thu, 05 Sep 2024 13:35:44 +0000

On July 19th, Rho Markets - a Compound V2 fork on Scroll - was involved in an incident that led to the creation of $7.5mil in bad debt. The root cause of the vulnerability was the misconfiguration of the oracle for ETH, i.e., setting the address to a wrong price feed, at initialization time, and not a bug in the code. The price mis-alignment was quickly exploited by an MEV bot that observed the opportunity.

SEAL 911: Lessons from the Frontlines of Web3 Security | Dedaub

Thu, 22 Aug 2024 14:34:20 +0000

SEAL 911

Today, I’d like to share my personal experience as a member of SEAL 911, the emergency hotline that assists Web3 projects in protecting their assets in case of hacks or malicious attacks.

I’ve been part of SEAL 911 since October 2023 and I witnessed:

Numerous vulnerability disclosures.
War rooms were set up to prevent the exploitation of live vulnerabilities or help protocols that were actively being exploited.

Dedaub Security Suite Updates Q3-24

Thu, 25 Jul 2024 15:00:00 +0000

Dedaub Security Suite is renowned for its powerful EVM bytecode decompiler, which users have hailed as the best in the industry. Just as a quick sample of how much it’s appreciated, one testimonial reads, “I love the Dedaub decompiler-No other tool even comes close to what Dedaub has created.” The Dedaub Security Suite is a collection of web3 security technology tools, with the decompiler being the most popular in the community. In this blog post, we share our suite’s latest milestones, new features, and platform improvements.

Were You Looking for Dedaub? The Correct Spelling

Wed, 10 Jul 2024 10:00:00 +0200

If you landed here after typing something like debaub, dedhub, dedub, deaub, debaud, or dedabu into a search engine, you are in the right place. You were looking for Dedaub, and this page will tell you exactly what it is, why it is spelled that way, and what it can do for you.

The correct spelling is D-E-D-A-U-B

Dedaub (pronounced deh-dawb). Not debaub. Not dedhub. Not debaud.

The name looks unusual because it is not a common English word. It carries a specific technical meaning that precisely describes what the company does.

Dedaub Selected as Arbitrum DAO Security Advisor

Fri, 10 May 2024 14:52:00 +0000

Dedaub is now the Security Advisor for Arbitrum DAO’s Procurement Committee (ADPC). The community backed us with 114.9M votes-99.39% approval. We’re delighted the community recognizes our expertise in securing Web3 infrastructure. Our partnership with Arbitrum DAO marks a significant step forward.

Dedaub Selected as Arbitrum DAO Security Advisor

What is the Arbitrum DAO Procurement Committee?

The Arbitrum DAO Procurement Committee (ADPC) is a specialized committee that manages procurement, contracts, and resource allocation to support growth. Its primary responsibilities include developing structured frameworks for selecting and onboarding vendors, managing budgets for community-approved initiatives, and ensuring transparency and accountability in funding processes. The ADPC manages the Security Subsidy Fund to subsidize security audits and services for projects within the ecosystem.

EIP-3074 Impact Study

Fri, 03 May 2024 14:40:09 +0000

Pectra’s EIP-3074, and its Impact on Deployed Smart Contracts

Introduction

Ethereum’s end-user experience (UX) is about to be significantly enhanced with the introduction of EIP-3074, which will be part of the upcoming Pectra update. This proposal intends to improve wallets’ functionality by directly enabling more complex operations similar to smart contracts within traditional wallet architectures. It improves blockchain user UX and solves problems like transaction bundling and sponsored transactions.

For a study commissioned by the Ethereum Foundation, Dedaub identified the potential impacts of EIP-3074 on all known deployed smart contracts as of the date of the study. The results of our analysis are becoming increasingly relevant as we approach the implementation EIP-3074. You can read the original study here.

Ethdenver 2024 | Dedaub Showcases Its Web3 Security Technology

Mon, 19 Feb 2024 12:28:00 +0000

Dedaub is excited to participate in ETHDenver 2024. During the conference, Dedaub will showcase its advanced security technology solutions. Its team will members discuss the safety of Web3 applications, build partnerships, and share insights to enhance security standards within the Web3 ecosystem.

Visit Dedaub at Booth #251 in Devtopia at ETHDenver 2024!

Dedaub’s booth, #251, is in the vibrant Devtopia space. We invite technology enthusiasts to visit and attend one of the Suite demos, where we’ll explore the cutting-edge capabilities of static analysis, formal verification, Monitoring, and Alerting service.

Dedaub Celebrates Seal’s Public Debut and the Launch of the Safe Harbor Initiative

Wed, 14 Feb 2024 12:31:00 +0000

As a founding collaborator of the Security Alliance (SEAL), Dedaub celebrates SEAL’s public debut, a significant milestone in crypto security. The alliance consists of more than 50 Web3 and cybersecurity organizations. Its goal is to strengthen the security of the cryptocurrency ecosystem. Before its public debut, SEAL connected users, developers, and experts and offered free Web3 simulation exercises.

Seal’s Public Debut |

SEAL’s dedication to setting high-security benchmarks within the crypto ecosystem aligns with our core capabilities. Dedaub is bringing to the table world-leading technologies and expertise in static and dynamic program analysis, reverse engineering, and ethical hacking. In the context of SEAL, we can contribute to developing more robust defense mechanisms against threats and ensure the blockchain ecosystem’s safety.

Bulk Storage Extraction | Dedaub's Trusted Security Insights

Wed, 07 Feb 2024 14:45:00 +0000

Most Dapp developers have heard of and probably use the excellent Multicall contract to bundle their eth_calls and reduce latency for bulk ETL in their applications (we do too, we even have a python library for it: Manifold).

Unfortunately, we cannot use this same trick when getting storage slots, as we discovered when developing our storage explorer, forcing developers to issue an eth_getStorageAt for each slot they want to query. Luckily, Geth has a trick up its sleeve, the “State Override Set”, which, with a little ingenuity, we can leverage to get bulk storage extraction.

Introducing Dedaub Tx Simulator Snap for Metamask

Thu, 18 Jan 2024 10:26:56 +0000

At Dedaub, we have solid expertise in Smart Contract security, which allows us to contribute significantly to protecting the Web3 ecosystem, and we have recently achieved another milestone in our mission to establish trust and improve safety in the blockchain industry.

We are thrilled to announce the launch of the Dedaub TX Simulator Snap, a tool to transform how users engage with blockchain transactions.

What is the Dedaub TX Simulator Snap?

The Dedaub TX Simulator Snap is a cutting-edge tool that enables users to simulate transactions, evaluate the reliability and credibility of the accounts involved, and determine the financial consequences of their actions. Leveraging the extensive Smart Contract Database of Dedaub in real time, it provides users with up-to-date and comprehensive insights to make informed decisions.

Arbitrum Sequencer Outage | Root Cause Analysis

Sun, 17 Dec 2023 15:21:00 +0000

The Arbitrum network experienced significant downtime on December 15 due to problems with its sequencer and feed. The network had been down for almost three hours. The major outage began at 10:29 a.m. ET amid a substantial increase in a type of network traffic called Inscriptions. Arbitrum’s layer-2 network had processed over 22.29 million transactions and had a total value locked of $2.3 billion. Despite the success of the network, the current design suffers from a significant chokepoint when posting transactions to L1, causing the sequener to stall. While advancements such as Arbitrum Nova and Proto-danksharding might alleviate these design issues, this is not the first time Arbitrum has experienced such issues - a bug in the sequencer also halted the network in June 2023.

Arbitrum Sequencer Outage

Thestandard.io Exploit | A Thorough Analysis by Dedaub

Sat, 16 Dec 2023 12:50:00 +0000

Hello everyone, this is Yannis Bollanos, Security Researcher at Dedaub. A few days ago, we published a tweet about the thestandard.io exploit that took place on November 6th, 2023, which you can find here: https://twitter.com/dedaub/status/1734598398055981471.

The positive response from the X audience indicates a strong interest in the topic. As a result, I have decided to expand it into a blog post that can be used as a reference in the future.

Web3 Monitoring

Sat, 16 Dec 2023 10:22:00 +0000

WEB3 Monitoring

Web3 Monitoring continuously tracks blockchain activities, such as transactions and smart contract interactions, to identify anomalies, ensure security, and maintain operational transparency across decentralized networks. Web3 Monitoring empowers developers and organizations with real-time insights to safeguard their projects.

Why Blockchain Monitoring is Important

The need for security on the blockchain is ever-increasing, and the demands for innovative security solutions have also surged in recent years. The complexity of hacks and security breaches leaves no room for errors as the blockchain has shown to be unforgiving by design in punishing any possible lapses. In the last few years, attacks from private transaction pools have increased because attackers can bypass traditional defenses and exploit vulnerabilities without detection, limiting current security approaches and elucidating the need for more proactive measures. As codebases strengthen to counter these security risks, social engineering presents malicious actors with new ways to defraud people, hence the increased need for monitoring activity on the blockchain.

Smart Contracts | Tale of Little Bugs

Thu, 14 Dec 2023 12:55:00 +0000

As most programmers would admit, the most annoying bugs are often the “little” ones. Tiny logic errors caused by a few wrong characters in a single line of code, compiling fine and remaining undetected, patiently waiting to crash our program at the worst possible moment. We’ve all written such bugs, spent countless hours debugging them, and uttered the most horrific profanities when we finally discovered that we lost our sleep over a couple of wrong characters.

Critical Thirdweb Vulnerability: Insights from 300+ Audits

Thu, 07 Dec 2023 12:58:00 +0000

Summary: The root cause of the thirdweb critical vulnerability is that independent libraries implementing ERC2771 & Multicall, such as OpenZeppelin Libraries, interact badly, when combined. This allows attackers to spoof the _msgSender() with all sorts of access control implications including loss of funds.

The issue is complex, but can be explained using a simple analogy. Imagine a bank that will let one of the bank officials carry out a transaction on your behalf, as long as the instruction is written on a piece of paper with your verified signature. This is a very common scenario, for instance with some preferred bank clients. So, you go to the bank official and hand him a signed piece of paper. Your instructions are “take this sealed box to the cashier, open it, and give him what’s inside”. The bank official happily executes your signed instructions, after checking your id against your signature. The sealed box contains another piece of paper reading …”do a withdrawal on behalf of Elon Musk”, signed with a fake signature. The cashier takes this piece of paper from the bank official, thinking that the signature was checked, when, really, the only signature that was checked was on the instructions to deliver and open the box. That’s it! Now let’s look into the technical mechanics for how this vulnerability works, and how to protect your project from this issue.

Smart Contract Audits Guide

Sat, 02 Dec 2023 12:59:00 +0000

Smart Contract Audit Essentials: Navigating the Web 3 Landscape with Expertise and Security

With blockchain platforms, Smart Contract Audits play a critical role in ensuring the security and reliability of decentralized applications. These audits are routine checks and an indispensable part of the development process, safeguarding all transactions and agreements that define the blockchain ecosystem.

Smart Contracts, with their immutable and autonomous nature, demand absolute precision in their code. Any oversight or vulnerability can lead to significant financial losses or erode trust in the technology.

Smart Contract Security Tools | A Guide to Dedaub Security Suite, Step-by-step Tutorial

Wed, 18 Oct 2023 13:01:00 +0000

Dedaub Security Suite (former Watchdog) is a comprehensive security system designed for Smart Contract analysis and transaction monitoring. To make the most of Dedaub Security Suite’s offers, we’ve released a detailed step-by-step tutorial to guide you through its various capabilities.

Let’s delve into how this tutorial empowers you to harness the full potential of Watchdog.

Smart Contract Security Tools | Static Analysis

Smart Contract security is always evolving, and staying ahead of threats is crucial. Dedaub Security Suite‘s Static Analysis serves as your first line of defense, rigorously examining contract bytecode to flag potential vulnerabilities before they manifest into real threats. Our tutorial shows you how to navigate this preemptive feature for a stronger, more resilient codebase.

Platypus Finance Hack

Thu, 12 Oct 2023 13:04:00 +0000

Platypus Finance Hack: The platform was targeted by a flashloan attack, resulting in an approximate $2 million loss. This sophisticated attack utilized flashloans alongside tactics to alter slippage calculations in various swaps, thereby manipulating the price of the swapped assets to benefit the attacker.

Platypus Finance Hack | The Attack Summary

At 12th Oct 2023, 06:32 UTC, an attacker on Avalanche C-Chain (addresses: 0x0cd4fd0eecd2c5ad24de7f17ae35f9db6ac51ee7 & 0x464073F659591507d9255B833D163ef1Af5ccc2C), performed multiple on-chain transactions via smart contracts deployed within the same transaction itself. We shall concentrate on a single instance on this attack, where the attacker profits around $570k. The operations performed are as follows:

Ethereum improvement proposal 4788 | EIP-4877 Summary

Sat, 07 Oct 2023 13:06:00 +0000

Dedaub was commissioned by the Ethereum Foundation to perform a security audit of the bytecode of a smart contract that was introduced to the EIP-4877 in a recent change, enabling the on-chain storing and accessing of the beacon block roots of recent blocks.

In this blog post, titled “EIP-4877 summary,” we highlight key insights from the audit. You can access the complete report here.

The audited contract uses the block’s timestamp as a key for their parent beacon blocks’ roots. To bind the contract’s storage footprint while retaining accurate information, a set of two ring buffers are used (using a HISTORY\_BUFFER\_LENGTH with a value of 98304):

Ethereum Study – Rlp to Ssz Mpt Commitment Migration

Thu, 06 Jul 2023 13:09:00 +0000

The Ethereum Foundation commissioned our team to examine the potential impact of Ethereum Improvement Proposals (EIPs) 6404 and 6466. These EIPs propose the modification of Merkle-Patricia Trie (MPT) commitments for transactions and receipts, respectively. Importantly, this entails a change in the serialization algorithm, from Recursive Length Prefix (RLP) format to the Simple Serialize (SSZ) format for the Receipts and Transactions containers. In turn, this changes the Receipts Root and Transactions Root fields in the execution layer headers.

Preparing for Your First Web3 Audit

Fri, 16 Jun 2023 13:13:31 +0000

Your project is at an advanced state of engineering and you have decided to hire an auditor to maximize security and legitimacy. Great decision! However, not all audit experiences are equal, so follow this guide to maximize your mileage.

During auditing, you are employing security consultants to go over your code. For auditors, studying your code and issuing an Web3 audit report is a complex balance. Auditors need to have some level of confidence to sign off on your project, yet they will not spend infinite time to gain this confidence. The time allotted has typically been scoped based on your code size and apparent complexity, using extensive past experience.

EIP-4758 and EIP-6780 | Removal of Selfdestruct

Tue, 30 May 2023 13:14:34 +0000

Dedaub was commissioned by the Ethereum Foundation to perform an impact study of Ethereum Improvement Proposals (EIPs) 4758 and 6780 on existing contracts. EIP-4758 proposes to deactivate SELFDESTRUCT by changing it to SENDALL, which recovers all funds (in ETH) to the beneficiary without deleting any code or storage. On the other hand, EIP-6780 modifies SELFDESTRUCT to work only in the same transaction in which the contract was created, while in all other cases it recovers all funds but does not delete any other account data.

I See Dead Code

Sat, 11 Feb 2023 04:52:00 +0000

What if I told you that over one-third of recently-deployed Ethereum smart contracts consist mostly of unusable junk?

Dead Code

We recently identified a bug in the solidity compiler, resulting in the inclusion of dead code in the deployed bytecode of contracts.

What we did not know (and did not expect!) was how pervasive the bug was, affecting (almost certainly) many tens of thousands of contracts and the majority of their deployed bytecode.

Poly Network Hack Postmortem

Tue, 07 Feb 2023 13:12:00 +0000

On July 2nd, 2023 06:47:20 PM UTC Poly Network suffered what was initially reported to be a notional $34b hack (the actual realized amounts were far less, due to most of the tokens being illiquid). The Poly team paused their smart contracts EthCrossChainManager on several chains, most notably on Metis, BSC and Ethereum. After our team reconstructed the attack, we concluded that the root cause was not a logical bug on the smart contract, but, most likely, stolen (or misused) private keys of 3 out of 4 of Poly network’s keepers (off-chain systems controlled by the team). In order to understand how the attack took place, we need to understand the architecture of Poly’s cross-chain managers.

Uniswap Reentrancy Vulnerability Disclosure

Fri, 16 Dec 2022 04:56:00 +0000

By the Dedaub team!

Uniswap Reentrancy | Uniswap Labs recently advertised a boosted $3M bounty program for bug reports over their smart contracts, and especially the new UniversalRouter and Permit2 functionality. We submitted a bug report and received a bounty - thank you! To our knowledge, ours was the only bug report that Uniswap acted upon (i.e., the only one to have apparently resulted in a commit-fix to smart contract code and a [new deployment of the UniversalRouter](https://app.dedaub.com/ethereum/address/0xef1c6e67703c7bd7107eed8303fb e6ec2554bf6b/bytecode)).

Latent Bugs in Billion-plus Dollar Code

Tue, 19 Apr 2022 05:02:00 +0000

You are probably safe, but be aware…!

Daniel Von Fange pinged me last week:

Hey, I just realized that the xSushi reward distribution contract that’s commonly cloned around would be vulnerable to complete theft if the deposit token used was an ERC777 style that allowed rentrancy.

The message set in motion the close examination of just ~15 lines of code, handling funds in the billions.

We found not one, but two latent bugs. Both have pretty specific conditions for becoming vulnerabilities. We did our best to ascertain that current deployments are not at risk. (There was a time when an attacker could steal $60M, though.) However, this doesn’t mean there’s no risk: there may be several tokens that if you intend to stake in, one can attack you, right now, let alone what can happen with future deployments.

Mass Disclosure of Griefing Vulnerabilities

Fri, 15 Apr 2022 05:14:00 +0000

This week, with the help of @drdr_zz and @wh01s7 of SecuRing, we tackled a backlog of warnings from the Dedaub Watchdog tool, notifying around 100 holders of vulnerable accounts, with some $80M in funds exposed. (@_trvalentine had earlier produced proof-of-concept code to demonstrate that the attack is valid.)

The warnings concern griefing vulnerabilities: cases where an attacker can move the victim’s funds to a contract, but this does not confer the attacker any direct benefit - only makes life harder for the victim, up to possible loss of funds.

Rari Capital Vulnerability

Sat, 02 Apr 2022 13:21:00 +0000

Security researchers actively participating in Tribe DAO’s Discord security channel, raised concerns about a security issue relating to Fuse pools. The Rari Capital team executed our pre-established emergency response plan and immediately fixed the vulnerability. Because of the identification of the vulnerability, and the quick actions in response, no funds were lost. This article will address the nature and identification of the vulnerability as well as the remediation steps executed by the Rari Capital team.

Elipmoc: Advanced EVM Smart Contract Decompilation | Dedaub

Fri, 01 Apr 2022 12:26:00 +0000

NEVILLE GRECH, University of Malta, Malta and Dedaub Ltd SIFIS LAGOUVARDOS, University of Athens, Greece and Dedaub Ltd ILIAS TSATIRIS, University of Athens, Greece and Dedaub Ltd YANNIS SMARAGDAKIS, University of Athens, Greece and Dedaub Ltd

Smart contracts on the Ethereum blockchain greatly benefit from cutting-edge analysis techniques and pose significant challenges. A primary challenge is the extremely low-level representation of deployed contracts. We present Elipmoc, a decompiler for the next generation of smart contract analyses. Elipmoc is an evolution of Gigahorse, the top research decompiler, dramatically improving over it and over other state-of-the-art tools, by employing several high-precision techniques and making them scalable. Among these techniques are a new kind of context sensitivity (termed “transactional sensitivity”) that provides a more effective static abstraction of distinct dynamic executions; a path-sensitive (yet scalable, through path merging) algorithm for inference of function arguments and returns; and a fully context sensitive private function reconstruction process. As a result, smart contract security analyses and reverse-engineering tools built on top of Elipmoc achieve high scalability, precision and completeness. Elipmoc improves over all notable past decompilers, including its predecessor, Gigahorse, and the state-of-the-art industrial tool, Panoramix, integrated into the primary Ethereum blockchain explorer, Etherscan. Elipmoc produces decompiled contracts with fully resolved operands at a rate of 99.5% (compared to 62.8% for Gigahorse), and achieves much higher completeness in code decompilation than Panoramix-e.g., up to 67% more coverage of external call statements-while being over 5x faster. Elipmoc has been the enabler for recent (independent) discoveries of several exploitable vulnerabilities on popular protocols, over funds in the many millions of dollars.

Dedaub Watchdog Service: Trusted Continuous Monitoring

Fri, 28 Jan 2022 04:58:00 +0000

The Dedaub Watchdog is a technology-driven continuous auditing service for smart contracts.

What does this even mean? “Technology-driven”? Is this a buzzword for “automated”? Do you mean I should trust a bot for my security? (You should never trust security to just automated solutions!) And “auditing” means manual inspection, right? Is this really just auditing with tools?

Let’s answer these questions and a few more…

Watchdog brings together four major elements for smart contract security:

Phantom Functions and the Billion-dollar No-op

Mon, 24 Jan 2022 05:18:00 +0000

By the Dedaub team

On Jan. 10 we made a major vulnerability disclosure to the Multichain project (formerly “AnySwap”). Multichain has made a public announcement that focuses on the impact on their clients and mitigation. The announcement was followed by attacks and a flashbots war. The total value of funds currently lost is around 0.5% of those directly exposed initially.

**[ADVISORY: If you have ever used Multichain/Anyswap, **check/revoke your approvalsfor vulnerable tokens. Make sure to check all chains andread the full instructionsif anything is unclear.]

Etheria | A Six-year-old Solc Riddle

Tue, 23 Nov 2021 05:22:00 +0000

By the Dedaub team

The Assignment

A few weeks ago, we were approached with a request to work on a project unlike any we’ve had before.

Cyrus Adkisson is the creator of Etheria, a very early Ethereum app that programmatically generates “tiles” in a finite geometric world. Etheria has a strong claim to being the first NFT project, ever! It was first presented at DEVCON1 and has been around since October 2015 - six years and counting. It is as much Ethereum “history” as can get.

Harvest Finance Vulnerability | $200k Bounty

Fri, 12 Nov 2021 04:16:00 +0000

We disclosed a critical bug to Harvest Finance. The contracts in scope held a total of $6.4M in Uniswap V3 positions. The attack was found by an automated analysis that attempted to generalize the elements of the OpenZeppelin UUPS uninitialized implementation vulnerability.

Symbolic Value-flow Static Analysis of Ethereum Smart Contracts

Thu, 28 Oct 2021 04:17:44 +0000

We present a static analysis approach that combines concrete values and symbolic expressions. This symbolic value-flow (“symvalic”) analysis models program behavior with high precision, e.g., full path sensitivity. To achieve deep modeling of program semantics, the analysis relies on a symbiotic relationship between a traditional static analysis fixpoint computation and a symbolic solver: the solver does not merely receive a complex “path condition” to solve, but is instead invoked repeatedly (often tens or hundreds of thousands of times), in close cooperation with the flow computation of the analysis.

Symbolic Value-Flow Static Analysis: Deep, Precise, Complete Modeling of Ethereum Smart Contracts

Fri, 01 Oct 2021 05:00:00 +0000

YANNIS SMARAGDAKIS, University of Athens, Greece NEVILLE GRECH, University of Malta, Malta SIFIS LAGOUVARDOS, University of Athens, Greece KONSTANTINOS TRIANTAFYLLOU, University of Athens, Greece ILIAS TSATIRIS, University of Athens, Greece

Verkle Tree Gas Metering Impact

Tue, 10 Aug 2021 04:19:00 +0000

Dedaub was commissioned by the Ethereum Foundation to investigate the impact of Vitalik Buterin’s Verkle tree gas metering proposal on existing smart contracts.

The impact is not negligible, with a 26% gas cost increase on average. However, this will be gauged against the impact to the security and scalability of the consensus of the network, and Verkle trees could be a game-changer in this regard.

INTRODUCTION

Dedaub was commissioned by the Ethereum Foundation to investigate the impact of Vitalik Buterin’s Verkle tree gas metering proposal on existing smart contracts. In order to appraise the impact of the proposed change, we performed extensive simulations of the proposed changes over past transactions; wrote a static analysis and applied it over most contracts deployed to the mainnet; examined bytecode, source, decompiled code, and low level traces of past transactions.

Yield Skimming: Forcing Bad Swaps on Yield Farming

Tue, 30 Mar 2021 05:29:00 +0000

By the Dedaub team

Yield Skimming

Last week we received bug bounties for disclosing smart contract vulnerabilities to Vesper Finance and BT Finance, via immunefi.com. Thank you, all!

(Notice for clients of these services: None of the vulnerabilities drain the original user funds. An attack would have financial impact, but not an overwhelming one. The maximum proceeds in the past few months would have been around $150K, and, once performed, the attack would be likely to alert the service to the vulnerability, making the attack non-repeatable. The vulnerabilities have since been mitigated and, to our knowledge, no funds are currently threatened.)

R-bounty / Primitive Finance Analysis

Thu, 18 Mar 2021 15:36:39 +0000

Three articles on the Primitive Finance vulnerability disclosure and rescue:

PrimitiveFi post-mortem analysis
Awarded R-Bounty/Founder’s Bounty
“Inside the War Room That Saved Primitive Finance“

Killing a Bad (Arbitrage) Bot … To Save Its Owner

Thu, 11 Feb 2021 15:35:00 +0000

Following the previous white-hat hacks (1, 2), on contracts flagged by our analysis tools, today we’ll talk about another interesting contract. It’s hackable for about $80K, or rather its users are: the contract is just an enabler, having approvals from users and acting on their commands. However, a vulnerability in the enabler allows stealing all the users’ funds. (Of course, we have mitigated the vulnerability before posting the article.)

The vulnerable contract is a sophisticated arbitrage bot, with no source on Etherscan. Being an arbitrage bot, it’s not surprising that we were unable to identify either the contract owner/deployer or its users.

“look Ma’, No Source!” Hacking a Defi Service With No Source Code Available

Tue, 02 Feb 2021 05:41:00 +0000

By the Dedaub team

This story describes a cool hack, for over $300K (even nearly $600K, if done at the right time). It is a white-hat hack. We performed it off-chain, demonstrated to Dinngo, the authors of the vulnerable service, and they reproduced it and applied it to rescue the funds of exposed accounts, securing them.

The hack is among the most instructive we have encountered, which is why we wanted to document it clearly. There’s something in it for everyone: it showcases the danger of token approvals, interesting financial manipulation, the use of different DeFi services (Aave, Compound, Uniswap) as part of the attack, and much more.

Ethereum Pawn Stars: “$5.7m in Hard Assets? Best I Can Do is $2.3m”

Thu, 07 Jan 2021 05:45:00 +0000

defi saver

Saving DeFi Saver with Static Contract Analysis

By the Dedaub team

In the complex DeFi protocols and decentralized finance landscape, managing debt positions and leverage often requires navigating intricate transactions within a single contract.

A little after midnight on Jan.5, we contacted the DeFi Saver team with news of a critical vulnerability we discovered in one of their deployed smart contracts and that we had just managed to (offline-)exploit. They responded immediately and we got on a channel with several DeFi Saver people within 5 minutes. Less than 20 hours later, client funds have been migrated to safety via a white-hack exploit.

Precise Static Modeling of Ethereum “Memory”

Wed, 04 Nov 2020 05:19:00 +0000

SIFIS LAGOUVARDOS, University of Athens, Greece NEVILLE GRECH, University of Athens, Greece ILIAS TSATIRIS, University of Athens, Greece YANNIS SMARAGDAKIS, University of Athens, Greece

Static analysis of smart contracts as-deployed on the Ethereum blockchain has received much recent attention. However, high-precision analyses currently face significant challenges when dealing with the Ethereum VM (EVM) execution model. A major such challenge is the modeling of low-level, transient “memory” (as opposed to persistent, on-blockchain “storage”) that smart contracts employ. Statically understanding the usage patterns of memory is non-trivial, due to the dynamic allocation nature of in-memory buffers. We offer an analysis that models EVM memory, recovering high-level concepts (e.g., arrays, buffers, call arguments) via deep modeling of the flow of values. Our analysis opens the door to Ethereum static analyses with drastically increased precision. One such analysis detects the extraction of ERC20 tokens by unauthorized users. For another practical vulnerability (redundant calls, possibly used as an attack vector), our memory modeling yields analysis precision of 89%, compared to 16% for a state-of-the-art tool without precise memory modeling. Additionally, precise memory modeling enables the static computation of a contract’s gas cost.

MadMax: Analyzing the Out-of-Gas World of Smart Contracts

Sun, 04 Oct 2020 05:40:04 +0000

Abstract Ethereum is a distributed blockchain platform, serving as an ecosystem for smart contracts: full-fledged intercommunicating programs that capture the transaction logic of an account. A gas limit caps the execution of an Ethereum smart contract: instructions, when executed, consume gas, and the execution proceeds as long as gas is available. Gas-focused vulnerabilities permit an attacker to force key contract functionality to run out of gas-effectively performing a permanent denial-of-service attack on the contract. Such vulnerabilities are among the hardest for programmers to protect against, as out-of-gas behavior may be uncommon in nonattack scenarios and reasoning about these vulnerabilities is nontrivial.

Ethainter: A Smart Contract Security Analyzer for Composite Vulnerabilities

Mon, 15 Jun 2020 06:38:22 +0000

Lexi Brent∗ Int’l Computer Science Institute Berkeley, CA, USA lexi@icsi.berkeley.edu

Neville Grech University of Athens Athens, Greece me@nevillegrech.com

Sifis Lagouvardos University of Athens Athens, Greece sifis.lag@di.uoa.gr

Bernhard Scholz University of Sydney Sydney, NSW, Australia bernhard.scholz@sydney.edu.au

Yannis Smaragdakis University of Athens Athens, Greece yannis@smaragd.org

Abstract Smart contracts on permission less blockchains are exposed to inherent security risks due to interactions with untrusted entities. Static analyzers are essential for identifying security risks and avoiding millions of dollars worth of damage. We introduce Ethainter, a security analyzer checking information flow with data sanitization in smart contracts. Ethainter identifies composite attacks that involve an escalation of tainted information, through multiple transactions, leading to severe violations. The analysis scales to the entire blockchain, consisting of hundreds of thousands of unique smart contracts, deployed over millions of accounts. Ethainter is more precise than previous approaches, as we confirm by automatic exploit generation (e.g., destroying over 800 contracts on the Ropsten network) and by manual inspection, showing a very high precision of 82.5% valid warnings for end-to- nd vulnerabilities. Ethainter’s balance of precision and completeness offers significant advantages over other tools such as Securify, Securify2, and teEther.

Rising Gas Prices Are Threatening Our Security (No, It’s Not the Saudi Attack)

Sun, 22 Sep 2019 05:52:00 +0000

Mr. Out of gas exception

EIP 1884 is set to be implemented into the upcoming Ethereum ‘Istanbul’ hard fork. It:

increases the cost of opcode SLOAD from 200 to 800 gas
increases the cost of BALANCE and EXTCODEHASH from 400 to 700 gas
adds a new opcode SELFBALANCE with cost 5.

Due to a fixed gas limit (2300) imposed by the .send(..) and .transfer(..) Solidity functions, fallback functions that use these opcodes may now start to fail due to an out-of-gas exception. This has significant implications for contracts relying heavily on default functions , which might not execute as expected under the new gas constraints.

Gigahorse: Smart Contract Decompiler by Dedaub

Sat, 25 May 2019 04:25:00 +0000

The rise of smart contract-autonomous applications running on blockchains-has led to a growing number of threats, necessitating sophisticated program analysis. However, smart contracts, which transact valuable tokens and cryptocurrencies, are compiled to very low-level bytecode. This bytecode is the ultimate semantics and means of enforcement of the contract.

We present the Gigahorse toolchain. At its core is a reverse compiler (i.e., a decompiler) that decompiles smart contracts from Ethereum Virtual Machine (EVM) bytecode into a high- level 3-address code representation.

Chronicle of an Attack Foretold

Wed, 27 Feb 2019 05:54:00 +0000

Co-written with

Neville Grech

In a few hours, an attacker will claim the prize for the first Consensys Diligence Ethereum hacking challenge. Here’s how they’ll do it, why nobody else can perform the same attack (any longer), and why the attacker has to wait…

The challenge consisted of a smart contract submitted to the mainnet, without sources. The contract is meant to be decoded, attacked, and drained of its minimal funds. The draining account will then get an off-contract bounty.

Bad Randomness is Even Dicier Than You Think

Thu, 14 Feb 2019 05:58:00 +0000

Co-written with Neville Grech

Bad Randomness

Trivial Exploits of Bad Randomness In Ethereum, and How To Do On-Chain Randomness (Reasonably) Well

Ethereum has been used as a platform for a variety of applications of financial interest. Several of these have a need for randomness - e.g., to implement a lottery, a competitive game, or crypto-collectibles. Unfortunately, writing a random number generator on a public blockchain is hard: computation needs to be deterministic, so that it can be replayed in a decentralized way, and all data that can serve as sources of randomness are also available to an attacker. Several exploits of bad randomness have been discussed exhaustively in the past. Next, we discuss near-trivial exploits of bad randomness, as well as ways to obtain true randomness in Ethereum.

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