Etheroll Fork Manipulation

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Etheroll

Etheroll is an online gambling site, which enables users to interact with a smart contract for "provably fair" gambling.

The contract, however, had an exploit, that allowed some players to get an advantage and win repeatedly.

The contract was shut down before significant loss, and subsequently fixed.

This exchange or platform is based in Switzerland, or the incident targeted people primarily in Switzerland.

About Etheroll

"Etheroll is an Ethereum smart contract for placing bets on our provably-fair dice game using Ether with no deposits or sign-ups. Each dice roll is provably random and cryptographically secure thanks to the nature of the Ethereum blockchain." The "Ethereum dice game is provably-fair, has a low 1% house edge and no sign-ups or deposits."

"Contract [was first placed] in lock-down mode." "After noticing some highly suspicious activity during game play [the team] put the contract into lock-down mode. This means the contract is currently not accepting any more bets, and all player payouts are frozen." "Any pending games [were] resolved and/or refunded."

"THE ATTACK: The attacker is monitoring honest players txs, oracle's txs and the chain. An honest player submits a bet, a request to the oracle for a random number (x), along with a betid occurs instantly on and off-chain. The betid is now ‘in-flight’ and destined to be returned to our contract in the future, in which case the address assigned to that betid receives payout on a win."

"Attacker is monitoring for chain forks, in which event the honest betid that was confirmed is not in the on-chain head anymore, the attacker pre-calculates that betid (trivial) then submits a tx which assigns that betid slot to be the same value as the one that is in-flight and now assigned to their address along with a new target x+1 (x being visible in-flight on the return), the in-flight callback completes and the payout is made."

"Attacker was also running contracts which were constantly submitting 90% bets to make sure there would be a bet to 'hijack' when/if a fork occurs. They essentially hijack their own bets which go missing during chain forks and 'reassign' the betid slot, whilst updating the target to be x+1."

"The attack was always going to be relatively slow as the method the attacker was using has constraints in that they needed to wait for a chain fork to occur in order to reassign the lost on-chain betid to their own address, which only happens every so often, which is probably why they decided to maximise their return when they finally did detect a chain fork and had set their target to be x+1. Essentially, they got greedy."

"Game contract [was subsequently] updated and deployed to production after security hardening. Additional data added to the oracle query id is verified in the callback (which is also included in the TLSNotary proof) that makes it impossible for an attacker to swoop in on forked query ids and change the forked player target and/or bet value."

This exchange or platform is based in Switzerland, or the incident targeted people primarily in Switzerland.

The background of the exchange platform, service, or individuals involved, as it would have been seen or understood at the time of the events.

Include:

• Known history of when and how the service was started.
• What problems does the company or service claim to solve?
• What marketing materials were used by the firm or business?
• Audits performed, and excerpts that may have been included.
• Business registration documents shown (fake or legitimate).
• How were people recruited to participate?
• Public warnings and announcements prior to the event.

Don't Include:

• Any wording which directly states or implies that the business is/was illegitimate, or that a vulnerability existed.
• Anything that wasn't reasonably knowable at the time of the event.

There could be more than one section here. If the same platform is involved with multiple incidents, then it can be linked to a main article page.

The Reality

This sections is included if a case involved deception or information that was unknown at the time. Examples include:

• When the service was actually started (if different than the "official story").
• Who actually ran a service and their own personal history.
• How the service was structured behind the scenes. (For example, there was no "trading bot".)
• Details of what audits reported and how vulnerabilities were missed during auditing.

What Happened

The specific events of the loss and how it came about. What actually happened to cause the loss and some of the events leading up to it.

Key Event Timeline - Etheroll Fork Manipulation

Date	Event	Description
April 25th, 2020	Main Event	Expand this into a brief description of what happened and the impact. If multiple lines are necessary, add them here.

Technical Details

This section includes specific detailed technical analysis of any security breaches which happened. What specific software vulnerabilities contributed to the problem and how were they exploited?

Total Amount Lost

No funds were lost.

How much was lost and how was it calculated? If there are conflicting reports, which are accurate and where does the discrepancy lie?

Immediate Reactions

How did the various parties involved (firm, platform, management, and/or affected individual(s)) deal with the events? Were services shut down? Were announcements made? Were groups formed?

Ultimate Outcome

What was the end result? Was any investigation done? Were any individuals prosecuted? Was there a lawsuit? Was any tracing done?

Total Amount Recovered

There do not appear to have been any funds recovered in this case.

What funds were recovered? What funds were reimbursed for those affected users?

Ongoing Developments

What parts of this case are still remaining to be concluded?

General Prevention Policies

No user funds were lost in this case.

While not directly related to exchanges, this helps to demonstrate the limitations of smart contracts when it comes to having certainty of security.

The best storage of funds is in simpler multi-sig setups with trusted entities holding the keys.

Individual Prevention Policies

No specific policies for individual prevention have yet been identified in this case.

For the full list of how to protect your funds as an individual, check our Prevention Policies for Individuals guide.

Platform Prevention Policies

Policies for platforms to take to prevent this situation have not yet been selected in this case.

For the full list of how to protect your funds as a financial service, check our Prevention Policies for Platforms guide.

Regulatory Prevention Policies

No specific regulatory policies have yet been identified in this case.

For the full list of regulatory policies that can prevent loss, check our Prevention Policies for Regulators guide.