Ethereum's Gray Glacier (or How I Learned to Stop Worrying and Love the Difficulty Bomb)

The delay of Ethereum’s Difficulty Bomb suggests the network’s Merge to proof-of-stake might be a bit further away than hoped.

AccessTimeIconJun 22, 2022 at 11:30 a.m. UTC
Updated May 11, 2023 at 7:09 p.m. UTC
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The crypto sector is rife with liquidations and layoffs, but Ethereum developers continue to chip away toward the Merge – the blockchain network’s upcoming shift to a new, more energy-efficient mechanism for issuing blocks and staying secure.

Ironically enough, the doom and gloom in the markets have coincided with an optimistic period in the development history of Ethereum. The network will soon shift away from its energy-intensive proof-of-work (PoW) consensus mechanism, whereby computers compete to issue blocks and earn rewards, and go to a more efficient proof-of-stake (PoS) mechanism, which randomly selects “validators” to add blocks to the blockchain if they “stake” 32 ethers with the network.

Ethereum had an encouraging Merge dress rehearsal a couple of weeks ago when its Ropsten testnet (test network) successfully switched to PoS. Testnets are networks that run in parallel to Ethereum and allow developers to experiment and test new apps without putting any real monetary value at risk.

Despite a few minor issues, the Ropsten Merge was generally considered a major success, and over the next few months, a bunch of similar trial runs will take place on other Ethereum testnets. If those test runs go off without too much of a hitch, Ethereum should, at long last, be ready to embark on its official Merge into a PoS network.

This article originally appeared in Valid Points, CoinDesk’s weekly newsletter breaking down Ethereum 2.0 and its sweeping impact on crypto markets. Subscribe to Valid Points here.

Wen Ice Age?

PoS has been on Ethereum’s road map since it launched in 2015, but the network’s plan to switch from PoW to PoS is an engineering endeavor without any real precedent. Ethereum maintains a market cap of $140 billion, and a screw-up could mean financial catastrophe.

With so much at stake, Ethereum’s developers have taken pains to dot every ‘I’ and cross every ’T’ in order to ensure the transition to PoS comes without any major hiccups. That caution, however warranted, has led to a series of setbacks for the project. The transition to PoS had been slated for as early as 2019, but every time the Merge (originally called “Ethereum 2.0”) appeared to be around the corner, the timeline seemed to shuffle back a few more months.

Ethereum’s core developers will bristle at the suggestion that the Merge has ever been “delayed.” Technically, it has never had a concrete release date. But that is really just semantics. The Merge timeline has, time and time again, extended past most peoples’ expectations.

The Merge really does appear to finally be near this time around, but the road to PoS appears to be lengthening yet again this month with the announcement that the so-called “Difficulty Bomb” will be delayed by a few months.

As EthHub explains, “Ethereum's ‘Difficulty Bomb’ refers to a mechanism that, at a predefined block number, increases the difficulty level of puzzles in the proof-of-work mining algorithm, resulting in longer-than-normal block times (and thus less ETH rewards for miners). This mechanism increases the difficulty exponentially over time and eventually leads to what is referred to as the 'Ice Age' – that is, the chain becomes so difficult to mine that it grinds to a halt and stops producing blocks (freezes).”

The Difficulty Bomb has historically been used by Ethereum’s developers as an artificial incentive for implementing the Merge. Moving the Difficulty Bomb means issuing an update to the entire network – something that will need to happen anyway with the Merge, but is a bit of a headache for developers if not completely necessary.

As the Bomb gets closer, the network will slow down until it eventually becomes unusable.

On Ethereum’s biweekly “All Core Devs” call on June 10, a developer noticed that the Difficulty Bomb, which isn’t expected to completely freeze the network for another couple of months, had already begun to slow down block issuance enough that it has become noticeable.

As a result, developers agreed to push the Bomb back by 700,000 blocks, or roughly 100 days. This will give them a few more months to run tests and prepare for the Merge without the risk of slowing down the network for no real reason.

But if the Bomb can be pushed back at will, what’s the point?

Is the Bomb pointless?

Ben Edgington, product lead at Ethereum development firm ConsenSys, described the Difficulty Bomb as “one of Ethereum’s oddities.”

“In terms of acting as a forcing function for devs, I don't feel it really serves that purpose very well,” Edgington argued. “Having these Bomb-only forks is an illustration. We're about to do the third one in Ethereum history.”

According to Edgington, that the Bomb has repeatedly been pushed back (without any update to PoS) is evidence that it is not working as intended.

In Edgington’s view, Ethereum developers already have enough motivation to roll out the Merge. “We’re aware that there is a cost to not delivering: There's an environmental cost, there's an issuance cost, there's a not being on the most secure consensus protocol cost. You know, we believe proof-of-stake is better than proof-of-work in many ways. So there are real costs to not merging soon,“ Edgington said.

Not everyone agrees with Edgington that the Bomb is pointless. Tim Beiko, who leads the All Core Devs call on behalf of the Ethereum Foundation, explained to CoinDesk that the “Bomb is extremely useful for many reasons” beyond just being a forcing function for the Merge.

“The first reason that it’s useful is that it forces people to make an active decision about their participation on the network,” Beiko said. Each time the Difficulty Bomb gets pushed back, client teams – which build the software powering the Ethereum network – need to upgrade their code. The most recent Difficulty Bomb pushback will come with the so-called Gray Glacier network upgrade, which is slated for June 29 and will require all client teams to update their software before June 27.

Whenever the network is upgraded, client teams must coordinate to update their software in unison. If the teams don’t work together, they risk fragmenting – or forking – the network into two blockchains. In Beiko’s view, the “active decision” to update and push back the Difficulty Bomb is a good exercise for client teams, because they will eventually need to flex their update muscles again for more consequential changes, like the Merge itself.

“The second reason [for the Difficulty Bomb] – and this is one I think is probably way underrated – is the idea that it makes it a bit harder to create a scam fork of Ethereum,” Beiko said. “Two years or three years ago, there was, like, Bitcoin Diamond, Bitcoin Unlimited, Bitcoin Gold, all these forks of forks of forks. The reason in large part you don't see those on Ethereum is because they require not only a one-line change – like a lot of these Bitcoin forks do – but they also require people to run the updated software.”

Beiko thinks the Difficulty Bomb can help prevent scam forks because it makes spinning up a new version of Ethereum a bit more complicated. Unless the team behind an Ethereum fork has an engineer capable of altering Ethereum’s code to remove the Difficulty Bomb, the fork will eventually grind to a halt once the Bomb hits – rendering it useless.

Moreover, Beiko said, “beyond doing the technical change, you need to convince people to download it.” You can’t just re-skin Ethereum, remove the Difficulty Bomb and invite people over to your new network. Node operators – the people with computers that keep blockchains up and running – will also need to upgrade their software in order to support an Ethereum fork.

That means launching an Ethereum fork also requires building a community that believes in your project enough that they are willing to put in a bit of extra work in order to upgrade their software.

“I think that's really healthy, both because it limits the amount of low-effort forks, but if you do have a legitimate fork, which I think are very healthy for blockchains … it puts a minimal technical bar on what they need to do,” Beiko said.

What does this mean for the Merge?

Edgington and Beiko both agree that the Bomb’s pushback won’t have much of an impact on the actual Merge timeline.

Bomb or not, they say delays and coordination challenges just come with the business of building open-source software across several different teams and time zones.

“In this distributed development community, there is a tendency for timelines to get elongated – to get prolonged – because often you move at the pace of the slowest, and often decision making is kind of hard, so it's easy to kick stuff for another week or another week and it all adds up over time,” Edgington said.

“As long as we're mindful and we keep a sense of urgency that we need to get this done, then I think we are on a good track to deliver the Merge pretty soon,” he continued.

Ethereum co-founder Vitalik Buterin recently predicted the Merge might be ready in August. Edgington predicts it will happen before Ethereum’s major developer conference, DevCon, which takes place in October.

Beiko, says something “catastrophic” would need to happen to prevent the Merge from taking place before the end of the year.

The Ropsten testnet Merge was a good indicator that a real Merge might finally be nearby, but the wait continues.

Pulse check

The following is an overview of network activity on the Ethereum Beacon Chain over the past week. For more information about the metrics featured in this section, check out our 101 explainer on Eth 2.0 metrics.

(, Etherscan)
(, Etherscan)
photoshop cl&s june 22.jpg

Disclaimer: All profits made from CoinDesk’s Eth 2.0 staking venture will be donated to a charity of the company’s choosing once transfers are enabled on the network.

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Sage D. Young was a tech protocol reporter at CoinDesk. He owns a few NFTs, gold and silver, as well as BTC, ETH, LINK, AAVE, ARB, PEOPLE, DOGE, OS, and HTR.

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