Attacks on Ethereum: Shocking? Why 1,920,000 Block was important by Prof. Naveen Kandwal

Attacks on Ethereum
Attacks on Ethereum explained

Ethereum Classic was created after the hacking of the Decentralized Autonomous Organization, a virtual venture capital fund based on Ethereum. On 16 June 2016, the attacker managed to steal approximately 3.6 million Ether from the DAO fund abusing a loophole, which is known as a “recursive call exploit”.

Following the attacks on Ethereum, members of Ethereum community decided to hard fork the network and revert the transactions. A hard fork involves an upgrade of a blockchain network that can incorporate major changes to the protocol.

As a result of the hard fork Ethereum(ETH) was born and Ethereum Classic remained — thus giving birth, or rebirth, to the blockchain, and its cryptocurrency, ETC.

History of Ethereum Blockchain 

Vitalik Buterin in late 2013 described Ethereum with the argument that Bitcoin needs a different programming language for execution of tasks and build applications on Blockchain. The Bitcoin community never supported this idea of Vitalik, but still the creation of Ethereum Classic(ETC) the original Ethereum blockchain took place in 2014.

Initial development efforts were funded through a crowdsale in July 2014, raising more than 25,000 BTC making it the largest ever crypto raising till 2014. 

The Ethereum project’s mainnet on Frontier initially released on 30 July 2015. However, due to DAO project theft (One of the biggest attacks on Ethereum), the Ethereum Foundation created a new version of the Ethereum mainnet on 20 July 2016 with an irregular state change implemented that erased The DAO theft from the Ethereum blockchain history.

The Ethereum Foundation applied their trademark to the new, altered version of the Ethereum blockchain; Ethereum (ETH). The older, unaltered version of Ethereum was renamed and continued on as Ethereum Classic (ETC).

Ethereum Classic is a decentralized computing platform that executes smart contracts. Applications that run exactly as programmed without the possibility of censorship, downtime, or third-party interference.

Ethereum Classic is a distributed network consisting of a blockchain ledger, native cryptocurrency (ETC) and robust ecosystem of on-chain applications and services.

  • Ethereum Classic provides a permissionless way to manage digital assets without the need for intermediaries, such as banks and other institutions.
  • Ethereum Classic allows uncensorable smart contracts to be written, deployed and executed; ETC enables truly unstoppable programmable money.
  • Ethereum Classic is the continuation of the unaltered history of the original Ethereum chain. The ETC network exists to preserve the principle of “Code is Law“.

Features in Ethereum Blockchain 


Ether is a basic token for operation of Ethereum Classic, which then provides a public distributed ledger for transactions. It is used to pay for a unit Gas, which is a unit of computation used in transactions and other state transitions. Additionally, the currency is referred to as Ethereum, Eth, Classic or ETC on digital platforms. It is also used to pay as a transaction fees and computational services on the Ethereum Classic network.


Ethereum Classic addresses starts with the prefix “0x”, a common identifier for hexadecimal code, concatenated with the rightmost 20 bytes of the Keccak-256 hash of the Elliptic Curve Digital Signature Algorithm (ECDSA) public key (the curve is called secp256k1, the same as bitcoin). 

In hexadecimal, two digits represent a byte, meaning addresses contain 40 hexadecimal digits. An example of an Ethereum Classic address is 0xb794f5ea0ba39494ce839613fffba74279579268. Contract addresses are in the same format as mentioned, however, they are determined by sender and creation transaction nonce. User accounts are indistinguishable from contract accounts given only an address for each and no blockchain data. Keccak-256 hash put into the described format is always valid, even if it does not correspond to an account with a private key or a contract.

Monetary policy

On 11 December 2017, the total supply of Ether on Ethereum Classic was hard capped at 210,700,000 ETC via the Gotham hard fork upgrade. This added a bitcoin-inspired deflationary emission schedule that is documented in Ethereum Classic Improvement Proposal (ECIP) 1017. The emission schedule, also known as “5M20”, reduces the block reward by 20% every 5,000,000 blocks. Socially, this block reward reduction event has taken the name of “the fifthening“.

Date5M20 eraBlockBlock rewardTotal era emission
2015-07-30Era 115 ETC25,000,000 ETC
2017-12-11Era 25,000,0014 ETC20,000,000 ETC
2020-03-17Era 310,000,0013.2 ETC16,000,000 ETC
2022-04-15Era 415,000,0012.56 ETC12,800,000 ETC
2024-05-07Era 520,000,0012.048 ETC10,240,000 ETC
Block Reward due to “The Fifthening” on Ethereum Classic (ETC)

Milestones in Ethereum Blockchain

Since July 2015, Ethereum Blockchain has witnessed many updates as required to make its Blockchain secure and reliable for smart contracts. 

Olympic ( Testnet ): Launched May 2015

Block 0: Frontier | July 30, 2015

Block  200,000: Ice Age | August 09,2015

Block 1,150,000: Homestead | May 14, 2016

Block 1,920,000: DAO Bailout | July 20, 2016 (To prevent Attacks on Ethereum)

Block 2,463,000: Tangerine Whistle

Block 3,000,000: Die Hard | January 13, 2017

Block 5,000,000: Gotham | December 11, 2017

Block 5,000,001: 5M20 Era 2 | December 11, 2017

Block 5,900,000: Diffuse Difficulty Bomb | May 29,2018 

Block 8,772,000: Atlantis | September 12, 2019

Block 9,573,000: Agharta | January 11, 2020

Block 10,000,001: 5M20 Era 3 | January 11, 2020

Block 10,500,839: Phoenix | June 01, 2020

Block 11,700,000: Thanos | November 28, 2020

Attacks on Ethereum Blockchain

The DAO Fork Attacks | Attacks on Ethereum

On 20 July 2016, due to reliance on the same clients, the DAO fork created a replay attack where a transaction was broadcast on both the ETC and ETH networks. On 13 January 2017, the Ethereum Classic network was updated to resolve transaction replay attacks. The networks are now officially operating separately.

RHG selling stolen ETC | Attacks on Ethereum

On 10 August 2016, the Robin Hood Group (RHG) transferred 2.9 million stolen ETC to Poloniex Exchange in an attempt to sell ETC for ETH on the advice of Bitly SA; 14% was successfully converted to ETH and other currencies, 86% was frozen by Poloniex.

On 30 August 2016, Poloniex returned the ETC funds to the RHG.

Classic Ether Wallet website attack | Attacks on Ethereum

On 29 June 2017, the Ethereum Classic Twitter account made a statement indicating that the website for Classic Ether Wallet had been compromised.

The Ethereum Classic Twitter account confirmed the details released via Threatpost with Bittrex Exchange Address involved in it 0xe94b04a0fed112f3664e45adb2b8915693dd5ff3.

The Ethereum Classic team worked with Cloudflare to place a warning on the compromised domain warning users of the phishing attack.

51% double spend attacks | Attacks on Ethereum

Rollback attacks are often referred to as 51-percent attacks, because, in theory, it requires an attacker to control a majority of the CPU power generating a blockchain. Such an arrangement violates a core requirement of any blockchain-based currency allowing a single entity to write the contents of its universal shared transaction history.

In January 2019, Ethereum Classic was subject to double-spending attacks. After 2016 attacks on Ethereum, it was something that challenged the double spending in Ethereum.

From July through August 2020, Ethereum Classic suffered many times from 51% attacks. 

We observed repeated deep reorganizations of the Ethereum Classic blockchain, most of which contained double spends. The total value of the double spends that we have observed thus far is 88,500 ETC (~$460,000).”

Coinbase security engineer Mark Nesbitt on his blog
Coinbase confirmed double spending | | Ethereum Classic attacks


Ethereum Blockchain has been compromised many times in the past due to attacks on Ethereum by third-party involvement since 2016. With time Ethereum Blockchain has received multiple updates in the form of milestones to make it trustable and safe for its community again and again. Today many blockchain projects are still based on the Ethereum platform making it the first preference for the development environment. The potential of Ethereum looks solid for now and with new updates going on for Ethereum 2.0 to be on mainnet in 2022.

Reference: Attacks on Ethereum 

Leave a Reply