What Is a 51% Attack?

A 51% attack is an attack on a cryptocurrency blockchain by a group of miners who control more than 50% of the network’s mining hash rate. Owning 51% of the nodes on the network gives the controlling parties the power to alter the blockchain.

The attackers would be able to prevent new transactions from gaining confirmations, allowing them to halt payments between some or all users. They would also be able to reverse transactions that were completed while they were in control. Reversing transactions could allow them to double-spend coins, one of the issues consensus mechanisms like proof-of-work were created to prevent.

Understanding a 51% Attack

A blockchain is a distributed ledger—essentially a database—that records transactions and information about them and then encrypts the data. The blockchain’s network reaches a majority consensus about transactions through a validation process, and the blocks where the information is stored are sealed. The blocks are linked together via cryptographic techniques where previous block information is recorded in each block. This makes the blocks nearly impossible to alter once they are confirmed enough times.

The 51% attack is an attack on the blockchain, where a group controls more than 50% of the hashing power—the computing that solves the cryptographic puzzle— of the network. This group then introduces an altered blockchain to the network at a very specific point in the blockchain, which is theoretically accepted by the network because the attackers would own most of it.

Changing historical blocks—transactions locked in before the start of the attack—would be extremely difficult even in the event of a 51% attack. The further back the transactions are, the more difficult it is to change them. It would be impossible to change transactions before a checkpoint, where transactions become permanent in Bitcoin’s blockchain.

Attacks Are Prohibitively Expensive

A 51% attack is a very difficult and challenging task on a cryptocurrency with a large participation rate. In most cases, the group of attackers would need to be able to control the necessary 51% and have created an alternate blockchain that can be inserted at the right time. Then, they would need to out-hash the main network. The cost of doing this is one of the most significant factors that prevent a 51% attack.

For example, the most advanced application-specific integrated circuit (ASIC) miner is the Bitmain S19 XP Hydro. It costs more than $19,800 and has a hash rate of 255 terahashes per second (TH/s).

The top three mining pools by hashrate are:

• FoundryUSA, at 54.42 exahashes per second (EH/s); 23.75% of the total Bitcoin network hashrate
• AntPool, at 41.49 EH/s; 18.12% of the total Bitcoin network hashrate
• Binance Pool, at 34.48 EH/s; 15.06% of the total network hashrate

Combined, these three pools make up 56.93% of the network hashrate, a whopping 130.4 EH/s (1.304 million TH/s). To equal that hashrate, the attackers would need more than 511,373 S19 XP Hydros—which would put fixed costs close to $10.13 billion, plus a building to host the equipment, maintenance staff, electricity, and cooling.

Major cryptocurrencies, such as Bitcoin, are unlikely to suffer from 51% attacks due to the prohibitive cost of acquiring that much hashing power. For that reason, 51% attacks are generally limited to cryptocurrencies with less participation and hashing power.

After Ethereum’s transition to proof-of-stake, a 51% attack on the Ethereum blockchain became even more expensive. To conduct this attack, a user or group would need to own 51% of the staked ETH on the network. It is possible for someone to own that much ETH, but it’s unlikely; according to Beaconchain, more than 13.8 million ETH were staked at the end of September 2022. An entity would need to own more than 6.9 million ETH (more than $9 billion worth) to attempt an attack.

Once the attack started, the consensus mechanism would likely recognize it and immediately slash the staked ETH, costing the attacker an extraordinary amount of money. Additionally, the community can vote to restore the “honest” chain, so an attacker would lose all of their ETH just to see the damage repaired.

Attack Timing

In addition to the costs, a group that attempts to attack the network using a 51% attack must not only control 51% of the network but must also introduce the altered blockchain at a very precise time. Even if they own 51% of the network hashing rate, they still might not be able to keep up with the block creation rate or get their chain inserted before valid new blocks are created by the ‘honest’ blockchain network.

Again, this is possible on smaller cryptocurrency networks because there is less participation and lower hash rates. Large networks make it nearly impossible to introduce an altered blockchain.

Outcome of a Successful Attack

In the event of a successful attack, the attackers could block other users’ transactions or reverse them and spend the same cryptocurrency again. This vulnerability, known as double-spending, is the digital equivalent of a perfect counterfeit. It is also the basic cryptographic hurdle blockchain consensus mechanisms were designed to overcome.

Successful 51% attackers may also implement a Denial-of-Service (DoS) attack, where they block the addresses of other miners for the period they control the network. This keeps the “honest” miners from reacquiring control of the network before the dishonest chain becomes permanent.

Who Is at Risk of 51% Attack?

The type of mining equipment is also a factor, as ASIC-secured mining networks are less vulnerable than those that can be mined with GPUs; they are much faster. Cloud services such as NiceHash—which considers itself a “hash-power broker”—theoretically make it possible to launch a 51% attack using only rented hash power, especially against smaller, GPU-only networks.

Bitcoin Gold has been a common target for attackers because it is a smaller cryptocurrency by hashrate. Since June 2019, the Michigan Institute for Technology’s Digital Currency Initiative has detected, observed, or been notified of more than 40 51% attacks—also called chain reorganizations, or reorgs—on Bitcoin Gold, Litecoin, and other smaller cryptocurrencies.

What Is an 18-Hour City?

Economists and real estate investors use the term 18-hour city to describe a mid-size city with attractive amenities, higher-than-average population growth, and a lower cost of living and cost of doing business than the biggest urban areas. The 18-hour city generally has a population of under one million, making it a second-tier city.

Eighteen-hour cities in the U.S. are increasingly seen as viable alternatives for investment and living to the Big Six markets of Boston, Chicago, Los Angeles, New York, San Francisco and Washington, D.C that make up America’s first-tier or 24-hour cities.

Understanding the 18-Hour City

While loosely defined, the term 18-hour city most often refers to a city that has public services, amenities and job opportunities that are comparable in quality to those in the big six markets.

Unlike the biggest cities, most of their services and amenities don’t operate on a 24-hour basis. However, they boast comparable advantages, including solid public transportation systems, modern infrastructure and strong economies. Housing prices are moderate in comparison.

The 18-Hour City Advantage

Eighteen-hour cities have emerged as an attractive alternative to big cities for starting a new business, relocating an existing one, or investing in real estate. They typically feature lower capitalization rate compression, meaning property values tend to remain stable rather than spiking up or down significantly.

Like first-tier cities, 18-hour cities often boast low real estate vacancy rates along with favorable supply concentrations, rental growth and absorption trends—all indicators of long-term real estate investment potential.

Aside from the numbers, Forbes.com cites a distinctive and lovable culture as a key factor in creating and maintaining a vibrant 18-hour city: “Austin is the live music capital of the world. Denver and the Research Triangle are outdoor meccas. Portland is just plain weird (and residents would like to keep it that way.”

One perceived downside is the increased risk inherent in cities that do not have the established track record of primary market cities.

Examples of 18-Hour Cities in the U.S.

CrowdStreet, a site for crowd-sourced real estate investments, cites Austin, Denver, and Nashville as recent stars among 18-hour cities. In 2020, it identified Charleston, South Carolina, as the next big success story in the category.

Realtor.com identified its top metropolitan areas for 2020 and beyond, with all of its top five picks squarely in the 18-hour city category. They include Boise, Idaho; Mc-Allen-Edinburg-Mission, Texas; Tucson, Arizona; Chattanooga, Tennessee, and Columbia, South Carolina.

The National Real Estate Investor website chose Charleston, Kansas City, and Columbus, Ohio, based on their stellar growth in jobs.

Follow the Millennials

These and other frequently-cited 18-hour city stars have become targets for millennials whose goal is launching or advancing their careers. They are characterized by the availability of recreation and entertainment opportunities that extend well beyond what the typical second-tier affords.

Employers are drawn to 18-hour cities because doing business is less expensive in these markets and this, in turn, attracts large numbers of job seekers and entrepreneurs.

What Is a 341 Meeting?

The term “341 meeting” refers to a meeting between creditors and debtors that is required to take place during the course of a Chapter 7 bankruptcy proceeding. Accordingly, its name is derived from section 341 of the bankruptcy code.

A 341 meeting is typically scheduled roughly one month after a debtor files for bankruptcy. To be considered legally valid, the meeting must include both the individual filing for bankruptcy and the court-appointed bankruptcy trustee.

How 341 Meetings Work

The 341 meeting is one of many stages involved in declaring bankruptcy in the United States. Its primary purpose is to establish the facts of the bankruptcy in question, and to ensure that all the paperwork necessary to carry out the bankruptcy proceedings are in order. Although the attorneys of the debtor and creditor are welcome to attend, the only parties whose presence at the 341 meeting is legally required are the debtor in question and the court-appointed trustee.

Prior to the 341 meeting, the trustee would have already reviewed the bankruptcy paperwork and financial records submitted by the debtor. The purpose of the 341 meeting, therefore, is principally for the trustee to confirm the facts stated by the debtor and to collect any additional paperwork that may be required. In the event that the debtor is attempting bankruptcy fraud, this would likely be detected by the trustee during or prior to the 341 meeting.

From the debtor’s perspective, the objective of the 341 meeting is to provide the necessary documents in order to prove that their identity is authentic, while also establishing their current assets, liabilities, income, expenses, and other relevant financial circumstances. If the creditors are in attendance, they will be able to ask clarifying questions, such as whether the debtor is entitled to any upcoming income sources, ie. tax rebates or inheritances, or whether the debtor owns undisclosed assets, such as shares in a private business or assets held overseas.

Real World Example of a 341 Meeting

Peter is a bankruptcy trustee currently presiding over a 341 meeting. The debtor present declared bankruptcy over a $5,000 debt, and has attended the meeting along with his bankruptcy lawyer. Likewise, the creditor and her lawyer are also present.

Peter’s first priority is to verify the identity and financial status of the debtor. Although Peter already reviewed many documents prior to the meeting, the 341 meeting provides an occasion to ask follow-up questions about the documents provided and to obtain any additional disclosures deemed necessary. In the unlikely event that the debtor were attempting bankruptcy fraud, this would also likely be detected due to discrepancies or inadequacies in the documents provided.

During the meeting, the lawyers for the debtor and creditor engaged in detailed conversation regarding the debtor’s assets, liabilities, and income sources; and were able to negotiate a general plan for the gradual repayment of the outstanding debt. As is the case with most 341 meetings, the meeting took place at Peter’s office, rather than in court before a judge.