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 Attribution Analysis?

Attribution analysis is a sophisticated method for evaluating the performance of a portfolio or fund manager. Also known as “return attribution” or “performance attribution,” it attempts to quantitatively analyze aspects of an active fund manager’s investment selections and decisions—and to identify sources of excess returns, especially as compared to an index or other benchmark.

For portfolio managers and investment firms, attribution analysis can be an effective tool to assess strategies. For investors, attribution analysis works as a way to assess the performance of fund or money managers.

How Attribution Analysis Works

Attribution analysis focuses on three factors: the manager’s investment picks and asset allocation, their investment style, and the market timing of their decisions and trades.

The method begins by identifying the asset class in which a fund manager chooses to invest. An asset class generally describes the type of investments that a manager chooses; within that, it can also get more specific, describing a geographical marketplace in which they originate and/or an industry sector. European fixed income debt or U.S. technology equities could both be examples.

Then, there is the allocation of the different assets—that is, what percentage of the portfolio is weighted to specific segments, sectors, or industries. 

Specifying the type of assets will help identify a general benchmark for the comparison of performance. Often, this benchmark will take the form of a market index, a basket of comparable assets.

Analyzing Investment Style

The next step in attribution analysis is to determine the manager’s investment style. Like the class identification discussed above, a style will provide a benchmark against which to gauge the manager’s performance.

The first method of style analysis concentrates on the nature of the manager’s holdings. If they are equities, for example, are they the stocks of large-cap or small-cap companies? Value- or growth-oriented?

American economist Bill Sharpe introduced the second type of style analysis in 1988. Returns-based style analysis (RBSA) charts a fund’s returns and seeks an index with comparable performance history. Sharpe refined this method with a technique that he called quadratic optimization, which allowed him to assign a blend of indices that correlated most closely to a manager’s returns.

Explaining Alpha

Once an attribution analyst identifies that blend, they can formulate a customized benchmark of returns against which they can evaluate the manager’s performance. Such an analysis should shine a light on the excess returns, or alpha, that the manager enjoys over those benchmarks.

The next step in attribution analysis attempts to explain that alpha. Is it due to the manager’s stock picks, selection of sectors, or market timing? To determine the alpha generated by their stock picks, an analyst must identify and subtract the portion of the alpha attributable to sector and timing. Again, this can be done by developing customize benchmarks based on the manager’s selected blend of sectors and the timing of their trades. If the alpha of the fund is 13%, it is possible to assign a certain slice of that 13% to sector selection and timing of entry and exit from those sectors. The remainder will be stock selection alpha.

Market Timing and Attribution Analysis

Though some managers employ a buy-and-hold strategy, most are constantly trading, making buy and sell decisions throughout a given period. Segmenting returns by activity can be useful, telling you if a manager’s decisions to add or subtract positions from the portfolio helped or hurt the final return—vis-à-vis a more passive buy-and-hold approach.

Enter market timing, the third big factor that goes into attribution analysis. A fair amount of debate exists on its importance, though.

Certainly, this is the most difficult part of attribute analysis to put into quantitative terms. To the extent that market timing can be measured, scholars point out the importance of gauging a manager’s returns against benchmarks reflective of upturns and downturns. Ideally, the fund will go up in bullish times and will decline less than the market in bearish periods.

Even so, some scholars note that a significant portion of a manager’s performance with respect to timing is random, or luck. As a result, in general, most analysts attribute less significance to market timing than asset selection and investment style.

What Is the Accounting Cycle?

The accounting cycle is a collective process of identifying, analyzing, and recording the accounting events of a company. It is a standard 8-step process that begins when a transaction occurs and ends with its inclusion in the financial statements.

The key steps in the eight-step accounting cycle include recording journal entries, posting to the general ledger, calculating trial balances, making adjusting entries, and creating financial statements.

How the Accounting Cycle Works 

The accounting cycle is a methodical set of rules to ensure the accuracy and conformity of financial statements. Computerized accounting systems and the uniform process of the accounting cycle have helped to reduce mathematical errors. Today, most software fully automates the accounting cycle, which results in less human effort and errors associated with manual processing.

Steps of the Accounting Cycle

There are eight steps to the accounting cycle.

1. Identify Transactions: An organization begins its accounting cycle with the identification of those transactions that comprise a bookkeeping event. This could be a sale, refund, payment to a vendor, and so on.
2. Record Transactions in a Journal: Next come recording of transactions using journal entries. The entries are based on the receipt of an invoice, recognition of a sale, or completion of other economic events.
3. Posting: Once a transaction is recorded as a journal entry, it should post to an account in the general ledger. The general ledger provides a breakdown of all accounting activities by account.
4. Unadjusted Trial Balance: After the company posts journal entries to individual general ledger accounts, an unadjusted trial balance is prepared. The trial balance ensures that total debits equal the total credits in the financial records.
5. Worksheet: Analyzing a worksheet and identifying adjusting entries make up the fifth step in the cycle. A worksheet is created and used to ensure that debits and credits are equal. If there are discrepancies then adjustments will need to be made.
6. Adjusting Journal Entries: At the end of the period, adjusting entries are made. These are the result of corrections made on the worksheet and the results from the passage of time. For example, an adjusting entry may accrue interest revenue that has been earned based on the passage of time.
7. Financial Statements: Upon the posting of adjusting entries, a company prepares an adjusted trial balance followed by the actual formalized financial statements.
8. Closing the Books: An entity finalizes temporary accounts, revenues, and expenses, at the end of the period using closing entries. These closing entries include transferring net income into retained earnings. Finally, a company prepares the post-closing trial balance to ensure debits and credits match and the cycle can begin anew.

Timing of the Accounting Cycle

The accounting cycle is started and completed within an accounting period, the time in which financial statements are prepared. Accounting periods vary and depend on different factors; however, the most common type of accounting period is the annual period. During the accounting cycle, many transactions occur and are recorded.

At the end of the year, financial statements are generally prepared, which are often required by regulation. Public entities are required to submit financial statements by certain dates. All public companies that do business in the U.S. are required to file registration statements, periodic reports, and other forms to the U.S. Securities and Exchange Commission. Therefore, their accounting cycle revolves around reporting requirement dates.

The Accounting Cycle Vs. Budget Cycle

The accounting cycle is different than the budget cycle. The accounting cycle focuses on historical events and ensures incurred financial transactions are reported correctly. Alternatively, the budget cycle relates to future operating performance and planning for future transactions. The accounting cycle assists in producing information for external users, while the budget cycle is mainly used for internal management purposes.