Consequently, the plot shows a smooth line on the low heights, denoting the constant byte length of public keys being used. The shift towards using compressed public keys is progressive, so the average public key size decreases from that point until block , when it stabilizes at around Such behaviour indicates that, despite the obvious advantage of using compressed public keys, some Bitcoin users are still using uncompressed keys.
Block average public key sizes for P2PKH outputs. P2SH inputs must contain the redeem script whose hash matches the one specified in the UTXO and any data that are required to make the redeem script evaluate to true. Both items must be taken into account when computing the size of the input. Table 4 breaks down the P2SH redeem scripts by type found in the blockchain, describing the average and the standard deviation of the length of their input script.
That is, they consider the size of both the redeem script and the data consumed by that script. Multisig scripts are by far the most common script encapsulated within P2SH, and they account for Because native multisig outputs are costly, it is common to encapsulate them in a P2SH, transferring the fees to the redeemer of the output. The size of a P2SH multisig input is determined by the number of allowed signers that determines the number of public keys and the number of required signers that determines the number of signatures.
The activation of segwit added four more types of output scripts to the existing set: two native scripts and the two P2SH nested versions. Non-standard redeem scripts may be of arbitrary length. However, the redeem script has to be pushed to the stack, so it is affected by the maximum stack element size of bytes.
The largest input script of this type is 9 bytes long. Inputs of P2SH scripts with nested P2PK scripts may be either or bytes long assuming byte signatures , depending on whether they use compressed or uncompressed public keys. Nevertheless, data show that almost all of them have compressed public keys there are just six of such scripts in the blockchain using uncompressed public keys.
Similarly, inputs of P2SH scripts with nested P2PKH scripts may be either or bytes long, although all of them used compressed keys. Finally, there are 82 redeem scripts that contain hash puzzles, that is, they ask for the preimage of a hash. These make input sizes of 25 and bytes, respectively.
In contrast with compressed and uncompressed public key usage, whose behaviour highly depends on the block height, we have found a small correlation between P2SH input script sizes and the block height where they are found figure There are no blocks with P2SH input scripts up until block and the script sizes start to decrease at height Inputs spending non-standard outputs may contain scripts of arbitrary length. Since such inputs do not have a predefined structure, we resort to analysing the sizes of inputs spending non-standard outputs in the blockchain.
We have found of such inputs in the blockchain, which correspond to 78 different input scripts. The average size of non-standard input scripts is 1. These non-standard inputs are found in just different blocks, so data is too disperse to evaluate its size with respect to block height. We have found P2WSH inputs with an average witness size of As P2SH input scripts, witness length is not clearly correlated with block height figure The first P2WSH input is found in block P2WSH inputs in the Bitcoin blockchain.
Average P2WSH witness size bytes. In previous sections, we have seen that the two parameters that affect the amount of fees needed to spend a transaction are the size of the transaction and the current fee-per-byte rate. After that, we analyse how unprofitability has evolved over time. To study the impact of dust, we have considered the fixed input size of bytes as defined by the Bitcoin client discounting segwit when needed.
As explained in the previous section, the use of compressed or uncompressed public keys was highly dependant on the block height. Therefore, to estimate variable sizes, we use the absolute average of the sizes found in the blockchain for P2SH, non-standard and P2WSH inputs, and the average for outputs at a given height for P2PKH. Table 6 presents a summary of the values used for the estimations. Note that P2PKH input scripts are always estimated to be between and bytes regardless of the analysed coin, although the exact distribution differs and is computed individually from the history of each coin.
Summary of script size estimations per script type and coin computed using data in the blockchain. As depicted in figure 8 , fee-per-byte rate is far from fixed and has high variability. Figure 13 a shows the fraction of UTXOs that are considered dust, unprofitable low and unprofitable est in the Bitcoin UTXO set blue, orange and green lines, respectively.
Note that 5 outputs will always be considered dust and unprofitable, regardless of the fee rate, because they have an amount of 0. Dust and unprofitable analysis for Bitcoin. UTXOs w. On the contrary, unprofitability will only take into account the size of the input.
For the lower bound, it will be either or depending if a compressed or uncompressed public key is considered, a decision taken on the basis of the block height. For the estimation, it will be any value between and and will depend on the average public key size found for outputs of the same height.
Therefore, on one hand, dust will always estimate higher sizes than both unprofitability metrics and, on the other hand, the two unprofitability distributions are very similar, with the estimation offering slightly higher sizes than the minimum recall figure Figure 13 b shows the relative size of dust and unprofitable output sets within the total UTXO set.
Finally, from an economic point of view, figure 13 c shows, as expected, how those dust and unprofitable UTXOs represent a negligible amount from the total value of the UTXO set, that is, the total number of bitcoins in circulation.
Those UTXOs have output amounts of just 1 litoshi recall figure 5 c. Therefore, the three metrics dust and the two unprofitability versions consider all those UTXOs unprofitable at the same fee rate. Dust and unprofitable analysis for Litecoin. Dust and unprofitable analysis for Bitcoin Cash. However, their value is negligible. We have seen how for the most recent analysed UTXO set snapshot, namely data from 6 February , the percentage of data that fall into any of the three categories dust, unprofitable low and unprofitable est is far from being negligible.
In this regard, we have analysed how such data have evolved since the early days of Bitcoin. To perform such analysis, we have focused on the unprofitable est metric since we think it is the most accurate one. For Bitcoin, data have been obtained from nine snapshots from different heights of the blockchain, starting from block 14 and stepping every 50 blocks until height Figure 16 shows the number of UTXOs in the set in Bitcoin over time dots indicate the snapshots used in our analysis; table 7.
The percentage of unprofitable outputs per snapshot is almost always increasing at any point in the chart, as we can see depicted in figure 17 a. However, there are a few exceptions, the K snapshot with respect to K and K being the most relevant. The explanation of such a huge difference is in the content of that snapshot: the K snapshot has an outstanding number of UTXOs holding exactly satoshis, whereas in the K and K snapshots the UTXOs are more uniformly distributed.
In fact, the Evolution of unprofitable outputs over time. Analysing the general trend of the data for figure 17 a , we see how the accumulation of unprofitable outputs in the lower fee rates tends to increase over time, which increases the number of outputs that will be hardly spent.
Similarly, we have analysed the evolution of the UTXO sets of Litecoin by studying 13 snapshots, from block up until block 1 stepping every blocks. Unprofitability is very stable, with most snapshots all but K showing very similar distributions figure 17 b. We have omitted the figures related to Bitcoin Cash since they share the same history with Bitcoin the snapshots up until K are thus exactly the same , and therefore do not provide any new information.
The size and performance of this set have a direct impact on how the system will perform, and it is thus a focus area where to improve the scalability and efficiency of these cryptocurrencies. For example, transaction generation performance in Bitcoin is greatly influenced by the size of the UTXO set [ 9 ].
We can currently find typical statics and simple visualizations of the UTXO set of Bitcoin [ 10 , 11 ], but we are not aware of a more in-depth study and comparison of the UTXO set of significant cryptocurrencies like the one presented in this paper.
We believe that knowing the composition and evolution of the UTXO set will undoubtedly provide the means to better understand it and develop strategies and tools to improve the UTXO set usage, thus enhancing the whole system performance. The relevance of the UTXO is not new, concerns about its size, composition and performance have been around for some time [ 12 ]. These concerns are specially relevant in light of the scalability problems of Bitcoin and are currently an important issue for the future of Bitcoin itself.
Both individual users and the whole system will benefit from better management of the UTXO set. From the user point of view, a strategy of consolidating UTXOs in order to prevent the creation of dust and unprofitable UTXOs in the future in case of higher fees has always been considered [ 15 ]. A consolidation will not always reduce the fees for a given user, specially if we cannot anticipate future fee rates.
On the other hand, some user will need to maintain a minimum number of UTXOs to be able to generate transactions in parallel. Furthermore, such strategies can undermine the privacy requirements of some users. Given these, sometimes conflicting, constraints and the unpredictability of future fee rates, there is currently no actual strategy for UTXO consolidation.
An important process that directly impacts and is influenced by the UTXO set composition and size is the coin selection decision performed by wallets [ 16 ]. Coin selection is the decision process that a wallet carries in order to choose UTXOs as inputs for a new transaction. Each implementation might use a different coin selection strategy [ 17 ].
For instance, if we take a look at Bitcoin, according to [ 18 ], several strategies are being used by different wallets. The Bitcoin Core wallet attempts to find a direct match always minimizing the change to be generated. The bitcoinj library [ 22 ] determines a priority metric from the age and value of the UTXOs in order to select new ones. It is by no means clear which strategy is better. Different goals and strategies can be conflicting, such as minimizing the generation of small UTXOs, minimizing the fees for the current and future transactions, or improving the user privacy.
Even so, nowadays a common goal shared by all involved parties for the coin selection is actually to prevent the growth of the UTXO set in Bitcoin [ 18 ]. In any case, our work introduces new analysis that can help improve these selection strategies. We think that the work presented in this paper provides an accurate estimation of such unprofitable UTXOs, which has not been previously considered. Our analysis shows that the three cryptocurrencies present both similarities and differences in their UTXO sets.
On the one hand, relevant differences were found in the coin sets of Litecoin with respect to both Bitcoin versions. The two major ones are related to the height where UTXOs are found and the value they carry. On the other hand, there are some common properties in the UTXO sets of the three cryptocurrencies. Second, the usage of coins from coinbase transactions is different than the rest of coins.
Third, there is a preference for outputs with powers of 10 values. Finally, regardless of the specific metric used to quantify if an output is worth spending namely, dust or unprofitability , we have found many outputs whose properties value and size make them non-economically rational to spend, because spending them results in losing money.
However, they are just a very small amount of the current coin supply 0. These results indicate the importance of designing proper coin selection strategies in UTXO-based cryptocurrencies. If these strategies are not properly designed and applied, the UTXO sets may end up full of outputs not worth spending. In turn, maintaining these UTXO sets becomes costly, and thus its management may grow into a problem for users with low computational resources available. Therefore, our work motivates the importance of designing proper coin selection strategies.
This work opens many lines of further research. On the one hand, by describing the composition and properties of the UTXO sets, our analysis can be used to optimize the management of the sets. On the other hand, our work is the first step towards solving the problem of not-worth-spending UTXOs.
With this regard, we envision the design of both strategies to disincentivize the creation of dust UTXOs and to incentivize dust consolidation. All authors discussed which data should be included in the paper and how the results would be graphically presented. All authors proof-read the paper and gave final approval for publication. This work is partially supported by the Spanish ministry under grant no.
R Soc Open Sci. Published online Jan Delgado-Segura , 1, 2 G. Navarro-Arribas , 1, 2 and J. Author information Article notes Copyright and License information Disclaimer. Author for correspondence: J. Received May 23; Accepted Nov This article has been cited by other articles in PMC.
Associated Data Supplementary Materials Reviewer comments. Keywords: cryptocurrencies, blockchain, wallets. Introduction Blockchain-based cryptocurrencies are built on top of an append-only ledger shared among all the users of the system. Open in a separate window. Figure 1. Table 1. Summary of the main properties of the UTXO sets. UTXOs 60 39 18 avg. UTXOs per tx 2. UTXOs per tx Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. Table 2. UTXO types. Bitcoin Bitcoin Cash Litecoin no.
Figure 7. Dust and unprofitable UTXOs An interesting type of output included in the UTXO set is that whose economic value is small enough to pose a problem when it has to be spent. Fee-per-byte rate Block space is a scarce resource. Figure 8. Figure 9. Table 3. Minimum-input size summary.
Estimating variable values As introduced in the last section, the inputs of some of the output script types contain values whose size cannot be known before actually seeing the input. Figure Table 4. Summary of P2SH redeem scripts in the blockchain. Table 5. Summary of multisig configurations found in P2SH redeem scripts in the blockchain. Block average P2SH input sizes. An analysis of dust and unprofitable outputs In previous sections, we have seen that the two parameters that affect the amount of fees needed to spend a transaction are the size of the transaction and the current fee-per-byte rate.
Table 6. Evolution of unprofitability over time We have seen how for the most recent analysed UTXO set snapshot, namely data from 6 February , the percentage of data that fall into any of the three categories dust, unprofitable low and unprofitable est is far from being negligible.
Table 7. UTXO types in each Bitcoin snapshot. Supplementary Material Reviewer comments: Click here to view. Authors' contributions C. Competing interests We declare we have no competing interests. Funding This work is partially supported by the Spanish ministry under grant no.
References 1. Zahnentferner J. Chimeric ledgers: translating and unifying UTXO-based and account-based cryptocurrencies. Bitcoin Core. Bitcoin Core 0. Obfuscate database files. Bitcoin Core Github Issue In Proc. Lecture Notes in Computer Science. Bitcoin core dust definition. Bitcoin core source code policy. Bitcoin Wiki. Elliptic curve digital signature algorithm. Wuille P. Answer to: What are the limits of m and n in m-of-n multisig addresses? Bitcoin StackExchange. Stone A.
Blog post. Lopp J. Unspent Transaction Output Set. Johansson TE. Andresen G. UTXO uh-oh …. Maxwell G. A deep dive into bitcoin core 0. SF Bitcoin Developers Meetup. Bitcoin Core version 0. How to cheaply consolidate coins to reduce miner fees. The challenges of optimizing unspent output selection. Erhardt M. Simulation-based evaluation of coin selection strategies.
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Bitcoin is a secure and anonymous digital currency. Bitcoins cannot be easily tracked back to you, and are safer and faster alternative to other donation methods. You can send BTC to the following address:. There are also services allowing trades of goods for Bitcoins. Bitcoins are not subject to central regulations and are still gaining value. For a more private transaction, you can click on the refresh button above to generate a random Segwit BIP address.
Please do not use old 1HB5X Bitcoin Cash is a cryptocurrency that started as a fork of Bitcoin, with increased block size and cheaper transaction fees. You can read more on the official site. Simillar to Bitcoin, Litecoin offers very fast and secure transactions worldwide, and there are many exchanges allowing you to trade for Litecoins. ZCash is a cryptocurrency that offers privacy and selective transparency of transactions.
ZCash payments are published on a public blockchain, but the sender, recipient, and amount of a transaction may remain private. Monero is an open-source cryptocurrency that focuses on privacy, decentralisation and scalability. Unlike many cryptocurrencies that are derivatives of Bitcoin, Monero is based on the CryptoNote protocol and possesses significant algorithmic differences relating to blockchain obfuscation.
Ether is a cryptocurrency whose blockchain is generated by the Ethereum platform. Ethereum is a decentralized platform that runs smart contracts: applications that run exactly as prorammed, without any possibility of downtime, censorship, fraud or third-party interference. Read more on official site. You can donate to us using the address below. You can post a cheque donation via postal mail from anywhere to Germany , Australia and France.
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Similarly, funds cannot be seized or frozen — because financial third parties have no control over the Bitcoin Cash network. Bitcoin Cash combines gold-like scarcity with the spendable nature of cash. With a limited total supply of 21 million coins, Bitcoin Cash is provably scarce and, like physical cash, can be easily spent.
Transactions are fast with transaction fees typically less than a tenth of a cent. Anybody can accept Bitcoin Cash payments with a smartphone or computer. Bitcoin Cash has various use cases. In addition to peer-to-peer payments between individuals, Bitcoin Cash can be used to pay participating merchants for goods and services in-store and online.
Very low fees enable new micro-transaction economies, such as tipping content creators and rewarding app users a few cents. Bitcoin Cash also reduces the fees and settlement times for remittances and cross-border trade. Other use cases include tokens, simplified smart contracts, and private payments with tools such as CashShuffle and CashFusion.
The result was a hard fork which created Bitcoin Cash, a new cryptocurrency considered by supporters to be the legitimate continuation of the Bitcoin project as peer-to-peer electronic cash. All Bitcoin holders at the time of the fork block , automatically became owners of Bitcoin Cash.
Bitcoin, which was invented by the pseudonymous Satoshi Nakomoto remains a separate cryptocurrency. An increased block size means Bitcoin Cash can now handle significantly more transactions per second TPS while keeping fees extremely low, solving the issues of payment delays and high fees experienced by some users on the Bitcoin BTC network.
Mining is the process in which new Bitcoin Cash transactions are confirmed and new blocks are added to the Bitcoin Cash blockchain. Miners use computing power and electricity to solve complex puzzles. By doing so, they gain the ability to produce new blocks of transactions.
If one of their blocks is accepted by the network, the miner, or mining pool, earns a block reward in the form of newly-issued Bitcoin Cash. Mining is highly competitive. As the price of Bitcoin Cash in the marketplace rises, more miners are incentivized to bring more hash rate into the ever-increasing miner competition to produce blocks and have them accepted by the Bitcoin Cash network. More miners make the network more secure by increasing and distributing the hash rate. This prevents a single miner from having control over the network.
Anyone can mine Bitcoin Cash. Mining requires specialized hardware called mining equipment, which can either be bought or rented. Miners also need to run a full node software with the majority of miners currently running BCHN to build blocks and connect to the rest of the Bitcoin Cash network. Mining can be done independently but miners often pool their hash rate together and share proportionally in the earned block rewards.
Bitcoin Cash is available at a variety of crypto exchanges, depending on your region. Moreover, many interesting economic aspects of Bitcoin are covered. Even experienced Bitcoin Wiki useres sometimes stumble on articles they find interesting but haven't seen before.
Here is a list of a few selected articles that are good entry points for the various Bitcoin aspects. The Bitcoin Wiki can be edited by any user. The only requirement is to pay a small Bitcoin fee to prevent spamming of the Wiki.
While StackExchange and reddit are not a Wikis, they have some characteristics of a Wiki. StackExchange is a network of question and answer sites. The knowledge provided there is therefore related to specific questions.
Therefore it makes a great Bitcoin Wiki complement. Once you started to get involved here, you will become a Bitcoin pro pretty soon. The number of posts here is huge and hard to follow on a daily basis. But it's definitely a good resource when you search it for particular topics of your interest. Besides the Bitcoin Wiki entries, there is a number of blogs that are relevant. Wiki Bitcoin shows you, which are the most popular Bitcoin blogs to stay up to date.
All of these blogs offer RSS feeds which makes it easy to follow them and never miss a good read. The blogs are listed in alphabetical order. Wiki Bitcoin doesn't claim to say which blog is better or more relevant. If a blog is listed here it means the blog does have a certain level of quality. This list provides links to Bitcoin charts on various sites. Most of them are price related and provide good Bitcoin trading support.
The following links don't perfectly fit into other categories of this site. They are however interesting sources for analysis and information. Wiki Bitcoin - Your Bitcoin knowledge sources Wiki comes from a Hawaiian word that stands for "fast" or "quick". It gives a good introduction into what Bitcoin is. This is your go to place for a first overview on Bitcoin. Since knowledge accumulation about Bitcoin has grown, so has Wikipedia. Therefore two other directly Bitcoin related entries exist.
Bitcoin protocol :: From a technological point of view Bitcoin is a protocol. That's exactly what this article covers. It's an overview about the technological building blocks of Bitcoin. History of Bitcoin :: Bitcoin exists since January Since then some notable things happened around this digital currency.
This Wikipedia entry records the most important historical Bitcoin events. Main page :: Your entry point to the Bitcoin Wiki. FAQ :: Answers to the most frequently asked questions. Software :: A lot of software is developed on top of Bitcoin. This is a good overview of what already exists.
Mining :: Today Bitcoin mining is mostly done by professionals. Hardware requirements to do Bitcoin mining have become too demaning. However, if you want to know what mining is and how to get started, this is the place to go. Forums :: The easiest way to get answers to your questions are Bitcoin forums. Here is a list of them. The most frequented Bitcoin forum is probably bitcointalk. Buying Bitcoins :: A comprehensive list of Bitcoin exchanges.
Trade :: Currently, new Bitcoin merchant directories come up almost on a daily basis. While there are some useful directories, the Trade section of the Bitcoin Wiki is probably still the best. Another reason to come back to the Wiki every once in a while. This is the best way to find places where you can spend your Bitcoins.
How to accept Bitcoin, for small businesses :: If you have a small business and consider the integration of Bitcoin is a means of payment this is your article. It's just great how simple it is. Promotional graphics :: Once you have set up everything to accept Bitcoins, you need to get noticed. Promotional graphics help your customers to notice your Bitcoin integration - online and offline.
Again, everything is free. The Bitcoin Wiki has all the info and resources you need. Controlled supply :: From an economic point of view the limited Bitcoin supply is one of the most interesting aspects. This entry explains the supply of Bitcoins over time.
An in-depth article that is based on the knowledge about limitied Bitcoin supply is Bitcoin money supply and money creation. Contracts :: This Bitcoin Wiki entry introduces some of the most exciting future Bitcoin use cases. Besides being a payment network, Bitcoin offers many new opportunities.
If you are interested in building new services based on the Bitcoin protocol, start with this entry. It gives you some creative ideas that you can take from here. Bitcoin blogs Besides the Bitcoin Wiki entries, there is a number of blogs that are relevant. Bitbond Blog :: Covers finance and banking related topics of Bitcoin. The blog is published by Bitcoin peer-to-peer lending platform Bitbond. Articles are published on a weekly basis. The site also runs a great bitcoin affiliate program.
Bitcoin Blogger :: A well written blog with up to date news about Bitcoin. Publishes articles almost daily. Bitcoin Examiner :: One of my favorite daily Bitcoin blogs. A good mix of relevant Bitcoin news and trivia. Their blog covers topics of larger meaning to Bitcoin itself. Also, they have a quarterly grant which they always announce on this blog. And that's what it is - a well written blog from the perspective of a user.
Bitcoin Magazine :: The Magazine was probably one of the first Bitcoin publications. They even have a printed paper issues that you can buy on Amazon. The blog publishes articles daily. The head-writer Vitalik Buterin has tremendous in-depth knowledge about a wide range of Bitcoin related topics.
Bitcoin sv wiki The bitcoinj-sv library is a Java implementation of the for each Bitcoin Cash (BCH), an owner got 1 Bitcoin SV (BSV). Need to convert 1 WIKI to BCH? Or BCH to WIKI with accurate, real-time prices? Try our WIKI to Bitcoin Cash currency conversion & calculator. bitcoin sv wikipedia bigger blocks than BTC and BCH which means BSV can scale to.