{"id":10,"date":"2026-04-10T20:08:15","date_gmt":"2026-04-10T20:08:15","guid":{"rendered":"https:\/\/qat-3.multilingualpress.syde.wpinfra.cloud\/?p=10"},"modified":"2026-04-10T20:08:15","modified_gmt":"2026-04-10T20:08:15","slug":"bitcoin-a-peer-to-peer-electronic-cash-system","status":"publish","type":"post","link":"https:\/\/qat-3.multilingualpress.syde.wpinfra.cloud\/it\/blog\/2026\/04\/10\/bitcoin-a-peer-to-peer-electronic-cash-system\/","title":{"rendered":"Bitcoin: A Peer-to-Peer Electronic Cash System"},"content":{"rendered":"\n<p><a href=\"https:\/\/github.com\/scottgriv\/bitcoin-white_paper\/blob\/master\/bitcoin.md#bitcoin-a-peer-to-peer-electronic-cash-system\"><\/a>author<\/p>\n\n\n\n<p>: Satoshi Nakamoto<\/p>\n\n\n\n<p>email<\/p>\n\n\n\n<p>: <a href=\"mailto:satoshin@gmx.com\">satoshin@gmx.com<\/a><\/p>\n\n\n\n<p>site<\/p>\n\n\n\n<p>: <a href=\"http:\/\/www.bitcoin.org\/\">http:\/\/www.bitcoin.org\/<\/a><\/p>\n\n\n\n<p><strong>Abstract.<\/strong> A purely peer-to-peer version of electronic cash would<br>allow online payments to be sent directly from one party to another<br>without going through a financial institution. Digital signatures<br>provide part of the solution, but the main benefits are lost if a<br>trusted third party is still required to prevent double-spending. We<br>propose a solution to the double-spending problem using a peer-to-peer<br>network. The network timestamps transactions by hashing them into an<br>ongoing chain of hash-based proof-of-work, forming a record that cannot<br>be changed without redoing the proof-of-work. The longest chain not only<br>serves as proof of the sequence of events witnessed, but proof that it<br>came from the largest pool of CPU power. As long as a majority of CPU<br>power is controlled by nodes that are not cooperating to attack the<br>network, they\\&#8217;ll generate the longest chain and outpace attackers. The<br>network itself requires minimal structure. Messages are broadcast on a<br>best effort basis, and nodes can leave and rejoin the network at will,<br>accepting the longest proof-of-work chain as proof of what happened<br>while they were gone.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Introduction<\/h2>\n\n\n\n<p>Commerce on the Internet has come to rely almost exclusively on<br>financial institutions serving as trusted third parties to process<br>electronic payments. While the system works well enough for most<br>transactions, it still suffers from the inherent weaknesses of the trust<br>based model. Completely non-reversible transactions are not really<br>possible, since financial institutions cannot avoid mediating disputes.<br>The cost of mediation increases transaction costs, limiting the minimum<br>practical transaction size and cutting off the possibility for small<br>casual transactions, and there is a broader cost in the loss of ability<br>to make non-reversible payments for nonreversible services. With the<br>possibility of reversal, the need for trust spreads. Merchants must be<br>wary of their customers, hassling them for more information than they<br>would otherwise need. A certain percentage of fraud is accepted as<br>unavoidable. These costs and payment uncertainties can be avoided in<br>person by using physical currency, but no mechanism exists to make<br>payments over a communications channel without a trusted party<\/p>\n\n\n\n<p>What is needed is an electronic payment system based on cryptographic<br>proof instead of trust, allowing any two willing parties to transact<br>directly with each other without the need for a trusted third party.<br>Transactions that are computationally impractical to reverse would<br>protect sellers from fraud, and routine escrow mechanisms could easily<br>be implemented to protect buyers. In this paper, we propose a solution<br>to the double-spending problem using a peer-to-peer distributed<br>timestamp server to generate computational proof of the chronological<br>order of transactions. The system is secure as long as honest nodes<br>collectively control more CPU power than any cooperating group of<br>attacker nodes.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Transactions<\/h2>\n\n\n\n<p>We define an electronic coin as a chain of digital signatures. Each<br>owner transfers the coin to the next by digitally signing a hash of the<br>previous transaction and the public key of the next owner and adding<br>these to the end of the coin. A payee can verify the signatures to<br>verify the chain of ownership.<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"img\/transactions.png\" alt=\"\"\/><\/figure>\n\n\n\n<p>The problem of course is the payee can\\&#8217;t verify that one of the owners<br>did not double-spend the coin. A common solution is to introduce a<br>trusted central authority, or mint, that checks every transaction for<br>double spending. After each transaction, the coin must be returned to<br>the mint to issue a new coin, and only coins issued directly from the<br>mint are trusted not to be double-spent. The problem with this solution<br>is that the fate of the entire money system depends on the company<br>running the mint, with every transaction having to go through them, just<br>like a bank.<\/p>\n\n\n\n<p>We need a way for the payee to know that the previous owners did not<br>sign any earlier transactions. For our purposes, the earliest<br>transaction is the one that counts, so we don\\&#8217;t care about later<br>attempts to double-spend. The only way to confirm the absence of a<br>transaction is to be aware of all transactions. In the mint based model,<br>the mint was aware of all transactions and decided which arrived first.<br>To accomplish this without a trusted party, transactions must be<br>publicly announced[^1], and we need a system for participants to agree<br>on a single history of the order in which they were received. The payee<br>needs proof that at the time of each transaction, the majority of nodes<br>agreed it was the first received.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Timestamp Server<\/h2>\n\n\n\n<p>The solution we propose begins with a timestamp server. A timestamp<br>server works by taking a hash of a block of items to be timestamped and<br>widely publishing the hash, such as in a newspaper or Usenet<br>post[^2][^3][^4][^5]. The timestamp proves that the data must have<br>existed at the time, obviously, in order to get into the hash. Each<br>timestamp includes the previous timestamp in its hash, forming a chain,<br>with each additional timestamp reinforcing the ones before it.<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"img\/timestamp.png\" alt=\"\"\/><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\">Proof-of-Work<\/h2>\n\n\n\n<p>To implement a distributed timestamp server on a peer-to-peer basis, we<br>will need to use a proof-of-work system similar to Adam Back\\&#8217;s Hashcash<br>[^6], rather than newspaper or Usenet posts. The proof-of-work involves<br>scanning for a value that when hashed, such as with SHA-256, the hash<br>begins with a number of zero bits. The average work required is<br>exponential in the number of zero bits required and can be verified by<br>executing a single hash.<\/p>\n\n\n\n<p>For our timestamp network, we implement the proof-of-work by<br>incrementing a nonce in the block until a value is found that gives the<br>block\\&#8217;s hash the required zero bits. Once the CPU effort has been<br>expended to make it satisfy the proof-of-work, the block cannot be<br>changed without redoing the work. As later blocks are chained after it,<br>the work to change the block would include redoing all the blocks after<br>it<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"img\/proof-of-work.png\" alt=\"\"\/><\/figure>\n\n\n\n<p>The proof-of-work also solves the problem of determining representation<br>in majority decision making. If the majority were based on<br>one-IP-address-one-vote, it could be subverted by anyone able to<br>allocate many IPs. Proof-of-work is essentially one-CPU-one-vote. The<br>majority decision is represented by the longest chain, which has the<br>greatest proof-of-work effort invested in it. If a majority of CPU power<br>is controlled by honest nodes, the honest chain will grow the fastest<br>and outpace any competing chains. To modify a past block, an attacker<br>would have to redo the proof-of-work of the block and all blocks after<br>it and then catch up with and surpass the work of the honest nodes. We<br>will show later that the probability of a slower attacker catching up<br>diminishes exponentially as subsequent blocks are added.<\/p>\n\n\n\n<p>To compensate for increasing hardware speed and varying interest in<br>running nodes over time, the proof-of-work difficulty is determined by a<br>moving average targeting an average number of blocks per hour. If<br>they\\&#8217;re generated too fast, the difficulty increases.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Network<\/h2>\n\n\n\n<p>The steps to run the network are as follows:<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li>New transactions are broadcast to all nodes.<\/li>\n\n\n\n<li>Each node collects new transactions into a block.<\/li>\n\n\n\n<li>Each node works on finding a difficult proof-of-work for its block.<\/li>\n\n\n\n<li>When a node finds a proof-of-work, it broadcasts the block to all<br>nodes.<\/li>\n\n\n\n<li>Nodes accept the block only if all transactions in it are valid and<br>not already spent.<\/li>\n\n\n\n<li>Nodes express their acceptance of the block by working on creating<br>the next block in the chain, using the hash of the accepted block as<br>the previous hash.<\/li>\n<\/ol>\n\n\n\n<p>Nodes always consider the longest chain to be the correct one and will<br>keep working on extending it. If two nodes broadcast different versions<br>of the next block simultaneously, some nodes may receive one or the<br>other first. In that case, they work on the first one they received, but<br>save the other branch in case it becomes longer. The tie will be broken<br>when the next proof-of-work is found and one branch becomes longer; the<br>nodes that were working on the other branch will then switch to the<br>longer one.<\/p>\n\n\n\n<p>New transaction broadcasts do not necessarily need to reach all nodes.<br>As long as they reach many nodes, they will get into a block before<br>long. Block broadcasts are also tolerant of dropped messages. If a node<br>does not receive a block, it will request it when it receives the next<br>block and realizes it missed one.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Incentive<\/h2>\n\n\n\n<p>By convention, the first transaction in a block is a special transaction<br>that starts a new coin owned by the creator of the block. This adds an<br>incentive for nodes to support the network, and provides a way to<br>initially distribute coins into circulation, since there is no central<br>authority to issue them. The steady addition of a constant of amount of<br>new coins is analogous to gold miners expending resources to add gold to<br>circulation. In our case, it is CPU time and electricity that is<br>expended.<\/p>\n\n\n\n<p>The incentive can also be funded with transaction fees. If the output<br>value of a transaction is less than its input value, the difference is a<br>transaction fee that is added to the incentive value of the block<br>containing the transaction. Once a predetermined number of coins have<br>entered circulation, the incentive can transition entirely to<br>transaction fees and be completely inflation free.<\/p>\n\n\n\n<p>The incentive may help encourage nodes to stay honest. If a greedy<br>attacker is able to assemble more CPU power than all the honest nodes,<br>he would have to choose between using it to defraud people by stealing<br>back his payments, or using it to generate new coins. He ought to find<br>it more profitable to play by the rules, such rules that favour him with<br>more new coins than everyone else combined, than to undermine the system<br>and the validity of his own wealth.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Reclaiming Disk Space<\/h2>\n\n\n\n<p>Once the latest transaction in a coin is buried under enough blocks, the<br>spent transactions before it can be discarded to save disk space. To<br>facilitate this without breaking the block\\&#8217;s hash, transactions are<br>hashed in a Merkle Tree[^7][^8][^9], with only the root included in the<br>block\\&#8217;s hash. Old blocks can then be compacted by stubbing off branches<br>of the tree. The interior hashes do not need to be stored.<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"img\/reclaiming-disk.png\" alt=\"\"\/><\/figure>\n\n\n\n<p>A block header with no transactions would be about 80 bytes. If we<br>suppose blocks are generated every 10 minutes, 80 bytes * 6 * 24 *<br>365 = 4.2MB per year. With computer systems typically selling with 2GB<br>of RAM as of 2008, and Moore\\&#8217;s Law predicting current growth of 1.2GB<br>per year, storage should not be a problem even if the block headers must<br>be kept in memory.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Simplified Payment Verification<\/h2>\n\n\n\n<p>It is possible to verify payments without running a full network node. A<br>user only needs to keep a copy of the block headers of the longest<br>proof-of-work chain, which he can get by querying network nodes until<br>he\\&#8217;s convinced he has the longest chain, and obtain the Merkle branch<br>linking the transaction to the block it\\&#8217;s timestamped in. He can\\&#8217;t<br>check the transaction for himself, but by linking it to a place in the<br>chain, he can see that a network node has accepted it, and blocks added<br>after it further confirm the network has accepted it.<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"img\/spv.png\" alt=\"\"\/><\/figure>\n\n\n\n<p>As such, the verification is reliable as long as honest nodes control<br>the network, but is more vulnerable if the network is overpowered by an<br>attacker. While network nodes can verify transactions for themselves,<br>the simplified method can be fooled by an attacker\\&#8217;s fabricated<br>transactions for as long as the attacker can continue to overpower the<br>network. One strategy to protect against this would be to accept alerts<br>from network nodes when they detect an invalid block, prompting the<br>user\\&#8217;s software to download the full block and alerted transactions to<br>confirm the inconsistency. Businesses that receive frequent payments<br>will probably still want to run their own nodes for more independent<br>security and quicker verification.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Combining and Splitting Value<\/h2>\n\n\n\n<p>Although it would be possible to handle coins individually, it would be<br>unwieldy to make a separate transaction for every cent in a transfer. To<br>allow value to be split and combined, transactions contain multiple<br>inputs and outputs. Normally there will be either a single input from a<br>larger previous transaction or multiple inputs combining smaller<br>amounts, and at most two outputs: one for the payment, and one returning<br>the change, if any, back to the sender.<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"img\/combining-splitting.png\" alt=\"\"\/><\/figure>\n\n\n\n<p>It should be noted that fan-out, where a transaction depends on several<br>transactions, and those transactions depend on many more, is not a<br>problem here. There is never the need to extract a complete standalone<br>copy of a transaction\\&#8217;s history.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Privacy<\/h2>\n\n\n\n<p>The traditional banking model achieves a level of privacy by limiting<br>access to information to the parties involved and the trusted third<br>party. The necessity to announce all transactions publicly precludes<br>this method, but privacy can still be maintained by breaking the flow of<br>information in another place: by keeping public keys anonymous. The<br>public can see that someone is sending an amount to someone else, but<br>without information linking the transaction to anyone. This is similar<br>to the level of information released by stock exchanges, where the time<br>and size of individual trades, the \\&#8221;tape\\&#8221;, is made public, but without<br>telling who the parties were.<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"img\/privacy.png\" alt=\"\"\/><\/figure>\n\n\n\n<p>As an additional firewall, a new key pair should be used for each<br>transaction to keep them from being linked to a common owner. Some<br>linking is still unavoidable with multi-input transactions, which<br>necessarily reveal that their inputs were owned by the same owner. The<br>risk is that if the owner of a key is revealed, linking could reveal<br>other transactions that belonged to the same owner.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Calculations<\/h2>\n\n\n\n<p>We consider the scenario of an attacker trying to generate an alternate<br>chain faster than the honest chain. Even if this is accomplished, it<br>does not throw the system open to arbitrary changes, such as creating<br>value out of thin air or taking money that never belonged to the<br>attacker. Nodes are not going to accept an invalid transaction as<br>payment, and honest nodes will never accept a block containing them. An<br>attacker can only try to change one of his own transactions to take back<br>money he recently spent.<\/p>\n\n\n\n<p>The race between the honest chain and an attacker chain can be<br>characterized as a Binomial Random Walk. The success event is the honest<br>chain being extended by one block, increasing its lead by +1, and the<br>failure event is the attacker\\&#8217;s chain being extended by one block,<br>reducing the gap by -1.<\/p>\n\n\n\n<p>The probability of an attacker catching up from a given deficit is<br>analogous to a Gambler\\&#8217;s Ruin problem. Suppose a gambler with unlimited<br>credit starts at a deficit and plays potentially an infinite number of<br>trials to try to reach breakeven. We can calculate the probability he<br>ever reaches breakeven, or that an attacker ever catches up with the<br>honest chain, as follows[^10]:<\/p>\n\n\n\n<p>| p = probability an honest node finds the next block<br>| q = probability the attacker finds the next block<br>| qz = probability the attacker will ever catch up from z blocks behind<\/p>\n\n\n\n<p>$$\\begin{aligned}<br>q_z =<br>\\begin{cases}<br>1 &amp; \\text{if } p \\leqslant q\\<br>\\left(q\/p\\right)^z &amp; \\text{if } p &gt; q<br>\\end{cases}<br>\\end{aligned}$$<\/p>\n\n\n\n<p>Given our assumption that p &gt; q, the probability drops exponentially as<br>the number of blocks the attacker has to catch up with increases. With<br>the odds against him, if he doesn\\&#8217;t make a lucky lunge forward early<br>on, his chances become vanishingly small as he falls further behind.<\/p>\n\n\n\n<p>We now consider how long the recipient of a new transaction needs to<br>wait before being sufficiently certain the sender can\\&#8217;t change the<br>transaction. We assume the sender is an attacker who wants to make the<br>recipient believe he paid him for a while, then switch it to pay back to<br>himself after some time has passed. The receiver will be alerted when<br>that happens, but the sender hopes it will be too late<\/p>\n\n\n\n<p>The receiver generates a new key pair and gives the public key to the<br>sender shortly before signing. This prevents the sender from preparing a<br>chain of blocks ahead of time by working on it continuously until he is<br>lucky enough to get far enough ahead, then executing the transaction at<br>that moment. Once the transaction is sent, the dishonest sender starts<br>working in secret on a parallel chain containing an alternate version of<br>his transaction.<\/p>\n\n\n\n<p>The recipient waits until the transaction has been added to a block and<br>z blocks have been linked after it. He doesn\\&#8217;t know the exact amount of<br>progress the attacker has made, but assuming the honest blocks took the<br>average expected time per block, the attacker\\&#8217;s potential progress will<br>be a Poisson distribution with expected value:<\/p>\n\n\n\n<p>$$\\lambda = z \\frac{q}{p}$$<\/p>\n\n\n\n<p>To get the probability the attacker could still catch up now, we<br>multiply the Poisson density for each amount of progress he could have<br>made by the probability he could catch up from that point:<\/p>\n\n\n\n<p>$$\\begin{aligned}<br>\\sum _{k=0}^\\infty \\frac{\\lambda ^k e^{-\\lambda}}{k!} \\cdot<br>\\begin{cases}<br>\\left(q\/p\\right)^{(z-p)} &amp; \\text{if } k \\leqslant z \\<br>1 &amp; \\text{if } k &gt; z<br>\\end{cases}<br>\\end{aligned}$$<\/p>\n\n\n\n<p>Rearranging to avoid summing the infinite tail of the distribution&#8230;<\/p>\n\n\n\n<p>$$1 &#8211; \\sum _{k=0}^z \\frac{\\lambda ^k e^{-\\lambda}}{k!} \\left(1 &#8211; \\left(q\/p\\right)^{(z-k)}\\right)$$<\/p>\n\n\n\n<p>Converting to C code&#8230;<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>#include &lt;math.h&gt;\ndouble AttackerSuccessProbability(double q, int z)\n{\n    double p = 1.0 - q;\n    double lambda = z * (q \/ p);\n    double sum = 1.0;\n    int i, k;\n    for (k = 0; k &lt;= z; k++)\n    {\n        double poisson = exp(-lambda);\n        for (i = 1; i &lt;= k; i++)\n            poisson *= lambda \/ i;\n        sum -= poisson * (1 - pow(q \/ p, z - k));\n    }\n    return sum;\n}<\/code><\/pre>\n\n\n\n<p>Running some results, we can see the probability drop off exponentially<br>with z.<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>q=0.1\nz=0 P=1.0000000\nz=1 P=0.2045873\nz=2 P=0.0509779\nz=3 P=0.0131722\nz=4 P=0.0034552\nz=5 P=0.0009137\nz=6 P=0.0002428\nz=7 P=0.0000647\nz=8 P=0.0000173\nz=9 P=0.0000046\nz=10 P=0.0000012\n\nq=0.3\nz=0 P=1.0000000\nz=5 P=0.1773523\nz=10 P=0.0416605\nz=15 P=0.0101008\nz=20 P=0.0024804\nz=25 P=0.0006132\nz=30 P=0.0001522\nz=35 P=0.0000379\nz=40 P=0.0000095\nz=45 P=0.0000024\nz=50 P=0.0000006<\/code><\/pre>\n\n\n\n<p>Solving for P less than 0.1%&#8230;<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>P \\&lt; 0.001\nq=0.10 z=5\nq=0.15 z=8\nq=0.20 z=11\nq=0.25 z=15\nq=0.30 z=24\nq=0.35 z=41\nq=0.40 z=89\nq=0.45 z=340<\/code><\/pre>\n\n\n\n<h2 class=\"wp-block-heading\">Conclusion<\/h2>\n\n\n\n<p>We have proposed a system for electronic transactions without relying on<br>trust. We started with the usual framework of coins made from digital<br>signatures, which provides strong control of ownership, but is<br>incomplete without a way to prevent double-spending. To solve this, we<br>proposed a peer-to-peer network using proof-of-work to record a public<br>history of transactions that quickly becomes computationally impractical<br>for an attacker to change if honest nodes control a majority of CPU<br>power. The network is robust in its unstructured simplicity. Nodes work<br>all at once with little coordination. They do not need to be identified,<br>since messages are not routed to any particular place and only need to<br>be delivered on a best effort basis. Nodes can leave and rejoin the<br>network at will, accepting the proof-of-work chain as proof of what<br>happened while they were gone. They vote with their CPU power,<br>expressing their acceptance of valid blocks by working on extending them<br>and rejecting invalid blocks by refusing to work on them. Any needed<br>rules and incentives can be enforced with this consensus mechanism.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">References<\/h2>\n\n\n\n<p>[^1]: W. Dai, \\&#8221;b-money,\\&#8221; <a href=\"http:\/\/www.weidai.com\/bmoney.txt\">http:\/\/www.weidai.com\/bmoney.txt<\/a>, 1998.<\/p>\n\n\n\n<p>[^2]: H. Massias, X.S. Avila, and J.-J. Quisquater, \\&#8221;Design of a<br>secure timestamping service with minimal trust requirements,\\&#8221;<br>In 20th Symposium on Information Theory in the Benelux,<br>May 1999.<\/p>\n\n\n\n<p>[^3]: S. Haber, W.S. Stornetta, \\&#8221;How to time-stamp a digital<br>document,\\&#8221; In Journal of Cryptology, vol 3, no 2, pages<br>99-111, 1991.<\/p>\n\n\n\n<p>[^4]: D. Bayer, S. Haber, W.S. Stornetta, \\&#8221;Improving the efficiency<br>and reliability of digital time-stamping,\\&#8221; In Sequences II:<br>Methods in Communication, Security and Computer Science, pages<br>329-334, 1993.<\/p>\n\n\n\n<p>[^5]: S. Haber, W.S. Stornetta, \\&#8221;Secure names for bit-strings,\\&#8221; In<br>Proceedings of the 4th ACM Conference on Computer and<br>Communications Security, pages 28-35, April 1997.<\/p>\n\n\n\n<p>[^6]: A. Back, \\&#8221;Hashcash &#8211; a denial of service counter-measure,\\&#8221;<br><a href=\"http:\/\/www.hashcash.org\/papers\/hashcash.pdf\">http:\/\/www.hashcash.org\/papers\/hashcash.pdf<\/a>, 2002.<\/p>\n\n\n\n<p>[^7]: R.C. Merkle, \\&#8221;Protocols for public key cryptosystems,\\&#8221; In Proc.<br>1980 Symposium on Security and Privacy, IEEE Computer Society, pages<br>122-133, April 1980.<\/p>\n\n\n\n<p>[^8]: H. Massias, X.S. Avila, and J.-J. Quisquater, \\&#8221;Design of a<br>secure timestamping service with minimal trust requirements,\\&#8221;<br>In 20th Symposium on Information Theory in the Benelux,<br>May 1999.<\/p>\n\n\n\n<p>[^9]: S. Haber, W.S. Stornetta, \\&#8221;Secure names for bit-strings,\\&#8221; In<br>Proceedings of the 4th ACM Conference on Computer and<br>Communications Security, pages 28-35, April 1997.<\/p>\n\n\n\n<p>[^10]: W. Feller, \\&#8221;An introduction to probability theory and its<br>applications,\\&#8221; 1957.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>author : Satoshi Nakamoto email : satoshin@gmx.com site : http:\/\/www.bitcoin.org\/ Abstract. A purely peer-to-peer version of electronic cash wouldallow online payments to be sent directly from one party to anotherwithout going through a financial institution. 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