Bitcoin — Wikipédia
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Jean-Paul Delahaye explains clearly in his article how the bitcoin protocol works, as well as the enthusiasm and fear it elicits. The major innovation behind bitcoin is the creation of an ecosystem that allows for a decentralized consensus.
Users no longer need a reliable central authority to interact with each other. While it is difficult to predict how blockchain technology will become important in our everyday activities over the jean paul delahaye bitcoin value few years—increasing our happiness, or not—the enthusiasm it elicits is growing.
It could have many applications, of which cryptocurrencies are only an initial example. Among the platforms arousing great interest is Ethereum, which allows users to manage and interact with smart-contracts.
Ethereum promises applications that work exactly as they were programmed and cannot be interrupted, censored, or modified in any way. It has been spoken of as one of the building blocks of web 3. Understanding precisely how all this works in practice is a fascinating subject.
How can a user, interacting with the network via only his smartphone, quickly verify that a transaction has been saved on the blockchain? One approach uses the concept of a Merkle tree. Another legitimate question that one might ask with reference to the mechanism of transaction validation is: There is more jean paul delahaye bitcoin value bitcoin than simply a currency of exchange.
To illustrate this, I will examine in some detail a transaction inscribed in the bitcoin blockchain. This has nothing to do with any financial transaction, on the contrary, it is connected to the idea of using the blockchain to write information, permanently, that is tamper-proof and visible to everyone. I will jean paul delahaye bitcoin value this using an example application for which a platform like Ethereum is perfectly adapted.
It is an even greater jean paul delahaye bitcoin value when you keep in mind that, unlike a gold ingot, a computer file can be duplicated infinitely many times at almost zero cost. Some of these have been well known for around forty years and have been widely used in many cryptographic systems.
It seems almost a miracle that a currency can be supported by a shared computer file and that it works. It is a miracle—and in the case of bitcoin, a currency—that depends entirely on mathematics. In terms of cryptography, the bitcoin platform relies on two fundamental mathematical concepts: One might think of the hash of a computer file as its digital fingerprint.
The initial computer file can be potentially very large from a few kilo- to several giga-bytes, depending on whether it is text, image, music or videowhile its fingerprint is only a few bytes. Calculating a hash is a very fast process, consumes few resources, and is an irreversible operation, since it is impossible, in practice, to reconstitute the original file from its fingerprint.
Importantly, it is extremely unlikely that two distinct files will produce the same hash. The electronic signature of a message proves that the person claiming to be its author is indeed its author.
The underlying mathematics ensures that it will not suffice to study in detail the messages signed by a person to be able to appropriate his signature and sign new messages without his knowledge. Bitcoin relies on the blockchain, a data structure that allows the data to be linked together. By organizing the data in blocks and indicating in the header of each block the hash of the preceding block.
Modifying a datum in a block modifies its hash and is therefore reflected in all subsequent blocks. Each block organizes the transactions it contains according to a Merkle tree, a data structure first described by Ralph Merkle in Imagine that one jean paul delahaye bitcoin value to verify that some data belongs to a set of data that is known in advance. In the case of the bitcoin blockchain, one wants to know whether a particular jean paul delahaye bitcoin value has been recorded in a given block.
A Merkle tree is a rooted binary tree; the data are attached to the leaves, the hashes of the corresponding data are attached to the parents of the leaves, and the hashes of the two child nodes are attached to all the other nodes. The root of the Merkle tree contains a fingerprint of the whole tree. If someone wants to verify that a transaction belongs to the block in question, and not simply trust a network node asserting that this is the case, he have jean paul delahaye bitcoin value ensure that the block belongs to the blockchain and to recalculate what the root of the Merkle tree of the jean paul delahaye bitcoin value should be.
He can then compare it to the value indicated in the header of the block. One does not need to know all the transactions from the block; it is enough to request the hashes of the branch that goes from the leaf containing the particular transaction all the way to the root. This represents a very small amount of data when compared to that comprising all the transactions in the block.
For the same reasons, if one changes a datum in a leaf, it is not necessary to recalculate the entire Merkle tree, but only the corresponding branch all the way to the root. One of the great strengths of this data structure is that it allows users to connect to the network via light clients on their smartphones and to verify the transactions of interest. Of course, nothing beats a full client, one that stores the entire blockchain and ensures the validity of all transactions without the help of any third party; these nodes can calculate the balance of a bitcoin address and trace precisely the origin of the bitcoins at the address in question.
The simplest ideas are often the most brilliant. Each block header contains the hash of the previous one, the root of the Merkle tree of the transactions contained in the block and thus a fingerprint of all the transactions in the block! Anyone can thus, in the blink of an eye, verify the validity of a block, while the miners have had to work hard to find the nonce in question.
This value is directly related to the computing capacity of the entire jean paul delahaye bitcoin value network and periodically adjusted. Since the distribution of hashes is random, a miner has no choice other than to randomly take a nonce and see if it works This is where the system acquires real economic value, moving from mathematics and computer science to physics, if you will.
The cost for a miner to validate a block is significant: A mined block gets its value from computing, in the same way that a gold ingot acquires value because it is a rare metal.
If it were easy to mine a block, a bitcoin would have no more value than a liter of air! That one can exchange goods or services for the result of a calculation is, in contemporary terms, a totally disruptive idea.
For their work, miner are paid in accordance with jean paul delahaye bitcoin value two basic rules of the bitcoin protocol: But in jean paul delahaye bitcoin value dispersed world, two valid blocks may be found at almost the same time at two ends of the network. The two blocks do not necessarily contain the same transactions, and may even contain contradictory transactions.
In other words, a user of the network tries to spend the same bitcoins twice. Jean paul delahaye bitcoin value blockchains then find themselves in competition, a situation we call a fork. But, a few minutes later, other blocks will be mined. Why do miners agree to play the game and why do they finally come to a consensus? If you are a miner, it means that you have purchased the necessary equipment and are willing to consume a significant amount of electricity.
When you look at the bitcoin protocol in detail, you realize that there is no economic incentive to hack the network; everything was designed so that attacks, in the end, are far more costly than any benefits that could be derived from them. This is how consensus emerges at the global level for validated transactions between actors who do not know each other and have no particular jean paul delahaye bitcoin value priori trust in each other.
Believe it or not, this has now been working for eight years! There is, however, a downside to this. This is unlikely, but not completely unimaginable, because of the jean paul delahaye bitcoin value of miners into pools.
There remain things a hacker would not be able to do. In particular, he would never be able to spend bitcoins that are not his. On the other hand, he would be able to spend his own bitcoins several times over, and to deny service by refusing to validate certain transactions. No miner—unless he wants to lose all the money he has invested from the beginning—has any real incentive to make the whole system collapse.
As ofsome users of the bitcoin platform have tried to write information unrelated to financial transactions into the blockchain. Because once written on the blockchain, it will remain jean paul delahaye bitcoin value ad vitam eternam.
It is not difficult to imagine some types of information, such as the terms of a contract, that we would like to always have available, from anywhere in the world, and maintained in a way that they cannot be tampered with.
The bitcoin blockchain was not designed for this purpose, but with a little ingenuity, it is nevertheless possible to implement this type of functionality. This jean paul delahaye bitcoin value pleased some people, because it demonstrates, if this is still necessary, the potential of the blockchain. It has not pleased others, who see this type of data as contaminating the protocol at two levels.
On the one hand, it can greatly increase the size of the blockchain and, on the other hand, transaction outputs UTXO are created that can never be unlocked but will remain consigned forever to the jean paul delahaye bitcoin value of all UTXOs.
Many websites allow real-time visualization of the bitcoin blockchain. We can see that it was validated on June 30, but we can also see that the first output script is. A conversion from hexadecimal to utf-8 4 reveals the message. Imagine three mathematician friends who would like to explain to a wide audience the fourth dimension, or the butterfly effect.
Since they wish to distribute their two films as widely as possible and for free, a platform like YouTube would suit them well. They decide to sell a double DVD containing the two films at a relatively modest price, covering printing and shipping costs, but that will also guarantee that one out of every three DVDs is free. On their website, they create a page for orders. To collect payments, they decide to use PayPal, an online payment service that allows users to pay for purchases, receive jean paul delahaye bitcoin value, and to send and receive money.
PayPal takes a commission not negligible, in fact from each transaction and pays the remainder into the account belonging to the three friends. The system works well and our three friends are, on the whole, content. All the same, they have two small regrets. The three friends give regular lectures, which are perfect opportunities to distribute their DVDs.
This is a little awkward, in practice, because they have to collect money from buyers, either in cash or checks, and then deposit it in a jean paul delahaye bitcoin value. Not forgetting, of course, buyers who want to pay via a credit card Additionally, the three mathematicians had hoped that, for every hundred DVDs sold, they could offer jean paul delahaye bitcoin value next order free of charge. This type jean paul delahaye bitcoin value gift is not easy to arrange via PayPal.
While our friends have no intention of cheating, their sole aim being to make their DVDs available to the biggest audience possible, buyer have to trust them regarding the exact number jean paul delahaye bitcoin value DVDs sold.
The three mathematicians released their films in andso they could not have known about the Ethereum platform, available only since Ethereum solves both these problems: In a sense, Ethereum is a decentralized computer that runs on many nodes. Presented in this way, it looks fantastic. There are, however, two caveats: In any blockchain-type platform, there is always a balance between economy and technology.
