Download Code Bitcoin: What You Need to Know Before You Start
Bitcoin Core requires a one-time download of about 500GB of data plus a further 5-10GB per month. By default, you will need to store all of that data, but if you enable pruning, you can store as little as 6GB total without sacrificing any security. For more information about setting up Bitcoin Core, please read the full node guide.
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Download verification is optional but highly recommended. Performing the verification steps here ensures that you have not downloaded an unexpected or tampered version of Bitcoin, which may result in loss of funds.
Ensure that the checksum produced by the command above matches one of the checksums listed in the checksums file you downloaded earlier. We recommend that you check every character of the two checksums to ensure they match. You can see the checksums you downloaded by running the following command:
Bitcoin releases are signed by a number of individuals, each with a unique public key. In order to recognize the validity of signatures, you must use GPG to load these public keys locally. You can find many developer keys listed in the bitcoin-core/guix.sigs repository, which you can then load into your GPG key database.
The output from the verify command may contain warnings that a public key is not available. As long as you have all the public keys of signers you trust, this warning can be disregarded. There may be additional warnings that a "key is not certified with a trusted signature." This means that to fully verify your download, you need to confirm that the signing key's fingerprint (e.g. E777 299F...) listed in the second line above matches what you had expected for the signers public key.
In the output produced by the above command, you can safely ignore any warnings and failures, but you must ensure the output lists "OK" after the name of the release file you downloaded. For example: bitcoin-25.0-x86_64-apple-darwin.dmg: OK
The output from the verify command may contain warnings that a public key is not available. As long as you have all the public keys of signers you trust, this warning can be disregarded. There may be additional warnings that a "key is not certified with a trusted signature." This means that to fully verify your download, you need to confirm that the signing key's fingerprint (e.g. E777 299F...) listed in the second line above matches what you had expected for the signers public key. See the GNU handbook section on key management for more details.
In the output produced by the above command, you can safely ignore any warnings and failures, but you must ensure the output lists "OK" after the name of the release file you downloaded. For example: bitcoin-25.0-x86_64-linux-gnu.tar.gz: OK
Reproducible builds allow anyone with a copy of Bitcoin Core's MIT-licensed source code to build identical binaries to those distributed on this website (meaning the binaries will have the same cryptographic checksums as those provided by this website).
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Once a new node joins the network, its first order of business is to download and validate the entire blockchain. This is an integral step to the distributed nature of bitcoin because only by doing this can a node claim that it has independently validated all transactions.
As the blockchain grows in size, the time required for IBD increases unless optimizations are made to the code. Various optimizations have been made since Satoshi's original client was released, but as of 2014, with increasing transaction volume, initial download on laptop hardware with an average connection could still take up to 24 hours. Developers agreed that this was unacceptable and a new approach was developed called "headers first" mode. This approach resulted in a substantial speedup.
With "headers-first" mode, a new node downloads all of the block headers first, which are very small (about 80 bytes, whereas a block can be up to 1MB). Once the node has all of the headers, from the genesis block up to the current tip of the blockchain (380,000 as of October 2015), only then does it begins downloading the full blocks.
Now that it has the headers, the node downloads blocks in parallel from multiple peers. (It downloads headers from only one peer, but that's no big deal since headers are small.) The node will download from up to 8 peers at once and will disconnect any peer that stalls for more 2 seconds, attempting to connect to a faster peer.
1) Proof-of-Work Meets Claimed Requirement: Here, the code checks that the block has the POW that the miner claims was necessary when constructing the block. Later, we'll re-check it against our blockchain. An honest miner should always pass both checks. Only a miner who lies about the required POW (block.nBits) would pass this check but fail the contextual check.
2) Timestamp not-too-late: The code checks that the timestamp is less than 2 days in the future. This is context-independent because the code just compares the block's timestamp against the system time.
The download code uses a "moving window" of 1024 blocks. The idea is that although you are downloading different chunks from multiple peers, at any given time the blocks you are downloading are fairly close together. The main purpose of this is so that blocks that are near one another on the blockchain are most likely contained in the same .dat file (where the raw block data is stored on disk). One advantage of having a correlation between blockchain location and block file location is that if the node chooses to "prune" block data at a later date, it's easier to delete older block files.
The second circumstance where we will disconnect a peer is where the peer manages to stall your entire download by preventing the moving window from progressing. Imagine your moving window is blocks 1000 to 2024 and you've downloaded everything from 1016 to 2024, but are waiting for Alice to serve up 1000 to 1016, which you may have requsted a few minutes earlier. In this siutation, if Alice continues to stall the moving window for 2 seconds, you will drop Alice and replace her with a more reliable peer. In the mantime, your node will request blocks 1000 to 1016 from one of your other peers so your moving window can start moving again.
What blocks do we request? The code to figure that out is in FindNextBlocksToDownload; it uses a block locator to figure out the last block we have in common with this peer, and starts from there. A block locator is a homemade algorithm that efficiently finds the fork point between our node and a given peer. The locator will pack a list of 32 blocks, starting with the last 10 (since in steady-state we are usually within 10 blocks of our peers), and then jumping back exponentially. (chain.cpp:25).
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Satoshi Nakamoto (born 5 April 1975) is the name used by the presumed pseudonymous person or persons who developed bitcoin, authored the bitcoin white paper, and created and deployed bitcoin's original reference implementation. As part of the implementation, Nakamoto also devised the first blockchain database. Nakamoto was active in the development of bitcoin up until December 2010.
Nakamoto stated that work on the writing of the code for Bitcoin began in 2007. On 18 August 2008, he or a colleague registered the domain name bitcoin.org, and created a web site at that address. On 31 October, Nakamoto published a white paper on the cryptography mailing list at metzdowd.com describing a digital cryptocurrency, titled "Bitcoin: A Peer-to-Peer Electronic Cash System".
Nakamoto continued to collaborate with other developers on the bitcoin software until mid-2010, making all modifications to the source code himself. He then gave control of the source code repository and network alert key to Gavin Andresen, transferred several related domains to various prominent members of the bitcoin community, and stopped his recognized involvement in the project.
Nakamoto owns between 750,000 and 1,100,000 bitcoin. In November 2021, when Bitcoin hit its still-highest value of over US$68,000, that would have made his net worth up to US$73 billion, which would have made him the 15th-richest person in the world at the time.
Some have considered that Nakamoto might be a team of people: Dan Kaminsky, a security researcher who read the bitcoin code, said that Nakamoto could either be a "team of people" or a "genius"; Laszlo Hanyecz, a developer who had emailed Nakamoto, had the feeling the code was too well designed for one person; Gavin Andresen has said of Nakamoto's code: "He was a brilliant coder, but it was quirky."