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https://github.com/bitcoinbook/bitcoinbook
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CH11-12: remove long & not-very-useful example code
Suggested by Jorge Lesmes
This commit is contained in:
David A. Harding
parent
825d52823c
commit
e0932e89f7
@ -437,44 +437,6 @@ diagram).
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.A merkle path used to prove inclusion of a data element
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image::images/mbc2_0905.png["merkle_tree_path"]
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The code in <<merkle_example>> demonstrates the process of creating a
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merkle tree from the leaf-node hashes up to the root, using the
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libbitcoin library for some helper functions.
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[[merkle_example]]
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[role="pagebreak-before"]
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.Building a merkle tree
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====
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[source, cpp]
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----
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include::code/merkle.cpp[]
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----
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====
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<<merkle_example_run>> shows the result of compiling and running the
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merkle code.
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[[merkle_example_run]]
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.Compiling and running the merkle example code
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====
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[source,bash]
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----
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$ # Compile the merkle.cpp code
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$ g++ -o merkle merkle.cpp $(pkg-config --cflags --libs libbitcoin)
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$ # Run the merkle executable
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$ ./merkle
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Current merkle hash list:
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32650049a0418e4380db0af81788635d8b65424d397170b8499cdc28c4d27006
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30861db96905c8dc8b99398ca1cd5bd5b84ac3264a4e1b3e65afa1bcee7540c4
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Current merkle hash list:
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d47780c084bad3830bcdaf6eace035e4c6cbf646d103795d22104fb105014ba3
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Result: d47780c084bad3830bcdaf6eace035e4c6cbf646d103795d22104fb105014ba3
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----
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====
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The efficiency of merkle trees becomes obvious as the scale increases.
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<<block_structure2>> shows the amount of data that needs to be exchanged
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as a merkle path to prove that a transaction is part of a block.
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@ -722,62 +722,6 @@ This
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every part of the phrase. Adding a single letter, punctuation mark, or
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any other character will produce a different hash.
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Now, if we change the phrase, we should expect to see completely
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different hashes. Let's try that by adding a number to the end of our
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phrase, using the simple Python scripting in
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<<sha256_example_generator>>.
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[[sha256_example_generator]]
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.SHA256 script for generating many hashes by iterating on a nonce
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====
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[role="c_less_space"]
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[source, python]
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----
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include::code/hash_example.py[]
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----
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====
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Running this will produce the hashes of several phrases, made different
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by adding a number at the end of the text. By incrementing the number,
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we can get different hashes, as shown in
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<<sha256_example_generator_output>>.
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[[sha256_example_generator_output]]
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.SHA256 output of a script for generating many hashes by iterating on a nonce
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====
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[source,bash]
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----
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$ python hash_example.py
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----
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----
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I am Satoshi Nakamoto0 => a80a81401765c8eddee25df36728d732...
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I am Satoshi Nakamoto1 => f7bc9a6304a4647bb41241a677b5345f...
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I am Satoshi Nakamoto2 => ea758a8134b115298a1583ffb80ae629...
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I am Satoshi Nakamoto3 => bfa9779618ff072c903d773de30c99bd...
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I am Satoshi Nakamoto4 => bce8564de9a83c18c31944a66bde992f...
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I am Satoshi Nakamoto5 => eb362c3cf3479be0a97a20163589038e...
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I am Satoshi Nakamoto6 => 4a2fd48e3be420d0d28e202360cfbaba...
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I am Satoshi Nakamoto7 => 790b5a1349a5f2b909bf74d0d166b17a...
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I am Satoshi Nakamoto8 => 702c45e5b15aa54b625d68dd947f1597...
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I am Satoshi Nakamoto9 => 7007cf7dd40f5e933cd89fff5b791ff0...
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I am Satoshi Nakamoto10 => c2f38c81992f4614206a21537bd634a...
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I am Satoshi Nakamoto11 => 7045da6ed8a914690f087690e1e8d66...
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I am Satoshi Nakamoto12 => 60f01db30c1a0d4cbce2b4b22e88b9b...
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I am Satoshi Nakamoto13 => 0ebc56d59a34f5082aaef3d66b37a66...
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I am Satoshi Nakamoto14 => 27ead1ca85da66981fd9da01a8c6816...
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I am Satoshi Nakamoto15 => 394809fb809c5f83ce97ab554a2812c...
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I am Satoshi Nakamoto16 => 8fa4992219df33f50834465d3047429...
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I am Satoshi Nakamoto17 => dca9b8b4f8d8e1521fa4eaa46f4f0cd...
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I am Satoshi Nakamoto18 => 9989a401b2a3a318b01e9ca9a22b0f3...
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I am Satoshi Nakamoto19 => cda56022ecb5b67b2bc93a2d764e75f...
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----
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====
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Each phrase produces a completely different hash result. They seem
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completely random, but you can reproduce the exact results in this
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example on any computer with Python and see the same exact hashes.
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The number used as a variable in such a scenario is called a _nonce_.
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The nonce is used to vary the output of a cryptographic function, in
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this case to vary the SHA256 fingerprint of the phrase.
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@ -1,18 +0,0 @@
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# example of iterating a nonce in a hashing algorithm's input
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from __future__ import print_function
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import hashlib
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text = "I am Satoshi Nakamoto"
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# iterate nonce from 0 to 19
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for nonce in range(20):
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# add the nonce to the end of the text
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input_data = text + str(nonce)
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# calculate the SHA-256 hash of the input (text+nonce)
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hash_data = hashlib.sha256(input_data).hexdigest()
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# show the input and hash result
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print(input_data, '=>', hash_data)
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@ -1,62 +0,0 @@
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#include <bitcoin/bitcoin.hpp>
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bc::hash_digest create_merkle(bc::hash_list& merkle)
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{
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// Stop if hash list is empty.
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if (merkle.empty())
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return bc::null_hash;
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else if (merkle.size() == 1)
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return merkle[0];
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// While there is more than 1 hash in the list, keep looping...
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while (merkle.size() > 1)
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{
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// If number of hashes is odd, duplicate last hash in the list.
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if (merkle.size() % 2 != 0)
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merkle.push_back(merkle.back());
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// List size is now even.
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assert(merkle.size() % 2 == 0);
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// New hash list.
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bc::hash_list new_merkle;
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// Loop through hashes 2 at a time.
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for (auto it = merkle.begin(); it != merkle.end(); it += 2)
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{
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// Join both current hashes together (concatenate).
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bc::data_chunk concat_data(bc::hash_size * 2);
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auto concat = bc::serializer<
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decltype(concat_data.begin())>(concat_data.begin());
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concat.write_hash(*it);
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concat.write_hash(*(it + 1));
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// Hash both of the hashes.
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bc::hash_digest new_root = bc::bitcoin_hash(concat_data);
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// Add this to the new list.
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new_merkle.push_back(new_root);
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}
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// This is the new list.
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merkle = new_merkle;
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// DEBUG output -------------------------------------
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std::cout << "Current merkle hash list:" << std::endl;
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for (const auto& hash: merkle)
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std::cout << " " << bc::encode_base16(hash) << std::endl;
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std::cout << std::endl;
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// --------------------------------------------------
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}
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// Finally we end up with a single item.
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return merkle[0];
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}
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int main()
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{
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// Replace these hashes with ones from a block to reproduce the same merkle root.
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bc::hash_list tx_hashes{{
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bc::hash_literal("0000000000000000000000000000000000000000000000000000000000000000"),
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bc::hash_literal("0000000000000000000000000000000000000000000000000000000000000011"),
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bc::hash_literal("0000000000000000000000000000000000000000000000000000000000000022"),
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}};
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const bc::hash_digest merkle_root = create_merkle(tx_hashes);
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std::cout << "Result: " << bc::encode_base16(merkle_root) << std::endl;
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return 0;
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}
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