CH11-12: remove long & not-very-useful example code

Suggested by Jorge Lesmes
develop
David A. Harding 10 months ago
parent 825d52823c
commit e0932e89f7

@ -437,44 +437,6 @@ diagram).
.A merkle path used to prove inclusion of a data element
image::images/mbc2_0905.png["merkle_tree_path"]
The code in <<merkle_example>> demonstrates the process of creating a
merkle tree from the leaf-node hashes up to the root, using the
libbitcoin library for some helper functions.
[[merkle_example]]
[role="pagebreak-before"]
.Building a merkle tree
====
[source, cpp]
----
include::code/merkle.cpp[]
----
====
<<merkle_example_run>> shows the result of compiling and running the
merkle code.
[[merkle_example_run]]
.Compiling and running the merkle example code
====
[source,bash]
----
$ # Compile the merkle.cpp code
$ g++ -o merkle merkle.cpp $(pkg-config --cflags --libs libbitcoin)
$ # Run the merkle executable
$ ./merkle
Current merkle hash list:
32650049a0418e4380db0af81788635d8b65424d397170b8499cdc28c4d27006
30861db96905c8dc8b99398ca1cd5bd5b84ac3264a4e1b3e65afa1bcee7540c4
Current merkle hash list:
d47780c084bad3830bcdaf6eace035e4c6cbf646d103795d22104fb105014ba3
Result: d47780c084bad3830bcdaf6eace035e4c6cbf646d103795d22104fb105014ba3
----
====
The efficiency of merkle trees becomes obvious as the scale increases.
<<block_structure2>> shows the amount of data that needs to be exchanged
as a merkle path to prove that a transaction is part of a block.

@ -722,62 +722,6 @@ This
every part of the phrase. Adding a single letter, punctuation mark, or
any other character will produce a different hash.
Now, if we change the phrase, we should expect to see completely
different hashes. Let's try that by adding a number to the end of our
phrase, using the simple Python scripting in
<<sha256_example_generator>>.
[[sha256_example_generator]]
.SHA256 script for generating many hashes by iterating on a nonce
====
[role="c_less_space"]
[source, python]
----
include::code/hash_example.py[]
----
====
Running this will produce the hashes of several phrases, made different
by adding a number at the end of the text. By incrementing the number,
we can get different hashes, as shown in
<<sha256_example_generator_output>>.
[[sha256_example_generator_output]]
.SHA256 output of a script for generating many hashes by iterating on a nonce
====
[source,bash]
----
$ python hash_example.py
----
----
I am Satoshi Nakamoto0 => a80a81401765c8eddee25df36728d732...
I am Satoshi Nakamoto1 => f7bc9a6304a4647bb41241a677b5345f...
I am Satoshi Nakamoto2 => ea758a8134b115298a1583ffb80ae629...
I am Satoshi Nakamoto3 => bfa9779618ff072c903d773de30c99bd...
I am Satoshi Nakamoto4 => bce8564de9a83c18c31944a66bde992f...
I am Satoshi Nakamoto5 => eb362c3cf3479be0a97a20163589038e...
I am Satoshi Nakamoto6 => 4a2fd48e3be420d0d28e202360cfbaba...
I am Satoshi Nakamoto7 => 790b5a1349a5f2b909bf74d0d166b17a...
I am Satoshi Nakamoto8 => 702c45e5b15aa54b625d68dd947f1597...
I am Satoshi Nakamoto9 => 7007cf7dd40f5e933cd89fff5b791ff0...
I am Satoshi Nakamoto10 => c2f38c81992f4614206a21537bd634a...
I am Satoshi Nakamoto11 => 7045da6ed8a914690f087690e1e8d66...
I am Satoshi Nakamoto12 => 60f01db30c1a0d4cbce2b4b22e88b9b...
I am Satoshi Nakamoto13 => 0ebc56d59a34f5082aaef3d66b37a66...
I am Satoshi Nakamoto14 => 27ead1ca85da66981fd9da01a8c6816...
I am Satoshi Nakamoto15 => 394809fb809c5f83ce97ab554a2812c...
I am Satoshi Nakamoto16 => 8fa4992219df33f50834465d3047429...
I am Satoshi Nakamoto17 => dca9b8b4f8d8e1521fa4eaa46f4f0cd...
I am Satoshi Nakamoto18 => 9989a401b2a3a318b01e9ca9a22b0f3...
I am Satoshi Nakamoto19 => cda56022ecb5b67b2bc93a2d764e75f...
----
====
Each phrase produces a completely different hash result. They seem
completely random, but you can reproduce the exact results in this
example on any computer with Python and see the same exact hashes.
The number used as a variable in such a scenario is called a _nonce_.
The nonce is used to vary the output of a cryptographic function, in
this case to vary the SHA256 fingerprint of the phrase.

@ -1,18 +0,0 @@
# example of iterating a nonce in a hashing algorithm's input
from __future__ import print_function
import hashlib
text = "I am Satoshi Nakamoto"
# iterate nonce from 0 to 19
for nonce in range(20):
# add the nonce to the end of the text
input_data = text + str(nonce)
# calculate the SHA-256 hash of the input (text+nonce)
hash_data = hashlib.sha256(input_data).hexdigest()
# show the input and hash result
print(input_data, '=>', hash_data)

@ -1,62 +0,0 @@
#include <bitcoin/bitcoin.hpp>
bc::hash_digest create_merkle(bc::hash_list& merkle)
{
// Stop if hash list is empty.
if (merkle.empty())
return bc::null_hash;
else if (merkle.size() == 1)
return merkle[0];
// While there is more than 1 hash in the list, keep looping...
while (merkle.size() > 1)
{
// If number of hashes is odd, duplicate last hash in the list.
if (merkle.size() % 2 != 0)
merkle.push_back(merkle.back());
// List size is now even.
assert(merkle.size() % 2 == 0);
// New hash list.
bc::hash_list new_merkle;
// Loop through hashes 2 at a time.
for (auto it = merkle.begin(); it != merkle.end(); it += 2)
{
// Join both current hashes together (concatenate).
bc::data_chunk concat_data(bc::hash_size * 2);
auto concat = bc::serializer<
decltype(concat_data.begin())>(concat_data.begin());
concat.write_hash(*it);
concat.write_hash(*(it + 1));
// Hash both of the hashes.
bc::hash_digest new_root = bc::bitcoin_hash(concat_data);
// Add this to the new list.
new_merkle.push_back(new_root);
}
// This is the new list.
merkle = new_merkle;
// DEBUG output -------------------------------------
std::cout << "Current merkle hash list:" << std::endl;
for (const auto& hash: merkle)
std::cout << " " << bc::encode_base16(hash) << std::endl;
std::cout << std::endl;
// --------------------------------------------------
}
// Finally we end up with a single item.
return merkle[0];
}
int main()
{
// Replace these hashes with ones from a block to reproduce the same merkle root.
bc::hash_list tx_hashes{{
bc::hash_literal("0000000000000000000000000000000000000000000000000000000000000000"),
bc::hash_literal("0000000000000000000000000000000000000000000000000000000000000011"),
bc::hash_literal("0000000000000000000000000000000000000000000000000000000000000022"),
}};
const bc::hash_digest merkle_root = create_merkle(tx_hashes);
std::cout << "Result: " << bc::encode_base16(merkle_root) << std::endl;
return 0;
}
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