Ruby Quiz - Challenge #2 - Calculate the Bitcoin Genesis Block Hash (SHA-256)

(Gerald Bauer) #1

Hello,

To kick start the new Ruby Quiz let's add another "real world" puzzle.

Challenge #2 - Calculate the Bitcoin Genesis Block Hash (SHA-256)

Let's calculate the classic bitcoin (crypto) block hash from scratch (zero).
with the unique block hash id
`000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f`.

Note: You can search and browse bitcoin blocks using (online)
block explorers. Example:

- blockchain.info/block/000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f
[1]
- blockexplorer.com/block/000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f
[2]
- and others.

The classic bitcoin (crypto) block hash gets calculated from

Field | Size (Bytes) | Comments |
------------|--------------|--------------------|
version | 4 byte | Block version number |
prev | 32 byte | 256-bit hash of the previous block header |
merkleroot | 32 byte | 256-bit hash of all transactions in the block |
time | 4 bytes | Current timestamp as seconds since

1970-01-01 00:00 |

bits | 4 bytes | Current difficulty target in compact

binary format |

nonce | 4 bytes | 32-bit number of the (mined) lucky

lottery number used once |

Note: 32 byte x 8 bit = 256 bit

Tip: Find out more about the Bitcoin Block hashing algorithm [3]
in the wiki page.

Using the data for the genesis block the setup is:

``````version    = 1
prev       = "0000000000000000000000000000000000000000000000000000000000000000"
merkleroot = "4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b"
time       = 1231006505
bits       = "1d00ffff"
nonce      = 2083236893
``````

The challenge: Code a calculate method that returns the Bitcoin hash.
Start from scratch or, yes, use any library / gem you can find.

``````def calculate( version, prev, merkleroot, time, bits, nonce )
# ...
end
``````

To qualify for solving the code challenge / puzzle you must pass the test:

``````require 'minitest/autorun'

class RubyQuizTest < MiniTest::Test

def test_calculate

hash = "000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f"

version    = 1
prev       =
"0000000000000000000000000000000000000000000000000000000000000000"
merkleroot =
"4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b"
time       = 1231006505
bits       = "1d00ffff"
nonce      = 2083236893

assert_equal hash, calculate( version, prev, merkleroot, time, bits, nonce )

end # method test_calculate
end # class RubyQuizTest
``````

Post your code snippets on the "official" Ruby Quiz Channel,
that is, the ruby-talk mailing list.

Happy hacking and crypto mining with Ruby.

PS: The Ruby Quiz - #1 Challenge is still open too for new code
snippets / solutions! [4]