Bitcoin Mining Ruby

btc_miner.rb

require 'digest/sha2'

# -----------------
# Utility Functions
# -----------------

# The hash function used in mining (convert hexadecimal to binary first, then SHA256 twice)
def hash256(data)
  binary = [data].pack("H*")
  hash1 = Digest::SHA256.digest(binary)
  hash2 = Digest::SHA256.hexdigest(hash1)
end

# Convert a number to fit inside a field that is a specific number of bytes e.g. field(1, 4) = 00000001
def field(data, size)
  hex = data.to_i.to_s(16).rjust(size * 2, '0')
end

# Reverse the order of bytes (happens often when working with raw bitcoin data)
def reversebytes(data)
  data.scan(/../).reverse.join
end

# ------------
# Block Header
# ------------

# Target (optional)
target = '000000000004864c000000000000000000000000000000000000000000000000'

# Block Header (Fields)
version    = '1'
prevblock  = '000000000002d01c1fccc21636b607dfd930d31d01c3a62104612a1719011250'
merkleroot = 'f3e94742aca4b5ef85488dc37c06c3282295ffec960994b2c0d5ac2a25a95766'
time       = '1293623863'  # Unixtime (29 Dec 2010, 11:57:43)
bits       = '1b04864c'
nonce      = 0             # 274148111

# Block Header (Serialized)
header = reversebytes(field(version, 4)) + reversebytes(prevblock) + reversebytes(merkleroot) + reversebytes(field(time, 4)) + reversebytes(bits)

# -----
# Mine!
# -----
loop do
  # hash the block header
  attempt = header + reversebytes(field(nonce, 4))
  result = reversebytes(hash256(attempt))

  # show result
  puts "#{nonce}: #{result}"

  # end if we get a block hash below the target
  if result.to_i(16) < target.to_i(16)
    break
  end
  
  # increment the nonce and try again...
  nonce += 1
end