block10.ruby

def bytes_to_bignum(bytes_string)
  bytes_string.bytes.reduce { |n, b| (n << 8) + b }
end
def bignum_to_bytes(n, length=nil)
  a = []
  while n > 0
    a << (n & 0xFF)
    n >>= 8
  end
  a.fill 0x00, a.length, length - a.length if length
  a.reverse.pack('C*')
end