Creating bitcoin address in ruby

Question

I am trying to create a bitcoin address in ruby according to the documentation of bitcoin wiki (bitcoin creation according bitcoin wiki). Starting point is just some random string which emulates the output of ripmed160. Unfortunately I don't quite succeed in doing so, here is my code:

require 'base58_gmp'
tx_hash = "a8d0c0184dde994a09ec054286f1ce581bebf46446a512166eae7628734ea0a5"

ripmed160 = tx_hash[0..39]
ripmed160_with_pre = "00" + ripmed160

sha1 = Digest::SHA256.hexdigest ripmed160_with_pre
sha2 = Digest::SHA256.hexdigest sha1

bin_address = Integer("0x" + ripmed160_with_pre + sha2[0..7])

bitcoin_address = "1" + Base58GMP.encode(bin_address, 'bitcoin')  # => "1GPcbTYDBwJ42MfKkedxjmJ3nrgoaNd2Sf"

Answer 1

When you calculate the SHA256 checksum, make sure to calculate it over the actual bytes of the previous step, not the hex encoding of those bytes:

# First convert to actual bytes.
bytes = [ripmed160_with_pre].pack('H*')

# Now calculate the first hash over the raw bytes, and
# return the raw bytes again for the next hash
# (note: digest not hexdigest).
sha1 = Digest::SHA256.digest bytes

# Second SHA256, using the raw bytes from the previous step
# but this time we can use hexdigest as the rest of the code
# assumes hex encoded strings
sha2 = Digest::SHA256.hexdigest sha1