And after we have our public key hash, we’re just a little ways away from arriving at our Bitcoin address.
The next step is to make our pub key hash a bit more human friendly.
First, we add a version byte in front of our previous RIPEMD-160 hash from the last section In the version byte, we specify which network we’re on: the main Bitcoin network, or a smaller test network.
We’ll save this for how and call it our extended RIPEMD-160 hash.
We then run a Base58Check encode, which first involves converting what we have so far into base 58.
Base 58 is an alphabet that’s like our usual 62 character alphabet.
It has all single digits 0 to 9 and all upper and lower case letters, except for those that are hard to distinguish from one another.
So we take out the 0 and capital letter O, and also capital “I” and lower case “l.” This is to avoid ambiguity when copying down your address.
Then, we calculate a checksum.
We perform SHA-256d on our extended RIPEMD-160 hash, running SHA-256 on it twice.
We take the first 4 bytes of our SHA-256d hash as our checksum, and append it to the end of our extended RIPEMD-160 hash.
After converting the result to base58, we finally have our Bitcoin address.
As a recap, in our address, we have successfully encoded our public key hash, which allows people to pay us, a version byte that says what network we’re on, and also a checksum that accounts for human error.
If someone types or copies down your address wrong, then the address would not be valid given the checksum.
And this is something that decoding software will do for us.
It can hash the beginning of our address and compare it with the checksum to see if it is valid.