Installing a payphone in my house | bertrand fan

When I was growing up in the 90s, I remember wanting to get on the Internet. My parents weren’t going to help me, so I called up an ISP and said I wanted to set up an account. They asked for my name and I gave them a fake name. And then they asked for a credit card number and I told them I had to find my wallet and call them back.

I knew a few things about credit card numbers that I had learned from the book Big Secrets and some issues of 2600. American Express cards were always 15 digits and started with a 3 and Visa cards were 16 digits and started with a 4. The first couple digits are the issuing bank, and then the account number, and then they use something called the Luhn algorithm to produce the last digit, which is a checksum of the previous digits.

The algorithm works like this - take a credit card number like:

4123456741234122

Remove the last digit, the check digit, and set it aside:

412345674123412 2

Now reverse the order of the digits:

214321476543214

Then multiple every other digit by 2, starting with the first digit:

2*2 1 4*2 3 2*2 1 4*2 7 6*2 5 4*2 3 2*2 1 4*4

That produces:

4 1 8 3 4 1 8 7 12 5 8 3 4 1 8

Next, separate any double digit numbers into single digits:

4 1 8 3 4 1 8 7 1 2 5 8 3 4 1 8

Add them all together:

4+1+8+3+4+1+8+7+1+2+5+8+3+4+1+8 = 68

Divide by 10 and keep the remainder:

68 mod 10 = 8

Subtract the remainder from 10:

10-8 = 2

This number is the check digit.

The algorithm is used to validate credit card numbers. If someone types in the wrong digit or mishears it on the phone, the check digit won’t match up. But this means that you could also generate valid credit card numbers. If you wanted to generate a Visa credit card number, you could start with 4, add a bunch of random numbers, and then calculate the check digit and add it to the end. The number would almost certainly not match to an actual credit card, but it would look like a valid credit card number.

So I wrote a program to generate credit card numbers exactly as I just described, called them back and gave it to them along with a random expiration date in the future and they said, “Great, now we just need a phone number to call you back.”

Now I’m not sure what the first rule of credit card fraud is but it might be “Don’t give the person you’re defrauding your actual telephone number”. I said I had just moved and needed to look it up and I’d call them back. Then I walked to a payphone outside a convenience store, wrote down the number, called them back and gave it to them. They hung up, waited a few minutes, and called the payphone, which I answered. They asked me for a username, gave me a random password, and thanked me for my business.

The Internet was everything I had hoped it would be, for a couple weeks at least. But one day my username and password didn’t work. They obviously had tried billing the credit card and failed. So I generated a new credit card number, walked back to the convenience store and called them from the payphone and asked to set up a new account. It was going great until I gave them the payphone number, at which point they did not thank me for my business.

My payphone number had been blacklisted, but the great thing about living in a metropolitan area in the U.S. in the 90s is that there was always another payphone. I called them from a different one, set up a new account, and was back on the Internet.

For the next few months, this became a bit of a cat-and-mouse game with me and the ISP. I printed out a list of credit card numbers that I had generated and would carry them around with me. Whenever I saw a payphone, I would either call them to set up a new account or write down its location for future use. Sometimes I would get a representative that I had talked to before that would recognize my voice, other times they would insist on calling back the next day, which meant camping out at a payphone hoping it would ring. If I was with a friend, I’d have them do it for me, writing down what I wanted them to say.

I did eventually get more permanent Internet access, but the experience made me fond of payphones and what they provided for me when I needed them the most.

Last year, my daughter Aurora and I were walking around in Muir Woods and we came across this payphone.

Excitedly, I explained what it was and we took turns listening to the dial tone. I put some quarters in and called my cell phone to show her how it worked.

I recently moved into a new place and finally got to ditch Comcast for Sonic, which previously wasn’t in my coverage area. This has a few benefits. It’s a fiber line, so my upload speeds are better. For some reason, they continue to run a server that you can play door games on:

And last but not least, they include a landline with your service. At first I ignored it, but it gnawed at me. A telephone jack that worked and nothing to plug into it.

So I went on The Internet (I have permanent access...