Explaining Handshake To Grandma

Imagine there’s only one phone book in the world.

My friend Lucas takes care of it. He’s a great guy, and I trust him. Whenever I need to call someone, Lucas gives me their up-to-date number.

Debbie, Lucas’s mother, doesn’t like that Lucas has the phone book. “Sometimes, I’ll try contacting him and he won’t respond. We couldn’t invite people to our Super Bowl party this year because Lucas didn’t give us any phone numbers until three days after it was all over!”

Debbie gets fed up. She decides to copy the phone book and distribute the copies to everyone. But she runs into a problem. When someone changes phones, she needs help from Lucas to run around updating everyone’s phone book with the new information.

Lucas is lazy. He doesn’t like running around. So he invents a way to automatically update everyone’s phone book with the correct information.

Here’s what Lucas does. He scans everyone’s phone book into a special digital format, so it’s accessible via smartphone or computer screen. Then he tells everyone:

“I will take away your phone book unless you promise to follow some rules.

Rule 1: If you want to make an update to your phone book, you have to tell all your neighbors about the update, and they can tell their neighbors in turn.

Rule 2: every 10 minutes, there will be a super hard math problem. Whoever solves it first gets their list of updates published as the ‘true’ updates we should all copy down.”

To make things easy, Lucas installs special software that automatically takes care of the rules. Nobody has to do much except let Lucas’s program run in the background, quietly communicating with all the other digital phone books, solving math problems, and publishing updates.

Lucas’s system works like a charm! For one thing, he doesn’t have to run around anymore, so Debbie can get off his back. For another, even if our friend Sam tries to give everyone a prank number, Sam won’t be able to solve math problems faster than everyone else all the time. Lucas, Debbie, and I keep our eyes peeled for Sam’s pranks. One of us will usually beat him at solving the math problem, so we’ll quickly correct any false updates he creates (likely within an hour or less).

Let’s review our two options here. We could do the thing we’ve always done, which is to have Lucas in charge of the single phone book. Or we could have the fancy digital phone books for everyone. Which would you prefer?

Debbie likes the fancy new second option. I don’t really care either way because the old method worked fine for me. But I understand Debbie’s pain. I also know Lucas sometimes charged money for his service. And I heard rumors that he let the Chinese government filter certain phone numbers when people in China would ask for them.

Overall, I think the second system works better. We don’t really need Lucas in the middle. The fancy new thing works great, it’s faster, and more secure.

Furthermore, we can all make new phone numbers which are longer, shorter, or even use letters (as long as our phones can dial them). Lucas liked ten digit numbers, but we are no longer constrained to his preferences.

So what’s the deal? Why wouldn’t we all just use the second thing?

Some people don’t understand the new option. It sounds technical and scary and folks don’t trust the math. Instead of taking the time to understand what’s going on, it’s easier to just do the thing we’ve always done.

Some people don’t trust Lucas’s engineering skills. A fair point—nobody’s perfect. What if the new system suddenly breaks, or someone finds a flaw that Lucas didn’t expect when he designed it? We may have to fix his original software. Or it might even be unfixable, and we’d have to start over again.

Some people think there are too many Sams out there pulling pranks. With sufficiently many pranksters, we might not get the right updates often enough.

There could be implementation problems. The above situation is pretty idealistic, and real life might not go so smoothly. Governments might fight the new system. Maybe Sam sees his pranks won’t work anymore, so he tries to sabotage the installation process. For whatever reason, if not enough people adopt it, the fancy system won’t be very helpful.

I hope we can tackle the understanding issue using stories like this one. We can tackle the engineering issue by experimenting and building a good system over time, with help from others in addition to Lucas. We can’t really do anything about so many pranksters…but maybe we don’t need to because most people care more about the phone books working well than pulling pranks. And we’ll just have to work hard to implement things well, collaborating with governments and everyone else.

In summary, all these issues seem tractable. Even more so because I left out some details, like the fact that Lucas created some new money that can help get everyone aligned using the fancy system for selfish reasons. In the end, we’ll just have to try it, experiment, and see if things work out!

This was a basic, simplified analogy to explain Handshake, a project which applies the blockchain to internet domain names and traffic routing.

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