Casa Blog - Bitcoin Security Made Easy

Most people don't know what a private key is, but they are one of the most powerful technologies that we all use every day. If you hold bitcoin or other crypto, there's a decent chance you have a vague idea of what a private key is but haven't thought much about why private key technology is so important.

Private keys have three fundamental superpowers. I like to call them by the incredibly catchy name "The Three U's."

Private keys are:

  • Unique
  • Unguessable
  • Unforgeable

Here's what that means.


A private key is actually a long, randomly generated string of letters and numbers. Here's what one looks like:


This is generated by multiplying some random large numbers together, doing some cryptography magic, and voila — that string pops out. Because of how that process works, every private key is unique — meaning no two private keys are the same.


Because private keys are a long string of random numbers and letters, you can't guess them like you would guess someone's password. Not only can you, a human, not guess them, but a computer can't either. Just google "how long would it take to brute force a bitcoin private key," and you'll find answers ranging from hundreds of millions to quadrillions and septillions of years. Hah.

On the other hand, it's trivial to create a private key. In mere seconds (or less), you can create an unguessable private key.


Finally, if you have a key, it's impossible for anyone else to forge that key — i.e. trick someone else into believing they have it when they don't. Just like it's trivial to create a private key, it's also trivial to prove beyond doubt that you have that key in your possession. This is because of the cryptographic pairing between a public and private key. You can give the public key out to the world, and then "sign" with your private key to prove that you own both keys.

Each public/private key pair is created by a cryptographic equation - it’s just math. You can’t fake math and there’s only one way to get the right cryptographic answer from this equation: the private key. Cryptographic signatures allow you to prove something no one else can.

The fact that keys are unforgeable makes them great for using as authentication in a decentralized network like bitcoin. No one can try to fake that they own a key, and therefore fake that they own bitcoin, that someone else owns.

Private keys and authentication

The Three U's make private keys an amazing form of authentication online. We have a digital representation of identity that is unique, can't be guessed, and can't be faked. On top of that, it takes a tiny amount of computing power for others to verify that you own a private key.

This is why private keys are used to secure bitcoin. The bitcoin network needs a rock-solid way to authenticate that you own X amount of bitcoin, and that you're authorized to move it. Private keys are that rock.

Private keys are making our lives easier and more secure. These superpowers, the Three U's, are the reasons why they are such game-changers for the world.

Get security updates delivered to your inbox

Want to learn about private keys and ways to secure your bitcoin and other assets? Our weekly Security Briefing help you stay informed of the latest developments in security from hacks to new exciting technology. Sign up below.

Read more

How to take control of your crypto keys
Not your keys, not your crypto. Learn how to take self-custody into your own hands with this overview.