How secure are 24 words?

Bitcoin seed phrases are all that stand between your bitcoin and attackers,

How secure are 24 words?

Seed phrases

24 words are all that stand between your bitcoin and an attacker. So, how secure are they?

24 word Seed phrases are just a human friendly way of displaying 256 bits. So your seed phrase and the respective binary might look something like this:

24 word seed phrase and the respective binary.

256 bits mean that there are 2^256 or 10^77 possible seed phrases. This incredibly large number is difficult for the human mind to comprehend. Let me put this into context with some real world examples.

What are the odds?

The odds of guessing a 24 word seed phrase is 1 in 115,792,089,237,316,195,423,570,985,008,687,907,853,269,984,665,640,564,039,457,584,007,913,129,639,936

That is equivalent to guessing:

  1. One random grain of sand on Earth correctly,
  2. then pinpointing 1 random star among all stars in the observable universe,
  3. then guessing a cell in the average human body,
  4. consecutively, 4000 times in a row.

But that's if you have 1 guess, and computers are capable of making millions. 


The fastest known supercomputer in the world, Frontier, can do 1 quintillion (10^18) operations per second. Although it's practically impossible to guess a seed phrase in only 1 operation, let's give Frontier the benefit of the doubt and assume that it can guess 10^18 seeds per second.

The frontier supercomputer

Now Imagine the following:

  1. Every single grain of sand on Earth was a Frontier supercomputer.
  2. Every single star in the observable universe had its own Earth-sized planet, each covered with these sand-grain supercomputers.
  3. The combined power of these galactic sand-computers can guess 1.5 x 10^60 seeds per second.

This means it would take all these computers over 2 billion years to crack a seed. For context, that's like going to when dinosaurs went extinct and back 15 times.

So how secure are 24 words?

They are pretty damn secure. Just make sure they are randomly generated, and stored offline. Here are my favourite hardware wallets:

The Best Bitcoin Hardware Wallets
The best bitcoin hardware wallets specifically designed to secure your digital wealth offline.