Mnemonic Phrase, Seed Phrase, Recovery Phrase, and BIP39: How they Work

If you’ve created your cryptocurrency wallet, you’re probably familiar with being told to write down your secret 12 or 24-word mnemonic phrase and keep it in a safe place. These are BIP39 wallets (which stands for “Bitcoin Improvement Proposal #39), and this method of security for many popular crypto wallets (both digital and hard wallets), including Metamask, Ledger, and Trezor. This mnemonic phrase, also known as a “Seed Phrase” or a “Recovery Phrase” allows you the ability to recover and unlock your wallet if you were to forget your password, or even lose access to your computer or mobile device for which you used to access your cryptocurrency wallet. But how does it really work?


Anyone with this 12-word or 24-word phrase will be able to recover and access your entire cryptocurrency wallet – so be sure you store it in a very, very safe place. We recommend that you go old-school and write it down with pen and paper – with ink that won’t fade and paper that won’t fade if it is to get wet. If you were to take a picture of it with your mobile device – you run the risk of if you were to lose your phone or get hacked – someone could come across that photo and secret phrase. This is the reason it could also be dangerous to store your mnemonic phrase on your “Notes” app on your computer or mobile device as well.

how bip39 and the 12 / 24-word phrases work

Mathematically speaking – it’s really, really, REALLY hard to brute force and “guess” a 12-word mnemonic phrase. As the github user “gurner” so eloquently puts it with regards to successfully executing a brute force attack, “…it seems pretty likely it would take longer than current the age of the universe to succeed–personally I’m not that patient.”

BIP39 uses a specific list of 2048 words. If you are so curious to know exactly what those 2048 words are, you can find them here. The mnemonic phrase is a unique combination of 12 words pulled from this list of 2048 words. Looking at the math, a 12-word mnemonic phrase 12 words from the BIP39 list of words would create this many possible combinations:

2048^12= 5.4445178707350154154139937189083e+39

As you might guess, a 24-word mnemonic phrase is even more secure, by a large degree. While the odds of someone guessing a 12 or 24 word phrase aren’t zero, it is extremely unlikely. In fact, a 12 word phrase is equivalent of 128-bit level of security – which is also one of the most secure encryption methods used in most modern encryption algorithms and technologies and widely considered to be logically unbreakable.

In Conclusion…

Though a 12 word phrase might sound like it should be easy to crack for even the most hardcore nefarious hackers out there – cryptographers have widely acknowledged that mathematically speaking – these mnemonic phrases are very secure (while technically speaking, it is not impossible to crack!). If you want to go a couple of steps further in securing your wallet’s phrase – you might want to check out a multi-sig approach or adding a 13th word to your security phrase (more to come in a future article!)

While there are many options out there, we would always recommend making sure to make strong efforts in securing your recovery phrase in a safe, safe place. If you’re looking for a wallet recommendation, our favorite is the Ledger.

Stay safe out there!