E322 Multisig versus Passphrase with a Bitcoin Executor

Multisig or a passphrase ("poor man’s multisig") are two ways to transfer custody to your bitcoin executor upon your death. Let’s compare, so you can decide which best fits your bitcoin inheritance plan.

Why multisig for bitcoin inheritance?

The main feature is splitting access to your bitcoin, so that it’s not catastrophic if just one of your keys is revealed, leaked, or hacked. While you should always be careful of how you manage your security materials, using a multisig allows you to be a little less uptight with your security practices. By contrast, if all of your stash is in a singlesig wallet, then access to that one key could cost you all of your bitcoin. If one key is lost, you lose it all. If one key is hacked, it’s all stolen.

Also, this is not necessarily what’s best for estate administration (which can last years), but rather the immediate transfer of custody to your executor. So this is not about how your executor will hold your keys during his tenure as your executor. This analysis is specifically regarding the pros and cons of how smooth the transfer will be from you to your executor upon death.

Lastly, the general pros and cons of multisig vs. singlesig with a passphrase (multi vs. single vendor risk, costs of multiple hardware wallets, ease of setup, etc.) are beyond the scope of this analysis.  For the purpose of this discussion, we are just looking at the pros and cons of transfer to your executor upon your passing.

Leaving a passphrase for your bitcoin executor

First, we’ll look at using a passphrase as a poor man’s multisig for your non-bitcoin executor. Your seed phrase and your additional passphrase combine as an imperfect 2-of-2 multisig of sorts.

A passphrase would be easier for a non-bitcoin executor, in theory, because it feels more like just a second password. By contrast, multisig can be more intimidating: and feel like those movies with a nuclear submarine where the captain and the first mate must each put a key in and turn on the count of three...

If you or your executor lose your passphrase, there’s at least theoretical hope to recover it with enough computing power (depending on length and complexity of the passphrase). People are not too great about choosing phrases randomly, and often use short passphrases that are easier to remember. A lost 12- 24-word seed phrase could not be recovered for the foreseeable future.

You could also hide your passphrase in plain sight, so that it’s easier to transfer to your executor. For example, writing a letter to your executor, where every fifth word comprises your passphrase. My understanding is this is poor opsec with a 12- or 24-word seed phrase, because seed phrase words are a finite set, and hackers have algorithms to scan text for seed phrase words.

But be aware: passphrases are not really designed for this, and there’s not much support for its use as a poor man's multisig. A non-professional executor may have trouble finding information online about passphrases as a 2-of-2 multisig. Whereas there are companies that, for a consultation fee, will take the time to walk the executor through the multisig process.

How your bitcoin executor will handle your multisig

With a 2-of-3 multsig, there are three independent keys (seed phrases and/or hardware devices), and you need two of them to access the bitcoin and make a transaction.

Multisg has more leeway for error: even if you lose one key, you still have two and can recover. This provides a margin for error in terms of catastrophic loss. With a passphrase (or any 2-of-2) set up, there are only two "keys", so if you lose either one, you can’t access your bitcoin.

A second benefit of multisig is that each key is strong and offers full protection because each key is a 12- or 24-word seed phrase, created with the fully researched cryptography security. Whereas you create your own passphrase, and we're all pretty bad at being sufficiently random (admit it, we use our kid’s name, anniversary, favorite movie quote, etc. as passwords).

Lastly, multisig has lower “smudge risk” than a passphrase.  Since 12- or 24-seed phrase words comes from a finite set of possible vocabulary words, if just of the handwritten seed words and smudgy, there is still good a chance of figuring out the word. But since your passphrase can be any word, in any language, or even gibberish, guessing a smudged word would be complete guessing.

The focus here is how your executor will solve the puzzle after your death so your bitcoin isn’t lost. For further reading on what executors deal with in general, check out my book on Amazon, “How Probate Works.”

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