Security

Keep the three pieces in three different places

Never let all three land in one spot — one laptop, one cloud account, one password manager, one safe, one inbox. If a single breach can reach all three, the whole scheme is defeated. Two of three in one place is fine; three is game over.

Deliver the beneficiary key on a different channel than the deadman switch

The deadman switch holds two of the three pieces — the encrypted seed and the benefactor key — and releases them when it triggers. That's safe only because the beneficiary key travels separately.

So if your switch delivers by email, do not also email the beneficiary key to the same inbox. Years later both legs would converge there, and whoever compromises that one account would hold all three. Instead hand the beneficiary key over out of band: in person, on paper, through a different account, or by a messaging app the switch will never touch.

Beneficiary: get your key out of the inbox

If you receive your beneficiary key by email or chat, treat that message as temporary. Copy the key into durable, private storage — write it on paper, or put it in your password manager — and then delete the original message. Don't leave it sitting in the same inbox that may one day receive the rest of the inheritance.

Make many copies of the encrypted seed

The encrypted seed is inert — without both keys it's just noise, so it can't hurt you to duplicate it. Do: keep several copies (print the QR, save the text, store it in a couple of places). The piece most likely to simply get lost over the years is the one you have the fewest copies of, and this one is free to back up.

Test the whole round trip before you rely on it

Right after you encrypt, decrypt it back with both keys and confirm you get your exact seed phrase — ideally in two places (the SeedSigner and Legacy-offline.html). A plan you've never tested is a plan you don't have. Rehearse the decrypt once with a throwaway seed so your beneficiary knows the steps too.

Use many words

Length beats cleverness. Each additional unrelated word multiplies the attacker's work. Aim for at least three words per key (six across the two). Four each is better. A short, punchy key is a weak key no matter how obscure the word.

Reach deep into the dictionary

Do use uncommon words — barbaric, flightless, crucible. Don't use the first words everyone's brain reaches for — happy, yellow, duck. Attackers try the common words first, so the deeper your vocabulary, the later in their list you sit.

Nothing personal

Avoid anything tied to you: pet names, birthdays, your town, your favorite book or character. A motivated attacker — especially if your use of Legacy is ever public — will profile you and build a wordlist from your life. Your keys should reveal nothing about you.

Best of all: let a generator pick

Human-chosen words are predictable in ways you can't feel — we cluster on common, related, meaningful words. A random word generator (diceware, or an EFF-wordlist tool) removes the bias entirely. You can keep a readable, memorable shape — adjective-adjective-noun, hyphenated — as long as each word is an independent random draw. Random guarantees the strength; picking from your head only hopes for it.

And no — a generator being public doesn't weaken you. The security is in the random selection, not in keeping the wordlist secret: a BIP-39 seed phrase is drawn from a list the whole world has, yet it's uncrackable because the choice is random. Knowing the list doesn't shrink the search by a single guess. (Just use a sizable list and a real random source.)

Symbols and punctuation add strength — just record them exactly

Beyond words, symbols are free entropy — use them. Put an unusual mark between your words instead of a plain hyphen (rusty~hollow*lantern), or drop one inside a word. Like a made-up or misspelled word, a symbol in an unexpected place knocks an attacker off the ready-made wordlists they start with. Legacy keeps your symbols and capitalization exactly as typed — it only tidies spacing and curly quotes — so what you choose is what protects you. A few things to keep in mind:

• The benefit comes from the unexpected. Swaps everyone makes — 3 for e, @ for a, ! on the end — are already in every attacker's rulebook and add little. An unusual symbol in an unusual spot adds real entropy.
• Stick to ordinary keyboard characters — letters, digits, spaces, and basic punctuation (no accents or emoji).
• Every character is one more to reproduce exactly. Copy-paste carries almost no risk; a handwritten key does — as mellon taught us, one changed character and it never decrypts. So if you write a key down, set down every symbol unmistakably and steer clear of ones that blur by hand: O vs 0, l/1/I, ! vs l, ; vs :, rn vs m. Slash your zeros, annotate — leave the reader nothing to guess.
• A deliberate made-up or misspelled word works the same way (attackers' dictionaries don't contain it) — again, only if it's stored as text and copied, never retyped from memory.

Don't reuse

These keys protect one thing. Don't reuse a password you use anywhere else, and don't reuse the same pair across different Legacy payloads. A key is only as safe as the most careless place you've ever used it.