[Secure physical locations:]

Involved are 3 Bitcoin holding parties: Alice, Bob and Charlie.

Alice and Bob are considered to be one household, but for accounting purposes, still want separate wallets.

Charlie wants a separate wallet, but also doesn't want either Alice or Bob being able to spend his funds, in order to mitigate against 5-Dollar-wrench-attacks against them. Only after Charlie dies, he wants Alice and Bob to have access. He doesn't trust lawyers.


Secure physical locations:

 * H: Alice and Bob's [H]ouse, all 3 have access
 * V: [V]acation-home, all 3 have access
 * S: \[S\]afe-Deposit-Box, only Charlie has access


2-of-3 Multi-Sig-Setup Alice and Bob

 * H: Trezor1 + Passphrase_Alice + Passphrase_Bob
 * V: LedgerS + Passphrase_Alice + Passphrase_Bob
 * S: TrezorT + Passphrase_Alice + Passphrase_Bob
 


2-of-3 Multi-Sig-Setup Charlie

 * H: Trezor1 + encrypted Passphrase_Charlie
 * V: LedgerS + encrypted Passphrase_Charlie
 * S: TrezorT + plaintext Passphrase_Charlie + decryption passphrase for encrypted Passphrase_Charlie
 * FinalMessage.io GMail's delayed sending to Alice and Bob: Decryption passphrase for Passphrase_Charlie

OR


3-of-4 Multi-Sig-Setup Charlie

 * H: Trezor1 + Passphrase_Charlie
 * S: TrezorT + Passphrase_Charlie
 * V: LedgerS + Passphrase_Charlie
 * FinalMessage.io and GMail's delayed sending to Alice and Bob: Electrum Seed


OR

Since S and Charlie's brain B have a certain connection, they can backups of one another. If Charlie dies, S and B are inaccessible.

So alternativley:

3-of-5 Multi-Sig-Setup Charlie

* H: Trezor1 + Passphrase_Charlie
* S: TrezorT + Passphrase_Charlie + Electrum_Seed_Brain
* V: LedgerS + Passphrase_Charlie
* GMail & FinalMessage: Electrum_Seed_GFM
* Brain: Electrum_Seed_Brain

plus sha256sum of Electrum_Seed_Brain as a passphrase to encrypt content of S (TrezorT+Passphrase_Charlie) and storing this with H and V.

If Charlie dies: H+V+Gmail&FinalMessage

If Charlie forgets Electrum_Seed_Brain: Nothing really happens

If Safe Deposit Box gets nuked: H+V+Brain


What do you think? What's the best way forward? Or something completely different?

Is it general good practice to salt your Electrum seed with for example your e-mail address in the seed extension? Kind of like WarpWallet does?

[Option A:]

Hi,

can anyone describe to me, what the relationship between the 12 word seed in Electrum and the extended private key is?

If someone were to get the master private key, or the master public key PLUS one or more private keys, should I go for

Option A: simply add one word to the seed as a password, thus totally changing the master private key and have a secure wallet once again.

Or could an attacker calculate the seed from the master public key and thus trivially brute force the one additional word? Which would mean I should opt for

Option B: make a completely new seed.

Thanks in advance.