OK, great, thank you!

Hello,

so i have decided to do it this way:

I diced six words from the BIP-39 word list with this method:
https://github.com/taelfrinn/Bip39-diceware

I have read that six words are largely sufficient for passphrase security here and that
it would take two milleniums to brute-force it even with the most sophisticated attack:
https://coldbit.com/can-bip-39-passphrase-be-cracked/

24-word-mnemonic and passphrase will be engraved in metal and stored at two separate secure locations.

Could you please give me your short thoughts if this is secure
and if the statements about cracking times on the Coldbit website are accurate?

Thank You!

All right,
i will dig deeper in the matter and find out how to create a good memorizable passphrase, maybe with lower or upper case letters.
I´ll return here for further questions.

Hello, i know there would be safer passphrases and on the Ledger Nano X you can enter maximum 100 characters but my set up is this:

24-Word-Seed "written" on Cryptosteel and deposited in a secure place and memorized in my head.
Now i want to add a passphrase "written" in Cryptosteel , deposit that in another secure place and also memorize it in my head.
To memorize it it can not be so difficult and to fit it in a Cryptosteel it should have not more than 24 characters.

If the seed would be found, how much time would i have before the passphrase could be brute forced if?

1. I would generate a seed and would take the first five words as the passphrase ( I would create multiple seeds and take the words from the one
that have maximum 24 characters. )

2. I pick myself randomly six 4-character words from the 2048-word-list and use them as my passphrase.

I have heard that you can mess up security exponentially with playing with the features but i also want to be able to retrieve my coins and not lock myself out.

Many thanks for your help!

OK, thank you!
My TAILS system is sometimes online. But i have 2 Ledger devices and will create the seed on the one i don't use.

My idea was to take six 4-character words from a dictionary "randomly" picked by me so that i can put them in a Cryptosteel/Billfodl in one row.
That would be easier to memorize for me than to create a 6-word-seed and use the first 4 letters of each word. 
If the words are also not from the 2048-word list it would be easier for my heirs to find out that it is a passphrase and not a seed.

Alternatively i could use just four or five seed words as long as they don't have more than 24 characters together and fill the rest of the row of the Cryptosteel with blank tiles. Is a mnemonic code converter used with TOR browser in an offline TAILS Linux system on a USB-stick safe enough?

Hello,

i´m fairly new into Bitcoin but have now a hardware wallet with a 24-word seed. Seed is stored securely. Now i´d like to add an additional passphrase to my seed and move my funds from the seed-only account to the seed-passphrase account.

Now to the passphrase: Is six english words with 4 characters chosen from an English dictionary secure enough for the passphrase?
I thought about 4-characters words because i want the passphrase not only to write down but to use a Cryptosteel/Billfodl type of metal device to store it. With those devices i could put six words in a row and leave the other rows empty.
 
Or should i create 6 random words with a BIP39 mnemonic converter offline and use those as a passphrase? Then i would have to engrave them into metal which i think is more complicated than using a Cryptosteel device. Passphrase will be stored in a different place as the 24-word seed.

Thank you in advance for your advice!