generating seed phrases offline and which wallets support custom passprhases?

[acme89]

Hi. I have two questions.

How could I safely generate custom seed phrases offline, and which tools are good for this operation?

What software supports generating seed phrases with  custom passphrases, and in which software wallets such phrases could be imported?

And I need wallets for other networks, not just for BTC.

[NeuroticFish]

Hi. I have two questions.

How could I safely generate custom seed phrases offline, and which tools are good for this operation?

What software supports generating seed phrases with  custom passphrases, and in which software wallets such phrases could be imported?

One of the best methods I was told of was the one that uses /dev/urandom and a copy of Ian Coleman's tool on an offline Linux machine:
https://bitcointalk.org/index.php?topic=5475496.msg63228430#msg63228430
This returns standard BIP39 seed and all proper wallets that work with seed will accept it.

Another, much easier method is to create a new seed with Electrum wallet. But this will work only on Electrum.
On the other hand, Sparrow wallet creates BIP39 seed, but it's not as widely available as Electrum or the first method I've linked.

Flipping a coin or rolling a dice is also a method, but you better search on the forum because it seems it's pretty easy to do it wrong.

Of course, hardware wallets also generate BIP39 standard seed, but some of them have lately... trust issues.


PS. Ian Coleman's tool also does this, but afaik in-browser random generator is not considered good enough for the job. That's why method 1 uses /dev/urandom separately.

[nc50lc]

How could I safely generate custom seed phrases offline, and which tools are good for this operation?

It's offline so it should be relatively safe compared to generating it online as long as the software's entropy sources aren't rigged.
If you do not have the means to review the software's code, stick to the famous well-reviewed wallets.

To be even more secure, pick an OS that has good RNG since the wallet software will be using it.
Most OS has good pRNG but only those "open-source" that you can audit.
Of course, the hardware as well but can anyone even verify its integrity without personally building each component?

But generally, keeping the wallet on an "air-gap" machine should be safe enough.
Generating the seed phrase offline, then using the created wallet online will just defeat that question's purpose.

What software supports generating seed phrases with custom passphrases, and in which software wallets such phrases could be imported?

There are a lot of good Bitcoin-exclusive wallets and almost all supports "BIP39 passphrase".
Unfortunately, for multi-coin wallet, it's hard to give recommendation to any.

[satscraper]

Hi. I have two questions.

How could I safely generate custom seed phrases offline, and which tools are good for this operation?

And I need wallets for other networks, not just for BTC.

If you need a bunch of SEEDs for other networks wallets I would advocate the use of BIP85 child seeds generated from the single master SEED.

You may use for this purpose Tails OS  with persistent volume enabled.

Copy into persistent volume the latest release of the  stand-alone script (bip39-standalone.html)  to generate master SEED and relevant child ones.

Run it , and shazam!

What software supports generating seed phrases with  custom passphrases, and in which software wallets such phrases could be imported?

Most of them do this.

[dkbit98]

How could I safely generate custom seed phrases offline, and which tools are good for this operation?

Easiest way to do this is by using airgapped hardware wallets since they already support Bitcoins and most of available altcoins.
I would only use devices with open source code, something like Keystone would probably work best in your case.
If you don't want to pay for hardware wallets than you just need offline laptop with clean Linux OS, or reset old smartphone (best with GrapheneOS or DivestOS) in airplane mode, with wifi and bluetooth disabled.
Note that newbies should be very careful doing anything they don't fully understand.

[Saint-loup]

One of the best methods I was told of was the one that uses /dev/urandom and a copy of Ian Coleman's tool on an offline Linux machine:
https://bitcointalk.org/index.php?topic=5475496.msg63228430#msg63228430
This returns standard BIP39 seed and all proper wallets that work with seed will accept it.

Another, much easier method is to create a new seed with Electrum wallet. But this will work only on Electrum.
On the other hand, Sparrow wallet creates BIP39 seed, but it's not as widely available as Electrum or the first method I've linked.

Flipping a coin or rolling a dice is also a method, but you better search on the forum because it seems it's pretty easy to do it wrong.

Of course, hardware wallets also generate BIP39 standard seed, but some of them have lately... trust issues.


PS. Ian Coleman's tool also does this, but afaik in-browser random generator is not considered good enough for the job. That's why method 1 uses /dev/urandom separately.

Electrum doesn't generate BIP39 seeds but it accepts them and it checks if the checksum is ok(and if words belong to the BIP39 wordlist). So since Electrum seeds are generated with the standard BIP39 wordlist why not using Electrum to generate a seed and then just changing the last word in order to have a valid BIP39 checksum and therefore a valid BIP39 seed? Finding a valid last word could be made by calculations or with just few "trial and error" in the import seed feature of the wallet.

[NeuroticFish]

So since Electrum seeds are generated with the standard BIP39 wordlist why not using Electrum to generate a seed and then just changing the last word in order to have a valid BIP39 checksum and therefore a valid BIP39 seed? Finding a valid last word could be made by calculations or with just few "trial and error" in the import seed feature of the wallet.

Well, that "few" trial and error is anywhere between 1 and 2047 attempts, I'd say. So .. hmm...
Even more, why not use a proper tool and generate the seed properly from start to end instead of "hacking around" and risk to weaken it?

So imho this is not a good approach. However, as I said, generating the seed with Electrum only is OK if one plans to use it with Electrum only (or maybe very few others; Sparrow?), which is quite usual actually.

I've made a list exactly to offer a not-too-bad range of alternatives, anyone can pick any. But no, I don't recommend this hack-around solution, sorry.

[Pmalek]

However, as I said, generating the seed with Electrum only is OK if one plans to use it with Electrum only (or maybe very few others; Sparrow?), which is quite usual actually.

Wait, are Electrum-native seeds supported by Sparrow wallet? I know that Blue Wallet is compatible with Electrum's seed format, but their greatest focus is on their mobile wallet. They have a desktop version as well, but only for macOS. There is sadly no support for Windows and Linux.

[NeuroticFish]

However, as I said, generating the seed with Electrum only is OK if one plans to use it with Electrum only (or maybe very few others; Sparrow?), which is quite usual actually.

Wait, are Electrum-native seeds supported by Sparrow wallet? I know that Blue Wallet is compatible with Electrum's seed format, but their greatest focus is on their mobile wallet. They have a desktop version as well, but only for macOS. There is sadly no support for Windows and Linux.

I was not sure, hence the question mark. Now I've checked on their page and:
* Sparrow supports importing Electrum wallet files, but not the seed (sorry, I guess I've mixed some things up)
* although Sparrow supports internally Electrum seed, they don't plan to recover an Electrum seed because they consider it confusing for their users (see here)

Thanks for helping clearing this up.

[Pmalek]

I was not sure, hence the question mark. Now I've checked on their page and:
* Sparrow supports importing Electrum wallet files, but not the seed (sorry, I guess I've mixed some things up)

Now I remember that I have seen that GitHub issue being mentioned on the forum in the past. I totally forgot about it, but I will make sure to keep it in mind. So, they don't support recovering an Electrum wallet from seed, but if you have an Electrum-native wallet file, Sparrow will recognize its format and let you recover it in its app.

Good to know, thanks!

[pooya87]

If you need a bunch of SEEDs for other networks wallets I would advocate the use of BIP85 child seeds generated from the single master SEED.

The problem with BIP85 is that it is not popular enough for users to find it in popular wallets. There are just implementations on Github that lack enough reviews hence they are not as safe as you'd want them to be.

The better option is to stick to a multi-coin wallet, or even hardware wallets, that supports this and you only need to rely on that one time seed phrase generation.

[Saint-loup]

Well, that "few" trial and error is anywhere between 1 and 2047 attempts, I'd say. So .. hmm...
[...]

Yes if you have a terrible bad luck, you could fail dozens or hundreds times theoretically. But Electrum seeds are on 12 words, it's 128bits for BIP39 seed.
128 mod 11 = 7 The last word is 7bits long (the 4bits remaining are used for the checksum).
2⁷ = 128 So 128 words should work.
2048/128 = 16 It's 1/16th of the list.

[dkbit98]

What software supports generating seed phrases with  custom passphrases, and in which software wallets such phrases could be imported?

Every passphrase is custom and it acts as salt on top of your seed words, there is no such thing as predefined passphrase for bitcoin wallets.
So if you and me use the same passphrase, we are still going to have totally different addresses generated because we have different seed words.

Software wallets I know have passphrase support are: Blue wallet, elecrtum wallet, blockstream green wallet, nunchuk wallet, sparrow, stack wallet, wasabi wallet.
Most hardware wallets also have support for multiple passphrases.