Bitcoin Forum

Hi everybody,

I have idea. I don't know - may be there is some draft of BIP. But i will try to write here.

There is BIP39 - mnemonic backup 12-24 words. But there is problem - if somebody will find paper phrases - he will stole all bitcoins.

But Shamir scheme exists. And i don't see normal tools for this. But i am sure that there can be BIP standard for this: mnemonic entropy (seed) to be encrypted in some Shamirs shares (based in seed and type of Shamir's scheme) which are encoded same way as mnemonic sentence (each 11 bit - one word from same list) but for each shares separately. User writes these words (i don't know which length of each share will be) in each share card and keeps them separately.

But my idea for Satoshi Lab too - to realise may be some BIP and to program its in Trezor. Trezor could be suggest to user to choose - plain backup BIP39 or BIPXX (Shamir). If user choose Shamir backup he should be asked scheme (for example 3/5). For this example the Trezor could be show words for each 5 shares separately and even an infected computer will not know which words are. User can write all shares in one time and will put them to some places. In this realisation will not be vulnerable computers/printers. Only code of Trezor, pen of user. So backup will be more better than BIP39. If he will need to restore - he should enter words in Trezor how he do it know with BIP39 (through computer in order known to Trezor only) for only 3 shares for example (if scheme is 3/5). After this Trezor to restore seed.

What do you think?

I think the length of Shamir's share will be same as entropy length

For example JavaScript realisation claims it:
https://github.com/amper5and/secrets.js#note-on-security

So if we have 24 words seed then the one card of Shamir's scheme will have 24 words too (with checksum)

For the record, we already done some basic work on this idea: https://github.com/trezor/python-mnemonic/blob/master/mnemonic/shamir.py However it's not finished and it need more thinking & writing specification around it.