📅 Original date posted:2013-11-03
📝 Original message:I think the communication would have to go the other way around. Trezor
has to commit to a value First. Like this:
Trezor picks random s and sends S=s*G to computer, keeping s secret.
Computer picks random t and sends t to Trezor. Trezor makes r := s+t
its internal master private key with corresponding master public key
R := (s+t)*G. Since R = S+t*G, the computer can verify the master
public key. As you say, the computer can then store R and can later
verify for each derived pubkey that it was indeed derived from R, hence
from his own entropy t.
However, Trezor could not use straight bip32 out of the box. The
chaincode would have to be something like SHA(R). And the seed (that
gets translated to mnemonic) would be r itself, making it 256 bit
instead of only 128 bit.
If the longer seed is bearable then this is a good way to do it.
One question remains: if you only write down the mnemonic how can you be
sure that it is correct and corresponds to the secret in Trezor? You
cannot verify that on paper. You would have to restore it on some
device, eg another empty Trezor, and see if it brings up the same master
pubkey. Right?
Timo
On Sun, Nov 03, 2013 at 08:03:54AM +0100, Thomas Voegtlin wrote:
>
> Le 03/11/2013 07:41, Timo Hanke a écrit :
> >No. You mean the computer would use B for this check? (k,K) could
> >be rigged by Trezor, who computes b as k-a. Timo
>
> I was just asking a question, in order to understand how this device
> works, and what are its requirements.
> if you think you can help, please explain.
>
>
--
Timo Hanke
PGP 1EFF 69BC 6FB7 8744 14DB 631D 1BB5 D6E3 AB96 7DA8
Timo Hanke [ARCHIVE] /
npub1dd…pgp9a
2023-06-07 15:08:32
in reply to nevent1q…phua
Author Public Key
npub1ddqaln8xsfmy6sxqplt9sz5ev99kh052sveqsh02q7hmc3a6n68shpgp9aPublished at
2023-06-07 15:08:32Event JSON
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"created_at": 1686150512,
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"content": "📅 Original date posted:2013-11-03\n📝 Original message:I think the communication would have to go the other way around. Trezor\nhas to commit to a value First. Like this:\n\nTrezor picks random s and sends S=s*G to computer, keeping s secret.\nComputer picks random t and sends t to Trezor. Trezor makes r := s+t\nits internal master private key with corresponding master public key \nR := (s+t)*G. Since R = S+t*G, the computer can verify the master\npublic key. As you say, the computer can then store R and can later\nverify for each derived pubkey that it was indeed derived from R, hence\nfrom his own entropy t.\n\nHowever, Trezor could not use straight bip32 out of the box. The\nchaincode would have to be something like SHA(R). And the seed (that\ngets translated to mnemonic) would be r itself, making it 256 bit\ninstead of only 128 bit.\n\nIf the longer seed is bearable then this is a good way to do it.\n\nOne question remains: if you only write down the mnemonic how can you be\nsure that it is correct and corresponds to the secret in Trezor? You\ncannot verify that on paper. You would have to restore it on some\ndevice, eg another empty Trezor, and see if it brings up the same master\npubkey. Right? \n\nTimo\n\nOn Sun, Nov 03, 2013 at 08:03:54AM +0100, Thomas Voegtlin wrote:\n\u003e \n\u003e Le 03/11/2013 07:41, Timo Hanke a écrit :\n\u003e \u003eNo. You mean the computer would use B for this check? (k,K) could\n\u003e \u003ebe rigged by Trezor, who computes b as k-a. Timo\n\u003e \n\u003e I was just asking a question, in order to understand how this device\n\u003e works, and what are its requirements.\n\u003e if you think you can help, please explain.\n\u003e \n\u003e \n\n-- \nTimo Hanke\nPGP 1EFF 69BC 6FB7 8744 14DB 631D 1BB5 D6E3 AB96 7DA8",
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