Bitcoin Forum

How would I implement Shamir's Secret Sharing Scheme (http://point-at-infinity.org/ssss/) with an encrypted Bitcoin wallet?

What are you trying to do?

Split up the encrypted wallet's private key with ssss and distribute it to several people. Basically, I want multiple people to have to consent to a BTC transaction before the wallet is unlocked. Capisci?

Then use multisignature transactions. SSSS is inappropriate because the secret dealer has access the entire key, and once all parties recreate the full key any one of them can do anything at all, they do not need to agree, just race each other.

You may be interested by another multisig schema proposed by @oleganza and called Blind signatures (http://blog.oleganza.com/post/77474860538/blind-signatures).
Hope it helps.

Oleg's scheme is also inappropriate because it gives no ability to the blindsigner to check what he is signing. (And if you give him enough information to verify this, he'll have enough information to sign anything he wants, so again you fail to have a threshold consent scheme.)

Sure. Blinded content to be signed introduces a risk. Imho, Oleg's scheme can be useful if you know the signers and can communicate with them on a second channel (bitmessage, ...) in order to confirm your request for a signature and to "validate" (at least weakly) the content to be signed.

Another point : The scheme is asymmetric by design (coins owned by 1 user and secured by n signers). Don't know if it matches with OP's needs.

interesting
thanks
I'll take a look.