Blind signatures for Bitcoin transactions
Oleg A. Andreev · 2014
Blind signatures allow maintaining privacy while using third-party services such as digital cash server. Existing proposals of blind signatures for ECC lack compatibility with standard ECDSA and thus cannot be used directly in Bitcoin transactions. We propose a scheme that allows generating a blind signature compatible with the existing Bitcoin protocol. The client requests a set of parameters from the signing server and synthesizes a public key to use in a Bitcoin transaction. To redeem the funds, the client transforms the hash of the transaction (blinds), sends to the server to sign and then transforms the signature (unblinds) to arrive at a valid ECDSA signature. The signed transaction is published revealing the synthetic public key and the unblinded signature. Signing server cannot learn about its participation neither from the public key nor from the signature.