Weighted threshold ECDSA for securing bitcoin wallet

Bitcoin is a digital currency based on cryptographic algorithms. All the transactions of this currency are recorded and stored in a publically available database called block chain. Since, these transactions are available to everyone; bitcoins must be stored in a secured wallet. These bitcoin wallets can be opened only by its secret key. And if once the secret key of the wallet is lost, it cannot be recovered because of the irreversible nature of bitcoin transaction. To root out this problem, researchers have proposed a solution of threshold signature scheme compatible with bitcoins signature by using elliptic curve digital signature algorithm (ECDSA) providing security policy of shared control of a wallet. In that scheme, the number of players in reconstruction phase was important for recovering the signature. Our contribution is to present a weighted threshold scheme with bitcoins ECDSA signature, in which all the players/participants do not have the same weight. More exactly, a positive weight is associated to each player and the signature can be reconstructed if and only if the sum of the weights of all shares is greater than or equal to a fixed threshold. In our scheme, the number of shares in reconstruction phase is important for recovering the signature. We extend the threshold ECDSA scheme to weighted threshold ECDSA scheme.