The Promise Protocol solves the private key security problem by using a new encryption scheme that allows delegation of signing by proxy re-signature.
Promise also delivers delegation and authorization control so that transactions for re-signatures and payments will have authorization respected at the consensus level.
Managing private keys and handling payment flow via proxy is hard. Delegating payment execution to services that can handle payments in a trustless environment makes it easier to allow peers to pay on behalf of peers.
Automated Subscription Payments
Proxy re-signatures allow for repeated payments to be delegated to a machine that may sign a scheduled transaction for a scheduled payment, without the need to reveal the original private key of the subscriber.
Loans and Business Credit
Credit is a measure of willingness and ability to repay. Proxy re-signatures lower the costs of re-paying promissory note and credit commitments by allowing more than one party to contribute to repayment while building credit for the borrowing party.
Anonymous Gifts and Charitable Giving
Gifts and charitable giving benefit from proxy re-signatures when benefactors wish to maintain anonymity and to make payments either as the charity or an organization making payments on behalf of a charity.
Proxy Re-signatures allow for payment flow control so that only authorized members may prox re-sign a transaction. This is important for compliance and repayment control where payments are only acceptable if delivered by a particular public key.