Graftroot: Private and efficient surrogate scripts under the taproot assumption

The context suggests that there is a method that allows for unilateral key rotation without invalidating the interests of other parties in the existing multisig. This method does not require any on-chain transaction and only requires storing the signed delegation. This method, as per the provided context, allows for the rotation of a previously unknown key. It is unclear what type of key this refers to. However, it is noteworthy that no on-chain transaction is required for this process. The cost of this process involves storing the signed delegation. It is unclear what exactly is meant by this, but it seems to suggest that some data needs to be stored somewhere. Overall, it seems that the context is discussing a method that allows for key rotation without disrupting the existing multisig setup. This method is efficient in that it does not require any on-chain transaction and only requires storing the signed delegation.