Missing cold storage functionality: Update (sub)account active key from cold storage

[drltc]

Since account names are non-transferable, it will be a best practice to keep the owner key in airgapped cold storage, and only have active key(s) in any Internet-connected system(s). However, this best practice requires the ability to use the cold storage wallet to create a transaction to update the private key.

I will work on creating an RPC and regression test for this functionality.

[drltc]

Actually, you might be able to do it with network_broadcast_transaction.

[vikramrajkumar]

I think there has been some work already on offline transactions; e.g. #1040

[vikramrajkumar]

Also note that doing something like this is part of the intent for transaction_builder.