A method of requesting an account authority to execute an instruction with regard to an account maintained by the account authority includes, (a) for a first account, composing an electronic message including, an instruction regarding the first account and a first unique identifier by which a first account authority identifies the first account, digitally signing the electronic message using a private key of a public-private key pair for which the public key is associated by the first account authority with the first account, and sending the electronic message and digital signature to the first account authority, and (b) for a second account digitally signing a similar message of instruction using the same private key of the public-private key pair, and sending the electronic message and digital signature to the second account authority.