PEAK
One outgrowth of the expansion of interstellar finance within the Third Imperioum was better methods of accounting. Credits are a purely virtual construction: there is no coin or bill.
Instead, each credit is really a serial number issued by a sector's central banking authority.
This means that a single credit can be validated against the central bank's ledger. This is what occurs each time a credit is used. A merchant queries a database then submits a transaction to log the credit in their name. The database logs the transaction and files the transfer with the central banking authority.
This system made anonymous transactions difficult. But of course, where there is a need, someone will supply a solution. In this case, 'private banking cooperatives' came in to being. PBCs function as a middle man. A credit is transferred to them. They mix the credit in with their other credits. They then reassign those credits into new accounts.
To add another layer, the PBCs will often name their accounts after a cypher. The account holder is issued a Personal Encrypted Account Key, or PEAK. The PEAK takes the place of the holder's identity information. Most often, PEAKs are small handheld console devices that function as both an account ID and a personal banking unit. The holder can initiate transactions with a third party through the PEAK, have the funds deposited in to their PBC account, and then reclaim the proceeds later by presenting the PEAK at the PBC's personal banking unit. This keeps the holder completely off record from the transaction.
The downside is that if their PEAK is stolen, they lose access to their account. PBCs assume the person with the PEAK is the holder of the account. That is the risk holders take for their anonymity.
Surprisingly, the Imperium has supported this system. Laws are in place to make theft of a PEAK a serious crime, but the unauthorized use of a PEAK is a minor infraction. Critics of the system observe that this system allows the nobility and corporations to fund illegal and off book operations.
To which everyone replies, 'Well yeah. Duh.'