In the “four corner model”, acquirers are apparently the less active party as their role seems ‘only’ to forward the transaction flow originating from the merchant to and from the issuer. In the model, the acquirer is the merchant’s bank.
An issuer is one of the corners in the ‘four corner’ model. An issuer is a financial organization (e.g. a bank) that produces payment cards and allows the cardholders to use them.
The “Four Corners'' model, also called the Four Party Scheme, is utilized in almost all standard card payment systems across the globe. Here we introduce that model and explain what type of hardware security module (HSM) is needed for each of its components involved in the cryptographic process.