What is Secured Electronic Transaction (SET) Protocol? Describe how purchase request, payment authorization and payment capture are done in SET? [

Secured Electronic Transaction (SET) Protocol

Secure Electronic Transaction is an open-source encryption and security specification designed to protect credit card transactions on the internet. The secure electronic transaction is not a payment system; it is a set of security protocols and formats that ensures that using online payment transactions on the internet is secure. Secure Electronic Transaction is also called SET.

i) Purchase Request: 

Before the purchase request exchange begins, the cardholder has completed browsing, selecting, and ordering. The end of this phase occurs when the merchant sends a completed order to the customer. All of the preceding occurs without the use of SET. The purchase request involves 4 messages:-

1. Initiate Request
2. Initiate Response
3. Purchase Request 
4. Purchase Response

When the merchant receives the Purchase Request message, it performs the following actions:

• It verifies the cardholder certificates by means of its CA signatures.
• It verifies the dual signature using the customer's public signature
• It processes the order and forwards the payment information to the payment gateway for authorization.
• It sends a purchase response to the cardholder.

ii) Payment Authorization: 

The payment authorization ensures that the transaction was approved by the issuer. This authorization guarantees that the merchant will receive payment; the merchant can therefore provide the services or goods to the customer. The payment authorization performs the following tasks:

• It verifies all certificates
• It decrypts digital envelope of authorization block to obtain the symmetric key and then decrypts authorization block
• It verifies the merchant's signature on the authorization block
• It decrypts digital envelope of payment block to obtain the symmetric key and then decrypts authorization block
• It verifies the dual signature on the payment block
• It sends an authorization response back to the merchant

iii) Payment Capture:

Payment capture is the process by which the merchant receives payment which includes again generating some request blocks to the gateway and the payment gateway in turn issues payment to the merchant. The payment capture performs the following tasks; merchant sends payment gateway a payment capture request gateway checks request then causes funds to be transferred to merchants to account notifies merchant using capture response.