Definitions
Checksum is the sum of certain pieces of data being transferred. It is used for checking any changes in the data during transfer.
About algorithm
HMAC
In cryptography, the HMAC is a form of message authentication code that contains a cryptographic hash function and a secret cryptographic key.
SHA-256 is a 32bit cryptographic hash algorithm.
How to use
The data receiver calculates the checksum using HMAC according to the given formula or combination of data from the data received; if it is equal to the sender’s checksum value, the information is considered guaranteed. But, if it is not equal with checksum value, the data accuracy is considered to be lost.
During data transfer, the merchant and bank checksum must be the same.
Create the correct checksum by accurately checking the formula, the combination of data from each request’s checksum field.
Created checksum is a hex string value containing lowerCase.
Pay attention that the checksum is on all the responses coming from the bank /including the push notification / and confirm the checksum according to your formula.