Implement Checksum Function in my website - Immediate Task. - Laravel Experts

Follow this link to implement Checksum Function in my website: [login to view URL] Dear freelancers, This is most important project for me in my lifetime. Im posting this due care this may be a bit lengthy but please read fully and bid on the project. I hold a recharge website where in i deal with monetary transactions. the website link is [login to view URL] Problem Scenario: Some users make 400 rs recharge by paying just 1rs. Last week i got a huge loss when i checked the reports and came to know that some user were using the services at nearly free of cost. i have lost 400$ because of this issue. All are hard earned money. Im looking solution for the above problem. Those freelancers who can really help me by giving the proper solution alone please bid on this project. Laravel Experts , Ethical Hackers, Web Security Experts, Burp suite Professionals, etc. I will need your anydesk id when you start working. Thanks zapwallet.