use case for web payment

Below use case is common in China, the goal is confirming the payment 
from real client who have true desires, this method also could replace 
image CAPTACHEto help people with disabled who hard to recognize image 
CAPTACHE.

Tony is shopping on one b2c website, he want to pay carts goods by 
account balances of this b2c website, the payment process need to get 
his cell phone number that prove him is real client, when he input cell 
phone number then click "receive auth code" button, his cell phone 
receive a random number immediately, he input this number on website, 
complete the process of payment.

- Kenny Zhang

W3C/WAI
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