macrozheng
Sep 8, 2020 · Information Security
How Do Offline Payment Codes Work? Inside the Tech Behind WeChat & Alipay
Even without network connectivity, mobile payment apps like WeChat and Alipay can complete transactions using offline payment codes; this article explains the two common QR payment methods, the online and offline code schemes, the underlying OTP and HMAC‑SHA1 algorithms, and their security trade‑offs.
HMAC-SHA1OTPinformation security
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