Paper 2026/526

Broken By Design: A Longitudinal Analysis of Cryptographic Failures in Alipay Mobile Payment Infrastructure

Abstract

We present a systematic security analysis of Alipay's APK signing certificate, issued in 2009 using md5WithRSAEncryption with RSA-1024 and still active in 2026, serving over one billion users. Through 15 reproducible proof-of-concept attacks organized as a complete kill chain, we demonstrate that every layer of Alipay's cryptographic infrastructure is exploitable using known techniques and commodity hardware. Our analysis spans four attack surfaces: (1) certificate-layer weaknesses including MD5 collision generation in 9 seconds and SHA-1 collision feasibility at $5K-$8K; (2) signature scheme vulnerabilities including Janus (CVE-2017-13156) code injection and five distinct v1 signature bypass techniques; (3) key management failures including hardcoded DES keys with Shannon entropy of 1.75-2.50 bits/byte (vs. 8.0 bits/byte ideal) and RSA key reuse across 69 APK modules; and (4) ecosystem-level PRNG failures evidenced by 8 shared prime factors across 28 RSA keys recovered via batch GCD from TLS server certificates associated with the mobile payment ecosystem. Our analysis reveals ecosystem-level cryptographic decay: 38 of 123 certificates (30.9%) use RSA-1024, and batch GCD factoring uncovers 8 shared primes across 28 keys. Liveness probing of 5 servers whose RSA private keys were fully recovered confirmed that 3 remain operational with vulnerable TLS configurations. Responsible disclosure to Ant Group on January 15, 2026 received a response classifying all findings as normal functionality on March 10, 2026. We release all proof-of-concept code and an automated APK cryptographic audit tool for independent verification.