Key points
- Protocol captures and extracted application code provided 25 complete samples for validating the request format, encryption, and signature.
- The request uses AES-ECB with PKCS#7 padding and a custom decimal signature derived from absolute-value MD5 words.
- Once the omitted uid field was identified, the reconstructed Node.Js implementation reproduced all historical samples and returned live store data.
Context
The case study demonstrates how traces, dumped client code, and controlled execution can be combined to reconstruct a mobile application's hidden API protocol. For developers maintaining complex client integrations, it offers a practical model for isolating data flow, validating cryptographic transformations, and replacing runtime dependencies with a reproducible service client.
What this means for you
Directly applicable
Developers can apply the same method to reconstruct obscured API dependencies, validate request cryptography, and build maintainable Node.js integrations independent of a mobile runtime.
Who benefits: Developers and technical decision-makers responsible for integrations with mini programs, obfuscated clients, or undocumented legacy protocols.
Analysis of complex client protocols and legacy dependencies with a focus on reproducible integrations, maintainability, and reduced runtime coupling.