Mobile Weak Cryptography

What Is Broken and Why

Mobile apps frequently implement cryptography incorrectly: using broken algorithms (DES, RC4), insecure modes (ECB), static/reused IVs, hardcoded keys embedded in source or resources, or non-cryptographic RNGs for key generation. Android's java.util.Random is not a CSPRNG. iOS's arc4random() is acceptable but older code uses rand(). ECB mode leaks plaintext patterns in ciphertext. Hardcoded keys are extractable via static analysis of the APK or IPA in seconds.

Key Signals

• Cipher.getInstance("AES/ECB/NoPadding") or Cipher.getInstance("DES/...") in Android code
• kCCAlgorithmDES, kCCAlgorithmRC4 in iOS CommonCrypto calls
• Hardcoded hex/base64 strings adjacent to crypto API calls
• new Random() or Math.random() used to generate keys or IVs
• arc4random() replaced by rand() or custom PRNG in security-critical iOS code
• Static byte arrays used as IV: byte[] iv = {0,0,0,0,...}
• SecretKeySpec initialized directly from a string literal: new SecretKeySpec("hardcoded".getBytes(), "AES")
• RSA without OAEP: Cipher.getInstance("RSA/ECB/PKCS1Padding")
• Key sizes below 128-bit (AES), 2048-bit (RSA), 256-bit (EC)

Methodology