MASTG-TEST-0221: Broken Symmetric Encryption Algorithms
Overview¶
To test for the use of broken encryption algorithms in Android apps, we need to focus on methods from cryptographic frameworks and libraries that are used to perform encryption and decryption operations.
Cipher.getInstance: Initializes a Cipher object for encryption or decryption. Thealgorithmparameter can be one of the supported algorithms.SecretKeyFactory.getInstance: Returns a SecretKeyFactory object that converts keys into key specifications and vice versa. Thealgorithmparameter can be one of the supported algorithms.KeyGenerator.getInstance: Returns aKeyGeneratorobject that generates secret keys for symmetric algorithms. Thealgorithmparameter can be one of the supported algorithms.
Some broken symmetric encryption algorithms include:
- DES (Data Encryption Standard): 56-bit key, breakable, withdrawn by NIST in 2005.
- 3DES (Triple DES, officially the Triple Data Encryption Algorithm (TDEA or Triple DEA)): 64-bit block size, vulnerable to Sweet32 birthday attacks, withdrawn by NIST on January 1, 2024.
- RC4: Predictable key stream, allows plaintext recovery RC4 Weakness, disapproved by NIST in 2014 and prohibited by IETF in 2015.
- Blowfish: 64-bit block size, vulnerable to Sweet32 attacks, never FIPS-approved, and listed under "Non-Approved algorithms" in FIPS.
Android also provides additional guidance on broken cryptographic algorithms.
Steps¶
- Run Static Analysis on Android with a tool such as semgrep on the app binary, or use Method Tracing (dynamic analysis) with a tool like Frida for Android, and look for uses of the cryptographic functions that perform encryption and decryption operations.
Observation¶
The output should contain a list of locations where insecure symmetric encryption algorithms are used.
Evaluation¶
The test case fails if you can find insecure or deprecated encryption algorithms being used.
Mitigations¶
Demos¶
MASTG-DEMO-0022: Uses of Broken Symmetric Encryption Algorithms in Cipher with semgrep