Cryptography is an essential ingredient when it comes to protecting data stored on a mobile device. It is also a category where things can go horribly wrong, especially when standard conventions are not followed. The purpose of the controls in this chapter is to ensure that the verified application uses cryptography according to industry best practices, including:
- Use of proven cryptographic libraries;
- Proper choice and configuration of cryptographic primitives;
- A suitable random number generator wherever randomness is required.
| # | MSTG-ID | Description | L1 | L2 |
|---|---|---|---|---|
| 3.1 | MSTG-CRYPTO-1 | The app does not rely on symmetric cryptography with hardcoded keys as a sole method of encryption. | ✓ | ✓ |
| 3.2 | MSTG-CRYPTO-2 | The app uses proven implementations of cryptographic primitives. | ✓ | ✓ |
| 3.3 | MSTG-CRYPTO-3 | The app uses cryptographic primitives that are appropriate for the particular use-case, configured with parameters that adhere to industry best practices. | ✓ | ✓ |
| 3.4 | MSTG-CRYPTO-4 | The app does not use cryptographic protocols or algorithms that are widely considered deprecated for security purposes. | ✓ | ✓ |
| 3.5 | MSTG-CRYPTO-5 | The app doesn't re-use the same cryptographic key for multiple purposes. | ✓ | ✓ |
| 3.6 | MSTG-CRYPTO-6 | All random values are generated using a sufficiently secure random number generator. | ✓ | ✓ |
The OWASP Mobile Security Testing Guide provides detailed instructions for verifying the requirements listed in this section.
- Android: Testing Cryptography - https://github.com/OWASP/owasp-mstg/blob/master/Document/0x05e-Testing-Cryptography.md
- iOS: Testing Cryptography - https://github.com/OWASP/owasp-mstg/blob/master/Document/0x06e-Testing-Cryptography.md
For more information, see also:
- OWASP Mobile Top 10: M5 (Insufficient Cryptography) - https://owasp.org/www-project-mobile-top-10/2016-risks/m5-insufficient-cryptography
- CWE 310 (Cryptographic Issues) - https://cwe.mitre.org/data/definitions/310.html
- CWE 321 (Use of Hard-coded Cryptographic Key) - https://cwe.mitre.org/data/definitions/321.html
- CWE 326 (Inadequate Encryption Strength) - https://cwe.mitre.org/data/definitions/326.html
- CWE 327 (Use of a Broken or Risky Cryptographic Algorithm) - https://cwe.mitre.org/data/definitions/327.html
- CWE 329 (Not Using a Random IV with CBC Mode) - https://cwe.mitre.org/data/definitions/329.html
- CWE 330 (Use of Insufficiently Random Values) - https://cwe.mitre.org/data/definitions/330.html
- CWE 337 (Predictable Seed in PRNG) - https://cwe.mitre.org/data/definitions/337.html
- CWE 338 (Use of Cryptographically Weak Pseudo Random Number Generator (PRNG)) - https://cwe.mitre.org/data/definitions/338.html