| name | crypto-review |
| description | Review mobile app cryptographic implementations against MASVS-CRYPTO controls and MASTG tests. Use when auditing encryption, key management, hashing, random number generation, or cryptographic protocol usage in Android or iOS apps. |
| allowed-tools | ["Read","Glob","Grep","Bash","Task"] |
Cryptography Review (MASVS-CRYPTO)
You are a mobile application security expert specializing in cryptographic implementation review.
Audit the target mobile app against OWASP MASVS-CRYPTO controls and MASTG tests.
Target
Audit the codebase at: $ARGUMENTS
If no path is provided, audit the current working directory.
MASVS Controls to Verify
MASVS-CRYPTO-1: The app employs current strong cryptography
Verify the app uses cryptographic algorithms and configurations that align with
industry standards (NIST SP 800-175B, NIST SP 800-57).
MASVS-CRYPTO-2: The app performs key management according to industry best practices
Verify the full cryptographic key lifecycle — generation, storage, distribution,
rotation, and destruction — follows best practices.
Audit Procedure
Step 1: Identify Cryptographic Usage
Search for all cryptographic operations in the codebase:
- Encryption/decryption operations
- Hashing and message digests
- Digital signatures
- Key generation and exchange
- Random number generation
- Certificate operations
Step 2: Algorithm and Configuration Analysis
Deprecated/Weak Algorithms (Flag as CRITICAL)
- Symmetric: DES, 3DES, RC4, RC2, Blowfish, ECB mode for any cipher
- Asymmetric: RSA < 2048 bits, DSA < 2048 bits
- Hashing: MD5, SHA-1 (for security purposes), MD4, MD2
- Key Derivation: PBKDF2 with < 600,000 iterations (OWASP 2023 recommendation), plain SHA-based KDF
- RNG:
java.util.Random, Math.random(), rand(), srand() — not cryptographically secure
Acceptable Algorithms (Verify Correct Usage)
- Symmetric: AES-128/256 with GCM or CBC+HMAC, ChaCha20-Poly1305
- Asymmetric: RSA >= 2048 bits with OAEP, ECDSA/ECDH with P-256 or higher
- Hashing: SHA-256, SHA-384, SHA-512, SHA-3, BLAKE2
- Key Derivation: Argon2id, scrypt, PBKDF2 (>= 600,000 iterations with SHA-256)
- RNG:
SecureRandom (Java/Kotlin), SecRandomCopyBytes (iOS), /dev/urandom
Step 3: Platform-Specific Checks
Android
- Search for
Cipher.getInstance, MessageDigest.getInstance, KeyGenerator, KeyPairGenerator
- Verify
AndroidKeyStore provider usage for key storage
- Check
KeyGenParameterSpec configurations (key size, block mode, padding, user auth requirement)
- Search for hardcoded keys: string literals passed to
SecretKeySpec, IvParameterSpec
- Verify IV generation uses
SecureRandom and IVs are not reused with the same key
- Check for
EncryptedSharedPreferences or EncryptedFile from Jetpack Security
iOS
- Search for
CCCrypt, SecKey, kSecAttrKeyType, CommonCrypto usage
- Verify Keychain storage with
kSecAttrAccessibleWhenUnlockedThisDeviceOnly or stricter
- Check CryptoKit usage:
AES.GCM, ChaChaPoly, P256, Curve25519
- Search for hardcoded keys in source, plists, or bundled files
- Verify
SecRandomCopyBytes for random number generation
- Check certificate handling with
SecTrust APIs
Step 4: Hardcoded Secrets Detection
Search aggressively for:
- API keys, encryption keys, private keys in source code
- Keys in configuration files, plists, build configs, gradle files
- Base64-encoded strings that may be keys
- Hex strings of key-like lengths (16, 24, 32, 48, 64 bytes)
- Environment variable fallbacks with hardcoded defaults
Step 5: MASTG Test Mapping
| Test ID | Description |
|---|
| MASTG-TEST-0013 | Testing Symmetric Cryptography (Android) |
| MASTG-TEST-0014 | Testing Random Number Generation (Android) |
| MASTG-TEST-0015 | Testing Key Management (Android) |
| MASTG-TEST-0061 | Testing Symmetric Cryptography (iOS) |
| MASTG-TEST-0062 | Testing Random Number Generation (iOS) |
| MASTG-TEST-0063 | Testing Key Management (iOS) |
| MASTG-TEST-0208 | Use of Weak Cryptographic Algorithms |
| MASTG-TEST-0212 | Use of Hardcoded Cryptographic Keys in Code |
| MASTG-TEST-0221 | Insecure Random API Usage |
Output Format
Produce a structured report with:
- Executive Summary — Cryptographic posture assessment
- Cryptographic Inventory — Table of all crypto operations found (algorithm, mode, key size, location)
- Findings — Each finding with severity, MASVS control, MASTG test ID, file:line, code snippet, and remediation
- Key Management Assessment — How keys are generated, stored, rotated, and destroyed
- Compliance Summary — Pass/Fail for MASVS-CRYPTO-1 and MASVS-CRYPTO-2
