• Platform: Android
• Weakness: MASWE-0012
• Weakness in the numbering of the MASWE beta: MASWE-0027
• Profiles: L1 (basic security), L2 (advanced security)
• Type: static, code, manual
• Prerequisites: identify-sensitive-data, identify-security-relevant-contexts
• Knowledge: MASTG-KNOW-0013
• Best practices: MASTG-BEST-0001

Overview

Android apps sometimes use an insecure [pseudorandom number generator (PRNG)](../../../Document/0x05e-Testing-Cryptography.md#random-number-generation), such as java.util.Random, which is a linear congruential generator and produces a predictable sequence for any given seed value. As a result, java.util.Random and Math.random() (the latter simply calls nextDouble() on a static java.util.Random instance) generate reproducible sequences across all Java implementations whenever the same seed is used. This predictability makes them unsuitable for cryptographic or other security-sensitive contexts.

In general, if a PRNG is not explicitly documented as being cryptographically secure, it should not be used where randomness must be unpredictable. Refer to the Android Documentation and the ["random number generation" guide](../../../Document/0x05e-Testing-Cryptography.md#random-number-generation) for further details.

Steps

1. Use MASTG-TECH-0013 to reverse engineer the app.
2. Use MASTG-TECH-0014 to look for the relevant APIs.

Observation

The output should contain a list of locations where insecure random APIs are used.

Evaluation

The test case fails if you can find random numbers generated using those APIs that are used in security-relevant contexts, such as generating passwords or authentication tokens.

Further Validation Required:

Inspect each reported code location using MASTG-TECH-0023 to determine whether the usage is security-relevant:

• Determine whether the generated random values are used for security-relevant purposes, such as generating cryptographic keys, initialization vectors (IVs), nonces, authentication tokens, session identifiers, passwords, or PINs.

Linkitetyt tehtävät

• OWASP -

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  • OWASP Mobile Application Security Verification Standard (MASVS) v2.1.0, January 2024, from OWASP/masvs: © The OWASP Foundation, licensed under CC BY-SA 4.0. Changes: converted into the GRCA format, the wording unchanged. These adaptations are shared under CC BY-SA 4.0 as well.
  • OWASP Mobile Application Security Weakness Enumeration (MASWE) v1.0.0, August 2026, from OWASP/maswe: © The OWASP Foundation, licensed under CC BY-SA 4.0. Changes: converted into the GRCA format, the wording unchanged, linked to the MASVS controls they map to. These adaptations are shared under CC BY-SA 4.0 as well.
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  • OWASP Application Security Verification Standard (ASVS) 5.0.0, Mai 2025, aus OWASP/ASVS: © 2008-2025 The OWASP Foundation, lizenziert unter CC BY-SA 4.0. Änderungen: in Abschnitte aufgeteilt und in das GRCA-Format umgewandelt, der Wortlaut unverändert. Diese Bearbeitungen stehen ebenfalls unter CC BY-SA 4.0.
  • OWASP Mobile Application Security Verification Standard (MASVS) v2.1.0, Januar 2024, aus OWASP/masvs: © The OWASP Foundation, lizenziert unter CC BY-SA 4.0. Änderungen: in das GRCA-Format umgewandelt, der Wortlaut unverändert. Diese Bearbeitungen stehen ebenfalls unter CC BY-SA 4.0.
  • OWASP Mobile Application Security Weakness Enumeration (MASWE) v1.0.0, August 2026, aus OWASP/maswe: © The OWASP Foundation, lizenziert unter CC BY-SA 4.0. Änderungen: in das GRCA-Format umgewandelt, der Wortlaut unverändert, mit den MASVS-Controls verknüpft, denen sie zugeordnet sind. Diese Bearbeitungen stehen ebenfalls unter CC BY-SA 4.0.
  • OWASP Mobile Application Security Testing Guide (MASTG) v2.0.0, Juni 2026, aus OWASP/mastg: © The OWASP Foundation, lizenziert unter CC BY-SA 4.0. Nur die Tests und Best Practices, ohne Codebeispiele, Bilder, Werkzeuge und Apps. Änderungen: in das GRCA-Format umgewandelt, der Wortlaut unverändert; Verweise auf andere Seiten des MASTG als Links zu mas.owasp.org; die Schwachstelle jedes Tests in der Nummerierung der MASWE v1 und mit ihr verknüpft. Diese Bearbeitungen stehen ebenfalls unter CC BY-SA 4.0.
  • OWASP Software Assurance Maturity Model (SAMM) v2.2.0, Juli 2026, aus owaspsamm/core: © The OWASP Foundation, lizenziert unter CC BY-SA 4.0. Änderungen: in das GRCA-Format umgewandelt, der Wortlaut unverändert; Kürzel (G-SM-1-A) aus dem Modell gebildet, die Assessment-Fragen als Prüfverfahren ihrer Aktivitäten. Diese Bearbeitungen stehen ebenfalls unter CC BY-SA 4.0.
  • OWASP Top 10:2025, aus OWASP/Top10: © 2003-2025 The OWASP® Foundation, Inc., lizenziert unter CC BY-SA 4.0. Die zehn Kategorien, ohne die Symbole. Änderungen: in das GRCA-Format umgewandelt, der Wortlaut unverändert. Diese Bearbeitungen stehen ebenfalls unter CC BY-SA 4.0. Die Namen der zugeordneten CWEs (Common Weakness Enumeration): © 2006–2026 The MITRE Corporation. MITRE erlaubt die Nutzung für Forschung, Entwicklung und kommerzielle Zwecke, wenn jede Kopie den Urheberrechtsvermerk und die Lizenz enthält; maßgeblich ist der englische Wortlaut der Lizenz oben und die CWE Terms of Use. CWE™ ist eine Marke der MITRE Corporation.