CWE-343 Predictable Value Range from Previous Values

The product's random number generator produces a series of values which, when observed, can be used to infer a relatively small range of possibilities for the next value that could be generated.

• Other: Varies by Context — In some cases, an attacker cannot predict the exact value that will be produced next, but can narrow down the possibilities significantly. This reduces the amount of effort to perform a brute force attack.

• [Architecture and Design, Implementation] The output of a random number generator should not be predictable based on observations of previous values. • [Implementation] Increase the entropy used to seed a PRNG. • [Architecture and Design, Requirements] Use products or modules that conform to FIPS 140-2 [REF-267] to avoid obvious entropy problems. Consult FIPS 140-2 Annex C ("Approved Random Number Generators"). • [Implementation] Use a PRNG that periodically re-seeds itself using input from high-quality sources, such as hardware devices with high entropy. However, do not re-seed too frequently, or else the entropy source might block.