Insufficient Entropy

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ASDR Table of Contents

Last revision (mm/dd/yy): 02/17/2009


When an undesirably low amount of entropy is available. Psuedo Random Number Generators are susceptible to suffering from insufficient entropy when they are initialized because entropy data may not be available to them yet.

Risk Factors




Related Attacks

  • In many cases a PRNG uses a combination of the system clock and entropy to create seed data. In the case where insufficient entropy is available, an attacker can reduce the size magnitude of the seed value considerably. Furthermore, by guessing values of the system clock, they can create a manageable set of possible PRNG outputs.

Related Vulnerabilities

Related Controls

  • Many PRNG's (/dev/random and /dev/urandom for example) store their last value before shutdown. By using this value at intialization, they can sometimes avoid insufficient or predictable starting entropy.

Related Technical Impacts


TBDCategory:Cryptography Category:Cryptographic Vulnerability