Pseudorandom Number Generator - Cryptographically Secure Pseudorandom Number Generators

Cryptographically Secure Pseudorandom Number Generators

A PRNG suitable for cryptographic applications is called a cryptographically secure PRNG (CSPRNG). A requirement for a CSPRNG is that an adversary not knowing the seed has only negligible advantage in distinguishing the generator's output sequence from a random sequence. In other words, while a PRNG is only required to pass certain statistical tests, a CSPRNG must pass all statistical tests that are restricted to polynomial time in the size of the seed. Though such property cannot be proven, strong evidence may be provided by reducing the CSPRNG to a problem that is assumed to be hard, such as integer factorization. In general, years of review may be required before an algorithm can be certified as a CSPRNG.

Some classes of CSPRNGs include the following:

  • Stream ciphers
  • Block ciphers running in counter or output feedback mode.
  • PRNGs that have been designed specifically to be cryptographically secure, such as Microsoft's Cryptographic Application Programming Interface function CryptGenRandom, the Yarrow algorithm (incorporated in Mac OS X and FreeBSD), and Fortuna.
  • Combination PRNGs which attempt to combine several PRNG primitive algorithms with the goal of removing any non-randomness.
  • Special designs based on mathematical hardness assumptions. Examples include Micali-Schnorr and the Blum Blum Shub algorithm, which provide a strong security proof. Such algorithms are rather slow compared to traditional constructions, and impractical for many applications.

Read more about this topic:  Pseudorandom Number Generator

Famous quotes containing the words secure and/or number:

    No Government can be long secure without a formidable Opposition. It reduces their supporters to that tractable number which can be managed by the joint influences of fruition and hope. It offers vengeance to the discontented, and distinction to the ambitious; and employs the energies of aspiring spirits, who otherwise may prove traitors in a division or assassins in a debate.
    Benjamin Disraeli (1804–1881)

    Black lady,
    what will I do
    without your two flowers?
    I have inhabited you, number by number.
    I have pushed you in and out like a needle.
    Anne Sexton (1928–1974)