What makes a good PRNG?

Uniformity – In cryptographic applications, the output of a PRNG will most likely be represented in binary format. There should be an equal number of 1’s and 0’s (Ripley, 1990), though not distributed in any discernable pattern. The sequence of random numbers should be uniform, and unbiased.

Why is using a pseudorandom number generator inappropriate for generating cryptographic keys?

It’s most secure to rely on upon OS-specific implementations to provide seeding. Providing a low-entropy predictable source could easily lead to generating predictable pseudo-random data, which is inappropriate for any cryptographic applications.

How is PRNG used in cryptography?

In cryptography, PRNG’s are used to construct session keys and stream ciphers. True Randomness is generated from some source such as thermal noise. Abstractly, a random source defines a distribution on { 0 , 1 } n . Example: -way independent bits b 1 , . . . , b n and Pr [ b i = 1 ] = p , Pr [ b i = 0 ] = 1 − p .

What makes a PRNG cryptographically secure?

A PRNG is said to be cryptographically secure if, assuming that it operates over a wide enough unknown n-bit key, its output is computationally indistinguishable from uniformly random bits.

What is a cryptographic random number generator (RNG)?

An RNG that is suitable for cryptographic usage is called a Cryptographically Secure Pseudo-Random Number Generator (CSPRNG). The strength of a cryptographic system depends heavily on the properties of these CSPRNGs.

How secure is a random number generator?

Generating a nonce, initialization vector or cryptographic keying materials all require a random number. The security of basic cryptographic elements largely depends on the underlying random number generator (RNG) that was used.

What is a cryptographically secure pseudo-random number generator?

An RNG that is suitable for cryptographic usage is called a Cryptographically Secure Pseudo-Random Number Generator (CSPRNG). The strength of a cryptographic system depends heavily on the properties of these CSPRNGs. Depending on how the generated pseudo-random data is applied, a CSPRNG might need to exhibit some (or all) of these properties:

What is the period or cycle length of a PRNG?

The period or cycle length of a PRNG is the number of values that can be generated after which it starts repeating the same random number stream. Many PRNGs have a fixed-size period, but for some only an expected average cycle length can be given, where the exact length depends on the seed.