# Questions tagged [pseudo-random-generator]

In cryptography, a pseudo-random generator (PRG) is a deterministic procedure that maps a random seed to a longer pseudo-random string such that no statistical test can distinguish between the output of the generator and the uniform distribution. Pseudo-random generators have numerous applications in cryptography. For instance, pseudo-random generators provide an efficient analog of one-time pads.

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### Is the following a PRG?

Let $G: \{0, 1\}^n → \{0, 1\}^m$ be a PRG. We construct a function $G': \{0, 1\}^{m + n} → \{0, 1\}^{2m}$ defined as follows $G'(x || y) = x || (G(y) ⊕ x)$ for all $x ∊ \{0, 1\}^m$ and $y ∊ \{0, 1\}^n$...
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### Efficient way to combine collection of hashes into a single hash?

I have a system where each user will submit a set of data. The data will be hashed and their hash will be submitted to the server. My plan is to combine each users hash (converted to bytes XOR'd with ...
443 views

There is four inputs in SP 800-90A DRBG that is entropy sources, nonce, personailisation string, additional input. I noticed the soundness of entropy_sources is most important thing for DRBG security ...
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### why can't use only one way function to construct a PRG, and don't use the hard core predicate?

The one-way function can expose some of the input and stay one-way, but still, that doesn't give the input. As I read, we can't just construct a PRG from a OWF, but we need to use the hard core ...
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### Permuting Small Sized Set in Practice

Imagine we have a set $S$ of $m$ elements and we wants to permutes the set elements. Thus the original position of each element should be unknown after permuting. If we define a permutation function ...
716 views

### Crypto++: How to re-generate pseudo random integers in Crypto++

I'm using Crypto++ to implement my protocol to mask a value $y_i$ by a pseudo-random value $r_i$ such that $m_i=y_i \cdot r_i$. Since there are many $r_i$'s I want to generate them using PRNG and then ...
871 views

### Reseeding a PRNG with the generated PRN

Would reseeding a PRNG with the PRN from the previous generation have any effects whatsoever on the quality of the generated numbers; if so, does this depend on the PRNG used, or are the effects ...
827 views

### Existence of PRF $\implies$ existence of PRG

Let $F:\{0,1\}^n\times \{0,1\}^m \to \{0,1\}^l$ be a PRF. I want to show that $G(-)=F(-,x_0)$ is a PRG for every $x_0\in \{0,1\}^m$. Proof attempt: Let $D$ be an efficient distinguisher against $G$...
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### random number generator and seed

I'm working with openssl cryptographic libraries, I'm new to all these cryptographic stuffs and slowly I'm learning all these. I have a doubt regarding random number generator, I'm using ...
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### Are there any practical differences between running a PRNG on a subset of bits from an RNG compared to running the RNG?

Given an RNG and a PRNG. We define RNG(k) to mean that the RNG produces k random bits. We define PRNG(k, seed) to mean that the PRNG uses seed to produce k pseudo-...
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### How to symmetrically encrypt 64bit values?

I'm curious about an algorithm that would be good for the following scenario: 32-bit "plaintext" input, taken from a counter 32 or 64-bit "ciphertext" output It should be possible to decrypt the ...
146 views

### Constructions of PRF (Pseudo Random Function)

I was taught only GGM based PRF construction in class. It's very inefficient. I am just curious about various PRF constructions from standard assumptions. Please provide a few PRF constructions from ...