A pseudo-random function is an efficiently-computable function which emulates a random oracle.

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Is IPsec IND-CCA secure provided the used block cipher is a pseudorandom function?

I am trying to solve the question whether "IPsec is IND-CCA secure provided the used block cipher is a pseudorandom function" (with IPsec using a variant of Encrypt-then-MAC) As a resource I am given ...
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Proving the existence of a pseudorandom function

I've been reading the Introduction to Modern Cryptography book by Katz and Lindell as part of my own learning and have come across this exercise which I am not sure how to approach. The exercise is: ...
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Is F' a pseudorandom function when F is composed with G, a pseudorandom generator?

If $F$ is a pseudorandom function, is $F'$ also a pseudorandom function in the following: $$ F'_k(x)=F_k(G(x)) \space \space \text, $$ where $G$ is $a$ pseudorandom generator? Also, does the other ...
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Pseudorandom Functions with different input and output lengths

I am working on a problem found in my Cryptography textbook that goes as follows: Let F be a pseudorandom function such that for $k \in \{0,1\}^n$, function $F_k$ maps $l_{in}(n)$-inputs to ...
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Pollard's Rho - Restricting the random function to the exponents

Pollard's Rho is usually constructed using a function $f:G \rightarrow G$ which behaves 'random enough' in order to detect a collision with Floyd's cycle detection trick. It is easy enough to observe, ...
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What might be assumed about a PRF if the key has been chosen?

The defining feature of a PRF $f:\{0,1\}^k\times\{0,1\}^s\mapsto\{0,1\}^*$ is that, if the first parameter is selected at random, it should be indistinguishable from a function ...
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Pseudorandom Function Proof

Given a set of pseudorandom functions $F=\{f_s^i\}_i$ for each $s\leftarrow\{0,1\}^n$ generated at random; moreover each $f_s^i$ uses a specific PRG $G^i:\{0,1\}^n\to\{0,1\}^{2n}$, where: ...
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Protocol/algorithms based on a variable-length input PRF

Are the proofs based on a PRF assumption still valid when using a variable-length input PRF ? The answer might be obvious, but I have a doubt.
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How to prove that a function F isn't a pseudo random function

Let $F$ be a length-preserving pseudorandom function. For the following constructions of a keyed function $F' : \{0, 1\}^n \times \{0, 1\}^{n−1} \to \{0, 1\}^{2n}$, state whether $F'$ is a ...
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If a PRG is constructed by iterating a PRF, is it backtracking-resistant?

Say we construct a pseudo-random number generator from a pseudo-random function $f$ (using some constant key $k$ and some initial value $v_0$). We do this by feeding the output block of the PRF back ...
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Implementing a pseudo random function in practice

Can anyone point me to a C++ crypto library with an implementation of a pseudo random function (PRF)? I don't have much background in crypto theory, but I am in the middle of a graduate course ...
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Special random distribution algorithm

I am implementing ring signatures as a part of an authorization system. Since the number of users could get high enough to make computation on end-user devices infeasible, I am thinking of ...
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Proof that this is not a secure pseudorandom function

$p$ is a large prime number. Consider the following function $F:\mathbb Z^*_p \times \mathbb D\rightarrow\mathbb Z^*_p$ where $\mathbb D=2,....,p-1$. $F_k(x)=x^k \bmod p$ Proof that it's ...
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how to prove sequence y uphold golomb's third axiom

given $\{ x_k \}$ is a m-seq of order $n$, we define $\{ y_k \}$ to be a $m$ digits number: $$ y_i=x_ix_{i+1}...x_{i+m-1} $$ for every integer $n \ge m \ge 1$ how can I show that $\{ y_k \}$ upholds ...
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Show that using a PRF with a non-uniform key may result in non-uniform values

In a homework assignment we have to use a key derivation function like HKDF. Suppose $k$ is a non-uniform secret key sampled from the key space $\{0, 1\}^{256}$. In particular, $k$ is sampled ...
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Existence of a random function under constraints

Let $F_1$ and $F_2$ be two random functions taking as input $N$ bits and returning $N$ bits. Let $C_1$ and $C_2$ two constants of $N$ bits. Is there a random function $P$ taking as input $2N$ bits and ...
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Making PRFs out of PRGs

Is it possible that we take a $PRG$ $G(k)$ of stretch $n\cdot2^n$, and read its output as the table of a $PRF$ $F(K)$ with input and output size of $n$? Intuitively it sounds possible however I read ...