dataset
stringclasses 1
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stringlengths 11
13
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stringlengths 64
1.92k
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stringlengths 12
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|---|---|---|---|---|
mcq_train
|
mcq_train_301
|
Question: A simple substitution cipher can be broken \dots
Options: by analysing the probability occurence of the language., only by using a quantum computer., by using the ENIGMA machine., by using public-key cryptogaphy.
|
by analysing the probability occurence of the language., only by using a quantum computer., by using the ENIGMA machine., by using public-key cryptogaphy.
|
A
|
mcq_train
|
mcq_train_302
|
Question: Which one of the following notions means that ``the information should make clear who the author of it is''?
Options: authentication, steganograhy, privacy, confidentiality
|
authentication, steganograhy, privacy, confidentiality
|
A
|
mcq_train
|
mcq_train_303
|
Question: Stream ciphers often use a nonce to \dots
Options: simplify the key schedule., reduce the size of the secret key., avoid the reuse of the key stream., improve the efficiency of the automaton.
|
simplify the key schedule., reduce the size of the secret key., avoid the reuse of the key stream., improve the efficiency of the automaton.
|
C
|
mcq_train
|
mcq_train_304
|
Question: Choose the \emph{correct} statement.
Options: $\mathbb{Z}_n$ is a field $\Leftrightarrow$ $n$ is a composite number, $\mathbb{Z}_n$ is a field $\Leftrightarrow$ $\mathbb{Z}_n^* = \mathbb{Z}_n$, $\mathbb{Z}_n$ is a field $\Leftrightarrow$ $n$ is a prime, $\mathbb{Z}_n$ is a field $\Leftrightarrow$ $\mathbb{Z}_n^* = \emptyset$
|
$\mathbb{Z}_n$ is a field $\Leftrightarrow$ $n$ is a composite number, $\mathbb{Z}_n$ is a field $\Leftrightarrow$ $\mathbb{Z}_n^* = \mathbb{Z}_n$, $\mathbb{Z}_n$ is a field $\Leftrightarrow$ $n$ is a prime, $\mathbb{Z}_n$ is a field $\Leftrightarrow$ $\mathbb{Z}_n^* = \emptyset$
|
C
|
mcq_train
|
mcq_train_305
|
Question: The group $\mathbb{Z}_{60}^*$ has \ldots
Options: 16 elements., 60 elements., 59 elements., 32 elements.
|
16 elements., 60 elements., 59 elements., 32 elements.
|
A
|
mcq_train
|
mcq_train_306
|
Question: Which of the following integers has the square roots $\{2,3\}$ when taken modulo $5$ \textbf{and} the square roots $\{3,10\}$ when taken modulo $13$.
Options: $4$., $9$., $6$., $5$.
|
$4$., $9$., $6$., $5$.
|
B
|
mcq_train
|
mcq_train_307
|
Question: Pick the \emph{false} statement.
Options: A ring is always commutative: $ab=ba$, A ring is always associative: $(ab)c=a(bc)$, A ring is always distributive: $a(b+c)=ab+ac$, $(a+b)c=ac+bc$, A ring is always Abelian: $a+b = b+a$
|
A ring is always commutative: $ab=ba$, A ring is always associative: $(ab)c=a(bc)$, A ring is always distributive: $a(b+c)=ab+ac$, $(a+b)c=ac+bc$, A ring is always Abelian: $a+b = b+a$
|
A
|
mcq_train
|
mcq_train_308
|
Question: Moore's Law ...
Options: is an empirical law., says that the cost of computers doubles every 18 months., will allow to break AES in 2015., is a main reason for discarding MD5 hash function.
|
is an empirical law., says that the cost of computers doubles every 18 months., will allow to break AES in 2015., is a main reason for discarding MD5 hash function.
|
A
|
mcq_train
|
mcq_train_309
|
Question: Tick the \emph{false} assertion. The index of coincidence
Options: is a probability., can help breaking Vigen\`ere cipher., is different for a random string than for some text in English., is the best known attack against the Vernam cipher.
|
is a probability., can help breaking Vigen\`ere cipher., is different for a random string than for some text in English., is the best known attack against the Vernam cipher.
|
D
|
mcq_train
|
mcq_train_310
|
Question: Select the \emph{incorrect} statement. Pedersen Commitment is
Options: unconditionally hiding., computationally binding., based on the hardness of the discrete logarithm problem., based on DSA.
|
unconditionally hiding., computationally binding., based on the hardness of the discrete logarithm problem., based on DSA.
|
D
|
mcq_train
|
mcq_train_311
|
Question: Select a correct statement
Options: Morse alphabet is a cipher, Morse alphabet is a code, Morse alphabet preserves confidentiality, Morse alphabet preserves authenticity
|
Morse alphabet is a cipher, Morse alphabet is a code, Morse alphabet preserves confidentiality, Morse alphabet preserves authenticity
|
B
|
mcq_train
|
mcq_train_312
|
Question: Let $p$ be a prime number. What is the cardinality of $\mathbf{Z}_p$?
Options: $p$, $p-1$, $\varphi(p)$, $\varphi(p-1)$
|
$p$, $p-1$, $\varphi(p)$, $\varphi(p-1)$
|
A
|
mcq_train
|
mcq_train_313
|
Question: Due to the birthday paradox, a collision search in a hash function with $n$-bit output has complexity\dots
Options: $2^{\sqrt{n}}$, $\sqrt{2^n}$, $2^n$, $2^{n-1}$
|
$2^{\sqrt{n}}$, $\sqrt{2^n}$, $2^n$, $2^{n-1}$
|
B
|
mcq_train
|
mcq_train_314
|
Question: Using a block cipher, we can build \ldots
Options: only hash functions., only MACs., only hash functions and MACs., hash functions, MACs, and stream ciphers.
|
only hash functions., only MACs., only hash functions and MACs., hash functions, MACs, and stream ciphers.
|
D
|
mcq_train
|
mcq_train_315
|
Question: What is the length in bits of the input and output of a DES S-Box respectively?
Options: 6 and 6, 4 and 6, 6 and 4, 4 and 4
|
6 and 6, 4 and 6, 6 and 4, 4 and 4
|
C
|
mcq_train
|
mcq_train_316
|
Question: Tick the \emph{minimal} assumption on the required channel to exchange the key of a Message Authentication Code (MAC):
Options: nothing., authentication and integrity only., confidentiality only., authentication, integrity, and confidentiality.
|
nothing., authentication and integrity only., confidentiality only., authentication, integrity, and confidentiality.
|
D
|
mcq_train
|
mcq_train_317
|
Question: Tick the \emph{true} assertion among the followings:
Options: Visual cryptography is perfectly secure (at an unreasonable cost)., The Vernam cipher was invented by Kerckoff., Just like coding theory, cryptography usually faces random noise., Enigma has never been broken.
|
Visual cryptography is perfectly secure (at an unreasonable cost)., The Vernam cipher was invented by Kerckoff., Just like coding theory, cryptography usually faces random noise., Enigma has never been broken.
|
A
|
mcq_train
|
mcq_train_318
|
Question: Which of the following is well preserved by 2G?
Options: Confidentiality, Message Integrity, Challenge freshness, Authentication of Mobile Station
|
Confidentiality, Message Integrity, Challenge freshness, Authentication of Mobile Station
|
D
|
mcq_train
|
mcq_train_319
|
Question: The collision resistance property of a hash function $H$ means that it is infeasible to\dots
Options: find $Y$ such that $H(X)=Y$ for a given $X$., find $X$ such that $H(X)=Y$ for a given $Y$., find $X'$ such that $H(X')=H(X)$ and $X\ne X'$ for a given $X$., find $X,X'$ such that $H(X)=H(X')$ and $X\ne X'$.
|
find $Y$ such that $H(X)=Y$ for a given $X$., find $X$ such that $H(X)=Y$ for a given $Y$., find $X'$ such that $H(X')=H(X)$ and $X\ne X'$ for a given $X$., find $X,X'$ such that $H(X)=H(X')$ and $X\ne X'$.
|
D
|
mcq_train
|
mcq_train_320
|
Question: Compared to the plain RSA cryptosystem and for equivalent key sizes, the plain Elgamal cryptosystem has\dots
Options: a simpler key generation algorithm., a simpler encryption algorithm., a simpler decryption algorithm., shorter ciphertexts.
|
a simpler key generation algorithm., a simpler encryption algorithm., a simpler decryption algorithm., shorter ciphertexts.
|
A
|
mcq_train
|
mcq_train_321
|
Question: Consider the exhaustive search of a uniformly distributed key in a set of size $N$. Think of the possible strategies and their complexities. Which of the following is \textbf{not} possible (We assume that memory access is constant.)
Options: Find the key with precomputation: $0$, memory: $O(1)$, time: $O(N)$., Find the key with precomputation: $O(N)$, memory: $O(N)$, time: $O(1)$., Find the key with precomputation: $O(N)$, memory: $O(N^{2/3})$, time: $O(N^{2/3})$., Find the key with precomputation: $0$, memory: $O(N)$, time: $O(1)$.
|
Find the key with precomputation: $0$, memory: $O(1)$, time: $O(N)$., Find the key with precomputation: $O(N)$, memory: $O(N)$, time: $O(1)$., Find the key with precomputation: $O(N)$, memory: $O(N^{2/3})$, time: $O(N^{2/3})$., Find the key with precomputation: $0$, memory: $O(N)$, time: $O(1)$.
|
D
|
mcq_train
|
mcq_train_322
|
Question: Tick the \textbf{true} assertion.
Options: It is asymptotically harder to do a collision than to do a preimage attack., The probability that a random number is prime increases whith the increase of size length., If $f(n)\in O(g(n))$ then $f(n)\in \Theta(g(n))$., If $f(n)\in \Theta(g(n))$ then $f(n)\in O(g(n))$.
|
It is asymptotically harder to do a collision than to do a preimage attack., The probability that a random number is prime increases whith the increase of size length., If $f(n)\in O(g(n))$ then $f(n)\in \Theta(g(n))$., If $f(n)\in \Theta(g(n))$ then $f(n)\in O(g(n))$.
|
D
|
mcq_train
|
mcq_train_323
|
Question: The Pohlig-Hellman algorithm can be used to \dots
Options: solve the DH problem when the order of the group is smooth., solve the RSA factorization problem when $p-1$ has smooth order., find square roots in $\mathbb{Z}_n$, where $n=pq$ for $p,q$ two large primes., compute the CRT of two numbers.
|
solve the DH problem when the order of the group is smooth., solve the RSA factorization problem when $p-1$ has smooth order., find square roots in $\mathbb{Z}_n$, where $n=pq$ for $p,q$ two large primes., compute the CRT of two numbers.
|
A
|
mcq_train
|
mcq_train_324
|
Question: Tick the \textbf{true} assertion. In a zero-knowledge interactive proof of knowledge, \ldots
Options: for any ppt verifier, any simulator can produce a transcript which is indistinguishable from the original conversation., the proof of knowledge denotes that the prover does not know why the statement is true., for any ppt verifier, there is a simulator which produces a conversation indistinguishable from the original conversation., the simulator is computationally unbounded.
|
for any ppt verifier, any simulator can produce a transcript which is indistinguishable from the original conversation., the proof of knowledge denotes that the prover does not know why the statement is true., for any ppt verifier, there is a simulator which produces a conversation indistinguishable from the original conversation., the simulator is computationally unbounded.
|
C
|
mcq_train
|
mcq_train_325
|
Question: Tick the \textbf{true} assertion. Let $X,Y$ be two random variables over the same probability space. Then,
Options: $X$ is always independent from $Y$., $E(XY)=E(X)\times E(Y)$, if $X$ and $Y$ are independent., $\Pr[X = x \, \text{and} \, Y = y ] = \Pr[X = x ] \times \Pr[Y = y]$., $X+Y$ does not make sense.
|
$X$ is always independent from $Y$., $E(XY)=E(X)\times E(Y)$, if $X$ and $Y$ are independent., $\Pr[X = x \, \text{and} \, Y = y ] = \Pr[X = x ] \times \Pr[Y = y]$., $X+Y$ does not make sense.
|
B
|
mcq_train
|
mcq_train_326
|
Question: Tick the \textbf{false} assertion.
Options: Black-box ZK (zero knowledge) is a stronger notion than (simple) ZK., We can give a black-box ZK protocol deciding 3-COL (coloring graphs with 3 colours)., The NP language has no ZK proofs., We can give a ZK protocol deciding ISO (graph isomorphisms).
|
Black-box ZK (zero knowledge) is a stronger notion than (simple) ZK., We can give a black-box ZK protocol deciding 3-COL (coloring graphs with 3 colours)., The NP language has no ZK proofs., We can give a ZK protocol deciding ISO (graph isomorphisms).
|
C
|
mcq_train
|
mcq_train_327
|
Question: Tick the \textbf{true} assertion. The advantage of a distinguisher of two distributions $P_0$ and $P_1$
Options: is always the Euclidean distance between $P_0$ and $P_1$., is $\mathsf{Adv}_{\mathcal{A}} (P_0 , P_1 ) = \Pr[P = P_1|A \rightarrow 1]-\Pr[P = P_0| A \rightarrow 1]$., is $\mathsf{Adv}_{\mathcal{A}} (P_0 , P_1 ) = \Pr[A \rightarrow 0|P = P_1 ]-\Pr[A \rightarrow 1|P = P_0]$., can touch the statistical distance $\frac{1}{2}\Sigma_{x}|P_0(x) - P_1(x)|$ between $P_0$ and $P_1$, when he makes only one query.
|
is always the Euclidean distance between $P_0$ and $P_1$., is $\mathsf{Adv}_{\mathcal{A}} (P_0 , P_1 ) = \Pr[P = P_1|A \rightarrow 1]-\Pr[P = P_0| A \rightarrow 1]$., is $\mathsf{Adv}_{\mathcal{A}} (P_0 , P_1 ) = \Pr[A \rightarrow 0|P = P_1 ]-\Pr[A \rightarrow 1|P = P_0]$., can touch the statistical distance $\frac{1}{2}\Sigma_{x}|P_0(x) - P_1(x)|$ between $P_0$ and $P_1$, when he makes only one query.
|
D
|
mcq_train
|
mcq_train_328
|
Question: The number of plaintext/ciphertext pairs required for a linear cryptanalysis is\dots
Options: $\approx \mathsf{LP}$, $\approx \frac{1}{\mathsf{LP}}$, $\approx \frac{1}{\mathsf{LP}^2}$, $\approx \log \frac{1}{\mathsf{LP}}$
|
$\approx \mathsf{LP}$, $\approx \frac{1}{\mathsf{LP}}$, $\approx \frac{1}{\mathsf{LP}^2}$, $\approx \log \frac{1}{\mathsf{LP}}$
|
B
|
mcq_train
|
mcq_train_329
|
Question: Tick the \emph{incorrect} assertion. For a cipher $C$, decorrelation theory says that \ldots
Options: A decorrelation $0$ of order $1$ means perfect secrecy when used once., $\mathsf{BestAdv}_n(C,C^\ast)=\frac{1}{2}\mathsf{Dec}^n_{\left|\left|\cdot\right|\right|_a}(C)$., A decorrelation $0$ of order $1$ always protects against linear cryptanalysis., $\mathsf{Dec}^n(C_1\circ C_2) \leq \mathsf{Dec}^n(C_1) \times \mathsf{Dec}^n(C_2)$, for $C_1$ and $C_2$ two independent random permutations.
|
A decorrelation $0$ of order $1$ means perfect secrecy when used once., $\mathsf{BestAdv}_n(C,C^\ast)=\frac{1}{2}\mathsf{Dec}^n_{\left|\left|\cdot\right|\right|_a}(C)$., A decorrelation $0$ of order $1$ always protects against linear cryptanalysis., $\mathsf{Dec}^n(C_1\circ C_2) \leq \mathsf{Dec}^n(C_1) \times \mathsf{Dec}^n(C_2)$, for $C_1$ and $C_2$ two independent random permutations.
|
C
|
mcq_train
|
mcq_train_330
|
Question: Given a function $f:\left\{ 0,1 \right\}^p \rightarrow \left\{ 0,1 \right\}^q$, given $a\in\left\{ 0,1 \right\}^p$ and $b \in \left\{ 0,1 \right\}^q$, we define $DP^{f}(a,b) = \Pr_{X}[f(X \oplus a) = f(X) \oplus b]$. We have that $\ldots$
Options: $DP^f(0,b) = 1$ if and only if $b \not= 0$., $DP^f(a,a) =1$., $\sum_{a \in \{0,1\}^p} \sum_{b \in \{0,1\}^q} DP^f(a,b)= 2^p $., when $f$ is a permutation and $p=q$, $DP^f(a,0) = 1$.
|
$DP^f(0,b) = 1$ if and only if $b \not= 0$., $DP^f(a,a) =1$., $\sum_{a \in \{0,1\}^p} \sum_{b \in \{0,1\}^q} DP^f(a,b)= 2^p $., when $f$ is a permutation and $p=q$, $DP^f(a,0) = 1$.
|
C
|
mcq_train
|
mcq_train_331
|
Question: In linear cryptanalysis,\dots
Options: one needs to do a chosen plaintext attack., one studies how the differences in the input propagate in the cipher., one chooses the deviant property with the smallest bias in order to optimize the attack., one needs to have about $\frac{1}{LP}$ pairs of plaintext-ciphertext in order to recover the correct key, where $LP$ is the linear probability of the cipher.
|
one needs to do a chosen plaintext attack., one studies how the differences in the input propagate in the cipher., one chooses the deviant property with the smallest bias in order to optimize the attack., one needs to have about $\frac{1}{LP}$ pairs of plaintext-ciphertext in order to recover the correct key, where $LP$ is the linear probability of the cipher.
|
D
|
mcq_train
|
mcq_train_332
|
Question: The worst case complexity of an exaustive search (with memory) against DES is\dots
Options: $1$, $\frac{2^{64}}{2}$, $2^{56}$, $2^{64}$
|
$1$, $\frac{2^{64}}{2}$, $2^{56}$, $2^{64}$
|
C
|
mcq_train
|
mcq_train_333
|
Question: Who invented linear cryptanalysis?
Options: Mitsuru Matsui, Eli Biham, Serge Vaudenay, Adi Shamir
|
Mitsuru Matsui, Eli Biham, Serge Vaudenay, Adi Shamir
|
A
|
mcq_train
|
mcq_train_334
|
Question: For a blockcipher $B:\{0,1\}^k\times \{0,1\}^n \rightarrow \{0,1\}^n$ that has decorrelation $Dec^q_{\| \cdot \|_{\infty}}(B,C^*)=d$ (from a perfect cipher $C^*$), the best advantage of \textit{any} distinguisher that makes $q$ queries is \ldots
Options: bounded by $d/2$., not related to $d$; we have to use the $a$-norm to get a more general result., bounded by $d$., bounded by $d-\frac{1}{2}$.
|
bounded by $d/2$., not related to $d$; we have to use the $a$-norm to get a more general result., bounded by $d$., bounded by $d-\frac{1}{2}$.
|
A
|
mcq_train
|
mcq_train_335
|
Question: I want to send a value to Bob without him knowing which value I sent and such that I cannot change my mind later when I reveal it in clear. I should use \dots
Options: a stream cipher., a PRNG., a commitment scheme., a digital signature.
|
a stream cipher., a PRNG., a commitment scheme., a digital signature.
|
C
|
mcq_train
|
mcq_train_336
|
Question: Tick the \textbf{false} assertion.
Options: $\mathcal{NP} \subseteq \mathcal{PSPACE}$, $\mathcal{IP}\ \bigcap\ \mathcal{PSPACE} = \emptyset$, $\mathcal{IP} = \mathcal{PSPACE}$, $\mathcal{IP} \supseteq \mathcal{PSPACE}$
|
$\mathcal{NP} \subseteq \mathcal{PSPACE}$, $\mathcal{IP}\ \bigcap\ \mathcal{PSPACE} = \emptyset$, $\mathcal{IP} = \mathcal{PSPACE}$, $\mathcal{IP} \supseteq \mathcal{PSPACE}$
|
B
|
mcq_train
|
mcq_train_337
|
Question: Tick the \textbf{true} assertion. $x\in \mathbf{Z}_{n}$ is invertible iff \ldots
Options: $\varphi(n)= n-1$., $x$ is prime., $x$ is not prime., $gcd(x,n) = 1$.
|
$\varphi(n)= n-1$., $x$ is prime., $x$ is not prime., $gcd(x,n) = 1$.
|
D
|
mcq_train
|
mcq_train_338
|
Question: Which of the following circuits does not change an input difference.
Options: A XOR to a constant gate., An SBox., A shift of all bits by one position to the right., A non-linear circuit.
|
A XOR to a constant gate., An SBox., A shift of all bits by one position to the right., A non-linear circuit.
|
A
|
mcq_train
|
mcq_train_339
|
Question: Which one of these attacks is not a side channel attack?
Options: sound analysis., electromagnetic fields analysis., differential fault analysis., brute force attack.
|
sound analysis., electromagnetic fields analysis., differential fault analysis., brute force attack.
|
D
|
mcq_train
|
mcq_train_340
|
Question: Tick the \emph{correct} assertion. The maximum advantage of an \textbf{adaptive} distinguisher limited to $q$ queries between two random functions $F$ and $F^*$ is always\dots
Options: $\frac{1}{2}|||[F]^q - [F^*]^q |||_{\infty}$., $\frac{1}{2}|||[F]^q - [F^*]^q |||_{a}$., $1$ when $F = F^*$., lower than the advantage of the best \textbf{non-adaptive} distinguisher.
|
$\frac{1}{2}|||[F]^q - [F^*]^q |||_{\infty}$., $\frac{1}{2}|||[F]^q - [F^*]^q |||_{a}$., $1$ when $F = F^*$., lower than the advantage of the best \textbf{non-adaptive} distinguisher.
|
B
|
mcq_train
|
mcq_train_341
|
Question: Tick the \textbf{false} assertion. A distinguisher can \ldots
Options: \ldots be a first step towards key recovery in block ciphers., \ldots be assumed deterministic when it is computationally unbounded., \ldots factorize big numbers., \ldots differentiate the encryption of two known plaintexts.
|
\ldots be a first step towards key recovery in block ciphers., \ldots be assumed deterministic when it is computationally unbounded., \ldots factorize big numbers., \ldots differentiate the encryption of two known plaintexts.
|
C
|
mcq_train
|
mcq_train_342
|
Question: Consider any block cipher $C$ and a uniformly distributed random permutation $C^*$ on $\{0,1\}^\ell$. Then, for any $n \ge 1$ we always have\dots
Options: $[C^* \circ C]^n = [C]^n$, $[C^* \circ C]^n = [C^*]^n$, $[C^* \circ C]^n = [C]^{2n}$, $[C^* \circ C]^n = [C]^n + [C^*]^n$
|
$[C^* \circ C]^n = [C]^n$, $[C^* \circ C]^n = [C^*]^n$, $[C^* \circ C]^n = [C]^{2n}$, $[C^* \circ C]^n = [C]^n + [C^*]^n$
|
B
|
mcq_train
|
mcq_train_343
|
Question: Let $X$, $Y$, and $K$ be respectively the plaintext, ciphertext, and key distributions. $H$ denotes the Shannon entropy. The consequence of perfect secrecy is \dots
Options: $H(K) \geq H(X)$, $H(K) \leq H(X)$, $H(K,X) \leq H(X)$, $H(Y) \leq H(X)$
|
$H(K) \geq H(X)$, $H(K) \leq H(X)$, $H(K,X) \leq H(X)$, $H(Y) \leq H(X)$
|
A
|
mcq_train
|
mcq_train_344
|
Question: Tick the \textbf{true} assertion. A first preimage attack on a hash function H is \ldots
Options: \ldots given $x$ find $y$ such that $H(x)=y$, \ldots given $x$ find $x'\neq x$ such that $H(x)=H(x')$, \ldots given $y$ find $x$ such that $H(x)=y$, \ldots find $x$ and $x'$ such that $x'\neq x$ and $H(x)=H(x')$
|
\ldots given $x$ find $y$ such that $H(x)=y$, \ldots given $x$ find $x'\neq x$ such that $H(x)=H(x')$, \ldots given $y$ find $x$ such that $H(x)=y$, \ldots find $x$ and $x'$ such that $x'\neq x$ and $H(x)=H(x')$
|
C
|
mcq_train
|
mcq_train_345
|
Question: In an interactive proof system for a language $L$, having $\beta$-soundness means that\dots
Options: if we run the protocol with input $x\not\in L$, with a \textbf{malicious prover}, and a \textbf{honest verifier} the probability that the protocol succeeds is upper-bounded by $\beta$., if we run the protocol with input $x\in L$, with a \textbf{malicious prover}, and a \textbf{honest verifier} the probability that the protocol succeeds is upper-bounded by $\beta$., if we run the protocol with input $x\in L$, with a \textbf{honest prover}, and a \textbf{malicious verifier} the probability that the protocol succeeds is upper-bounded by $\beta$., if we run the protocol with input $x\in L$, with a \textbf{honest prover}, and a \textbf{honest verifier} the probability that the protocol succeeds is upper-bounded by $\beta$.
|
if we run the protocol with input $x\not\in L$, with a \textbf{malicious prover}, and a \textbf{honest verifier} the probability that the protocol succeeds is upper-bounded by $\beta$., if we run the protocol with input $x\in L$, with a \textbf{malicious prover}, and a \textbf{honest verifier} the probability that the protocol succeeds is upper-bounded by $\beta$., if we run the protocol with input $x\in L$, with a \textbf{honest prover}, and a \textbf{malicious verifier} the probability that the protocol succeeds is upper-bounded by $\beta$., if we run the protocol with input $x\in L$, with a \textbf{honest prover}, and a \textbf{honest verifier} the probability that the protocol succeeds is upper-bounded by $\beta$.
|
A
|
mcq_train
|
mcq_train_346
|
Question: A proof system is computational-zero-knowledge if \dots
Options: for any PPT verifier and for any simulator $S$, $S$ produces an output which is hard to distinguish from the view of the protocol., there exists a PPT simulator $S$ such that for any \emph{honest} verifier, $S$ produces an output which is hard to distinguish from the view of the verifier., for any PPT verifier, there exists a PPT simulator that produces an output which is hard to distinguish from the view of the protocol., for any \emph{honest} verifier and for any simulator $S$, $S$ produces an output which is hard to distinguish from the view of the protocol.
|
for any PPT verifier and for any simulator $S$, $S$ produces an output which is hard to distinguish from the view of the protocol., there exists a PPT simulator $S$ such that for any \emph{honest} verifier, $S$ produces an output which is hard to distinguish from the view of the verifier., for any PPT verifier, there exists a PPT simulator that produces an output which is hard to distinguish from the view of the protocol., for any \emph{honest} verifier and for any simulator $S$, $S$ produces an output which is hard to distinguish from the view of the protocol.
|
C
|
mcq_train
|
mcq_train_347
|
Question: Tick the \textbf{false} assertion. Assume that $C$ is a random permutation.
Options: BestAdv$_n(C,C^\ast)=\frac{1}{2}Dec^n_{\left|\left|\left|\cdot\right|\right|\right|_a}(C)$, BestAdv$_n^{n.a.}(C,C^\ast)=\frac{1}{2}Dec^n_{\left|\left|\left|\cdot\right|\right|\right|_\infty}(C)$, $E(LP^{C}(a,b))\leq 1$, $Dec^n(C\circ C)\leq Dec^n(C)^2$.
|
BestAdv$_n(C,C^\ast)=\frac{1}{2}Dec^n_{\left|\left|\left|\cdot\right|\right|\right|_a}(C)$, BestAdv$_n^{n.a.}(C,C^\ast)=\frac{1}{2}Dec^n_{\left|\left|\left|\cdot\right|\right|\right|_\infty}(C)$, $E(LP^{C}(a,b))\leq 1$, $Dec^n(C\circ C)\leq Dec^n(C)^2$.
|
D
|
mcq_train
|
mcq_train_348
|
Question: Standard encryption threats do not include:
Options: Known-plaintext attacks., Chosen-plaintext attacks., Universal forgeries., Key-recovery attacks.
|
Known-plaintext attacks., Chosen-plaintext attacks., Universal forgeries., Key-recovery attacks.
|
C
|
mcq_train
|
mcq_train_349
|
Question: Tick the \textbf{false} assertion. In Linear Cryptanalysis, the corresponding mask circuit of \ldots
Options: \ldots a XOR gate ($X\oplus Y = Z$) is $a\cdot Z=(a\cdot X)\oplus (a\cdot Y)$, \ldots a XOR to constant gate ($Y=X\oplus K$) is $a\cdot Y = (a\cdot X)\oplus (a\cdot K)$, \ldots a linear circuit ($Y=M\times X$) is $a\cdot Y = (M\times a)\cdot X$, \ldots a duplicate gate ($X=Y=Z$) is $(a\oplus b)\cdot X=(a\cdot Y)\oplus (b\cdot Z)$
|
\ldots a XOR gate ($X\oplus Y = Z$) is $a\cdot Z=(a\cdot X)\oplus (a\cdot Y)$, \ldots a XOR to constant gate ($Y=X\oplus K$) is $a\cdot Y = (a\cdot X)\oplus (a\cdot K)$, \ldots a linear circuit ($Y=M\times X$) is $a\cdot Y = (M\times a)\cdot X$, \ldots a duplicate gate ($X=Y=Z$) is $(a\oplus b)\cdot X=(a\cdot Y)\oplus (b\cdot Z)$
|
C
|
mcq_train
|
mcq_train_350
|
Question: Tick the \textbf{true} assertion. In a zero-knowledge interactive proof for $L$, \ldots
Options: for any ppt verifier, there is a simulator which for any $x \in L$ produces a conversation indistinguishable from the original conversation., for any ppt verifier, for some $x \in L$, any simulated conversation is indistinguishable from the original conversation., the simulator imitates the verifier., the simulator is computationaly unbounded.
|
for any ppt verifier, there is a simulator which for any $x \in L$ produces a conversation indistinguishable from the original conversation., for any ppt verifier, for some $x \in L$, any simulated conversation is indistinguishable from the original conversation., the simulator imitates the verifier., the simulator is computationaly unbounded.
|
A
|
mcq_train
|
mcq_train_351
|
Question: What is the Squared Euclidean Imbalance?
Options: $\displaystyle P_0(x)\sum_x(P_1(x)-P_0(x))^2$, $\displaystyle\frac{1}{P_0(x)}\sum_x(P_1(x)-P_0(x))^2$, $\displaystyle\sum_x\frac{(P_1(x)-P_0(x))^2}{P_0(x)}$, $\displaystyle\sum_x\left(\frac{P_1(x)}{P_0(x)}-1\right)^2$
|
$\displaystyle P_0(x)\sum_x(P_1(x)-P_0(x))^2$, $\displaystyle\frac{1}{P_0(x)}\sum_x(P_1(x)-P_0(x))^2$, $\displaystyle\sum_x\frac{(P_1(x)-P_0(x))^2}{P_0(x)}$, $\displaystyle\sum_x\left(\frac{P_1(x)}{P_0(x)}-1\right)^2$
|
C
|
mcq_train
|
mcq_train_352
|
Question: Tick the \textbf{false} assertion. A cipher with a good decorrelation of order 2 protects against \ldots
Options: \ldots non-adaptive distinguishers limited to two queries., \ldots unbounded attacks., \ldots differential cryptanalysis., \ldots linear cryptanalysis.
|
\ldots non-adaptive distinguishers limited to two queries., \ldots unbounded attacks., \ldots differential cryptanalysis., \ldots linear cryptanalysis.
|
B
|
mcq_train
|
mcq_train_353
|
Question: For any function $f:\{0,1\}^p\rightarrow \{0,1\}^q$ and for any $a\in\{0,1\}^p$, we have\ldots
Options: $\Sigma _{b\in \{0,1\}^q}\mathsf{DP}^f(a,b)=1$, $\Sigma _{b\in \{0,1\}^q}\mathsf{DP}^f(a,b)=0$, $\Sigma _{b\in \{0,1\}^q}\mathsf{DP}^f(a,b)=\frac{1}{2}$, $\Sigma _{b\in \{0,1\}^q}\mathsf{DP}^f(a,b)=\frac{1}{\sqrt{2}}$
|
$\Sigma _{b\in \{0,1\}^q}\mathsf{DP}^f(a,b)=1$, $\Sigma _{b\in \{0,1\}^q}\mathsf{DP}^f(a,b)=0$, $\Sigma _{b\in \{0,1\}^q}\mathsf{DP}^f(a,b)=\frac{1}{2}$, $\Sigma _{b\in \{0,1\}^q}\mathsf{DP}^f(a,b)=\frac{1}{\sqrt{2}}$
|
A
|
mcq_train
|
mcq_train_354
|
Question: Tick the \textbf{incorrect} assertion regarding plain Rabin, i.e., Rabin without any redundancy.
Options: The Rabin Key Recovery Problem relies on the discrete logarithm problem., Plain Rabin suffers from a chosen ciphertext key recovery attack., The decryption of plain Rabin is ambiguous., The Rabin Decryption Problem is equivalent to the factoring problem.
|
The Rabin Key Recovery Problem relies on the discrete logarithm problem., Plain Rabin suffers from a chosen ciphertext key recovery attack., The decryption of plain Rabin is ambiguous., The Rabin Decryption Problem is equivalent to the factoring problem.
|
A
|
mcq_train
|
mcq_train_355
|
Question: Tick the \emph{incorrect} assertion. A cipher $C$ perfectly decorrelated at order 2 implies\dots
Options: perfect secrecy when used twice., security against differential cryptanalysis., security against linear cryptanalysis., security against exhaustive search.
|
perfect secrecy when used twice., security against differential cryptanalysis., security against linear cryptanalysis., security against exhaustive search.
|
D
|
mcq_train
|
mcq_train_356
|
Question: Tick the \textbf{false} assertion. A distinguisher \ldots
Options: \ldots can break PRNG., \ldots is an algorithm calling an oracle., \ldots recovers the secret key of a stream cipher., \ldots can differentiate the encryption of two known plaintexts.
|
\ldots can break PRNG., \ldots is an algorithm calling an oracle., \ldots recovers the secret key of a stream cipher., \ldots can differentiate the encryption of two known plaintexts.
|
C
|
mcq_train
|
mcq_train_357
|
Question: Tick the \emph{incorrect} assertion regarding the security of the Diffie-Hellman key exchange over a subgroup $\langle g \rangle \subset \mathbb{Z}_p^*$.
Options: $\langle g \rangle$ should have prime order., We must ensure that $X\in \langle g \rangle$ for every received $X$., The binary representation of the output of the key exchange is a uniformly distributed bitstring., We must ensure that $X\neq1$ for every received $X$.
|
$\langle g \rangle$ should have prime order., We must ensure that $X\in \langle g \rangle$ for every received $X$., The binary representation of the output of the key exchange is a uniformly distributed bitstring., We must ensure that $X\neq1$ for every received $X$.
|
C
|
mcq_train
|
mcq_train_358
|
Question: Tick the \textbf{false} assertion. In Differential Cryptanalysis, the corresponding differential circuit of \ldots
Options: \ldots a linear circuit ($Y=M\times X$) is $\Delta X=a\Rightarrow \Delta Y=^tM\times a$, \ldots a duplicate gate ($X=Y=Z$) is $\Delta X=a\Rightarrow \Delta Y = \Delta Z = a$, \ldots a XOR gate ($X\oplus Y = Z$) is $(\Delta X=a,\ \Delta Y=b)\Rightarrow \Delta Z = a\oplus b$, \ldots a XOR to constant gate ($Y=X\oplus K$) is $\Delta X = a \Rightarrow \Delta Y = a$
|
\ldots a linear circuit ($Y=M\times X$) is $\Delta X=a\Rightarrow \Delta Y=^tM\times a$, \ldots a duplicate gate ($X=Y=Z$) is $\Delta X=a\Rightarrow \Delta Y = \Delta Z = a$, \ldots a XOR gate ($X\oplus Y = Z$) is $(\Delta X=a,\ \Delta Y=b)\Rightarrow \Delta Z = a\oplus b$, \ldots a XOR to constant gate ($Y=X\oplus K$) is $\Delta X = a \Rightarrow \Delta Y = a$
|
A
|
mcq_train
|
mcq_train_359
|
Question: Tick the \emph{correct} assertion. Linear cryptanalysis \ldots
Options: was invented long before the Caesar cipher., is a chosen plaintext key recovery attack., requires $\frac{1}{DP}$ pairs of plaintext-ciphertext., breaks DES with $2^{43}$ known plaintexts.
|
was invented long before the Caesar cipher., is a chosen plaintext key recovery attack., requires $\frac{1}{DP}$ pairs of plaintext-ciphertext., breaks DES with $2^{43}$ known plaintexts.
|
D
|
mcq_train
|
mcq_train_360
|
Question: Let $p>2$ be a prime. Then \dots
Options: for any $x \in \mathbb{Z}_p^*$, we have $x^p \bmod{p} = 1$., the set of quadratic residues modulo $p$ form a field., the set of quadratic residues modulo $p$ is of order $(p-1)/2$., $\phi(p^2) = (p-1)^2$.
|
for any $x \in \mathbb{Z}_p^*$, we have $x^p \bmod{p} = 1$., the set of quadratic residues modulo $p$ form a field., the set of quadratic residues modulo $p$ is of order $(p-1)/2$., $\phi(p^2) = (p-1)^2$.
|
C
|
mcq_train
|
mcq_train_361
|
Question: Which assertion has not been proven?
Options: SAT $\in P$., SAT is $NP$-complete., SAT $\in NP$., SAT $\in IP$.
|
SAT $\in P$., SAT is $NP$-complete., SAT $\in NP$., SAT $\in IP$.
|
A
|
mcq_train
|
mcq_train_362
|
Question: Tick the \emph{incorrect} assertion. In hypothesis testing \ldots
Options: the statistical distance between $P_0$ and $P_1$ gives an upper bound on the advantage of all distinguishers using a single sample., a distinguisher needs $\frac{1}{C(P_0,P_1)}$ samples in order to be able to distinguish between $P_0$ and $P_1$., a distinguisher can use a deviant property of a cipher $C$, that holds with high probability, in order to distinguish between $C$ and $C^{*}$., a distinguisher with a single sample obtains always a better advantage than one that has access to $2$ samples.
|
the statistical distance between $P_0$ and $P_1$ gives an upper bound on the advantage of all distinguishers using a single sample., a distinguisher needs $\frac{1}{C(P_0,P_1)}$ samples in order to be able to distinguish between $P_0$ and $P_1$., a distinguisher can use a deviant property of a cipher $C$, that holds with high probability, in order to distinguish between $C$ and $C^{*}$., a distinguisher with a single sample obtains always a better advantage than one that has access to $2$ samples.
|
D
|
mcq_train
|
mcq_train_363
|
Question: Consider the cipher defined using the key $K\in \{0,1\}^{64} $ by $$\begin{array}{llll} C : & \{0,1\}^{64} & \rightarrow & \{0,1\}^{64} \\ & x & \mapsto & C(x)=x \oplus K \\ \end{array} $$ Let $x=1\dots 11$, the value $\mathsf{LP}^{C_K}(x,x)$ is equal to
Options: $0$, $1/4$, $1/2$, $1$
|
$0$, $1/4$, $1/2$, $1$
|
A
|
mcq_train
|
mcq_train_364
|
Question: Tick the \textbf{incorrect} assertion. Let $H:\left\{ 0,1 \right\}^*\rightarrow\left\{ 0,1 \right\}^n$ be a hash function.
Options: We can use $H$ to design a commitment scheme., We can use $H$ to design a key derivation function., Finding $x,y\in\left\{ 0,1 \right\}^*$ such that $x\neq y$ and $h(x) = h(y)$ can be done in $O(2^{n/2})$ time., Given $x\in\left\{ 0,1 \right\}^*$, finding a $y \in \left\{ 0,1 \right\}^*$ such that $x\neq y$ and $h(x) = h(y)$ can be done in $O(2^{n/2})$ time.
|
We can use $H$ to design a commitment scheme., We can use $H$ to design a key derivation function., Finding $x,y\in\left\{ 0,1 \right\}^*$ such that $x\neq y$ and $h(x) = h(y)$ can be done in $O(2^{n/2})$ time., Given $x\in\left\{ 0,1 \right\}^*$, finding a $y \in \left\{ 0,1 \right\}^*$ such that $x\neq y$ and $h(x) = h(y)$ can be done in $O(2^{n/2})$ time.
|
D
|
mcq_train
|
mcq_train_365
|
Question: In which group is the discrete logarithm problem believed to be hard?
Options: In a subgroup of $\mathbb{Z}_p^*$ with large prime order., In $\mathbb{Z}_n$, where $n= pq$ for two large primes $p$ and $q$., In a group $G$ of smooth order., In $\mathbb{Z}_2^p$, for a large prime $p$.
|
In a subgroup of $\mathbb{Z}_p^*$ with large prime order., In $\mathbb{Z}_n$, where $n= pq$ for two large primes $p$ and $q$., In a group $G$ of smooth order., In $\mathbb{Z}_2^p$, for a large prime $p$.
|
A
|
mcq_train
|
mcq_train_366
|
Question: Consider two distributions $P_0,P_1$ with the same supports and a distinguisher $\mathcal{A}$ that makes $q$ queries. Tick the \textit{incorrect} assertion.
Options: When $q=1$, $\mathsf{Adv}(\mathcal{A})\leq d(P_0,P_1)$ where $d$ is the statistical distance., When $q>1$, $\mathsf{Adv}(\mathcal{A})\leq \frac{d(P_0,P_1)}{q}$ where $d$ is the statistical distance., When $q=1$, the strategy ``return 1 $\Leftrightarrow \frac{P_0(x)}{P_1(x)}\leq 1$'' achieves the best advantage., To achieve good advantage, we need to have $q\approx 1/C(P_0,P_1)$ where $C$ is the Chernoff information.
|
When $q=1$, $\mathsf{Adv}(\mathcal{A})\leq d(P_0,P_1)$ where $d$ is the statistical distance., When $q>1$, $\mathsf{Adv}(\mathcal{A})\leq \frac{d(P_0,P_1)}{q}$ where $d$ is the statistical distance., When $q=1$, the strategy ``return 1 $\Leftrightarrow \frac{P_0(x)}{P_1(x)}\leq 1$'' achieves the best advantage., To achieve good advantage, we need to have $q\approx 1/C(P_0,P_1)$ where $C$ is the Chernoff information.
|
B
|
mcq_train
|
mcq_train_367
|
Question: What is the complexity of prime number generation for a prime of length $\ell$?
Options: $\mathbf{O}\left(\frac{1}{\ell^4}\right)$, $\mathbf{O}(\ell^4)$, $\Theta\left(\frac{1}{\ell^4}\right)$, $\Theta(\ell^4)$
|
$\mathbf{O}\left(\frac{1}{\ell^4}\right)$, $\mathbf{O}(\ell^4)$, $\Theta\left(\frac{1}{\ell^4}\right)$, $\Theta(\ell^4)$
|
B
|
mcq_train
|
mcq_train_368
|
Question: In ElGamal signature scheme, if we avoid checking that $0 \leq r < p$ then \ldots
Options: \ldots a universal forgery attack is possible., \ldots an existential forgery attack is avoided., \ldots we can recover the secret key., \ldots we need to put a stamp on the message.
|
\ldots a universal forgery attack is possible., \ldots an existential forgery attack is avoided., \ldots we can recover the secret key., \ldots we need to put a stamp on the message.
|
A
|
mcq_train
|
mcq_train_369
|
Question: Tick the \textbf{true} assertion. MAC is \ldots
Options: \ldots a computer., \ldots the name of a dish with chili., \ldots a Message Authentication Code., \ldots the encryption of KEY with the Ceasar cipher.
|
\ldots a computer., \ldots the name of a dish with chili., \ldots a Message Authentication Code., \ldots the encryption of KEY with the Ceasar cipher.
|
C
|
mcq_train
|
mcq_train_370
|
Question: For $K$ a field, $a,b\in K$ with $4a^3+27b^2 \neq 0$, $E_{a,b}(K)$ is
Options: a field., a group., a ring., a ciphertext.
|
a field., a group., a ring., a ciphertext.
|
B
|
mcq_train
|
mcq_train_371
|
Question: The number of plaintext/ciphertext pairs required for a differential cryptanalysis is\dots
Options: $\approx DP$, $\approx \frac{1}{DP}$, $\approx \frac{1}{DP^2}$, $\approx \log \frac{1}{DP}$
|
$\approx DP$, $\approx \frac{1}{DP}$, $\approx \frac{1}{DP^2}$, $\approx \log \frac{1}{DP}$
|
B
|
mcq_train
|
mcq_train_372
|
Question: Given the distribution $P_0$ of a normal coin, i.e. $P_0(0)=P_0(1)=\frac{1}{2}$, and distribution $P_1$ of a biased coin, where $P_1(0)=\frac{1}{3}$ and $P_1(1) = \frac{2}{3}$ , the maximal advantage of a distinguisher using a single sample is\dots
Options: $\frac{1}{6}$., $3$., $\frac{1}{3}$., $0$.
|
$\frac{1}{6}$., $3$., $\frac{1}{3}$., $0$.
|
A
|
mcq_train
|
mcq_train_373
|
Question: To how many plaintexts we expect to decrypt a ciphertext in the Rabin cryptosystem when we don't use redundancy?
Options: 4., 2., 1., 8.
|
4., 2., 1., 8.
|
A
|
mcq_train
|
mcq_train_374
|
Question: For an interactive proof system, the difference between perfect, statistical and computational zero-knowledge is based on \ldots
Options: \ldots the distinguishability between some distributions., \ldots the percentage of recoverable information from a transcript with a honest verifier., \ldots the number of times the protocol is run between the prover and the verifier., \ldots whether the inputs are taken in $\mathcal{P}$, $\mathcal{NP}$ or $\mathcal{IP}$.
|
\ldots the distinguishability between some distributions., \ldots the percentage of recoverable information from a transcript with a honest verifier., \ldots the number of times the protocol is run between the prover and the verifier., \ldots whether the inputs are taken in $\mathcal{P}$, $\mathcal{NP}$ or $\mathcal{IP}$.
|
A
|
mcq_train
|
mcq_train_375
|
Question: What is the name of the encryption threat that corresponds to \emph{force the sender to encrypt some messages selected by the adversary}?
Options: Chosen Ciphertext Attack, Chosen Plaintext Attack, Known Ciphertext Attack, Known Plaintext Attack
|
Chosen Ciphertext Attack, Chosen Plaintext Attack, Known Ciphertext Attack, Known Plaintext Attack
|
B
|
mcq_train
|
mcq_train_376
|
Question: Let $C$ be a perfect cipher with $\ell$-bit blocks. Then, \dots
Options: for $x_1 \neq x_2$, $\Pr[C(x_1) = y_1, C(x_2)=y_2] = \frac{1}{2^{2\ell}}$., the size of the key space of $C$ should be at least $(2^{\ell}!)$., given pairwise independent inputs to $C$, the corresponding outputs are independent and uniformly distributed., $C$ has an order $3$ decorrelation matrix which is equal to the order $3$ decorrelation matrix of a random function.
|
for $x_1 \neq x_2$, $\Pr[C(x_1) = y_1, C(x_2)=y_2] = \frac{1}{2^{2\ell}}$., the size of the key space of $C$ should be at least $(2^{\ell}!)$., given pairwise independent inputs to $C$, the corresponding outputs are independent and uniformly distributed., $C$ has an order $3$ decorrelation matrix which is equal to the order $3$ decorrelation matrix of a random function.
|
B
|
mcq_train
|
mcq_train_377
|
Question: The exponent of the group $\mathbb{Z}_9^*$ is
Options: 6., 9., 8., 3.
|
6., 9., 8., 3.
|
A
|
mcq_train
|
mcq_train_378
|
Question: Tick the \emph{incorrect} statement. When $x\rightarrow+\infty$ \ldots
Options: $x^3 + 2x + 5 = \mathcal{O}(x^3)$., $\frac{1}{x^2} = \mathcal{O}(\frac{1}{x})$., $2^{\frac{x}{\log x}} = \mathcal{O}(2^x)$., $n^x = \mathcal{O}(x^n)$ for any constant $n>1$.
|
$x^3 + 2x + 5 = \mathcal{O}(x^3)$., $\frac{1}{x^2} = \mathcal{O}(\frac{1}{x})$., $2^{\frac{x}{\log x}} = \mathcal{O}(2^x)$., $n^x = \mathcal{O}(x^n)$ for any constant $n>1$.
|
D
|
mcq_train
|
mcq_train_379
|
Question: In order to avoid the Bleichenbacher attack in ElGamal signatures, \ldots
Options: \ldots authors should put their name in the message., \ldots groups of prime order should be used., \ldots groups of even order should be used., \ldots groups with exponential number of elements should be used.
|
\ldots authors should put their name in the message., \ldots groups of prime order should be used., \ldots groups of even order should be used., \ldots groups with exponential number of elements should be used.
|
B
|
mcq_train
|
mcq_train_380
|
Question: Tick the \textbf{incorrect} assumption. A language $L$ is in NP if\dots
Options: $x \in L$ can be decided in polynomial time., $x \in L$ can be decided in polynomial time given a witness $w$., $L$ is NP-hard., $L$ (Turing-)reduces to a language $L_2$ with $L_2$ in $P$, i.e., if there is a polynomial deterministic Turing machine which recognizes $L$ when plugged to an oracle recognizing $L_2$.
|
$x \in L$ can be decided in polynomial time., $x \in L$ can be decided in polynomial time given a witness $w$., $L$ is NP-hard., $L$ (Turing-)reduces to a language $L_2$ with $L_2$ in $P$, i.e., if there is a polynomial deterministic Turing machine which recognizes $L$ when plugged to an oracle recognizing $L_2$.
|
C
|
mcq_train
|
mcq_train_381
|
Question: In which of the following groups is the decisional Diffie-Hellman problem (DDH) believed to be hard?
Options: In $\mathbb{Z}_p$, with a large prime $p$., In large subgroup of smooth order of a ``regular'' elliptic curve., In a large subgroup of prime order of $\mathbb{Z}_p^*$, such that $p$ is a large prime., In $\mathbb{Z}_p^*$, with a large prime $p$.
|
In $\mathbb{Z}_p$, with a large prime $p$., In large subgroup of smooth order of a ``regular'' elliptic curve., In a large subgroup of prime order of $\mathbb{Z}_p^*$, such that $p$ is a large prime., In $\mathbb{Z}_p^*$, with a large prime $p$.
|
C
|
mcq_train
|
mcq_train_382
|
Question: In ElGamal signature scheme and over the random choice of the public parameters in the random oracle model (provided that the DLP is hard), existential forgery is \ldots
Options: \ldots impossible., \ldots hard on average., \ldots easy on average., \ldots easy.
|
\ldots impossible., \ldots hard on average., \ldots easy on average., \ldots easy.
|
B
|
mcq_train
|
mcq_train_383
|
Question: Which of the following primitives \textit{cannot} be instantiated with a cryptographic hash function?
Options: A pseudo-random number generator., A commitment scheme., A public key encryption scheme., A key-derivation function.
|
A pseudo-random number generator., A commitment scheme., A public key encryption scheme., A key-derivation function.
|
C
|
mcq_train
|
mcq_train_384
|
Question: In plain ElGamal Encryption scheme \ldots
Options: \ldots only a confidential channel is needed., \ldots only an authenticated channel is needed., \ldots only an integer channel is needed, \ldots only an authenticated and integer channel is needed.
|
\ldots only a confidential channel is needed., \ldots only an authenticated channel is needed., \ldots only an integer channel is needed, \ldots only an authenticated and integer channel is needed.
|
D
|
mcq_train
|
mcq_train_385
|
Question: Tick the \textbf{true} assertion. Let $X$ be a random variable defined by the visible face showing up when throwing a dice. Its expected value $E(X)$ is:
Options: 3.5, 3, 1, 4
|
3.5, 3, 1, 4
|
A
|
mcq_train
|
mcq_train_386
|
Question: Consider an arbitrary cipher $C$ and a uniformly distributed random permutation $C^*$ on $\{0,1\}^n$. Tick the \textbf{false} assertion.
Options: $\mathsf{Dec}^1(C)=0$ implies $C=C^*$., $\mathsf{Dec}^1(C)=0$ implies $[C]^1=[C^*]^1$., $\mathsf{Dec}^1(C)=0$ implies that $C$ is perfectly decorrelated at order 1., $\mathsf{Dec}^1(C)=0$ implies that all coefficients in $[C]^1$ are equal to $\frac{1}{2^n}$.
|
$\mathsf{Dec}^1(C)=0$ implies $C=C^*$., $\mathsf{Dec}^1(C)=0$ implies $[C]^1=[C^*]^1$., $\mathsf{Dec}^1(C)=0$ implies that $C$ is perfectly decorrelated at order 1., $\mathsf{Dec}^1(C)=0$ implies that all coefficients in $[C]^1$ are equal to $\frac{1}{2^n}$.
|
A
|
mcq_train
|
mcq_train_387
|
Question: Tick the \textit{incorrect} assertion. Let $P, V$ be an interactive system for a language $L\in \mathcal{NP}$.
Options: The proof system is $\beta$-sound if $\Pr[\text{Out}_{V}(P^* \xleftrightarrow{x} V) = \text{accept}] \leq \beta$ for any $P^*$ and any $x \notin L$., The soundness of the proof system can always be tuned close to $0$ by sequential composition., It is impossible for the proof system to be sound and zero knowledge at the same time., Both the verifier $V$ and the prover $P$ run in time that is polynomial in $|x|$, if we assume that $P$ gets the witness $w$ as an extra input.
|
The proof system is $\beta$-sound if $\Pr[\text{Out}_{V}(P^* \xleftrightarrow{x} V) = \text{accept}] \leq \beta$ for any $P^*$ and any $x \notin L$., The soundness of the proof system can always be tuned close to $0$ by sequential composition., It is impossible for the proof system to be sound and zero knowledge at the same time., Both the verifier $V$ and the prover $P$ run in time that is polynomial in $|x|$, if we assume that $P$ gets the witness $w$ as an extra input.
|
C
|
mcq_train
|
mcq_train_388
|
Question: Tick the assertion related to an open problem.
Options: $NP\subseteq IP$., $P\subseteq IP$., $PSPACE=IP$., $NP = \text{co-}NP$.
|
$NP\subseteq IP$., $P\subseteq IP$., $PSPACE=IP$., $NP = \text{co-}NP$.
|
D
|
mcq_train
|
mcq_train_389
|
Question: Let $X$ be a plaintext and $Y$ its ciphertext. Which statement is \textbf{not} equivalent to the others?
Options: the encyption scheme provides perfect secrecy, only a quantum computer can retrieve $X$ given $Y$, $X$ and $Y$ are statistically independent random variables, the conditionnal entropy of $X$ given $Y$ is equal to the entropy of $X$
|
the encyption scheme provides perfect secrecy, only a quantum computer can retrieve $X$ given $Y$, $X$ and $Y$ are statistically independent random variables, the conditionnal entropy of $X$ given $Y$ is equal to the entropy of $X$
|
B
|
mcq_train
|
mcq_train_390
|
Question: Tick the \textbf{\emph{incorrect}} assertion. A $\Sigma$-protocol \dots
Options: has special soundness., is zero-knowledge., is a 3-move interaction., has the verifier polynomially bounded.
|
has special soundness., is zero-knowledge., is a 3-move interaction., has the verifier polynomially bounded.
|
B
|
mcq_train
|
mcq_train_391
|
Question: The statistical distance between two distributions is \dots
Options: unrelated to the advantage of a distinguisher., a lower bound on the advantage of \emph{all} distinguishers (with a unique sample)., an upper bound on the advantage of \emph{all} distinguishers (with a unique sample)., an upper bound on the advantage of all distinguishers making statistics on the obtained samples.
|
unrelated to the advantage of a distinguisher., a lower bound on the advantage of \emph{all} distinguishers (with a unique sample)., an upper bound on the advantage of \emph{all} distinguishers (with a unique sample)., an upper bound on the advantage of all distinguishers making statistics on the obtained samples.
|
C
|
mcq_train
|
mcq_train_392
|
Question: Tick the \textbf{\emph{correct}} assertion. A random oracle $\ldots$
Options: returns the same answer when queried with two different values., is instantiated with a hash function in practice., has predictable output before any query is made., answers with random values that are always independent of the previous queries.
|
returns the same answer when queried with two different values., is instantiated with a hash function in practice., has predictable output before any query is made., answers with random values that are always independent of the previous queries.
|
B
|
mcq_train
|
mcq_train_393
|
Question: Consider an Sbox $S:\{0,1\}^m \rightarrow \{0,1\}^m$. We have that \ldots
Options: $\mathsf{DP}^S(0,b)=1$ if and only if $S$ is a permutation., $\sum_{b\in \{0,1\}^m} \mathsf{DP}^S(a,b)$ is even., $\sum_{b\in \{0,1\}^m \backslash \{0\}} \mathsf{DP}^S(0,b)= 0$, $\mathsf{DP}^S(0,b)=1$ if and only if $m$ is odd.
|
$\mathsf{DP}^S(0,b)=1$ if and only if $S$ is a permutation., $\sum_{b\in \{0,1\}^m} \mathsf{DP}^S(a,b)$ is even., $\sum_{b\in \{0,1\}^m \backslash \{0\}} \mathsf{DP}^S(0,b)= 0$, $\mathsf{DP}^S(0,b)=1$ if and only if $m$ is odd.
|
C
|
mcq_train
|
mcq_train_394
|
Question: Tick the \textbf{true} assertion. In RSA \ldots
Options: \ldots decryption is known to be equivalent to factoring., \ldots key recovery is provably not equivalent to factoring)., \ldots decryption is probabilistic., \ldots public key transmission needs authenticated and integer channel.
|
\ldots decryption is known to be equivalent to factoring., \ldots key recovery is provably not equivalent to factoring)., \ldots decryption is probabilistic., \ldots public key transmission needs authenticated and integer channel.
|
D
|
mcq_train
|
mcq_train_395
|
Question: Consider the cipher defined by $$\begin{array}{llll} C : & \{0,1\}^{4} & \rightarrow & \{0,1\}^{4} \\ & x & \mapsto & C(x)=x \oplus 0110 \\ \end{array} $$ The value $LP^C(1,1)$ is equal to
Options: $0$, $1/4$, $1/2$, $1$
|
$0$, $1/4$, $1/2$, $1$
|
D
|
mcq_train
|
mcq_train_396
|
Question: Let $n=pq$ be a RSA modulus and let $(e,d)$ be a RSA public/private key. Tick the \emph{correct} assertion.
Options: Finding a multiple of $\lambda(n)$ is equivalent to decrypt a ciphertext., $ed$ is a multiple of $\phi(n)$., The two roots of the equation $X^2 - (n-\phi(n)+1)X+n$ in $\mathbb{Z}$ are $p$ and $q$., $e$ is the inverse of $d$ mod $n$.
|
Finding a multiple of $\lambda(n)$ is equivalent to decrypt a ciphertext., $ed$ is a multiple of $\phi(n)$., The two roots of the equation $X^2 - (n-\phi(n)+1)X+n$ in $\mathbb{Z}$ are $p$ and $q$., $e$ is the inverse of $d$ mod $n$.
|
C
|
mcq_train
|
mcq_train_397
|
Question: Tick the \emph{true} assertion. A distinguishing attack against a block cipher\dots
Options: is a probabilistic attack., succeeds with probability $1$., outputs the secret key., succeeds with probability $0$.
|
is a probabilistic attack., succeeds with probability $1$., outputs the secret key., succeeds with probability $0$.
|
A
|
mcq_train
|
mcq_train_398
|
Question: Tick the \textbf{true} assertion. Let $n >1 $ be a composite integer, the product of two primes. Then,
Options: $\phi(n)$ divides $\lambda(n)$., $\lambda(n)$ divides the order of any element $a$ in $\mathbb{Z}_n$., $\mathbb{Z}^{*}_n$ with the multiplication is a cyclic group., $a^{\lambda(n)} \mod n=1$, for all $a \in \mathbb{Z}^{*}_n$.
|
$\phi(n)$ divides $\lambda(n)$., $\lambda(n)$ divides the order of any element $a$ in $\mathbb{Z}_n$., $\mathbb{Z}^{*}_n$ with the multiplication is a cyclic group., $a^{\lambda(n)} \mod n=1$, for all $a \in \mathbb{Z}^{*}_n$.
|
D
|
mcq_train
|
mcq_train_399
|
Question: Let $C$ be a permutation over $\left\{ 0,1 \right\}^p$. Tick the \emph{incorrect} assertion:
Options: $\text{DP}^C(a,0) = 1$ for some $a \neq 0$., $\text{DP}^C(0,b) = 0$ for some $b \neq 0$., $\sum_{b \in \left\{ 0,1 \right\}^p}\text{DP}^C(a,b) = 1$ for any $a\in \left\{ 0,1 \right\}^p$., $2^p \text{DP}^C(a,b) \bmod 2 = 0$, for any $a,b\in \left\{ 0,1 \right\}^p$.
|
$\text{DP}^C(a,0) = 1$ for some $a \neq 0$., $\text{DP}^C(0,b) = 0$ for some $b \neq 0$., $\sum_{b \in \left\{ 0,1 \right\}^p}\text{DP}^C(a,b) = 1$ for any $a\in \left\{ 0,1 \right\}^p$., $2^p \text{DP}^C(a,b) \bmod 2 = 0$, for any $a,b\in \left\{ 0,1 \right\}^p$.
|
A
|
mcq_train
|
mcq_train_400
|
Question: Tick the \textbf{true} assertion. Assume an arbitrary $f:\{0,1\}^p \rightarrow \{0,1\}^q$, where $p$ and $q$ are integers.
Options: $\mathsf{DP}^f(a,b)=\displaystyle\Pr_{X\in_U\{0,1\}^p}[f(X\oplus a)\oplus f(X)\oplus b=1]$, for all $a \in \{0,1\}^p$, $b \in \{0,1\}^q$., $\Pr[f(x\oplus a)\oplus f(x)\oplus b=0]=E(\mathsf{DP}^f(a,b))$, for all $a, x \in \{0,1\}^p$, $b \in \{0,1\}^q$., $2^p\mathsf{DP}^f(a,b)$ is odd, for all $a \in \{0,1\}^p, b \in \{0,1\}^q$., $\displaystyle\sum_{b\in\{0,1\}^q} \mathsf{DP}^f(a,b)=1$, for all $a \in \{0,1\}^p$.
|
$\mathsf{DP}^f(a,b)=\displaystyle\Pr_{X\in_U\{0,1\}^p}[f(X\oplus a)\oplus f(X)\oplus b=1]$, for all $a \in \{0,1\}^p$, $b \in \{0,1\}^q$., $\Pr[f(x\oplus a)\oplus f(x)\oplus b=0]=E(\mathsf{DP}^f(a,b))$, for all $a, x \in \{0,1\}^p$, $b \in \{0,1\}^q$., $2^p\mathsf{DP}^f(a,b)$ is odd, for all $a \in \{0,1\}^p, b \in \{0,1\}^q$., $\displaystyle\sum_{b\in\{0,1\}^q} \mathsf{DP}^f(a,b)=1$, for all $a \in \{0,1\}^p$.
|
D
|
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