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mcq_train
mcq_train_101
Question: Tick the \textbf{false} statement. Moore's Law ... Options: is partly a reason why some existing cryptosystems are insecure., was stated by the founder of Intel., assumes the number of transistors per CPU increases exponentially fast with time., implies that the heat generated by transistors of CPU doubles every 18 months.
is partly a reason why some existing cryptosystems are insecure., was stated by the founder of Intel., assumes the number of transistors per CPU increases exponentially fast with time., implies that the heat generated by transistors of CPU doubles every 18 months.
D
mcq_train
mcq_train_102
Question: The elements of $\mathbf{Z}_{14}^*$ are Options: $\{ 0, 1, 3, 5, 9, 11, 13\}$, $\{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13\}$, $\{ 1, 3, 5, 9, 11, 13\}$, $\{ 1, 2, 3, 9, 11 \}$
$\{ 0, 1, 3, 5, 9, 11, 13\}$, $\{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13\}$, $\{ 1, 3, 5, 9, 11, 13\}$, $\{ 1, 2, 3, 9, 11 \}$
C
mcq_train
mcq_train_103
Question: Tick the \textbf{false} statement. Options: RSA can be accelerated by using CRT (Chinese Remainder Theorem)., An isomorphism is defined as a bijective homomorphism., The CRT states $\mathbb{Z}_{mn} \equiv \mathbb{Z}_{m} \cup \mathbb{Z}_{n}$., The CRT implies $\varphi(mn)=\varphi(m)\varphi(n)$ for $\mathsf{gcd}(m,n)=1$.
RSA can be accelerated by using CRT (Chinese Remainder Theorem)., An isomorphism is defined as a bijective homomorphism., The CRT states $\mathbb{Z}_{mn} \equiv \mathbb{Z}_{m} \cup \mathbb{Z}_{n}$., The CRT implies $\varphi(mn)=\varphi(m)\varphi(n)$ for $\mathsf{gcd}(m,n)=1$.
C
mcq_train
mcq_train_104
Question: What is the advantage of using a salt in a password authentication protocol? Options: It protects against online attacks., It avoids multi-target bruteforce attacks from the database., It avoids single-target exhaustive search attacks from the database., It makes the protocol more spicy.
It protects against online attacks., It avoids multi-target bruteforce attacks from the database., It avoids single-target exhaustive search attacks from the database., It makes the protocol more spicy.
B
mcq_train
mcq_train_105
Question: Select \emph{incorrect} statement. The birthday paradox Options: implies that in class of $23$ students we have two student with same birthday with approximately $50\%$ probability., can be used to find collisions in hash function., implies that in a list of $\Theta\sqrt{N}$ random numbers from $\mathbb{Z}_N$ we have at least one number twice with probability $1- e^{-{\Theta^2\over 2}}$., implies that majority of people is born at full moon.
implies that in class of $23$ students we have two student with same birthday with approximately $50\%$ probability., can be used to find collisions in hash function., implies that in a list of $\Theta\sqrt{N}$ random numbers from $\mathbb{Z}_N$ we have at least one number twice with probability $1- e^{-{\Theta^2\over 2}}$., implies that majority of people is born at full moon.
D
mcq_train
mcq_train_106
Question: Which scheme is the most secure? Options: DES., Two-key triple DES., Three-key triple DES., Double DES.
DES., Two-key triple DES., Three-key triple DES., Double DES.
A
mcq_train
mcq_train_107
Question: Tick the \emph{false} assertion concerning WPA-TKIP. Options: WPA-TKIP uses a fixed RC4 key., WPA-TKIP avoids replay attacks using a counter., WPA-TKIP provides much more confidentiality than WEP., WPA-TKIP doesn't protect well the integrity of the messages.
WPA-TKIP uses a fixed RC4 key., WPA-TKIP avoids replay attacks using a counter., WPA-TKIP provides much more confidentiality than WEP., WPA-TKIP doesn't protect well the integrity of the messages.
A
mcq_train
mcq_train_108
Question: Tick the \emph{correct} assertion. In ElGamal $\ldots$ Options: the encryption algorithm is deterministic., the key recovery problem is equivalent to the Computational Diffie Hellman problem., the size of the ciphertext is always bigger than the size of the corresponding plaintext., the decryption problem can be hard even if the discrete logarithm is easy to compute in the underlying group.
the encryption algorithm is deterministic., the key recovery problem is equivalent to the Computational Diffie Hellman problem., the size of the ciphertext is always bigger than the size of the corresponding plaintext., the decryption problem can be hard even if the discrete logarithm is easy to compute in the underlying group.
C
mcq_train
mcq_train_109
Question: One-time pad ... Options: never uses a key $K$ which is picked from a uniform distribution., pads the message at least once before encryption., allows an efficient key management., uses an invertible group operation such as ``$\oplus$" for encryption.
never uses a key $K$ which is picked from a uniform distribution., pads the message at least once before encryption., allows an efficient key management., uses an invertible group operation such as ``$\oplus$" for encryption.
D
mcq_train
mcq_train_110
Question: The Merkle-D{\aa}mgard construction is Options: a method which iterates a hash function to obtain a compression function., a method which iterates a compression function to obtain a hash function., a method which constructs a compression function from a block cipher., a method which constructs a block cipher function from a hash function.
a method which iterates a hash function to obtain a compression function., a method which iterates a compression function to obtain a hash function., a method which constructs a compression function from a block cipher., a method which constructs a block cipher function from a hash function.
B
mcq_train
mcq_train_111
Question: The Fermat Test outputs `maybe prime' with probability which may be high given though $n$ is composite when ... Options: $n$ is an even composite., $n$ is a Fermat number., $n$ is the multiplication of two primes., $n$ is a Carmichael number.
$n$ is an even composite., $n$ is a Fermat number., $n$ is the multiplication of two primes., $n$ is a Carmichael number.
D
mcq_train
mcq_train_112
Question: What should the minimal length of the output of a hash function be to provide security against \emph{collision attacks} of $2^{256}?$ Options: $2^{256}$ bits., $2^{512}$ bits., $256$ bits., $512$ bits.
$2^{256}$ bits., $2^{512}$ bits., $256$ bits., $512$ bits.
D
mcq_train
mcq_train_113
Question: Let $G$ be a group generated by $g$. What is the discrete logarithm problem? Options: find $y$ such that $g^x=y$ for a given $x$., find $x$ such that $g^x=y$ for a given $y$., find $x,y$ such that $g^x=y$., find $x,x'$ such that $g^x=g^{x'}$ and $x\ne x'$.
find $y$ such that $g^x=y$ for a given $x$., find $x$ such that $g^x=y$ for a given $y$., find $x,y$ such that $g^x=y$., find $x,x'$ such that $g^x=g^{x'}$ and $x\ne x'$.
B
mcq_train
mcq_train_114
Question: Bluetooth is \dots Options: a long-range wireless technology., first introduced by vikings., \emph{not} designed to transmit data., a short-range wireless technology.
a long-range wireless technology., first introduced by vikings., \emph{not} designed to transmit data., a short-range wireless technology.
D
mcq_train
mcq_train_115
Question: Tick the \emph{false} answer. In a group, the operation\dots Options: is commutative, is associative., has a neutral element., associates an inverse to each value.
is commutative, is associative., has a neutral element., associates an inverse to each value.
A
mcq_train
mcq_train_116
Question: Consider a public-key cryptosystem. Let $K_p$, $K_s$, $X$, and $Y$ be respectively the public key, private key, plaintext and ciphertext. Which assertion is \emph{always true}? Options: $Enc_{K_p}(Dec_{K_s}(X))=X$, $Enc_{K_s}(Dec_{K_p}(Y))=Y$, $Dec_{K_p}(Enc_{K_s}(Y))=Y$, $Dec_{K_s}(Enc_{K_p}(X))=X$
$Enc_{K_p}(Dec_{K_s}(X))=X$, $Enc_{K_s}(Dec_{K_p}(Y))=Y$, $Dec_{K_p}(Enc_{K_s}(Y))=Y$, $Dec_{K_s}(Enc_{K_p}(X))=X$
D
mcq_train
mcq_train_117
Question: Select the \emph{incorrect} statement. Euler Theorem Options: is a generalization of Little Fermat Theorem., states that any $x \in \{0, \dots, N-1 \}$ and any $k$, we have $x^{k\varphi(N)+1}=x \pmod N$, where $N=pq$ for $p$,$q$ distinct primes., gives the basis for polynomial time factoring., allows us to prove that RSA decryption works.
is a generalization of Little Fermat Theorem., states that any $x \in \{0, \dots, N-1 \}$ and any $k$, we have $x^{k\varphi(N)+1}=x \pmod N$, where $N=pq$ for $p$,$q$ distinct primes., gives the basis for polynomial time factoring., allows us to prove that RSA decryption works.
C
mcq_train
mcq_train_118
Question: Tick the \textit{correct} assertion. Options: In a finite field $K$, every element has exactly two square roots., In a finite field $K$, 1 has exactly one square roots and it is 1., The set of quadratic residues in $\mathbb{Z}_n$ is a field., An element can have more than two square roots in $\mathbb{Z}_n$.
In a finite field $K$, every element has exactly two square roots., In a finite field $K$, 1 has exactly one square roots and it is 1., The set of quadratic residues in $\mathbb{Z}_n$ is a field., An element can have more than two square roots in $\mathbb{Z}_n$.
D
mcq_train
mcq_train_119
Question: Let $p$ be a prime number and $n$ be an integer. What is the order of $\mathrm{GF}(p^n)$? Options: $p^n$, $p^n-1$, $p^{n-1}$, $1-p^n$
$p^n$, $p^n-1$, $p^{n-1}$, $1-p^n$
A
mcq_train
mcq_train_120
Question: Under which condition is an element $x\in \mathbb{Z}_n$ invertible? Options: $\mathsf{gcd}(x,\varphi (n)) = 1$., $\mathsf{gcd}(x,n-1) = 1$., $\mathsf{gcd}(x,n) = 1$., $\mathsf{gcd}(x,n) \ne 1$.
$\mathsf{gcd}(x,\varphi (n)) = 1$., $\mathsf{gcd}(x,n-1) = 1$., $\mathsf{gcd}(x,n) = 1$., $\mathsf{gcd}(x,n) \ne 1$.
C
mcq_train
mcq_train_121
Question: If Alice receives a message proven to be coming from Bob, we say that the message is\dots Options: confidential, fresh, authenticated, correct
confidential, fresh, authenticated, correct
C
mcq_train
mcq_train_122
Question: Which cryptographic primitive(s) is (are) used in S/Key - OTP ? Options: Only encryption and a hash function, Only encryption and a MAC algorithm, Only a hash function, Only a MAC
Only encryption and a hash function, Only encryption and a MAC algorithm, Only a hash function, Only a MAC
C
mcq_train
mcq_train_123
Question: Let $(e,N)$ be the public parameters of the RSA cryptosystem. What is the advantage of taking a \emph{small} value for $e$? Options: The complexity of the parameters generation is smaller., The complexity of the encryption step is smaller., The complexity of the decryption step is smaller., The whole system is stronger against several attacks.
The complexity of the parameters generation is smaller., The complexity of the encryption step is smaller., The complexity of the decryption step is smaller., The whole system is stronger against several attacks.
B
mcq_train
mcq_train_124
Question: Let $p$ and $q$ be two distinct prime numbers and let $x \in \mathbf{Z}_{pq}^*$. Which of the following assertion is always true in $\mathbf{Z}_{pq}^*$? Options: $x^{p} = 1$, $x^{q} = 1$, $x^{pq} = 1$, $x^{(p-1)(q-1)} = 1$
$x^{p} = 1$, $x^{q} = 1$, $x^{pq} = 1$, $x^{(p-1)(q-1)} = 1$
D
mcq_train
mcq_train_125
Question: Let $h$ be a cryptographic hash function based on the Merkle-Damg{\aa}rd scheme. The Merkle-Damg{\aa}rd Theorem states that\dots Options: \dots $h$ is collision-resistant., \dots $h$ is resistant to a first preimage attack., \dots if the compression function is collision-resistant, then $h$ is collision-resistant., \dots if $h$ is collision-resistant, then the compression function is collision-resistant.
\dots $h$ is collision-resistant., \dots $h$ is resistant to a first preimage attack., \dots if the compression function is collision-resistant, then $h$ is collision-resistant., \dots if $h$ is collision-resistant, then the compression function is collision-resistant.
C
mcq_train
mcq_train_126
Question: $\mathbb{Z}_{37}^*$ denotes ... Options: a field., an additive group., a multiplicative group., a ring.
a field., an additive group., a multiplicative group., a ring.
C
mcq_train
mcq_train_127
Question: Visual cryptography is a nice visual application of \ldots Options: \ldots the Vigen\`ere cipher., \ldots the Vernam cipher., \ldots the Caesar cipher., \ldots ROT13.
\ldots the Vigen\`ere cipher., \ldots the Vernam cipher., \ldots the Caesar cipher., \ldots ROT13.
B
mcq_train
mcq_train_128
Question: Select the \emph{incorrect} statement. Options: The order of an element is always multiple of the order of its group., An ideal $I$ of commutative ring $R$ is a subgroup closed under multiplication by all elements of $R$., Given a prime $p$, we have $a^{p} = a$ for every $a \in \mathbb{Z}_p$., Any element of order $\varphi(n)$ is a generator of $\mathbb{Z}_n^*$.
The order of an element is always multiple of the order of its group., An ideal $I$ of commutative ring $R$ is a subgroup closed under multiplication by all elements of $R$., Given a prime $p$, we have $a^{p} = a$ for every $a \in \mathbb{Z}_p$., Any element of order $\varphi(n)$ is a generator of $\mathbb{Z}_n^*$.
A
mcq_train
mcq_train_129
Question: Which one of these is a closed set? Options: $\mathbb{Z}$ with the addition., $\mathbb{Z}^\star$ with the addition., $\mathbb{Z}^\star$ with the substaction., $\mathbb{Z}-\{0\}$ with the division.
$\mathbb{Z}$ with the addition., $\mathbb{Z}^\star$ with the addition., $\mathbb{Z}^\star$ with the substaction., $\mathbb{Z}-\{0\}$ with the division.
A
mcq_train
mcq_train_130
Question: Tick the \textbf{incorrect} assertion. Options: ECDSA uses elliptic curves., PKCS\#1v1.5 uses plain RSA as an internal routine., An ECDSA signature consists in the message and a pair of elements in $\mathbb{Z}_n$., Subtraction is hard to perform on an elliptic curve.
ECDSA uses elliptic curves., PKCS\#1v1.5 uses plain RSA as an internal routine., An ECDSA signature consists in the message and a pair of elements in $\mathbb{Z}_n$., Subtraction is hard to perform on an elliptic curve.
D
mcq_train
mcq_train_131
Question: Select the \emph{correct} statement. The Plain RSA Signature scheme Options: has modulus $N=p^2$., has public modulus $e$ to be selected so that $\text{gcd} (e, \varphi(N)) > 1$., allows us to pick a fixed public key exponent like $e=3$ or $e=2^{16}+1$., has a secret modulus $d$ to be selected so that $e+d = 0 \pmod{\varphi(N)}$.
has modulus $N=p^2$., has public modulus $e$ to be selected so that $\text{gcd} (e, \varphi(N)) > 1$., allows us to pick a fixed public key exponent like $e=3$ or $e=2^{16}+1$., has a secret modulus $d$ to be selected so that $e+d = 0 \pmod{\varphi(N)}$.
C
mcq_train
mcq_train_132
Question: Which of the following is an element of $\mathbb{Z}_{60}^*$? Options: 49, 30, 26, 21
49, 30, 26, 21
A
mcq_train
mcq_train_133
Question: Which of the following algorithms is \emph{not} a hash function? Options: SHA-1, MD5, RC4, MD4
SHA-1, MD5, RC4, MD4
C
mcq_train
mcq_train_134
Question: Select the \emph{correct} answer. Options: The dictionary attack needs no precomputation., The dictionary attack has a memory complexity of order 1., The multi-target dictionary attack needs no precomputation., The success probability of the dictionary attack depends on the size of the dictionary.
The dictionary attack needs no precomputation., The dictionary attack has a memory complexity of order 1., The multi-target dictionary attack needs no precomputation., The success probability of the dictionary attack depends on the size of the dictionary.
D
mcq_train
mcq_train_135
Question: Tick the \emph{false} assertion. Given a ring $R$, $R^\star$ is\ldots Options: a group., the set of invertible elements in $R$., $R-\{0\}$., the set of units.
a group., the set of invertible elements in $R$., $R-\{0\}$., the set of units.
C
mcq_train
mcq_train_136
Question: Select the \emph{incorrect} statement. Bluetooth is Options: a short-range wireless technology., designed both for data and voice transmission., a standard for RFID tags., able to transmit 1Mbit/sec in 10m distance.
a short-range wireless technology., designed both for data and voice transmission., a standard for RFID tags., able to transmit 1Mbit/sec in 10m distance.
C
mcq_train
mcq_train_137
Question: Which cipher is AES? Options: SAFER, BLOWFISH, RIJNDAEL, RC5
SAFER, BLOWFISH, RIJNDAEL, RC5
C
mcq_train
mcq_train_138
Question: Which of the following algorithms is a stream cipher? Options: FOX, IDEA, RC4, AES
FOX, IDEA, RC4, AES
C
mcq_train
mcq_train_139
Question: Consider a public key cryptosystem. The channel used to transmit the public key has to be\dots Options: \dots encrypted., \dots authenticated., \dots confidential., \dots authenticated and confidential.
\dots encrypted., \dots authenticated., \dots confidential., \dots authenticated and confidential.
B
mcq_train
mcq_train_140
Question: KEM/DEM refers to\dots Options: an encryption scheme., a digital signature scheme., a commitment scheme., a hash function.
an encryption scheme., a digital signature scheme., a commitment scheme., a hash function.
A
mcq_train
mcq_train_141
Question: Tick the \textbf{false} statement. Options: The cardinality of $E_{a,b}(\mathsf{GF}(q))$ is bounded by $q+1+2\sqrt{q}$., $E_{a,b}$ is non-singular if $4a^3+27b^2 \neq 0$ over a finite field of characteristic $p>3$., In $(\mathsf{GF}(2^k))$, we have $\mathsf{Tr}(a+b)=\mathsf{Tr}(a)+\mathsf{Tr}(b)$., Two Elliptic curves cannot have the same $j$-invariant.
The cardinality of $E_{a,b}(\mathsf{GF}(q))$ is bounded by $q+1+2\sqrt{q}$., $E_{a,b}$ is non-singular if $4a^3+27b^2 \neq 0$ over a finite field of characteristic $p>3$., In $(\mathsf{GF}(2^k))$, we have $\mathsf{Tr}(a+b)=\mathsf{Tr}(a)+\mathsf{Tr}(b)$., Two Elliptic curves cannot have the same $j$-invariant.
D
mcq_train
mcq_train_142
Question: Select \emph{incorrect} statement. The brute force technique against a cipher with key $256$ bits is Options: impossible even if we can compute without burning an energy., impossible since the number of possible keys is too high $2^{256} \approx 10^{77}$., impossible in future even if we consider Moore's law., feasible using all clusters at EPFL.
impossible even if we can compute without burning an energy., impossible since the number of possible keys is too high $2^{256} \approx 10^{77}$., impossible in future even if we consider Moore's law., feasible using all clusters at EPFL.
D
mcq_train
mcq_train_143
Question: Select the \emph{weakest} algorithm. Options: A5/4, A5/2, A5/3, A5/1
A5/4, A5/2, A5/3, A5/1
B
mcq_train
mcq_train_144
Question: Tick the \textit{incorrect} assertion. Options: Plain CBCMAC resists forgery attacks., GCM is a blockcipher mode of operation that provides both confidentiality and authenticity for messages., A message authentication scheme that resists a chosen message forgery attack will also resist a known message forgery attack., HMAC is a message authentication code based on a hash function.
Plain CBCMAC resists forgery attacks., GCM is a blockcipher mode of operation that provides both confidentiality and authenticity for messages., A message authentication scheme that resists a chosen message forgery attack will also resist a known message forgery attack., HMAC is a message authentication code based on a hash function.
A
mcq_train
mcq_train_145
Question: The Moore law Options: implies the key size is doubled every every 18 months to preserve confidentiality, says that CPU speed doubles every 18 months, has no relevance for cryptography since it only considers speed of computation, states that anything that can go wrong will
implies the key size is doubled every every 18 months to preserve confidentiality, says that CPU speed doubles every 18 months, has no relevance for cryptography since it only considers speed of computation, states that anything that can go wrong will
B
mcq_train
mcq_train_146
Question: Select the \emph{incorrect} statement. The Bluetooth project aims for Options: low complexity., low power., low cost., low security.
low complexity., low power., low cost., low security.
D
mcq_train
mcq_train_147
Question: Tick the \emph{false} assertion. The ambiguity issue in the decryption algorithm of the Rabin cryptosystem can be solved by\dots Options: encrypting the message twice., encrypting the message appended to itself., appending some integrity checks to the message before encryption., ensuring that the other possible plaintexts make no sense.
encrypting the message twice., encrypting the message appended to itself., appending some integrity checks to the message before encryption., ensuring that the other possible plaintexts make no sense.
A
mcq_train
mcq_train_148
Question: What is the order of $2^{124}$ in $(\mathbb{Z}_{2^{128}},+)$? Options: 8., $\varphi(2^{128})$., 124., 16.
8., $\varphi(2^{128})$., 124., 16.
D
mcq_train
mcq_train_149
Question: Which problem in communication is \emph{not} treated by cryptography? Options: confidentiality, integrity, authenthication, data transmission
confidentiality, integrity, authenthication, data transmission
D
mcq_train
mcq_train_150
Question: What are the complexities for the single-target dictionary attacks, when there are $N$ keys? Options: Preprocessing: $N$, Memory: $N$, Time: 1, Preprocessing: $N$, Memory: $1$, Time: $N$, Preprocessing: $1$, Memory: $N$, Time: $N$, Preprocessing: $0$, Memory: $1$, Time: $\sqrt{N}$
Preprocessing: $N$, Memory: $N$, Time: 1, Preprocessing: $N$, Memory: $1$, Time: $N$, Preprocessing: $1$, Memory: $N$, Time: $N$, Preprocessing: $0$, Memory: $1$, Time: $\sqrt{N}$
A
mcq_train
mcq_train_151
Question: Tick the \emph{incorrect} assertion. The Diffie-Hellman key agreement protocol \ldots Options: allows two participants to set up a key so that they can communicate securely., requires the hardness of the Discrete Logarithm problem., uses ElGamal encryption in order to establish the key., is easy to break when working on the group $\mathbf{Z}_{n}$.
allows two participants to set up a key so that they can communicate securely., requires the hardness of the Discrete Logarithm problem., uses ElGamal encryption in order to establish the key., is easy to break when working on the group $\mathbf{Z}_{n}$.
C
mcq_train
mcq_train_152
Question: Which of these components was not part of the Enigma machine? Options: A reflector, A pseudo-random number generator, A Rotor, A plugboard with a wire connection
A reflector, A pseudo-random number generator, A Rotor, A plugboard with a wire connection
B
mcq_train
mcq_train_153
Question: Consider password-based access control. Tick the \textit{incorrect} assertion. Options: Double hashing the password can help avoid the problems related to low-entropy passwords., Salt can be used to thwart multi-target attacks., Increasing the delay between authentication attempts can protect from online attacks., Blocking the access after 10 unsuccessful authentication attempts can protect from online attacks.
Double hashing the password can help avoid the problems related to low-entropy passwords., Salt can be used to thwart multi-target attacks., Increasing the delay between authentication attempts can protect from online attacks., Blocking the access after 10 unsuccessful authentication attempts can protect from online attacks.
A
mcq_train
mcq_train_154
Question: Select the \emph{incorrect} statement. In ElGamal signature Options: public parameters are a prime number $p$ and a generator $g$ of $\mathbb{Z}_p^*$., the public key is $K_p = y = g^x$, where $x$ is the secret key., verification checks whether $y^rr^s=g^{H(M)}$ for signature $\sigma=(r, s)$ of the message $M$ and the hash function $H$., requires a secure channel to transfer the signature.
public parameters are a prime number $p$ and a generator $g$ of $\mathbb{Z}_p^*$., the public key is $K_p = y = g^x$, where $x$ is the secret key., verification checks whether $y^rr^s=g^{H(M)}$ for signature $\sigma=(r, s)$ of the message $M$ and the hash function $H$., requires a secure channel to transfer the signature.
D
mcq_train
mcq_train_155
Question: You are given the task of choosing the parameters of a hash function. What value of the output will you recommend in order to be minimal and secure against second preimage attacks? Options: 40 bits, 80 bits, 160 bits, 320 bits
40 bits, 80 bits, 160 bits, 320 bits
C
mcq_train
mcq_train_156
Question: $\mathrm{GF}(2^k)$ is represented by the set of\dots Options: polynomials of degree at most $k-1$ with binary coefficients., polynomials of degree at most $k-1$ with coefficients in $\mathbb{Z}_k$., polynomials of degree at most $2^k$ with coefficients in $\mathbb{Z}$., polynomials of degree at most $2$ with coefficients in $\mathbb{Z}_k$.
polynomials of degree at most $k-1$ with binary coefficients., polynomials of degree at most $k-1$ with coefficients in $\mathbb{Z}_k$., polynomials of degree at most $2^k$ with coefficients in $\mathbb{Z}$., polynomials of degree at most $2$ with coefficients in $\mathbb{Z}_k$.
A
mcq_train
mcq_train_157
Question: Thick the \emph{incorrect} assertion. Options: The goal of SAS-based cryptography is to reduce the length of the string that has to be authenticated., One way to authenticate a SAS is to use your phone., One can obtain a secure channel from a narrowband authenticated channel using SAS-based cryptography., SAS-based cryptography always requires the SAS to be collision-resistant.
The goal of SAS-based cryptography is to reduce the length of the string that has to be authenticated., One way to authenticate a SAS is to use your phone., One can obtain a secure channel from a narrowband authenticated channel using SAS-based cryptography., SAS-based cryptography always requires the SAS to be collision-resistant.
D
mcq_train
mcq_train_158
Question: According to the Kerckhoffs Principle: Options: The internal design of a cryptosystem should be public., The internal design of a cryptosystem should \emph{not} be public., If there is a single security hole in a cryptosystem, somebody will discover it., The security of the cryptosystem should \emph{not} rely on the secrecy of the cryptosystem itself.
The internal design of a cryptosystem should be public., The internal design of a cryptosystem should \emph{not} be public., If there is a single security hole in a cryptosystem, somebody will discover it., The security of the cryptosystem should \emph{not} rely on the secrecy of the cryptosystem itself.
D
mcq_train
mcq_train_159
Question: KEM \dots Options: stands for Keyless Encryption Mechanism., is a Korean encryption mechanism., is a symmetric-key algorithm., is a public-key algorithm.
stands for Keyless Encryption Mechanism., is a Korean encryption mechanism., is a symmetric-key algorithm., is a public-key algorithm.
D
mcq_train
mcq_train_160
Question: Tick the \emph{false} assertion. Two-keys triple DES\dots Options: is more secure than double encryption., is less secure than AES., is as secure as a block cipher using a key twice longer., is vulnerable to a certain variant of a meet-in-the-middle attacks.
is more secure than double encryption., is less secure than AES., is as secure as a block cipher using a key twice longer., is vulnerable to a certain variant of a meet-in-the-middle attacks.
C
mcq_train
mcq_train_161
Question: Tick the \textbf{true} statement regarding $\mathbb{Z}_p^*$, where $p$ is an arbitrary prime number. Options: It is a group of prime order when $p>3$., It has $\varphi(p-1)$ generators., For any $x \in \mathbb{Z}_p^*$ we have $x^{p}=1 \pmod p$, It is isomorphic to $\mathbb{Z}_n^*$ for all $n >0$.
It is a group of prime order when $p>3$., It has $\varphi(p-1)$ generators., For any $x \in \mathbb{Z}_p^*$ we have $x^{p}=1 \pmod p$, It is isomorphic to $\mathbb{Z}_n^*$ for all $n >0$.
B
mcq_train
mcq_train_162
Question: Tick the \textbf{false} statement regarding the DES round function. Options: There is an expansion operation $E$ from 32 to 48 bits., A round key is XORed to an internal register., There are $8$ identical S-boxes (substitution boxes) of size $6 \times 4$., There is a permutation $P$ on 32-bits.
There is an expansion operation $E$ from 32 to 48 bits., A round key is XORed to an internal register., There are $8$ identical S-boxes (substitution boxes) of size $6 \times 4$., There is a permutation $P$ on 32-bits.
C
mcq_train
mcq_train_163
Question: Which of the following ciphers is based on arithmetics over the finite field $\mathrm{GF}(2^8)$? Options: AES, DES, A5/1, RC4
AES, DES, A5/1, RC4
A
mcq_train
mcq_train_164
Question: Ensuring the information integrity means that\dots Options: \dots the information should not leak to any unexpected party., \dots the information must be protected against any malicious modification., \dots the information should make clear who the author of it is., \dots DES is secure.
\dots the information should not leak to any unexpected party., \dots the information must be protected against any malicious modification., \dots the information should make clear who the author of it is., \dots DES is secure.
B
mcq_train
mcq_train_165
Question: Given an odd prime $p$, for any $a \in \mathbb{Z}_p$ the equation Options: $x^2 - a = 0$ always has a solution., $x^2 - a = 0$ has exactly two solutions., $x^2 - a = 0$ has at most two solutions., $x^2 - a = 0$ may have four solutions.
$x^2 - a = 0$ always has a solution., $x^2 - a = 0$ has exactly two solutions., $x^2 - a = 0$ has at most two solutions., $x^2 - a = 0$ may have four solutions.
C
mcq_train
mcq_train_166
Question: Which one of the following notions is not in the fundamental trilogy of cryptography? Options: authentication, confidentiality, integrity, privacy
authentication, confidentiality, integrity, privacy
D
mcq_train
mcq_train_167
Question: Consider a mobile station (MS) with a SIM card associated to a home network (HN). The MS tries to connect to a visited network (VN). In the GSM authentication, who knows the key $K_i$? Options: SIM only., SIM and HN., SIM, MS and HN., SIM, MS, VN and HN.
SIM only., SIM and HN., SIM, MS and HN., SIM, MS, VN and HN.
B
mcq_train
mcq_train_168
Question: Select \emph{incorrect} statement. Brithday paradox Options: is a brute force technique., can be implemented with constant memory using Rho ($\rho$) method., is used to recover the secret key of AES in $2^{64}$ computations., can be implemented using a table of size $\Theta\sqrt{N}$
is a brute force technique., can be implemented with constant memory using Rho ($\rho$) method., is used to recover the secret key of AES in $2^{64}$ computations., can be implemented using a table of size $\Theta\sqrt{N}$
C
mcq_train
mcq_train_169
Question: The Kerckhoffs principle says: Options: security should not rely on the secrecy of the key., the speed of CPUs doubles every 18 months, cryptosystems must be published., security should not rely on the secrecy of the cryptosystem itself.
security should not rely on the secrecy of the key., the speed of CPUs doubles every 18 months, cryptosystems must be published., security should not rely on the secrecy of the cryptosystem itself.
D
mcq_train
mcq_train_170
Question: Tick the \emph{correct} assertion. The Vernam cipher provides \dots Options: authenticity., integrity., confidentiality., none of the mentioned properties.
authenticity., integrity., confidentiality., none of the mentioned properties.
C
mcq_train
mcq_train_171
Question: What is the average complexity of exhaustive search when the key is distributed uniformly at random over $N$ keys? Options: $\log N$, $2^N$, $\frac{N+1}{2}$, $\sqrt{N}$
$\log N$, $2^N$, $\frac{N+1}{2}$, $\sqrt{N}$
C
mcq_train
mcq_train_172
Question: Select \emph{incorrect} statement. Generic attacks on DES include Options: time memory tradeof against 2 key Triple DES., collision attack against 3 key Triple DES., meet in the middle attack against 3 key Triple DES., known plaintext attack by Van Oorschot-Wiener agains 2 key Triple DES.
time memory tradeof against 2 key Triple DES., collision attack against 3 key Triple DES., meet in the middle attack against 3 key Triple DES., known plaintext attack by Van Oorschot-Wiener agains 2 key Triple DES.
B
mcq_train
mcq_train_173
Question: AES\dots Options: \dots has a variable key length \emph{and} a variable block length., \dots has a variable key length \emph{and} a fixed block length., \dots has a fixed key length \emph{and} a variable block length., \dots has a fixed key length \emph{and} a fixed block length.
\dots has a variable key length \emph{and} a variable block length., \dots has a variable key length \emph{and} a fixed block length., \dots has a fixed key length \emph{and} a variable block length., \dots has a fixed key length \emph{and} a fixed block length.
B
mcq_train
mcq_train_174
Question: Given that $100000000003$ is prime, what is the cardinality of $\mathbf{Z}_{200000000006}^*$? Options: $2$, $100000000002$, $100000000003$, $200000000006$
$2$, $100000000002$, $100000000003$, $200000000006$
B
mcq_train
mcq_train_175
Question: Select the \emph{incorrect} statement. Elliptic Curve Diffie-Hellman is Options: based on the difficulty of factoring the polynomial of EC., based on the difficulty of computing the discrete logarithm in EC., used in Bluetooth 2.1., used for epassports.
based on the difficulty of factoring the polynomial of EC., based on the difficulty of computing the discrete logarithm in EC., used in Bluetooth 2.1., used for epassports.
A
mcq_train
mcq_train_176
Question: In which attack scenario does the adversary ask for the decryption of selected messages? Options: Known plaintext attack, Chosen plaintext attack, Ciphertext only attack, Chosen ciphertext attack
Known plaintext attack, Chosen plaintext attack, Ciphertext only attack, Chosen ciphertext attack
D
mcq_train
mcq_train_177
Question: An element of the finite field $\mathrm{GF}(2^8)$ is usually represented by\dots Options: \dots one hexadecimal digit., \dots eight bytes., \dots two hexadecimal digits., \dots an irreducible polynomial of degree 8.
\dots one hexadecimal digit., \dots eight bytes., \dots two hexadecimal digits., \dots an irreducible polynomial of degree 8.
C
mcq_train
mcq_train_178
Question: Consider $GF(8)$ defined as $\mathbb{Z}_2[X]/(P(X))$ with $P(x) = X^3 + X + 1$. Compute $X^2 \times (X + 1)$ in $\mathbb{Z}_2[X]/(P(X))$ Options: $X^2+X+1$., $X^2 + 1$., $X^2$., $X+1$.
$X^2+X+1$., $X^2 + 1$., $X^2$., $X+1$.
A
mcq_train
mcq_train_179
Question: Let $n$ be a positive integer. An element $x \in \mathbb{Z}_n$ is \emph{always} invertible when \dots Options: $x$ and $n$ are coprime., $x$ and $\varphi(n)$ are coprime., $x$ is even., $n$ is prime.
$x$ and $n$ are coprime., $x$ and $\varphi(n)$ are coprime., $x$ is even., $n$ is prime.
A
mcq_train
mcq_train_180
Question: Which of these attacks applies to the Diffie-Hellman key exchange when the channel cannot be authenticated? Options: Meet-in-the-middle attack, Birthday Paradox, Attack on low exponents, Man-in-the-middle attack
Meet-in-the-middle attack, Birthday Paradox, Attack on low exponents, Man-in-the-middle attack
D
mcq_train
mcq_train_181
Question: Which of the following is an acceptable commitment scheme, i.e., one that verifies the hiding and binding property (for a well chosen primitive and suitable $x$ and $r$): Options: $Commit(x;r) = Enc_r(x)$, where $Enc_r$ is a symmetric encryption scheme with key $r$., $Commit(x;r) = H(x)$, where $H$ is a hash function., $Commit(x;r) = x \oplus r$, where $\oplus$ is the bitwise xor operation., $Commit(x;r) = H(r\|x)$, where $H$ is a hash function and $\|$ denotes the concatenation.
$Commit(x;r) = Enc_r(x)$, where $Enc_r$ is a symmetric encryption scheme with key $r$., $Commit(x;r) = H(x)$, where $H$ is a hash function., $Commit(x;r) = x \oplus r$, where $\oplus$ is the bitwise xor operation., $Commit(x;r) = H(r\|x)$, where $H$ is a hash function and $\|$ denotes the concatenation.
D
mcq_train
mcq_train_182
Question: A 128-bit key ... Options: has 128 decimal digits., is too long for any practical application., provides reasonable security for at least four decades., adresses $n^2$ problem for $n=2^{64}$.
has 128 decimal digits., is too long for any practical application., provides reasonable security for at least four decades., adresses $n^2$ problem for $n=2^{64}$.
C
mcq_train
mcq_train_183
Question: Consider a hash function $H$ with $n$ output bits. Tick the \emph{incorrect} assertion. Options: Due to birthday paradox, an output collision of $H$ can be found much faster than with running time $2^n$., It is possible to find an output collision of $H$ with $O(2^{\frac{n}{2}})$ memory and $O(2^{\frac{n}{2}})$ running time., It is possible to find an output collision of $H$ with $O(1)$ memory and $O(2^{\frac{n}{2}})$ running time., It is possible to find an output collision of $H$ with $O(2^{\frac{n}{2}})$ memory and $O(1)$ running time.
Due to birthday paradox, an output collision of $H$ can be found much faster than with running time $2^n$., It is possible to find an output collision of $H$ with $O(2^{\frac{n}{2}})$ memory and $O(2^{\frac{n}{2}})$ running time., It is possible to find an output collision of $H$ with $O(1)$ memory and $O(2^{\frac{n}{2}})$ running time., It is possible to find an output collision of $H$ with $O(2^{\frac{n}{2}})$ memory and $O(1)$ running time.
D
mcq_train
mcq_train_184
Question: Enigma Options: was a predecessor of a Turing machine model - a basis of Von Neumann architecture, achieves perfect security as was required due to military application, follows the Kerkhoffs principle, has approximately $2^{256}$ possible keys
was a predecessor of a Turing machine model - a basis of Von Neumann architecture, achieves perfect security as was required due to military application, follows the Kerkhoffs principle, has approximately $2^{256}$ possible keys
C
mcq_train
mcq_train_185
Question: Tick the \emph{incorrect} assertion. In RSA with public key $(e,N)$ and private key $(d,N)$ \ldots Options: we can recover $d$ if we can compute square root modulo $N$ efficiently., $e=3$ can be a valid choice of the public key-exponent., to decrypt a ciphertext $c$, we compute $c^d \bmod{N}$., we must have that $\gcd(e,d) = 1$ to be able to decrypt unambiguously.
we can recover $d$ if we can compute square root modulo $N$ efficiently., $e=3$ can be a valid choice of the public key-exponent., to decrypt a ciphertext $c$, we compute $c^d \bmod{N}$., we must have that $\gcd(e,d) = 1$ to be able to decrypt unambiguously.
D
mcq_train
mcq_train_186
Question: Tick the \emph{false} assertion concerning WEP Options: In WEP, encryption is based on RC4., In WEP, IVs repeat themselves too often., In WEP, encryption is based on a block cipher., WPA-TKIP was designed as a quick fix for WEP.
In WEP, encryption is based on RC4., In WEP, IVs repeat themselves too often., In WEP, encryption is based on a block cipher., WPA-TKIP was designed as a quick fix for WEP.
C
mcq_train
mcq_train_187
Question: Let $n$ be an integer. Which of the following is \emph{not} a group in the general case? Options: $(\mathbf{R},+)$, $(\mathbf{Q}\setminus \{0\},\times)$, $(\mathbf{Z}_n,+ \pmod{n})$, $(\mathbf{Z}_n,\times \pmod{n})$
$(\mathbf{R},+)$, $(\mathbf{Q}\setminus \{0\},\times)$, $(\mathbf{Z}_n,+ \pmod{n})$, $(\mathbf{Z}_n,\times \pmod{n})$
D
mcq_train
mcq_train_188
Question: Tick the \textbf{true} statement. Options: If $x \in \mathbb{Z}_n^*$ has an order of $m$, then $x^i \equiv x^{i \pmod{m}} \pmod{n} $ for all $i\in \mathbb{Z}$., For all $x \in \mathbb{Z}_n$, we have $x^{\varphi(n)}\equiv 1 \pmod{n}$., For all $n \geq 2$, $\mathbb{Z}_n^*$ has order of $n-1$., For all $n \geq 2$ and all $x \in \mathbb{Z}_n$, $x$ is invertible if and only if $x$ divides $n$.
If $x \in \mathbb{Z}_n^*$ has an order of $m$, then $x^i \equiv x^{i \pmod{m}} \pmod{n} $ for all $i\in \mathbb{Z}$., For all $x \in \mathbb{Z}_n$, we have $x^{\varphi(n)}\equiv 1 \pmod{n}$., For all $n \geq 2$, $\mathbb{Z}_n^*$ has order of $n-1$., For all $n \geq 2$ and all $x \in \mathbb{Z}_n$, $x$ is invertible if and only if $x$ divides $n$.
A
mcq_train
mcq_train_189
Question: What is $\varphi(48)$? Options: $47$, $16$, $24$, $30$
$47$, $16$, $24$, $30$
B
mcq_train
mcq_train_190
Question: Tick the true assertion. Options: A dictionary attack requires less memory than a time-memory tradeoff., Double-DES succumbs under a Meet-in-the-Middle attack., AES is the ancestor of DES., IDEA has the same round functions as DES.
A dictionary attack requires less memory than a time-memory tradeoff., Double-DES succumbs under a Meet-in-the-Middle attack., AES is the ancestor of DES., IDEA has the same round functions as DES.
B
mcq_train
mcq_train_191
Question: Tick the \emph{correct} assertion. Options: MD5 is using a compression function based on the Davies-Meyer scheme., The Keccak hash function is based on the Merkle-Damg{\aa}rd construction., Plain CBCMAC is resistant to forgery attacks., GCM is an efficient MAC based on the CBC mode.
MD5 is using a compression function based on the Davies-Meyer scheme., The Keccak hash function is based on the Merkle-Damg{\aa}rd construction., Plain CBCMAC is resistant to forgery attacks., GCM is an efficient MAC based on the CBC mode.
A
mcq_train
mcq_train_192
Question: The Time-Memory Tradeoff Attack ... Options: is useful for finding a preimage within complexity $O\big(\big({\frac{2}{3}}\big)^N\big).$, is useful for finding a preimage within complexity $O(N^{\frac{2}{3}}).$, is a dedicated method which works only on SHA1., can be combined with birthday paradox to find the order of the group in RSA efficiently.
is useful for finding a preimage within complexity $O\big(\big({\frac{2}{3}}\big)^N\big).$, is useful for finding a preimage within complexity $O(N^{\frac{2}{3}}).$, is a dedicated method which works only on SHA1., can be combined with birthday paradox to find the order of the group in RSA efficiently.
B
mcq_train
mcq_train_193
Question: Let $f: \mathbb{Z}_{m n} \rightarrow \mathbb{Z}_m \times \mathbb{Z}_n$ be defined by $f (x) = (x \bmod m,x \bmod n)$. Then $f$ is a ring isomorphism between $\mathbb{Z}_{180}$ and: Options: $\mathbb{Z}_{2} \times \mathbb{Z}_{90}$., $\mathbb{Z}_{4} \times \mathbb{Z}_{45}$., $\mathbb{Z}_{10} \times \mathbb{Z}_{18}$., $\mathbb{Z}_{6} \times \mathbb{Z}_{30}$.
$\mathbb{Z}_{2} \times \mathbb{Z}_{90}$., $\mathbb{Z}_{4} \times \mathbb{Z}_{45}$., $\mathbb{Z}_{10} \times \mathbb{Z}_{18}$., $\mathbb{Z}_{6} \times \mathbb{Z}_{30}$.
B
mcq_train
mcq_train_194
Question: A Carmichael number $n$ ... Options: is a prime number., will always pass Fermat's test for any $0 < b < n$., verifies that $\forall b$, $\mathsf{gcd}(b,n)=1$ implies that $b^{n-1} \equiv 1 \ \pmod n $., will be considered as a prime by the Miller-Rabin algorithm.
is a prime number., will always pass Fermat's test for any $0 < b < n$., verifies that $\forall b$, $\mathsf{gcd}(b,n)=1$ implies that $b^{n-1} \equiv 1 \ \pmod n $., will be considered as a prime by the Miller-Rabin algorithm.
C
mcq_train
mcq_train_195
Question: Which symmetric key primitive is used in WPA2 encryption? Options: RC4 CBC Mode, KASUMI ECB Mode, MD5 OFB Mode, AES CCM Mode
RC4 CBC Mode, KASUMI ECB Mode, MD5 OFB Mode, AES CCM Mode
D
mcq_train
mcq_train_196
Question: Let $n$ be an integer. What is the cardinality of $\mathbf{Z}^*_n$? Options: $n$, $n-1$, $\varphi(n)$, $\varphi(n-1)$
$n$, $n-1$, $\varphi(n)$, $\varphi(n-1)$
C
mcq_train
mcq_train_197
Question: Let $n$ be any positive integer. Three of the following assertions are equivalent. Tick the remaining one. Options: $\mathbb{Z}_n$ is a field., $\varphi(n)=n-1 $, where $\varphi$ denotes the Euler totient function., $n$ is a prime power., Any element $x \in \mathbb{Z}_n \backslash \{0\}$ is invertible.
$\mathbb{Z}_n$ is a field., $\varphi(n)=n-1 $, where $\varphi$ denotes the Euler totient function., $n$ is a prime power., Any element $x \in \mathbb{Z}_n \backslash \{0\}$ is invertible.
C
mcq_train
mcq_train_198
Question: Birthday attacks \dots Options: are used to break Google Calendars., can be used to find collisions in hash functions., are equivalent to exhaustive search., imply that a majority of people is born in Spring.
are used to break Google Calendars., can be used to find collisions in hash functions., are equivalent to exhaustive search., imply that a majority of people is born in Spring.
B
mcq_train
mcq_train_199
Question: What is the number of secret bits in a WEP key? Options: 64 or 128 bits., 40 or 104 bits., 64 or 128 bytes., 40 or 104 bytes.
64 or 128 bits., 40 or 104 bits., 64 or 128 bytes., 40 or 104 bytes.
B
mcq_train
mcq_train_200
Question: Tick the \emph{incorrect} assertion. In a multiplicative cyclic group $G$ of order $m > 1$ with neutral element $e_G$ \ldots Options: $\lambda = m$, where $\lambda$ is the exponent of $G$., the order of every element $x \in G$ is $m$., there exists $g \in G$ that generates the whole group., for any $x \in G$, we have that $x^m = e_{G}$.
$\lambda = m$, where $\lambda$ is the exponent of $G$., the order of every element $x \in G$ is $m$., there exists $g \in G$ that generates the whole group., for any $x \in G$, we have that $x^m = e_{G}$.
B