computer security fundamentals
In the context of Cryptography the initials C, I, A are used? What does A stand for?
Availability
What is the difference between Block and Stream ciphers?
Block ciphers encrypt blocks of data at the same time (128 or 64 bits) cannot extract the info that you want until you encrypted the whole block, may have to wait. Stream ciphers are encrypted bit-by-bit and is on real time.
In C.I.A. What does the "I" stand for?
Integrity
The Multiple Access (MA) Problem. Base Stations need to serve many cellphones at the same time. We need a multiple access (MA) scheme, that must address the interference among different cellphones. For this purpose there are several technologies that can be used (and combined). Below we describe their functionality at a high level that captures their basic functionality a. "everyone talks quietly so that only their neighbors can hear" b. "everyone talks in a different room to prevent interference" c. "everyone takes turns to talk" d. "everyone speaks in a different language" The technologies that are modeled by these descriptions are called (in a randomized order): Time Division MA (TDMA), Frequency Division MA (FDMA), Code Division MA (CDMA) and Space Division MA (SDMA). Which one of the four high level descriptions above corresponds to: Space Division MA (SDMA) ?
a
The elements of the Galois field G F ( 2 8 ) can be written as bytes, pairs of HEX numbers, or polynomials. The addition is binary while the multiplication is polynomial modulo an irreducible polynomial p ( x ) . We shall take this polynomial to be p ( x ) = x 8 + x 4 + x 3 + x + 1. Consider three bytes of G F ( 2 8 ): X 1 = 00000010 , X 2 = 00000100 and X 3 = 01110000 . What is the product X 1 ⋅ X 3 as a polynomial and a HEX pair? a. x 7 + x 6 + x 5 , [E0] b. x 6 + x 5 + x 4 , [70] c. x 7 + x 6 + x 5 , [D0]
a
The elements of the field G F ( 2 8 ) can be written as polynomials, e.g., x 7 + x 5 + x + 1, as bytes 10100011, or as pairs of HEX numbers A 3. Suppose that the (irreducible) polynomial: x 8 + x 4 + x 3 + x + 1 is used. Consider the two elements X = 00000010 and Y = 00110000 . What is the HEX representation of X and Y ? a. 02 and 30 b. 10 and 30 c. 20 and 03
a
The motivation for the Feistel cipher is that the key size of an n-bit to n-bit block substitution is very large. How many different n-bit block to n-bit block mappings (substitutions) are there? a. ( 2^n )^2^n b. log 2( 2^n ) ! c. (2^n)! d. n × 2^n
a
Two techniques are used for symmetric key encryption: substitution and transposition. a. Substitution is used to establish confusion. b. Substitution is used to establish diffusion.
a
Two techniques are used for symmetric key encryption: substitution and transposition. a. Transposition is used to establish diffusion. b. Transposition is used to establish confusion.
a
We discussed 4 basic types of attacks on encryption schemes: in each one of them the adversary has some knowledge and uses this to attack (break) the system. This knowledge involves one or more of the following: EA: the encryption algorithm; C: ciphertexts; (P,C): plaintext-ciphertext corresponding pairs; (P,C) known P : known plaintexts with their corresponding ciphertext pairs; (P,C)chosen P : chosen plaintexts with their corresponding ciphertext pairs; (C,P)chosen C : chosen ciphertexts with their corresponding plaintext pairs. 1. In a ciphertext only attack the adversary has access to: a. EA and some C b. C and some (P,C) c. EA and (P,C) known P
a
We discussed in class 3 digital signature schemes: the ElGamal scheme, the Schnorr scheme and the DSA. The last one builds on the first two. The quiz concerns the lengths (in bits) of these schemes. As with all MACs digital schemes use a hash function to reduce the size of the message. These schemes use a modulus that is a prime number that is typically 1,024 bits long. For a 1,024 bit prime number modulus the length of an ElGamal digital signature is: a. 2,048 bits long b. 1, 184 bits long c. other
a
We discussed in class 5 modes of operation for block ciphers: Electronic Codebook (ECB), Cipher Block Chaining (CBC), Cipher Feedback (CFB), Output Feedback (OFB) and Counter (CTR). In one of the simplest modes of encryption each plaintext is encrypted separately, so that each ciphertext block is decrypted separately. What is this mode of encryption called. a. ECB b. CBC c. CFB d. OFB e. CTR
a
What encryption operations are used in RC4? a. DES and XOR b. modulo operation and byte swapping c. byte swapping and transposition
a
In each round AES uses four different operations to process a 4 byte by 4 byte array: a. Substitution bytes, b. ShiftRows, c. MixColumns and d. AddRoundKey. Two of these makes use of arithmetic over GF(28 )?
a and c
In each round, AES uses four different operations to process a 4-byte by 4-byte array: a. Substitution bytes, b. ShiftRows, c. MixColumns and d. AddRoundKey. In which one of these is the key bitwise XORed with the 4-byte by 4-byte array?
d
The Multiple Access (MA) Problem. Base Stations need to serve many cellphones at the same time. We need a multiple access (MA) scheme, that must address the interference among different cellphones. For this purpose there are several technologies that can be used (and combined). Below we describe their functionality at a high level that captures their basic functionality a. "everyone talks quietly so that only their neighbors can hear" b. "everyone talks in a different room to prevent interference" c. "everyone takes turns to talk" d. "everyone speaks in a different language" The technologies that are modeled by these descriptions are called (in a randomized order): Time Division MA (TDMA), Frequency Division MA (FDMA), Code Division MA (CDMA) and Space Division MA (SDMA). Which one of the four high level descriptions above corresponds to: Code Division MA (CDMA) ?
d
What is the key size of an n-bit to n-bit block substitution (the length of its description) ? a. ( 2^n )^2^n b. log 2( 2^n ) ! c. (2^n)! d. n × 2^n
d
A small change in the encryption key or the plaintext should produce a small change in the ciphertext.
false
We have symmetric and asymmetric (public key) encryption. What can you say about the encryption and decryption keys of symmetric encryption, Are they the same?
same
Diffusion dissipates the statistics of the plaintext into the statistics of the ciphertext.
true
The AES cipher begins with an AddRoundKey operation.
true
In the Galois field G F ( 11 ) the (multiplicative) the value of x in 2 x = 9 is (one of):
x = 10
This question concerns Code Division Multiple Access (CDMA). Sender 1 is assigned code1 = (1,-1) and sender 2 is assigned code2 = (1,1) (these are orthogonal (1,−1)∗(1,1)=1−1=0(1,−1)∗(1,1)=1−1=0 ). Sender 1 wants to transmit data (1,1,1,0), while sender 2 wants to transmit data (1,0,1,0). The senders first encode their data by replacing 0 by -1. Then they encode them using their assigned codes (this will double the length of their data to 8 bits). What is the (combined) raw signal?
(0,-2,2,0,0,-2,0,2)
[01]⋅ [02]
02
[01]⋅ [0a]
0a
The 10 First Principles of Cybersecurity 1. Domain Separation 2. Process Isolation 3. Resource Encapsulation 4. Least privilege 5. Layering 6. Abstraction 7. Information Hiding 8. Modularity 9. Simplicity 10. Minimization For which one does the following apply: "areas where resources are located are separated to prevent accidents and loss of data".
1. Domain Separation
The 10 First Principles of Cybersecurity 1. Domain Separation 2. Process Isolation 3. Resource Encapsulation 4. Least privilege 5. Layering 6. Abstraction 7. Information Hiding 8. Modularity 9. Simplicity 10. Minimization Which one limits what access people have to your resources.
4. Least Privilege
Find an integer that satisfies the equation: 3 x ≡ 4 ( mod 7 )
6
The 10 First Principles of Cybersecurity 1. Domain Separation 2. Process Isolation 3. Resource Encapsulation 4. Least privilege 5. Layering 6. Abstraction 7. Information Hiding 8. Modularity 9. Simplicity 10. Minimization For which number "X" is the following true: "Current mobile phones do not satisfy the X Principle. If a part breaks, the device will most likely have to be replaced. iPhone is a good example: if a hardware part breaks, it cannot easily be fixed".
8. Modularity
In the Galois field G F ( 11 ) the (multiplicative) inverse of 5 is (one of):
9
In the context of Cryptography the initials C, I, A are used? What does C stand for?
Confidentiality
Base Stations need to serve many mobile terminals at the same time. We need a multiple access scheme that allows cellphones to transmit to the same Base Station at the same time. There are several Multiple Access (MA) technologies that can be used for this purpose. We discussed in class four such technologies. One of these uses time slots. What is it called?
TDMA
[03]⋅ [01]
`03
The elements of the Galois field G F ( 2 8 ) can be written as bytes, pairs of HEX numbers, or polynomials. The addition is binary while the multiplication is polynomial modulo an irreducible polynomial p ( x ) . We shall take this polynomial to be p ( x ) = x 8 + x 4 + x 3 + x + 1. Consider three bytes of G F ( 2 8 ): X 1 = 00000010 , X 2 = 00000100 and X 3 = 01110000 . What is the product X 2 ⋅ X 3 as a polynomial and a HEX pair? a. x 8 + x 7 + x 6 , [E0] b. x 7 + x 6 + x 4 + x 3 + x + 1 , [DB] c. x 7 + x 6 + x 4 + x 3 + x , [DA]
b
Message authentication protects two parties who exchange messages from any third party.
true
With the ElGamal digital signature scheme a user A selects a random integer XA such that 1<XvA<q−1 and computes YA=αX^A mod q . The private signature key of A is XA and the public signature key of A is YA .
true
How many keys are used in asymmetric (public key) encryption?
two
The Advanced Encryption Standard (AES), is a block cipher adopted by the National Institute of Standards and Technology (NIST) in 2001. The basic parameters of this cipher are:
Block size 128 bits; Key length 128 bits; No of rounds: 10
Alice and Bob use the Diffie-Hellman key exchange with common prime p = 11 and generator α = 2 . If the private key of Alice is X A = 6 what is her public key Y A ? Answer: a. 8 b. 9 c. 10
b
As in Question 5. What is the polynomial representation of X and Y ? a. x and x 6 + x 5 b. x and x 5 + x 4
b
Perform encryption using the RSA algorithm given that: p = 3 , q = 11 , e = 7 , M = 5 For these values the ciphertext C is: a. 12 b. 14 c. 16
b
Several modes of operation involve chaining, by binding blocks of consecutive encryptions. In one mode each ciphertext block is added (XORed) to the plaintext block of the next encryption. The result is then encrypted using the cipher algorithm in the usual way. What is this mode of encryption called. a. ECB b. CBC c. CFB d. OFB e. CTR
b
The ElGamal encryption scheme is based on the Diffie-Hellman key exchange. If p is the common modulus and α is a generator, then the public key of Alice is ( Y A , p ) , where Y A = α x ( mod p ), x ∈ Z p , and the private key is: ( x , p ) . To encrypt a message m , 0 < m < p , Bob computes C 1 = α k ( mod p ) , k ∈ Z p , and C 2 = Y A k ⋅ m ( mod p ) . Show how this is down for the special case: p = 11 , α = 2 , x = 3 , k = 2 , and m = 6. What is the public key Y A of Alice? a. 6 b. 8 c. 10
b
The elements of the Galois field G F ( 2 8 ) can be written as bytes, pairs of HEX numbers, or polynomials. The addition is binary while the multiplication is polynomial modulo an irreducible polynomial p ( x ) . We shall take this polynomial to be p ( x ) = x 8 + x 4 + x 3 + x + 1. Consider three bytes of G F ( 2 8 ): 00000010, 00000100 and 01110000. What is their HEX representation? a. [02], [03], [72] b. [02], [04], [70] c. [02], [08], [70]
b
The elements of the Galois field G F ( 2 8 ) can be written as bytes, pairs of HEX numbers, or polynomials. The addition is binary while the multiplication is polynomial modulo an irreducible polynomial p ( x ) . We shall take this polynomial to be p ( x ) = x 8 + x 4 + x 3 + x + 1. Consider three bytes of G F ( 2 8 ): 00000010, 00000100 and 01110000. What is their polynomial representation: a. x , x + 1 , x 6 + x 5 + x 4 b. x , x 2 , x 6 + x 5 + x 4 c. x , x 3 , x 6 + x 5 + x 4 + x
b
We discussed 2 basic types of random number generators: TRNG, True random Number Generators and PRNG, Pseudo Random Number Generators. One of these is deterministic. a. TRNG is deterministic b. PRNG is deterministic
b
What is the key size of an n-bit to n-bit block permutation (the length of its description) ? a. ( 2^n )^2^n b. log 2( 2^n ) ! c. (2^n)! d. n × 2^n
b
Find the decryption key of the RSA algorithm given that: p = 3 , q = 11 , e = 7 For these values the decryption key is: a. d = 5 b. d = 4 c. d = 3
c
For the RSA parameters: p = 5 , q = 11 , e = 3 , find the encryption of M = 9 and the decryption key d . a. C = 14 , d = 17 b. C = 15 , d = 7 c. C = 14 , d = 27
c
How many different invertible n-bit block to n-bit block mappings (permutations) are there? a. ( 2^n )^2^n b. log 2( 2^n ) ! c. (2^n)! d. n × 2^n
c
AES is a stream cipher
false
A digital signature is a bit pattern that must depend on the message being signed.
true
An example of a steganography technique is to take the sequence of first letters of each word of a message.
true
Security attacks are distinguished as passive or active. In a passive attack the adversary attempts to learn information from the system.
true
The output of a hash function has fixed length.
true
In the Quantum Crypto experiment based on Schroedinger's paradox Alice sends Bob four steel boxes. Bob observes that none of the boxes have been opened ( tampered). Bob then opens the boxes and finds that all the cats are alive with the first three being black and the last white. What is the exchanged 4-bit string?
1110
A hash function H that is one-way and collision-free is called a cryptographic hash function. A Message Authentication Code is: 1. a cryptographic hash function. 2. a keyed cryptographic hash function.
2
The 10 First Principles of Cybersecurity 1. Domain Separation 2. Process Isolation 3. Resource Encapsulation 4. Least privilege 5. Layering 6. Abstraction 7. Information Hiding 8. Modularity 9. Simplicity 10. Minimization For which one does the following apply: "keeping processes isolated prevents the failure of one process from negatively impacting another".
2. Process Isolation
The physical distance between co-channel cells is roughly: (answer should be "x cell" or "x cells")
2.5 cells
Find an integer that satisfies the equation: 3 x ≡ 4 ( mod 5 )
3
The 10 First Principles of Cybersecurity 1. Domain Separation 2. Process Isolation 3. Resource Encapsulation 4. Least privilege 5. Layering 6. Abstraction 7. Information Hiding 8. Modularity 9. Simplicity 10. Minimization For which one does the following apply: "resources (such as hardware, system objects, or processes) must be separated and used as intended".
3. Resource Encapsulation
the sum of the values in G F ( 7 ) of 3 × 5 and 3 × 3 is:
4
There are also two other more secure versions of AES. For these the parameters are: For these the parameters are:
Block size 128 bits; Key size 192 or 256 bits; No of rounds 12 or 14
We discussed in class four MA technologies. One of these assigns to cellphones non overlapping frequency ranges. What is it called?
FDMA
The input of a hash function has fixed length.
False
In each round AES uses four different operations to process a 4-byte by 4-byte array: a. Substitution bytes, b. ShiftRows, c. MixColumns and d. AddRoundKey. In which one of these are the bytes of the 4 byte by 4 byte array substituted by other bytes using a table?
a
The Multiple Access (MA) Problem. Base Stations need to serve many cellphones at the same time. We need a multiple access (MA) scheme, that must address the interference among different cellphones. For this purpose there are several technologies that can be used (and combined). Below we describe their functionality at a high level that captures their basic functionality a. "everyone talks quietly so that only their neighbors can hear" b. "everyone talks in a different room to prevent interference" c. "everyone takes turns to talk" d. "everyone speaks in a different language" The technologies that are modeled by these descriptions are called (in a randomized order): Time Division MA (TDMA), Frequency Division MA (FDMA), Code Division MA (CDMA) and Space Division MA (SDMA). Which one of the four high level descriptions above corresponds to: Frequency Division MA (FDMA) ?
b
The parameters of DES are: a. Block length of plaintext = Block length of ciphertext = Block length of key = 64 bits b. Block length of plaintext = Block length of ciphertext = 64 bits, Block length of key = 56 bits
b
We discussed in class 3 digital signature schemes: the ElGamal scheme, the Schnorr scheme and the DSA. The last one builds on the first two. The quiz concerns the lengths (in bits) of these schemes. As with all MACs digital schemes use a hash function to reduce the size of the message. These schemes use a modulus that is a prime number that is typically 1,024 bits long. For a 1,024 bit prime number modulus the length of a Schnorr digital signature is: a. 2,048 bits long b. 1, 184 bits long c. other
b
What is the difference between statistical randomness and unpredictability? An unpredictable sequence is one in which knowledge of the sequence generation method is . . . X . . . to determine the sequence . a. X = sufficient b. X = insufficient
b
Alice and Bob use the Diffie-Hellman key exchange with common prime p = 11 and generator α = 2 . Given that their private keys are X A = 6 and X B = 8 , what is their shared key ? Hint: The shared key is α X A ⋅ X B ( mod p ) , and by Fermat's theorem α p − 1 = 1 ( mod p ) (since p is a prime). a. 9 b. 6 c. 3
c
Alice and Bob use the Diffie-Hellman key exchange with common prime p = 11 and generator α = 2 . If the private key of Bob is X B = 8 what is his public key Y B ? Answer: a. 7 b. 5 c, 3
c
As in Question 5. What is X × Y as a polynomial, as a byte and as a HEX ? a. x 6 + x 5 ; 01100000 ; B0 b. x 5 + x 4 ; 00110000 ; 30 c. x 6 + x 5 ; 01100000 ; 60
c
In another mode of operation the ciphertext block of a round is input to the next round to get encrypted and then added (XORed) to the plaintext (of the next round) to get the next ciphertext block. In this mode we have ciphertext feedback (into the input to the next round). What is this mode of encryption called. a. ECB b. CBC c. CFB d. OFB e. CTR
c
Let the first row of the Mix Column transformation be [02,03,01,01]. To get the transformed value s'00 of s00 we multiply each byte of the first row of the Mix Column transformation by the corresponding byte of the first column [00,01,02,0a] of the input (using Galois Field arithmetic) and then XORing the 4 resulting numbers. In the previous 4 questions the correct answers were: 0a, 03, 02, 00. Now you must XOR these. You can write these as binary polynomials: 0a = x 3 + x 2 03 = x + 1 02 = x 00 = 0 Now XOR them as binary polynomials, then convert the result to a pair of hexadecimals Answer: a. 0f b. 0e c. 0d
c
The ElGamal encryption scheme is based on the Diffie-Hellman key exchange. If p is the common modulus and α is a generator, then the public key of Alice is ( Y A , p ) , where Y A = α x ( mod p ), x ∈ Z p , and the private key is: ( x , p ) . To encrypt a message m , 0 < m < p , Bob computes C 1 = α k ( mod p ) , k ∈ Z p , and C 2 = Y A k ⋅ m ( mod p ) . Show how this is down for the special case: p = 11 , α = 2 , x = 3 , k = 2 , and m = 6. What is the encryption C 1 , C 2 of the message m = 6 ? a. 6, 4 b. 4, 8 c. 4, 10
c
The Multiple Access (MA) Problem. Base Stations need to serve many cellphones at the same time. We need a multiple access (MA) scheme, that must address the interference among different cellphones. For this purpose there are several technologies that can be used (and combined). Below we describe their functionality at a high level that captures their basic functionality a. "everyone talks quietly so that only their neighbors can hear" b. "everyone talks in a different room to prevent interference" c. "everyone takes turns to talk" d. "everyone speaks in a different language" The technologies that are modeled by these descriptions are called (in a randomized order): Time Division MA (TDMA), Frequency Division MA (FDMA), Code Division MA (CDMA) and Space Division MA (SDMA). Which one of the four high level descriptions above corresponds to: Time Division MA (TDMA) ?
c
This knowledge involves one or more of the following: EA: the encryption algorithm; C: ciphertexts; (P,C): plaintext-ciphertext corresponding pairs; (P,C)chosen P : chosen plaintexts with their corresponding ciphertext; pairs; (C,P)chosen C : chosen ciphertexts with their corresponding plaintext pairs. 4. In a chosen ciphertext attack the adversary has access to: a. some (P,C)chosen b. EA and some (P,C)chosen P c. EA and some (C,P)chosen C
c
We discussed 4 basic types of attacks on encryption schemes: in each one of them the adversary has some knowledge and uses this to attack (break) the system. This knowledge involves one or more of the following: EA: the encryption algorithm; C: ciphertexts; (P,C): plaintext-ciphertext corresponding pairs; (P,C)chosen P : chosen plaintexts with their corresponding ciphertext; pairs; (C,P)chosen C : chosen ciphertexts with their corresponding plaintext pairs. 2. In a known plaintext attack the adversary has access to: a. some (P,C) b. EA and some (P,C) c. EA and some (P,C) known P
c
We discussed 4 basic types of attacks on encryption schemes: in each one of them the adversary has some knowledge and uses this to attack (break) the system. This knowledge involves one or more of the following: EA: the encryption algorithm; C: ciphertexts; (P,C): plaintext-ciphertext corresponding pairs; (P,C)chosen P : chosen plaintexts with their corresponding ciphertext; pairs; (C,P)chosen C : chosen ciphertexts with their corresponding plaintext pairs. 3. In a chosen plaintext attack the adversary has access to: a. some (P,C) b. EA and some (P,C) c. EA and some (P,C)chosen P
c
We discussed in class 3 digital signature schemes: the ElGamal scheme, the Schnorr scheme and the DSA. The last one builds on the first two. The quiz concerns the lengths (in bits) of these schemes. As with all MACs digital schemes use a hash function to reduce the size of the message. These schemes use a modulus that is a prime number that is typically 1,024 bits long. For a 1,024 bit prime number modulus the length of a Digital Signature Algorithm is roughly: a. 2,048 bits long b. 1, 184 bits long c. other
c
Following is an application where authentication is needed: withdraw money from an ATM. List what is needed.
card, pin (personal identification number)
Heisenberg's duality principle says that there is a natural tradeoff between knowing a particle's position and its momentum (speed): the greater the uncertainty in it's position, the smaller the uncertainty in its momentum. Schroedinger found it absurd the possibility that particles can have simultaneously different states and proposed a thought experiment (paradox) in which "objects" could have two different states at the same time (each with a certain probability). What "object" did this experiment involve? (answer is one word)
cat
Another mode of operation that creates keystream bits in which the successive encryptions of an Initial Vector (IV) are added (XORed) to the plaintext bocks to encrypt them as a stream. In this mode there is feedback of the input of the next cycle to the previous output cipher of a thread of encryptions (starting at IV). What is this mode of encryption called? a. ECB b. CBC c. CFB d. OFB e. CTR
d
Cellular Network technology uses electromagnetic waves for communication. Cellphones operate in narrow frequency ranges. Following are some high frequency frequency ranges: Ultra High Frequency (UHF): 300MHz - 3 GHz, Super High Frequency (SHF): 3GHz - 30GHz, and , Extremely High Frequency (SHF): 30GHz - 300GHz. Allowing for all five generations of cellphones the frequencies used are: a. UHF b. SHF c. EHF d. All of these
d
The rest of this Quiz has to do with the Mix Column transformation that uses Galois Field operations to compute the values of the substituted bytes in each column. The input is a 4-byte by 4-byte array. In the Mix Column transformation each byte sij of this array is substituted by a byte s'ij . Let the 4 bytes of the first column be the word [s00,s10,s20,s30] = [00,01,02,0a]. Here each byte is represented by a pair of hexadecimal numbers, e.g., 0a = 0x0a (decimal 10). Let the first row of the Mix Column transformation be [02,03,01,01]. To get the transformed value s'00 of s00 we multiply each byte of the first row of the Mix Column transformation by the corresponding byte of the first column [00,01,02,0a] of the input (using Galois Field arithmetic) and then XORing the 4 resulting numbers. In the next 4 questions you will have to do these multiplications: [02]⋅ [00] is, a. 0a b. 02 c. 03 d. 00
d
We have symmetric and asymmetric (public key) encryption. What can you say about the encryption and decryption keys of asymmetric encryption, Are they the same?
different
One way makes the block cipher work as a stream cipher. Keystream bits are created regardless of content of the data blocks to be encrypted. In this mode, consecutive values of an increasing counter are added (XORed) to a nonce value (=a number that is unique: used only once) and the result is encrypted as usual. The output is then added (XORed) with a block of the plaintext. This is one of the most popular and secure modes of operation. In particular if one bit of a plaintext or ciphertext message is corrupted then only one corresponding output bit is corrupted. What is this mode of encryption called. a. ECB b. CBC c. CFB d. OFB e. CTR
e
Message authentication protects two parties who exchange messages from each other.
false
The collision-free property of a cryptographic hash function H requires that it is easy (computationally feasible) to find a pair x,y,x≠y such that H(x)=H(y).
false
With AES, in the standard mode, the key is expanded into forty 32-bit words.
false
How many keys are used in symmetric encryption?
one
Following is an applications where authentication is needed: list the item needed to implement it?Access to a terminal (one word): --------------
password
Following is an applications where authentication is needed: list the items needed to implement it?Access to a (recent) iPhone: ---------- , ------------
password, facial recognition Key, facial recognition password, face key, face
Security attacks are distinguished as passive or active. In an active attack the adversary attempts to affect (alter) system resources
true
The 5G high frequency bandwidth is in the millimeter-wave frequency range (24.25 GHz and above).
true
The ElGamal digital signature scheme uses the same global parameters as the ElGamal encryption scheme: a (large) prime number qq and a primitive root of αα of qq.
true
The one-way property of a cryptographic hash function H requires that for any pre-specified hash value y it is computationally infeasible to find a value x such that y=H(x) (in other words to "invert" H ).
true
What is the difference between statistical randomness and unpredictability? Statistical randomness refers to a property of a sequence of numbers or letters, such that: the sequence appears random and passes certain statistical tests that indicate that the sequence has the properties of randomness.
true
With AES a data block of 16 bytes is processed as a 4-byte by 4-byte matrix using substitutions and permutations.
true
