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Cryptography Final Exam Study Set.
Save The ______________ is the message after decryption - ANSWERplaintext What type of cipher is the Vigenere cipher? - ANSWERpolyalphabetic What is the decryption of bsujqsyodysw by use of Vigenere cipher with the key "USF?" - ANSWERhappynewyear In Vernam cipher, its pad must be used just one time. - ANSWERtrue What is the encryption of HAPPYNEWYEAR by use of Caesar cipher with its encryption key 10? - ANSWERrkzzixogiokb Vigenere cipher overcomes the problem of a small key space in Caesar cipher by ____________ - ANSWERhaving a sequence of letters, a word, as a secret key For a Caesar cipher, a cyclic shift algorithm is used to encrypt each letter - ANSWERtrue Caesar cipher is insecure because - ANSWERthe frequencies of letters remain unchanged
A(n) __________ algorithm transforms ciphertext to plaintext - ANSWERdecryption Suppose C = 33 is the public key of the scheme described in the video "Prime Numbers and Public Key Cryptography." What is the corresponding private key? - ANSWERp1 = 3 and p2 = 11 27 is a prime number - ANSWERfalse The principle of Fail-Safe default means that _____________ - ANSWERunless access is specifically granted to an object, access should be denied Kerckhoff's principle means that one must never reveal the design of a cipher
- ANSWERfalse Prime number is an integer that can be ______________ - ANSWERdivided only by 1 and itself The modular arithmetic/remainder of 17 mod 5 is ____________ - ANSWER 2 You flip a coin and count 0 if it falls on "heads" and 1 if it falls on "tail." What is the expected value of your count? - ANSWER1/ The random variable is ________________ - ANSWERto capture the likelihood of events and to make an idea of random events
When encryption keys are more random, it is more difficult for attackers to find out where they are - ANSWERtrue As a keyspace grows, there are more potential values to represent different keys - ANSWERtrue In cryptography, the key take-home message of the birthday phenomenon is to ___________ when collisions matter - ANSWERlook up The Vigenere cipher is not a mono-alphabetic cipher - ANSWERtrue What is the decryption of the ciphertext pbqmcciqpboewwnq with the key LOVE by using Vigenere cipher - ANSWEREnvironmentalism In the Vernam cipher, a message and its secret key have _________________
- ANSWERlook up For the Caesar cipher, the fact that there are only 26 keys renders the scheme insecure - ANSWERtrue For the Caesar cipher, the letter frequencies of the plaintext remain unchanged, and it can be expected that the most frequent letter in the ciphertext corresponds to the most frequent letter in the English language - ANSWERtrue What is the encryption of the plaintext, Rocky the Bull, with the Caesar cipher and the key 7? - ANSWERyvjrf aol lbss
If a secret key in the Vernam cipher is chosen to be a true random string, how many times should it be used for encryption? - ANSWERonce What is the decryption of the ciphertext, THXOJJ, with the cipher key/one- time pad ONEUSF by using the Vernam cipher? - ANSWERlook up Assume there are 365 days in a year, given 10 people in room, the probability that at least two people were born on the same day is the same as the probability that at least two people were born on January 9th. - ANSWERfalse Suppose that the outcome of each face in a six-sided dice is equally likely. What is the probability of getting an odd number in tossing the dice one time? - ANSWER1/ If we assume that the encryption of PLAINTEXT with a Caesar cipher is VRGOTZKDZ, what key is used in the encryption? - ANSWER 6 The LCM (lease common multiple) of 5 and 12 is ______________ - ANSWER 60 The modular arithmetic/remainder of 16 mod 5 is __________________ - ANSWER 1 What security objective aims at restricting/detecting unauthorized data modification? - ANSWERintegrity
Steganography can be used to achieve confidentiality - ANSWERtrue Steganography is a method of hiding data in another media type - ANSWERtrue 79 is a prime number - ANSWERtrue RSA is symmetric-key cryptography - ANSWERfalse Data Encryption Standard (DES) is a ____________ cipher - ANSWERblock Side-channel attacks can use both software and hardware - ANSWERtrue When we talk about attacks, it is important to precisely stat which security goals are violated and what tools an adversary have - ANSWERtrue Exhaustive key search is a type of encryption scheme attack - ANSWERtrue Known plaintext is NOT a type of encryption scheme attack - ANSWERfalse Chosen ciphertext and known plaintext are types of encryption scheme attacks - ANSWERtrue In asymmetric-key cryptography, the number of public keys needed for 9 users is ________________ - ANSWER 9
A stream cipher is considered asymmetric-key cryptography - ANSWERfalse A block cipher is considered symmetric-key cryptography - ANSWERtrue For asymmetric-key encryption, a shared or secret key is generated for each two users - ANSWERfalse For asymmetric-key encryption, the keys are simply identical large numbers that have been paired together - ANSWERfalse Asymmetric-key encryption simplifies key management in case of a large number of users - ANSWERtrue For asymmetric-key encryption, a key pair is generated where they are a public key that can be published and a private key that should be kept in secret - ANSWERtrue A trapdoor is a one-way function - ANSWERtrue RC4 is a stream cipher that is asymmetric - ANSWERfalse The main concern of initial security analysis includes inputs and outputs - ANSWERtrue Electromagnetic emanation and running time information could be used in side-channel attacks - ANSWERtrue
A man-in-the-middle attack is an attempt to make a machine or network resource unavailable to its intended users so as to temporarily or indefinitely interrupt or suspend services of a host connected to the Internet - ANSWERfalse Serious weaknesses can be introduced even if an encryption algorithm is correctly implemented based on its theoretical description - ANSWERtrue Side-channel attacks can be used to reveal a secret key - ANSWERtrue A differential power analysis does not rely on the availability of multiple power traces - ANSWERfalse If an attacker knows the ciphertext of a message and its encryption algorithm based on an 8-bits key, how many keys will the attacker have to attempt one by one to find the key used in the decryption? - ANSWERlook up Data encryption standard (DES) is an asymmetric block cyber - ANSWERfalse Electromagnetic emanation, power consumption, and cache misses can be used in side-channel attacks - ANSWERtrue In an asymmetric cryptosystem, a PUBLIC key is used to decrypt messages ONLY - ANSWERfalse Both public keys and secret keys can be made freely available to everyone in asymmetric encryption - ANSWERfalse
RSA is asymmetric-key cryptography - ANSWERtrue For a stream cipher, the plaintext is considered as a stream - ANSWERtrue A stream cipher tries to mimic a one-time pad at a lower cost - ANSWERtrue For public-key encryption, it is easy to compute on every input, but it is hard to compute in its reverse direction - ANSWERtrue When one implements cryptographic algorithms, it may be necessary to avoid the usual way of performing a computation, possibly at the cost of efficiency - ANSWERtrue Side-channel information can enable an attacker to isolate key bits, thereby avoiding an exhaustive search over a large key space - ANSWERtrue In the absence of noise, a simple power analysis can't reveal a complete secret exponent in a square and multiply algorithm - ANSWERfalse If a plaintext is much larger than the block size of a block cipher, then its solution is to - ANSWERselect a suitable mode of operation to the block cipher to handle the scenario Claude Shannon's Communication Theory of Secrecy Systems implies that the seemingly inefficient use of key material in the one-time pad is inevitable if we want to achieve perfect secrecy - ANSWERtrue
RC4 is a byte-oriented block cipher - ANSWERfalse Permutation and substitution are two basic building blocks in classical encryption scheme - ANSWERtrue Stream and block ciphers are symmetric-key cryptography - ANSWERtrue The main different between symmetric and asymmetric encryption is that while the same key is used in two parties in symmetric encryption, two separate keys are generated in asymmetric encryption - ANSWERtrue A man-in-the-middle attack is one which the attacker secretly intercepts and relays messages between two parties who believe they are communicating directly with each other - ANSWERtrue Known ciphertext attack, known plaintext attack, and exhaustive key search are encryption scheme attacks - ANSWERtrue In a Merkle-Damgard Design Paradigm, a compression function takes only one message block as its input - ANSWERfalse The properties of a cryptographic hash function is collision resistance, preimage resistance, and second preimage resistance - ANSWERtrue The design goal of MACs is to ensure confidentiality - ANSWERfalse
The minimum key length of AES is less than the size of a block, 128-bit - ANSWERfalse MD5 is a typical hash function that follows the Merkle-Damgard Design Paradigm - ANSWERtrue For MD5, finding short colliding messages is not feasible - ANSWERfalse RSA is a type of mode operation - ANSWERfalse The number of rounds in DES is 16 - ANSWERtrue AES has MixColumns, AddRoundKey, ShiftRows, and SubBytes operations - ANSWERtrue MAC is based on the tag generation, key generation, and verification algorithms - ANSWERtrue MACs in the hash function module stand for - ANSWERmessage authentication code Same plaintext blocks will yield same ciphertext blocks is a property of CBC mode of operation - ANSWERfalse The initialization vector of CBC is usually randomly generated and should not be reused - ANSWERtrue
The DES encryption could have 64-bit block size, 56-bit key length, 8 s-boxes, 16 rounds, and 48-bit subkey length - ANSWERtrue In the DES algorithm, a subkey has 64 bits - ANSWERfalse MAC is a result of CTR mode of operations - ANSWERfalse In the Merkle-Damgard Design Paradigm, bits are appended to an input message in a random order - ANSWERfalse In each of key-dependent rounds of AES, the 128-bit round key can be derived from 128-bit, 192-bit, or 256-bit provided key - ANSWERtrue The basic task of a block cipher is to encrypt an n-bit plaintext as an n-bit ciphertext based on some secret key - ANSWERtrue RSA and RC4 are modes of operation - ANSWERfalse In the DES algorithm, each input is divided into two parts: the left half Li and the right half Ri, where i represents the ith round. Which part is modified in the ith round? - ANSWERthe left half Li In the AES algorithm, what operation is at the beginning and at the end of the encryption process to reduce AES' vulnerability to a chosen plaintext attack or chosen ciphertext attack? - ANSWERAddRoundKey AES can operate on 128-bit plaintext blocks - ANSWERtrue
AES supports several different key lengths - ANSWERtrue AES is based on a Feistel design - ANSWERfalse A major structural difference between DES and AES is that DES is based on the Feistel design while AES is based on a SQUARE structure - ANSWERtrue What block size of an input message does the AES-192 use - ANSWER128 bits Data Encryption Standard (DES) is a block cipher that operates on 64-bit blocks - ANSWERtrue In DES, the effective key space is of size - ANSWER2^ It is unnecessary to use the block cipher's decryption operation to decrypt a ciphertext in the CFB mode - ANSWERtrue In the CFB mode, an unpredictable initialization vector is used, but it does not have to be secret - ANSWERtrue In the CFB mode, the plaintext never enters the block cipher - ANSWERtrue If multiple encryption engines are available, the Electronic Code Book (ECB) mode can be easily ____________ - ANSWERparallelized
Keyed-Hash MAC (HMAC) builds on a hash function using the Merkle Damgard design - ANSWERtrue A MAC by default does not provide any guarantees on - ANSWERconfidentiality MD4 and MD5 have three rounds - ANSWERfalse The specification of a hash function is publicly available - ANSWERtrue RSA-OAEP is a public-key encryption scheme based on RSA and the Optimal Asymmetric Encryption Padding (OAEP) method - ANSWERtrue The Diffie-Hellman protocol dates back to the 1961s - ANSWERfalse Public-key encryption uses more number of keys than secret-key encryption/symmetric-key encryption for secure communication among a large group of people, assuming no group key for more than two entities is permitted - ANSWERfalse The Diffie-Hellman protocol is an algorithm used to establish a shared secret between two parties - ANSWERtrue RSA was named after its inventors, Rivest, Shannon, and Adleman - ANSWERfalse Which modes of operation are NOT stream ciphers - ANSWERECB, CBC, CTR
Which modes of operation are stream ciphers - ANSWEROFB, CFB Elliptic curves offer a mathematical platform, where the discrete logarithm problem seems more challenging than in finite fields - ANSWERtrue What would this command do: openssl enc - aes- 128 - cbc - e - in abc.txt - out out.txt - ANSWERencrypt the contents of abc.txt and output it to out.txt In CBC mode the initialization vector should be random, unpredictable and secret - ANSWERfalse There is no padding needed for encryption mode CFB and OFB because they are block ciphers - ANSWERfalse ECB, CBC, OFB, CFB modes of operation can be used for the AES- 128 algorithm - ANSWERtrue RSA is a cryptosystem used for secure data transmission - ANSWERtrue RSA is secret key cryptosystem - ANSWERfalse In RSA, each entity has its own pair of a public key and a private key - ANSWERtrue
