Sis Prvi Kolokvijum Teorija

The given correct answer states that DES algorithm is a "blokovski algoritam Fejstelovog tipa" which translates to "block cipher algorithm of the Feistel type" in English. This means that DES is a type of symmetric encryption algorithm that operates on fixed-size blocks of data using a Feistel network structure. It divides the input into blocks and applies a series of transformations to each block to produce the encrypted output. Therefore, the answer correctly identifies DES as a block cipher algorithm of the Feistel type.

The correct answer is "blok sifrata je iste duzine kao blok otvorenog teksta" because in block cipher algorithms, the length of the ciphertext block is the same as the length of the plaintext block. This means that each block of plaintext is encrypted into a block of ciphertext with the same length.

The correct answer states that the task of modern encryption algorithms is to transform bit sequences carrying information from the plaintext into a new binary sequence in such a way that unauthorized parties cannot access the information present in the plaintext through analysis of the ciphertext.

In steganalysis, the process of detecting hidden messages, visual detection is used. This means that the detection is done through visual analysis of the carrier file or image. This method involves examining the pixels, color patterns, and any visual anomalies that may indicate the presence of hidden messages. By visually inspecting the steganographic carrier, one can identify any alterations or hidden information that may be present.

The correct answer is "deluje na sve bitove unutar bloka" (it operates on all bits within the block). This means that the algorithm affects every individual bit within the block of data being processed. It does not operate on a single byte of open text or encrypt byte by byte within each block. Instead, it considers and manipulates all the bits within the block as a whole.

The correct answer is "racunski siguran." The question is asking for the name of a cipher system where the time required to break it is longer than the time it takes for the information to remain secret. "Racunski siguran" translates to "computationally secure," which means that it would take an infeasible amount of time and resources to break the cipher using computational methods.

By embedding the timestamp of the message in the message itself, it becomes possible to detect if the same message is being resent. This is because each time the message is sent, it will have a different timestamp, allowing for the detection of duplicate messages.

The given correct answer, "vodeni pecat," refers to the technique of embedding additional information such as authorship and ownership into digital content. This technique is commonly used to protect the intellectual property rights of the content and to provide attribution to the original creator. The term "vodeni pecat" translates to "watermark" in English, which is a commonly used term in the digital content industry.

The correct answer is "da budu efikasne" (to be efficient). This is because efficiency is important for the function to perform well and achieve its intended purpose. Efficiency ensures that the function uses minimal resources, time, and effort to produce the desired outcome. It allows for optimal utilization of resources and maximizes productivity. Therefore, it is crucial for functions to be efficient in order to be effective and successful.

In the context of Diffie-Hellman key exchange, the prime number p used for modular exponentiation should be a large prime number. This is because using a large prime number enhances the security of the key exchange algorithm and makes it more difficult for attackers to calculate the shared secret key. The other options mentioned, such as any prime number, any large number, or the product of two large prime numbers, do not necessarily provide the same level of security as a large prime number.

In the given scenario, Alisa and Bob are using the Diffie-Hellman algorithm to exchange keys. Alisa chooses the number 3 and Bob chooses the number 7. They perform the calculations using the given parameters p=17 and q=5. The calculation 5 ^ 3(mod 17) means that Alisa raises 5 to the power of 3 and then takes the remainder when divided by 17. The result is 6. Therefore, the answer is 5 ^ 3(mod 17) = 6.

In the given question, it is stated that the price of breaking the code exceeds the value of the encrypted information. This refers to a system called "racunski siguran" which translates to "computationally secure" in English. In such a system, the cost and effort required to decrypt the information are so high that it is not worth the value of the encrypted data. Therefore, "racunski siguran" is the correct answer.

The given correct answer is AES algorithm. ByteSub, ShiftRow, MaxColumn, and AddRoundKey are operations that are associated with the AES algorithm. AES (Advanced Encryption Standard) is a widely used symmetric encryption algorithm that is used to secure sensitive data. The ByteSub operation involves substituting each byte in the state matrix with a corresponding byte from the S-box. The ShiftRow operation involves shifting the rows of the state matrix. The MaxColumn operation involves selecting the maximum value from each column in the state matrix. The AddRoundKey operation involves XORing the state matrix with a round key. Together, these operations form the basis of the AES algorithm.

The correct answer states that asymmetric algorithms are slower than symmetric algorithms. This means that when comparing the execution speeds of these two types of algorithms, asymmetric algorithms tend to be slower.

In order to successfully decrypt a cipher using a sequential cipher system, it is necessary to possess both a random key and a pseudo-random number generator. The random key provides the initial starting point for the decryption process, while the pseudo-random number generator generates the sequence of numbers needed to decrypt the cipher. Having only one of these components (either the random key or the generator) would not be sufficient for successful decryption.

The security of a cryptosystem relies on the secrecy of the decryption key. The encryption key is used to encrypt the message, but it is the decryption key that is needed to decrypt the message and retrieve the original information. If the decryption key is not kept secret, an attacker could potentially obtain it and easily decrypt the encrypted messages, compromising the security of the system. Therefore, the secrecy of the decryption key is crucial for the security of the cryptosystem.

The correct answer is DCT metoda. DCT (Discrete Cosine Transform) is commonly used to hide information within a video file. It is a transformation technique that converts spatial information into frequency information, allowing for efficient compression and hiding of data. This method is widely used in video compression algorithms such as MPEG.

The result of the given operation is 'a' because XOR operation returns 1 if the number of 1's in the operands is odd, and 0 if it is even. In this case, since 'a' is 0 and 'b' is 1, the first XOR operation ((0 XOR 1) XOR 0) will result in 1. And the second XOR operation (0 XOR 1) will also result in 1. Therefore, the final XOR operation (1 XOR 1) will give the result as 0. Hence, the answer is 'a'.

The given expression (((x XOR x) XOR y) XOR y) XOR x simplifies to x because XOR operation with the same value on both sides results in 0, and XOR operation with 0 on one side and any value on the other side gives the same value. Therefore, since there are two XOR operations with x, they cancel each other out and the final result is x.

A digital signature is a service that aims to provide integrity and non-repudiation. This means that it ensures the data has not been tampered with and verifies the identity of the sender, preventing them from denying their involvement. The digital signature also ensures the authenticity of the message, confirming that it was indeed sent by the claimed sender.

The given question asks for the sequential algorithm among the options provided. Out of the given options, AS/1 is the only algorithm that is sequential. Twofish, AES, and DES are all examples of symmetric key algorithms, but they are not specifically mentioned as sequential algorithms. Therefore, the correct answer is AS/1.

The correct answer is "kod kojih je kljuc za sifrovanje i desirforvanje isti." This means that in symmetric cryptosystems, the key used for encryption is the same as the key used for decryption.

The given expression ((a XOR b) XOR b) XOR (a XOR b) XOR 0 can be simplified using the properties of XOR operation. XOR of any number with itself gives 0, so (a XOR b) XOR b simplifies to a. Similarly, (a XOR b) XOR (a XOR b) simplifies to 0. Therefore, the entire expression reduces to a XOR 0, which is equal to a. Hence, the correct answer is a.

The security of the RSA algorithm lies in the complexity of finding the prime factors of large numbers. This is because the RSA algorithm is based on the difficulty of factoring large composite numbers into their prime factors. The larger the prime factors, the more secure the RSA encryption becomes. Therefore, the complexity of finding prime factors of large numbers is crucial for the security of the RSA algorithm.

To reduce the length of a digital signature, the hash of the message is calculated and then digitally signed. This is because hashing algorithms can convert a message of any length into a fixed-length string of characters, which makes it more efficient to sign and verify the integrity of the message. By signing the hash of the message instead of the entire message, the digital signature becomes shorter and easier to handle.

The given answer states that the result of calculating 11 raised to the power of 9, modulo 17 is 6. In the Diffie-Hellman algorithm, both Alice and Bob choose a private number and exchange their public keys. They then use each other's public keys and their own private keys to calculate a shared secret key. In this case, Bob's private key is 9 and Alice's public key is 11. Therefore, Bob calculates 11 raised to the power of 9, modulo 17, which results in 6.

The correct answer is "istim blokovima odgovaraju isti sifrati." This means that in ECB mode, the same plaintext block will always be encrypted into the same ciphertext block. This lack of randomness and variability in the encryption process can be a security weakness, as patterns in the plaintext can be easily observed in the ciphertext. This makes it easier for an attacker to analyze and potentially break the encryption.

The correct answer is "polialfabetska." Polialfabetska substitution is a type of substitution cipher where one character is not always replaced by the same character but by a character from a permitted set of characters. This means that multiple substitutions can occur for the same character, increasing the complexity and security of the encryption.

The advantage of encrypting hash values (during authentication and integrity verification) with an asymmetric algorithm compared to symmetric algorithm is that there is no need for internal trust. This means that there is no requirement for a trusted party or entity to ensure the security and integrity of the process. Asymmetric encryption allows for verification without relying on a central authority or internal trust, providing a more decentralized and potentially more secure solution.

The question is asking to select the public components of the Diffie-Hellman key exchange between Alisa and Bob. In the Diffie-Hellman algorithm, p represents a large prime number, g is a primitive root modulo p, a and b are private exponents chosen by Alisa and Bob respectively. The public components that can be shared are p (the prime number), g ^ a (Alisa's calculated value), g (the primitive root modulo p), and g ^ b (Bob's calculated value). These public components allow both parties to compute the shared secret key.

The correct answer is "CA potpisuje svojim tajnim kljucem." This means that the Certification Authority (CA) confirms the validity of public keys by signing them with its private key. This ensures the authenticity and integrity of the public keys, as only the CA possesses the private key necessary to sign the certificates.

The correct answer is a one-way function that takes an input of arbitrary finite size and produces an output of fixed length. This means that the function is deterministic, meaning that given the same input, it will always produce the same output. Additionally, it is computationally infeasible to reverse-engineer the original input from the output, making it a one-way function. The fact that the output has a fixed length ensures that the function will always produce an output of the same size, regardless of the input size.

The given question is in Serbian language and it translates to "Functions that can be relatively easily calculated but their inverse value can be determined only by an extremely complex procedure are called one-way functions." Therefore, the correct answer is "one-way functions".

DOS (Denial of Service) je napad koji ima za cilj onesposobiti ili ometati pristup određenom resursu ili usluzi. Napad na raspoloživost znači da se napadač fokusira na preopterećenje ili onesposobljavanje mrežnih ili računalnih resursa kako bi onemogućio njihovu normalnu upotrebu. To može uključivati ​​preplavljivanje mreže ili poslužitelja velikim brojem zahtjeva ili korištenje drugih metoda za iscrpljivanje resursa. Napad na raspoloživost može rezultirati nedostupnošću usluga za legitimne korisnike.

Asimetricni kriptografski sistemi se koriste za digitalno potpisivanje. Ovi sistemi koriste dva ključa, javni i privatni, koji su međusobno povezani. Javni ključ se koristi za enkripciju podataka, dok se privatni ključ koristi za dekripciju. Kada se koristi za digitalno potpisivanje, privatni ključ se koristi za potpisivanje poruke, dok se javni ključ koristi za verifikaciju potpisa. Ova tehnika omogućava sigurnu razmenu informacija i potvrdu identiteta pošiljaoca.

The correct answer is "Razmenu simetričnih ključeva" which translates to "Exchange of symmetric keys" in English. The Diffie-Hellman algorithm is used for securely exchanging symmetric keys between two parties over an insecure channel. It allows the two parties to agree on a shared secret key without actually transmitting the key itself. This shared key can then be used for symmetric encryption and decryption of messages between the parties.

The correct answer is "poverljivost." Poverljivost refers to the set of activities that need to be ensured in order to prevent unauthorized parties from accessing confidential information in communication. It involves safeguarding sensitive data and restricting access to authorized individuals only.

The given statement states that if a cipher system cannot be broken even with unlimited resources of manpower and time, then it is unconditionally secure. This means that the system is completely secure and cannot be decrypted or compromised by any means, ensuring the confidentiality and integrity of the information.

In the given question, the correct answer is "tehnicku steganografiju". This is because the question asks about the classification of steganographic techniques, and "tehnicka steganografija" is a specific type of steganography that involves hiding information within technical elements or aspects of a computer system. It is different from other options such as "resetkasti kod" (grid code), "bezsifrarne tehnike" (unencrypted techniques), and "semagrame" (semagrams), which do not specifically refer to steganography techniques.

The AES (Advanced Encryption Standard) can have 10, 12, or 14 rounds. The number of rounds in AES determines the level of security and encryption strength. The more rounds, the more secure the encryption, but also the slower the encryption process. The choice of the number of rounds depends on the specific security requirements and performance considerations of the application using AES.

The correct answer is "pozeljno je". In this context, "pozeljno je" means "it is desirable". Therefore, the explanation for this answer is that the Hes function should possess the property of the avalanche effect.

The question asks for the number of possible keys when using the English alphabet as a key of length 4, without repeating any letters. The correct answer is 26 * 25 * 24 * 23, which represents the number of choices for each position in the key. Since there are 26 letters in the English alphabet, there are 26 choices for the first position, 25 choices for the second position (excluding the letter already chosen), 24 choices for the third position, and 23 choices for the fourth position. Multiplying these choices together gives us the total number of possible keys.

The correct answer is "poruka se sifruje blokovskim algoritmom a zatim se pamti samo poslednji blok sifrata." This means that the message is encrypted using a block cipher algorithm, and only the last block of the ciphertext is stored. This method of obtaining a MAC ensures that the integrity of the message is maintained, as any modifications to the message will result in a different MAC value. Storing only the last block of the ciphertext helps to save memory and storage space.

The answer states that the key must be a random bit sequence and should not be transmitted through an insecure channel, which means that the other party needs to generate the same random bit sequence for decryption, which is impossible. Additionally, the process of generating a large amount of random binary sequences that have the properties of randomness is slow and can only be used once. The basic requirement for the key to be a completely random bit sequence is technically infeasible.

Asimetricni kriptografski algoritmi se ne često koriste za šifrovanje veoma poverljivih podataka. Ovi algoritmi koriste javni i privatni ključ za enkripciju i dekripciju podataka. Javni ključ je dostupan svima, dok je privatni ključ tajna informacija koja se koristi za dekripciju. Asimetrična kriptografija je sporija i zahteva više resursa od simetrične kriptografije, zbog čega se često koristi samo za razmenu ključeva ili digitalno potpisivanje. Za šifrovanje veoma poverljivih podataka se obično koristi simetrična kriptografija, koja je brža i efikasnija.

The correct answer is "jedno idejno resenje blokovske sifre." This means that the Fejstel cipher (network) represents one conceptual solution of a block cipher. A block cipher is a type of encryption algorithm that operates on fixed-size blocks of data. The Fejstel cipher is a specific design of a block cipher that uses multiple rounds of substitution and permutation operations to encrypt and decrypt data. This answer correctly identifies the Fejstel cipher as a conceptual solution for a block cipher.

This question is asking about the type of attack that involves unauthorized changes to data, access rights, or the functioning of a system. The correct answer is "Integritet." In the context of computer security, integrity refers to the accuracy, consistency, and trustworthiness of data. An attack on integrity would involve tampering with or modifying data in a way that compromises its reliability or validity.

The correct answer is "blokovski algoritam." This is because the question asks for the name of the algorithm that processes blocks of plaintext during encryption. "Blokovski algoritam" translates to "block algorithm" in English, which accurately describes the process of encrypting data in blocks rather than as a whole.

The correct answer is "postojanje internog poverenja." This means that the authentication process that uses encryption of hash values with a symmetric algorithm relies on the existence of internal trust within the system. In other words, the authentication mechanism assumes that there is a level of trust within the system itself, allowing for secure communication. This trust can be established through various means, such as through the use of trusted certificates or secure channels.

The correct answer is "poligramska." The explanation for this answer is that "poligramska" refers to the substitution cipher where the basic element is the substitution of groups of characters. In this type of cipher, groups of characters are replaced with other groups of characters according to a specific rule or key. This technique is commonly used in cryptography to encrypt and decrypt messages.

The correct answer is "iterativni blokovski algoritam". The explanation is that the AES algorithm is an iterative block cipher algorithm. It operates on fixed-size blocks of data and uses multiple rounds of encryption to transform the input data into ciphertext. Each round consists of several operations, including substitution, permutation, and mixing of the data. This iterative process increases the security of the algorithm and makes it resistant to various cryptographic attacks.

Linear shift registers are used as building blocks for more complex generators. They are not a complete solution for generating a random sequence of numbers, but rather a component that is used in combination with other elements to create more sophisticated generators.

Staticka detekcija je metoda koja se koristi za postojanje skrivenih poruka u steganoanalizi.

The correct answer is "u postupku autentifikacije" (in the authentication process). The explanation for this is that the primary use of a hash function is in the authentication process. Hash functions are commonly used to verify the integrity of data and ensure that it has not been tampered with during transmission or storage. In the context of authentication, hash functions are used to create a unique identifier for a piece of data, such as a password, and compare it with the stored hash value to verify the authenticity of the user.

ECB (Electronic Codebook Mode) encrypts each block of plaintext separately using the same key K. It does not depend on the previous blocks or their ciphertexts for encryption. Each block of plaintext is encrypted by performing an XOR operation between that block and the ciphertext of the previous block. To encrypt a block of plaintext, a subkey is generated from the previous block's subkey and the previous block of plaintext.

The given correct answer states that the property of cryptographic algorithms where all keys are equally probable during a brute force attack is called the property of confusion. This means that the algorithm should provide a level of complexity and randomness in the relationship between the key and the cipher text, making it difficult for an attacker to determine the key through exhaustive search. The confusion property adds an additional layer of security by making it harder for an attacker to derive meaningful information from the cipher text without knowing the correct key.

Integritet podataka se odnosi na skup aktivnosti koje se preduzimaju kako bi se sprečila ili detektovala neovlašćena izmena ili brisanje podataka, bez obzira na to da li se podaci čuvaju ili prenose. Ovo je važno kako bi se osiguralo da podaci ostanu tačni, celoviti i nepromenjeni tokom svog životnog ciklusa. Integritet podataka je ključan za održavanje pouzdanosti i kvaliteta podataka.

The given correct answer is "monoalfabetska". This is because the question is asking for the name of the substitution in which one character is always replaced by the same character. "Monoalfabetska" refers to a substitution cipher where each letter of the plaintext is consistently replaced by a corresponding letter from a fixed alphabet.

The correct answer is "potvrdu vlasnistva nad javnim kljucem" which translates to "confirmation of ownership of the public key" in English. A certificate is used to verify the ownership of a public key, ensuring that the key belongs to the intended owner and has not been tampered with. It is commonly used in authentication processes to establish trust between parties in a secure communication environment.

A cryptographic system that uses a public key system for exchanging a symmetric key and then switches to symmetric cryptography is called a hybrid system. In this system, the public key encryption is used to securely exchange a symmetric key, which is then used for the actual encryption and decryption of the data. This combination of both asymmetric and symmetric cryptography provides the benefits of both systems - the secure key exchange of asymmetric encryption and the efficiency of symmetric encryption for bulk data encryption.

The given correct answer is "sekvencijalni algoritam". This is because the question asks for the name of an algorithm that processes the elements of an open text one by one. "Sekvencijalni algoritam" translates to "sequential algorithm" in English, which accurately describes the process of sequentially processing the elements of the open text.

The correct answer is "Viznerova" because the Vigenère cipher, also known as the Vigenère-Vernam cipher or Viznerova šifra in Croatian, is a polyalphabetic substitution cipher that uses a series of different Caesar ciphers based on the letters of a keyword. This means that different letters in the plaintext will be shifted by different amounts, making it more secure than a simple Caesar cipher. The other options listed, Afina, Cezarova, and Hilova, do not refer to known polyalphabetic ciphers.

MAC (Message Authentication Code) može da se koristi u procesu provere integriteta. Verifikuje se da li je poruka bila izmenjena tokom prenosa tako što se generiše i šalje kod koji se zasniva na sadržaju poruke i tajnom ključu. Primalac zatim generiše isti kod koristeći primljenu poruku i tajni ključ i upoređuje ga sa primljenim kodom. Ako se poklapaju, to znači da poruka nije bila izmenjena i integritet je potvrđen.

The explanation for the given answer is that in CB (Cipher Block Chaining), each block of plaintext is encrypted by performing an XOR operation between that block and the ciphertext of the previous block. This ensures that each block is dependent on the previous block, adding an extra layer of security to the encryption process.

This answer is correct because the given statement describes an active attack where unauthorized changes are made to access rights or the functioning of a system. Such an attack compromises the integrity of the data, as it manipulates or alters the data in an unauthorized manner, potentially leading to loss or corruption of information.

A pseudo-random number sequence is used as a key for sequential cipher systems.

The correct answer is Vernamova and Hilova. The question is asking for the ciphers among the given options. Vernamova refers to the Vernam cipher, also known as the one-time pad, which is a symmetric encryption algorithm. Hilova refers to the Hill cipher, which is a polygraphic substitution cipher. Afin and Cezareva are not ciphers, so they are not the correct answers.

The given correct answer is "supstitucija homofona". This term refers to a substitution in which most of the characters are replaced with the same ones, except for the most frequent ones, which can be replaced in multiple ways. In other words, it is a type of substitution where the majority of characters are changed in a consistent manner, except for the most common characters that can be substituted in various ways.

The correct answer is Afina, Cezarova, and Prosta supstitucija. These three codes are examples of monoalphabetic ciphers, where each letter in the plaintext is consistently replaced by a corresponding letter in the ciphertext. In Afina cipher, a letter is shifted by a certain number of positions in the alphabet. Cezarova cipher is a specific type of Afina cipher where the shift is always by three positions. Prosta supstitucija cipher involves substituting each letter with a different letter from the alphabet. Hilova cipher, on the other hand, is not a monoalphabetic cipher as it uses a different substitution for each occurrence of a letter.

The correct answer is "Hilova, Plejferova." These are the names of different types of polygraphic ciphers. "Hilova" refers to the Hill cipher, a polygraphic substitution cipher that uses linear algebra to encrypt and decrypt messages. "Plejferova" refers to the Playfair cipher, another type of polygraphic substitution cipher that uses a 5x5 grid of letters to encrypt and decrypt messages.

The correct answer is "autorizacija". When the sender encrypts a message with the recipient's public key and sends such a ciphertext to the recipient, the lack of authorization is the drawback of such communication. This means that anyone who has the recipient's public key can encrypt a message and send it to the recipient, without any verification or permission. This lack of authorization can lead to unauthorized access and potential security breaches in the communication process.