Final answer:
Confidentiality involves protecting information from unauthorized access, integrity ensures data remains accurate, and availability refers to accessibility. AES-ECB mode encrypts blocks independently, resulting in encrypted data without patterns. In CBC and CTR modes, the impact of errors on decryption varies. The function f(x) = x mod 10000 lacks preimage resistance. To exchange large files without a secret key, Alice and Bob can use hybrid encryption and public-key cryptography.
Step-by-step explanation:
(A) Confidentiality: Confidentiality is one of the three pillars of information security and refers to the protection of sensitive information from unauthorized access or disclosure. For example, if a hacker gains access to a database of customer information and exposes personal details such as names, addresses, and credit card numbers, it violates the confidentiality of that data.
Integrity: Integrity ensures that data remains intact, accurate, and trustworthy throughout its lifecycle. When integrity is violated, unauthorized modification or tampering with data occurs. An example of integrity violation is if an attacker alters the contents of a file, changing critical information without detection.
Availability: Availability refers to the accessibility and usability of data or systems when needed. An example of availability violation is a Distributed Denial of Service (DDoS) attack, where an attacker floods a network or website with traffic, causing it to become unavailable for legitimate users.
(B) AES-ECB mode, or Electronic CodeBook mode, encrypts data by dividing it into fixed-size blocks and applying the AES encryption algorithm to each block independently. In this mode, each block is encrypted separately, resulting in encrypted blocks that do not reveal patterns. As a result, when Alice encrypts a high-resolution BMP file using AES-ECB mode, the encrypted result may look like noise without any discernible patterns.
(C) In CBC (Cipher Block Chaining) and CTR (Counter) modes of operation in AES, each block of ciphertext is generated based on the previous block's encryption. In CBC mode, the error in the 2nd bit of the third block in the ciphertext affects the decryption of subsequent blocks, rendering them unreadable. However, Bob can still correctly decrypt the bits that were not impacted by the error. In CTR mode, errors in specific blocks do not propagate, and Bob can decrypt all the unaffected bits correctly.
(D) The function f(x) = x mod 10000 is not a good one-way hash function because it lacks the property of preimage resistance. A one-way hash function should make it computationally infeasible to determine the original input given only the hash value. However, in this case, an attacker could easily find inputs that produce the same hash value (collision) by trying different values of x that are congruent modulo 10000.
(E) To efficiently exchange a large data file of several GBs without sharing a secret key, Alice and Bob can use a combination of techniques such as hybrid encryption and public-key cryptography. They can generate a symmetric encryption key specifically for that file, encrypt the file using the key, and then encrypt the symmetric key itself with Bob's public key. Alice can send the encrypted file along with the encrypted symmetric key to Bob, who can then decrypt the symmetric key using his private key and use it to decrypt the file.