All Introduction-to-Cryptography Test Inside WGU Questions

Bit-flipping exploits target encryption modes or protocols that do not provide strong integrity, allowing attackers to modify ciphertext so that predictable changes occur in plaintext after decryption. To defend against this, protocols add an integrity mechanism that detects tampering. In WPA (including enterprise deployments), TKIP introduced a Message Integrity Check (MIC) called “Michael.” The MIC is computed over the frame contents (with additional fields) and verified by the receiver; if an attacker flips bits in transit, the MIC verification fails, and the frame is rejected. While AES (used by WPA2’s CCMP) also provides integrity via authenticated encryption, the option presented that directly names the tamper-detection mechanism associated with guarding against bit-flipping is MIC. A pre-shared key is an authentication/keying method (and not enterprise-mode anyway), and a “global encryption key” would be the opposite of what you want—global/static keys worsen security. Therefore, the intended mechanism that mitigates bit-flipping by detecting unauthorized modifications is the Message Integrity Check.

Digital signatures provide integrity, authenticity, and typically non-repudiation by using an asymmetric key pair. The signer uses the private key to create a signature over a message (usually over a hash/digest of the message). Because the private key is kept secret, only the legitimate signer should be able to produce a valid signature. Anyone who has the corresponding public key can then validate the signature: they verify that the signature matches the message digest under the public key and that the signed data has not been altered. This is why the public key can be widely distributed (often inside an X.509 certificate) while the private key must be protected by the signer. If a public key were used to sign, anyone could forge signatures; if a private key were required for validation, only the signer could validate, defeating the purpose of public verifiability. Therefore, the correct key roles are private key for signing and public key for signature validation.

3DES (Triple DES) applies the DES block cipher three times to increase effective security, and its commonly cited valid key sizes correspond to how many independent DES keys are used. Two-key 3DES uses two 56-bit DES keys (K1 and K2) in an EDE sequence (Encrypt with K1, Decrypt with K2, Encrypt with K1), yielding 112 bits of keying material (ignoring parity bits). Three-key 3DES uses three independent 56-bit keys for a total of 168 bits of keying material, but that option is not listed here. A 56-bit key corresponds to single DES, not 3DES. 128-bit is associated with AES, not 3DES. 2,048-bit is typical for RSA keys, not symmetric ciphers. Therefore, among the choices provided, 112-bit is a valid 3DES key size. While 3DES is now deprecated for many uses due to its 64-bit block size and performance limitations, understanding its keying options remains important for legacy system assessment.

Frequency analysis is a classical cryptanalysis technique that exploits predictable statistical patterns in natural language. In English, certain letters (like E, T, A, O, I, N) occur more frequently than others, and common digrams/trigrams (TH, HE, IN, ER) appear with recognizable distribution. When a cipher preserves character boundaries (as in many substitution ciphers), the ciphertext will also show frequency patterns—though mapped to different symbols. The analyst counts ciphertext character occurrences, compares the distribution to expected English letter frequencies, and infers likely plaintext mappings. “Spotting variations” refers to observing differences in how often symbols appear and using that to plot relationships between ciphertext and standard English. Brute force instead tries all keys; known-plaintext attacks rely on having plaintext–ciphertext pairs; chosen-ciphertext attacks involve decrypting attacker-selected ciphertexts. Those are different attack models. Frequency analysis is specifically about statistical correlation between ciphertext symbols and language characteristics, which is why it is effective against monoalphabetic substitution and weak polyalphabetic schemes with short periods.