PDF 312-50v13 Study Guide

Blowfish is the only option that matches all the technical characteristics described. In CEH cryptography concepts, symmetric algorithms are commonly distinguished by their structure (block cipher versus stream cipher), block size, and supported key lengths. The question states the algorithm encrypts data in 64-bit blocks and supports a variable key size ranging from 32 bits up to 448 bits, and it was introduced as a replacement for DES. Blowfish fits precisely: it is a symmetric block cipher with a 64-bit block size and a configurable key length from 32 to 448 bits, designed to be fast in software and positioned historically as an alternative to older ciphers such as DES.

The other choices do not align with these identifying properties. RC4 is a stream cipher and does not operate on fixed-size blocks, so it cannot match the 64-bit block requirement. AES is a block cipher but uses a 128-bit block size with fixed key sizes of 128, 192, or 256 bits, not 32 to 448 bits. Twofish, while related historically as a successor-era design, also uses a 128-bit block size and fixed key sizes up to 256 bits, so it does not match either.

From a CEH perspective, the mention of variable key sizes also hints at risk evaluation: shorter keys in any cipher can be brute-forced, so secure deployments require strong key length selection and proper key management. Additionally, Blowfish’s 64-bit block size can be a concern in large-volume encryption scenarios due to block collision risks, which is why modern systems often prefer 128-bit block ciphers for new designs.

Ping of Death is a classic Denial-of-Service technique in which an attacker sends oversized or malformed IP packets that exceed the maximum allowed size when reassembled. In IP networks, the maximum packet size is 65,535 bytes. Historically, attackers exploited fragmentation by sending a series of IP fragments that, when reassembled by the target, resulted in a packet larger than the permitted limit or produced an invalid buffer condition. Vulnerable systems could crash, reboot, or become unstable because the network stack mishandled the reassembly process or failed to properly validate packet length and structure.

The scenario matches this behavior precisely: Sofia transmits “oversized, malformed packets” and the server “crashes intermittently due to processing failures.” That symptom is more consistent with a malformed-packet handling flaw than with pure traffic volume. An ICMP flood and an ACK flood are volumetric or resource-exhaustion attacks that overwhelm bandwidth or connection-handling capacity, typically degrading performance rather than directly causing crashes from malformed packet parsing. A Smurf attack is an amplification-based ICMP attack using broadcast addresses to multiply traffic toward a victim; again, it is about volume, not crafted malformed packets that trigger parsing failures.

CEH guidance highlights that PoD-style attacks exploit improper packet validation and reassembly logic. Modern systems are generally patched, but poorly maintained devices, legacy OS stacks, and some embedded implementations can still exhibit instability when exposed to malformed fragmentation and reassembly edge cases.

Insufficient logging and monitoring is the most direct threat highlighted by the scenario. In CEH-aligned cloud security concepts, visibility is foundational: without adequate telemetry, security teams cannot detect, investigate, or respond to malicious activity in time. The question explicitly states attackers “remained undetected” because the organization lacked mechanisms to track function-level activity and capture anomalous events. In a serverless architecture, this visibility gap can be especially damaging because there are no traditional servers for defenders to log into, and many security signals must be collected from cloud-native sources such as function invocation logs, API gateway logs, identity events, and centralized monitoring pipelines.

While privilege escalation is a common cloud threat, the question’s root cause is not described as excessive permissions or role abuse; it is the lack of detection capability. Loss of governance refers to weak policies, mismanaged accounts, and lack of control over cloud resources, which may contribute indirectly but is not the immediate failure described. Side-channel attacks are specialized and do not match the evidence of missed alerts and absent operational telemetry.

CEH guidance emphasizes implementing centralized logging, continuous monitoring, alerting, and anomaly detection as core controls. For serverless, this includes capturing detailed function execution logs, tracing, identity and access events, and integrating them into a SIEM/SOAR workflow. Effective monitoring enables rapid detection of abnormal invocation patterns, suspicious API calls, unusual data access, and persistence attempts—reducing dwell time and preventing small compromises from becoming major outages.

This scenario describes Linear Cryptanalysis, a technique detailed in CEH v13 Cryptography. Linear cryptanalysis involves finding linear approximations that relate plaintext bits, ciphertext bits, and key bits using XOR operations. By analyzing a large number of known plaintext–ciphertext pairs, attackers can identify statistical biases that reveal information about the secret key.

CEH v13 explains that linear cryptanalysis differs from differential cryptanalysis in its approach. While differential cryptanalysis studies how differences in plaintext affect differences in ciphertext, linear cryptanalysis focuses on linear relationships and probability distributions.

The mention of XOR combinations and statistical analysis of plaintext–ciphertext pairs directly aligns with linear cryptanalysis. Brute-force attacks attempt all keys without analysis. Differential cryptanalysis focuses on input differences, not linear equations. Side-channel attacks exploit physical characteristics such as power consumption or timing.

Modern block ciphers like AES are designed to resist linear cryptanalysis by ensuring that linear approximations occur with probabilities close to random. CEH v13 highlights linear cryptanalysis as a foundational attack method used to evaluate cipher strength.

Therefore, Option C is correct.