EC-Council 312-50 Exam Materials: What Encryption Algorithm Uses The Same Pre-Shared Key To Encrypt And Decrypt Data?

In the intricate and ever-evolving world of cybersecurity, the ability to protect sensitive information from unauthorized access is paramount. At the heart of this protection lies cryptography, the science of secure communication in the presence of adversaries. Among the various cryptographic techniques, encryption stands as the primary method for transforming readable data into an unreadable format, ensuring its confidentiality. For aspiring ethical hackers and cybersecurity professionals preparing for the EC-Council 312-50 (Certified Ethical Hacker - CEH) Eertification Exam, a deep understanding of encryption algorithms is not merely theoretical; it's a fundamental skill for identifying vulnerabilities, assessing security postures, and implementing robust defenses. This article delves into a specific, foundational concept: the encryption algorithm that uses the same pre-shared key for both encryption and decryption. We will explore its core principles, operational mechanisms, characteristics, common algorithms, and its vital relevance within the context of ethical hacking and the CEH exam.

Introduction: The Art of Cryptographic Concealment

Imagine sending a confidential message across enemy lines. If the message falls into the wrong hands, critical information could be compromised. To prevent this, you would likely employ some form of secret code or cipher, ensuring that only the intended recipient, who possesses the key to decipher the code, can understand the message. This ancient human practice of concealing information is the essence of cryptography in the digital age.

In the realm of computers and networks, where data flows constantly across diverse and often insecure channels, the need for cryptographic concealment is more critical than ever. Personal identifiable information (PII), financial transactions, intellectual property, and government secrets are all susceptible to interception and compromise if left unprotected. Encryption serves as the digital lock and key, transforming plaintext (readable data) into ciphertext (unreadable, encrypted data) using a mathematical algorithm and a cryptographic key. Only someone with the correct key can reverse the process, decrypting the ciphertext back into plaintext.

Cryptography is a vast and complex field, encompassing various techniques, protocols, and algorithms. These generally fall into two broad categories based on how keys are managed: symmetric-key cryptography and asymmetric-key (public-key) cryptography. While both are indispensable, they serve different purposes and have distinct characteristics. For ethical hackers, understanding both types is crucial for identifying weaknesses in cryptographic implementations, bypassing security controls (where ethical and authorized), and advising on secure system design.

The EC-Council 312-50 (CEH) certification exam is designed to validate the skills required to be an ethical hacker. This includes a strong emphasis on cryptographic principles, understanding how encryption algorithms work, and recognizing their strengths and weaknesses. The ability to identify the type of encryption in use, and its associated vulnerabilities, is a core competency for any certified ethical hacker. This article will focus on the fundamental concept of using a single, shared key for both encryption and decryption, a cornerstone of many real-world security implementations.

The Core Concept: Symmetric Encryption – The One-Key Solution

When facing the question, "What encryption algorithm uses the same pre-shared key to encrypt and decrypt data?", the unequivocal answer is symmetric encryption algorithms.

Symmetric encryption, also known as private-key cryptography or secret-key cryptography, is a method of encryption where the same cryptographic key is used for both the encryption of plaintext and the decryption of ciphertext. This single key is a shared secret between the communicating parties.

Imagine two individuals, Alice and Bob, who want to communicate securely. In a symmetric encryption system:

1. Key Generation: Alice and Bob must first agree upon and securely exchange a single, secret key. This key is often referred to as a "pre-shared key" because it must be known to both parties before secure communication can begin.
2. Encryption (Alice): When Alice wants to send a confidential message to Bob, she uses the agreed-upon secret key and a specific symmetric encryption algorithm to transform her plaintext message into ciphertext.
3. Transmission: The ciphertext is then transmitted over an insecure channel (e.g., the internet). If an unauthorized party intercepts the ciphertext, it appears as gibberish and cannot be understood without the secret key.
4. Decryption (Bob): When Bob receives the ciphertext, he uses the exact same secret key and the corresponding symmetric decryption algorithm to transform the ciphertext back into Alice's original plaintext message.

The "one-key solution" aspect is both the greatest strength and the greatest challenge of symmetric encryption.

• Strength: It makes symmetric encryption algorithms incredibly fast and efficient for encrypting and decrypting large amounts of data, far more so than asymmetric encryption. This speed is why symmetric encryption is widely used for data confidentiality in bulk encryption scenarios.
• Challenge: The critical prerequisite is the secure exchange of the shared secret key. If the key is intercepted during its initial exchange, or if it falls into the wrong hands at any point, the entire security of the communication is compromised. This "key distribution problem" is the Achilles' heel of symmetric cryptography.

Despite this challenge, symmetric encryption remains a fundamental component of modern cryptography due to its speed and efficiency. It is often used in conjunction with asymmetric encryption (which solves the key distribution problem) in hybrid cryptographic systems, where asymmetric encryption is used to securely exchange the symmetric key, and then the symmetric key is used for the bulk data encryption. Understanding this core concept is essential for any cybersecurity professional, as it forms the basis for many secure communication protocols and data at rest encryption solutions.

How Symmetric Encryption Works

Delving a bit deeper, the mechanics of how symmetric encryption algorithms transform data are fascinating and foundational for a CEH. While the specific mathematical operations vary between algorithms, the general principles involve two main types: stream ciphers and block ciphers.

1. Stream Ciphers:

• Mechanism: A stream cipher encrypts plaintext one bit or one byte at a time. It generates a pseudo-random keystream (a sequence of bits or bytes) using the secret key, and then combines this keystream with the plaintext using a simple operation, typically the XOR (exclusive OR) logical operation.
• Encryption: Ciphertexti​=Plaintexti​⊕Keystreami​
• Decryption: Plaintexti​=Ciphertexti​⊕Keystreami​ (since x⊕y⊕y=x)
• Characteristics:
• Speed: Generally very fast.
• Low Error Propagation: A single bit error in the ciphertext typically only affects that single bit in the plaintext.
• Sensitivity to Key Reuse: Crucially, if the same keystream is used with the same key to encrypt two different plaintexts, the security can be severely compromised. This is why stream ciphers often use a nonce (a "number used once") or initialization vector (IV) to ensure a unique keystream for each encryption.
• Examples: RC4 (though largely deprecated due to vulnerabilities), Salsa20, ChaCha20.
• Analogy: Imagine a long sequence of random numbers (the keystream) known to both parties. To encrypt, you add (XOR) your message's numbers to the random numbers. To decrypt, the recipient adds (XORs) the same random numbers to the encrypted message to get the original back.

2. Block Ciphers:

• Mechanism: A block cipher encrypts data in fixed-size blocks (e.g., 64-bit blocks, 128-bit blocks). The algorithm takes a block of plaintext and, using the secret key, transforms it into a ciphertext block. This transformation involves multiple rounds of substitutions (replacing data with other data based on the key) and permutations (rearranging the order of data bits).
• Characteristics:
• Rounds: Most block ciphers are iterative, performing the encryption process in multiple "rounds" to increase security.
• Modes of Operation: To encrypt messages larger than the block size, or to ensure that identical plaintext blocks don't produce identical ciphertext blocks (which would leak information), block ciphers use various "modes of operation" (e.g., Electronic Codebook (ECB), Cipher Block Chaining (CBC), Counter Mode (CTR), Galois/Counter Mode (GCM)). These modes introduce randomness (like an IV) and link blocks together.
• Error Propagation: Error propagation varies significantly depending on the mode of operation. For instance, an error in one ciphertext block in CBC mode can affect subsequent blocks.
• Examples: AES (Advanced Encryption Standard), DES (Data Encryption Standard - deprecated), Triple DES (3DES), Blowfish, Twofish.
• Analogy: Imagine a complex machine with many gears (the algorithm) and a secret combination (the key). You feed a small chunk of your message into the machine, turn the gears according to the combination, and a scrambled chunk comes out. The recipient uses the same machine and combination to reverse the process.

The Role of the Key:

In both types, the key is the absolute critical element. The strength of the encryption (assuming a strong algorithm) relies entirely on:

• Key Length: Longer keys generally provide stronger encryption, making brute-force attacks computationally infeasible.
• Key Randomness: Keys must be generated using cryptographically secure random number generators.
• Key Secrecy: The key must be kept absolutely secret. If the key is compromised, the encryption is useless.

A CEH needs to understand not just that these algorithms exist but also their basic operational differences, their strengths, and weaknesses (e.g., why ECB mode is insecure for most data, why RC4 is deprecated), and how these factors impact overall system security. This deep dive into the mechanisms is crucial for assessing cryptographic implementations.

Characteristics of Symmetric Encryption: Advantages and Disadvantages (CEH Perspective)

From an ethical hacker's (CEH) perspective, understanding the inherent characteristics of symmetric encryption is vital for both identifying robust security measures and pinpointing potential weaknesses to exploit (ethically, of course).

Advantages of Symmetric Encryption:

1.     Speed and Efficiency:

• High Throughput: Symmetric algorithms are significantly faster than asymmetric algorithms. They use simpler mathematical operations, making them ideal for encrypting large volumes of data quickly.
• Resource Efficiency: They require less computational power and memory, making them suitable for resource-constrained devices (e.g., IoT devices, mobile phones) and high-traffic network links.
• CEH Relevance: A CEH will encounter symmetric encryption protecting bulk data transfers (e.g., VPN tunnels, TLS sessions after the initial handshake) or data at rest (e.g., encrypted hard drives). Understanding their speed helps analyze network performance impacts and identify where bulk encryption is likely used.

2.     Strong Security (with proper implementation):

• Resilience to Brute Force: With sufficient key length (e.g., 128-bit or 256-bit for AES), symmetric encryption is highly resistant to brute-force attacks. The number of possible keys makes it computationally infeasible to guess.
• Mature Algorithms: Algorithms like AES have undergone extensive scrutiny by cryptographers worldwide and are considered highly secure when implemented correctly.
• CEH Relevance: A CEH needs to assess if the chosen symmetric algorithm and key length are strong enough for the data's classification. They also look for implementation flaws that weaken the encryption, such as predictable IVs or improper mode usage.

3.     Simplicity of Concept:

• The core idea of a single key for both operations is conceptually straightforward compared to the public/private key pair of asymmetric encryption.
• CEH Relevance: While simple in concept, implementation errors are common. A CEH can quickly grasp the intended security model and then look for deviations.

Disadvantages of Symmetric Encryption:

1.     Key Distribution Problem:

• The Biggest Challenge: The most significant hurdle. The shared secret key must be securely exchanged between the communicating parties before any encrypted communication can begin. If this initial key exchange is compromised, the entire security of subsequent communications is lost.
• Practical Difficulties: How do Alice and Bob securely exchange the key if they don't already have a secure channel? This often requires out-of-band methods (e.g., physical delivery, trusted courier) or, more commonly in practice, using asymmetric encryption for key exchange.
• CEH Relevance: This is a prime target for ethical hackers. Weaknesses in key distribution protocols (e.g., weak Diffie-Hellman parameters, reliance on insecure channels for key exchange) are major vulnerabilities. A CEH will look for methods to intercept or derive shared keys.

2.     Key Management Complexity (Especially in Large Networks):

• Scalability Issue: In a network with 'n' participants, each pair wishing to communicate securely needs a unique shared key. This leads to n×(n−1)/2 keys. For a small number of users, it's manageable; for a large organization, it becomes an unmanageable key management nightmare.
• Key Revocation and Update: If a key is compromised, it must be revoked and new keys distributed to all affected parties, which is complex in large environments.
• CEH Relevance: A CEH will assess an organization's key management practices. Poor key management (e.g., reusing keys, weak key storage, lack of rotation) is a critical finding.

3.     No Non-Repudiation:

• Shared Secret: Since the same key encrypts and decrypts, both parties possess the secret. If Alice sends a message to Bob, Bob cannot definitively prove that Alice sent it (and not someone else who also had the key).
• CEH Relevance: A CEH understands that symmetric encryption alone does not provide non-repudiation. For digital signatures and verifiable authenticity, asymmetric cryptography is required. This influences how security models are designed.

4.     Forward Secrecy Concerns (in some applications):

• If a long-term symmetric key is compromised, all past and future communications encrypted with that key are compromised.
• CEH Relevance: Ethical hackers understand that protocols need to incorporate mechanisms like Perfect Forward Secrecy (PFS), often using ephemeral Diffie-Hellman key exchanges, to mitigate this risk.

From the perspective of a CEH, understanding these characteristics is about more than just definitions. It's about recognizing the inherent trade-offs, potential attack surfaces, and the strategic decisions involved in deploying cryptographic solutions. A CEH leverages this knowledge to identify misconfigurations, weak implementations, and conceptual flaws that could be exploited.

Common Symmetric Encryption Algorithms (CEH Relevance)

The EC-Council 312-50 (CEH) exam expects candidates to be familiar with the most common symmetric encryption algorithms, understanding their relative strengths, weaknesses, and typical applications.

1. DES (Data Encryption Standard):

• Key Length: 56-bit (effectively).
• Block Size: 64-bit.
• Status: Deprecated and considered insecure for most applications today. Its key length is too short, making it vulnerable to brute-force attacks (can be broken in hours or even minutes with modern hardware).
• CEH Relevance: Important for historical context and understanding legacy systems. A CEH might encounter DES in old systems or protocols and should immediately flag it as a critical vulnerability. Understanding why it's weak (small key space) is crucial.

2. 3DES (Triple DES / Triple Data Encryption Algorithm - TDEA):

• Key Length: 112-bit or 168-bit (using two or three DES keys).
• Block Size: 64-bit.
• Mechanism: Applies the DES algorithm three times (Encrypt-Decrypt-Encrypt or EEE), usually with two or three different keys.
• Status: While more secure than DES, it's slow and generally being phased out in favor of AES. It still has some use in legacy financial systems due to its long-standing approval. It is susceptible to meet-in-the-middle attacks (with reduced complexity compared to brute-forcing a 168-bit key).
• CEH Relevance: A CEH might encounter 3DES in older protocols or hardware (e.g., some VPNs, older payment terminals). While stronger than DES, its performance overhead and the existence of more modern alternatives mean a CEH should recommend migration. Understanding meet-in-the-middle attack concepts is relevant.

3. AES (Advanced Encryption Standard / Rijndael):

• Key Lengths: 128-bit, 192-bit, or 256-bit.
• Block Size: 128-bit.
• Status: The current global standard for symmetric encryption. It is highly secure, efficient in both hardware and software, and widely adopted across virtually all modern secure communication protocols (e.g., TLS, SSH, IPsec, disk encryption).
• CEH Relevance: This is the most important symmetric algorithm for a CEH. They must know AES's strengths, typical key lengths, and its ubiquitous presence. A CEH will assess if AES is being used correctly (e.g., appropriate mode of operation like GCM, proper IV/nonce usage). Vulnerabilities found in AES implementations are extremely rare and highly significant.

4. Blowfish:

• Key Length: 32-bit to 448-bit.
• Block Size: 64-bit.
• Status: A fast and generally secure algorithm, but its 64-bit block size is becoming a concern with the rise of birthday attacks (which exploit the probability of collisions in block cipher outputs). Not as widely adopted as AES.
• CEH Relevance: A CEH might encounter Blowfish in specific applications (e.g., some password managers, file encryption utilities, VPN clients). Awareness of its characteristics and the diminishing security of its 64-bit block size is relevant.

5.     Twofish:

• Key Length: 128-bit, 192-bit, or 256-bit.
• Block Size: 128-bit.
• Status: Was a finalist in the AES competition and is considered very strong and secure. It offers good performance and flexibility.
• CEH Relevance: While less commonly encountered than AES, a CEH should be aware of Twofish as a strong alternative. Its robustness aligns with secure design principles.

6.     RC4 (Rivest Cipher 4):

• Key Length: Variable, typically 40-bit to 256-bit.
• Type: Stream cipher.
• Status: Largely deprecated and considered insecure for most applications. It has known biases and vulnerabilities, especially if the initial bytes of the keystream are reused.
• CEH Relevance: A CEH might find RC4 used in older versions of WEP (Wireless Equivalent Privacy) or TLS. Identifying RC4 in use should immediately trigger a critical vulnerability flag due to its known weaknesses.

A CEH's role is to identify and report weaknesses. Knowing which algorithms are strong, which are weak, and why they are weak, is critical for vulnerability assessments and penetration testing. The exam will definitely test this knowledge. For comprehensive preparation, resources like Study4Pass provide targeted information on these algorithms, ensuring you know their details for the EC-Council 312-50 exam.

Typical Applications of Symmetric Encryption

Symmetric encryption, despite its key distribution challenge, is the workhorse of cryptography due to its speed and efficiency. A CEH needs to recognize where symmetric encryption is commonly applied, as these are often targets for security assessments and potential exploits.

1. Data at Rest Encryption:

• Application: Encrypting data stored on hard drives, SSDs, USB drives, or cloud storage.
• Examples:
• Full Disk Encryption (FDE): Tools like BitLocker (Windows), FileVault (macOS), and LUKS (Linux) use AES to encrypt entire disk partitions.
• Database Encryption: Encrypting sensitive data fields within databases.
• File Encryption: Using tools to encrypt individual files or folders.
• CEH Relevance: A CEH would assess how keys for FDE are managed (e.g., TPM integration, key escrow), how database encryption keys are protected, and look for weaknesses in key strength or storage that could lead to data exfiltration.

2. Secure Communication Protocols:

• Application: Providing confidentiality for data transmitted over networks.
• Examples:
• TLS/SSL (Transport Layer Security/Secure Sockets Layer): While initial key exchange uses asymmetric encryption, the bulk of the data transfer in an HTTPS session is protected by AES or 3DES (in older versions). This is a hybrid encryption approach.
• IPsec (Internet Protocol Security): Used for VPNs. IPsec often uses AES or 3DES for data confidentiality within the tunnel.
• SSH (Secure Shell): Uses symmetric encryption (like AES) for data transfer once a secure channel is established.
• Wireless Encryption (WPA2/WPA3): Uses AES (specifically AES-CCMP for WPA2, AES-GCMP for WPA3) to secure Wi-Fi communications.
• CEH Relevance: Understanding how these protocols use symmetric encryption is fundamental. A CEH will look for misconfigurations in these protocols (e.g., use of weak ciphers like RC4 in TLS, weak WPA2 pre-shared keys, susceptibility to downgrade attacks).

3. Data Archiving and Backup:

• Application: Encrypting large datasets for long-term storage or backup purposes.
• CEH Relevance: Assessing the strength of the encryption used for backups. Are the keys stored securely? Is the encryption robust enough for the data's sensitivity?

4. Hardware Encryption:

• Application: Built-in encryption capabilities in hardware devices.
• Examples: Self-Encrypting Drives (SEDs), some network appliances.
• CEH Relevance: Evaluating the implementation and security of hardware-based encryption, looking for weaknesses in the firmware or key management.

5. Random Number Generation (RNG):

• Application: While not directly for encrypting user data, symmetric algorithms are often used as components within cryptographically secure pseudorandom number generators (CSPRNGs), which are crucial for generating strong cryptographic keys and nonces.
• CEH Relevance: Understanding the importance of truly random or cryptographically secure pseudorandom numbers for key generation. Weak RNGs are a major vulnerability.

For the CEH exam, it's not enough to just list the algorithms; you need to connect them to their real-world applications and understand the security implications within those contexts. This practical understanding is what distinguishes a competent ethical hacker.

EC-Council 312-50 (CEH) Exam Relevance

The EC-Council 312-50 (Certified Ethical Hacker) exam places significant emphasis on cryptography, and symmetric encryption is a foundational element within this domain. A CEH's role is to understand vulnerabilities from an attacker's perspective while possessing the knowledge to secure systems from those very threats. Therefore, deep knowledge of symmetric encryption is critical for several exam objectives:

1. Cryptography Concepts (Domain 08: Cryptography):

• Core Definition: Directly tested. You must know that symmetric encryption uses the same key for encryption and decryption.
• Algorithm Types: Understanding the difference between stream ciphers and block ciphers, and knowing examples of each.
• Modes of Operation: Recognizing common block cipher modes (ECB, CBC, CTR, GCM) and their security implications (e.g., why ECB is generally insecure).
• Key Management: Understanding the key distribution problem and its solutions (often involving asymmetric crypto in hybrid schemes).

2. Vulnerability Analysis (Domain 06: Vulnerability Analysis):

• Weak Cryptographic Implementations: Identifying where weak or deprecated symmetric algorithms (e.g., DES, RC4) are in use, or where strong algorithms are implemented incorrectly (e.g., static IVs, insufficient key length, predictable keys).
• Cryptographic Attacks: Understanding attacks relevant to symmetric encryption, such as brute-force attacks (especially against short keys), chosen-plaintext/ciphertext attacks, meet-in-the-middle attacks (against 3DES), and side-channel attacks.

3. System Hacking (Domain 03: System Hacking) and Network Hacking (Domain 04: Network Hacking):

• Password Cracking: Understanding how symmetric encryption is used for password hashing/storage (though often combined with salting and stretching) and the techniques to crack them.
• Wireless Hacking: Knowledge of WEP/WPA/WPA2/WPA3 encryption standards and their associated symmetric algorithms (e.g., RC4 for WEP, AES for WPA2/3), and common attacks against them.
• VPN Exploitation: Understanding how IPsec and TLS/SSL VPNs utilize symmetric encryption for data confidentiality, and looking for weaknesses in their configuration.

4. Security Testing (Domain 07: Hacking Web Servers & Applications; Domain 09: Cloud Computing; Domain 10: IoT Hacking):

• Web Application Security: Identifying weak encryption in web application traffic or data storage.
• Cloud Security: Understanding how symmetric encryption is used for data at rest and in transit within cloud environments.
• IoT Security: Assessing the often-resource-constrained IoT devices for weak or poorly implemented symmetric encryption.

The CEH exam is known for its breadth, and cryptography is a foundational pillar. You'll encounter questions that require you to identify the algorithm, choose the correct mode, understand the vulnerabilities, and propose mitigation strategies. For thorough preparation, reliable study materials are essential.

Study4Pass offers comprehensive EC-Council 312-50 certification exam materials that precisely cover these cryptographic concepts. Their practice tests are invaluable for solidifying your understanding, simulating the real exam environment, and identifying areas where you need more study. With detailed explanations for each question, you not only learn the answer but also why it's correct. Moreover, a study4pass practice test pdf is just in 19.99 USD, making high-quality exam preparation accessible and affordable. This investment will equip you with the knowledge to confidently answer questions on symmetric encryption and all other critical CEH domains, ensuring you are well-prepared for the challenges of ethical hacking.

Bottom Line: The Power and Peril of the Shared Secret

The question "What encryption algorithm uses the same pre-shared key to encrypt and decrypt data?" leads us directly to the heart of symmetric encryption. This fundamental cryptographic paradigm, characterized by its "one-key solution," underpins a vast majority of the world's digital security infrastructure due to its unparalleled speed and efficiency in handling large volumes of data.

From securing your daily web Browse (via the symmetric session key in TLS) to encrypting entire hard drives, symmetric algorithms like AES are the invisible guardians of our digital confidentiality. However, their power comes with a significant peril: the absolute dependence on the secrecy and secure distribution of that single, shared key. The key distribution problem and the complexities of key management in large-scale environments represent the primary Achilles' heel of symmetric cryptography.

For anyone preparing for the EC-Council 312-50 (Certified Ethical Hacker) exam, a comprehensive understanding of symmetric encryption is non-negotiable. It's about more than just definitions; it's about recognizing the common algorithms, appreciating their strengths and weaknesses, identifying their applications, and, crucially, being able to pinpoint and exploit (ethically) vulnerabilities in their implementation. A CEH must be adept at assessing everything from the chosen algorithm's strength to the security of key storage and management.

In the dynamic arena of cybersecurity, the shared secret of symmetric encryption remains both a powerful tool for defense and a critical target for attack. Mastery of this concept is a testament to a cybersecurity professional's foundational knowledge, enabling them to effectively secure systems and detect potential weaknesses in the cryptographic fabric.

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Actual Questions from EC-Council 312-50 Certification Exam

Here are 5 actual-style questions from the EC-Council 312-50 (Certified Ethical Hacker) certification exam, focusing on symmetric encryption and related concepts:

Which of the following describes an encryption algorithm that uses the same key for both encryption and decryption?

A. Asymmetric encryption

B. Hashing algorithm

C. Symmetric encryption

D. Digital signature

A security professional is evaluating a legacy system that uses DES for data encryption. From a cryptographic perspective, what is the MOST significant vulnerability associated with DES in modern applications?

A. It has too complex a key exchange mechanism.

B. Its 64-bit block size is susceptible to birthday attacks.

C. Its 56-bit key length is too short and vulnerable to brute-force attacks.

D. It does not provide non-repudiation.

Which symmetric encryption algorithm is the current global standard, widely used for data confidentiality in protocols like TLS, IPsec, and WPA3, and supports key lengths of 128, 192, and 256 bits?

A. 3DES

B. RC4

C. AES

D. Blowfish

In a symmetric encryption system, what is the primary challenge that must be overcome to establish secure communication between two parties, Alice and Bob?

A. The high computational cost of encryption and decryption.

B. The secure exchange of the shared secret key.

C. The inability to encrypt large amounts of data.

D. The lack of available cryptographic algorithms.

A security auditor identifies that an application uses the Electronic Codebook (ECB) mode of operation for encrypting sensitive but identical plaintext blocks. What is the main security risk associated with using ECB mode for most data?

A. It is extremely slow for bulk encryption.

B. It is vulnerable to chosen-plaintext attacks that can reveal patterns.

C. It does not allow for parallel processing of blocks.

D. It requires a unique Initialization Vector (IV) for each block, which is difficult to manage.