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Quizzes > Computers & IT

Asymmetric Encryption: Choose Two Items

Quick, free public and private keys quiz. Instant results.

Editorial: Review CompletedCreated By: Minhaaj Bin ShahidUpdated Aug 26, 2025
Difficulty: Moderate
2-5mins
Learning OutcomesCheat Sheet
Paper art lock and key on teal background for asymmetric encryption quiz.

This quiz helps you choose the two items used in asymmetric encryption and see how they work together. Build confidence for exams with our public key cryptography quiz, explore broader topics in the cryptography knowledge quiz, and connect keys to certificates with the digital certificate quiz.

What are the two keys used in asymmetric encryption?
Secret key and session key
Public key and private key
Master key and session key
Symmetric key and IV
Asymmetric encryption relies on a pair of mathematically linked keys: a public key for encryption and a private key for decryption. The public key can be shared openly, while the private key must remain confidential. This dual-key mechanism enables secure communication without sharing a secret key in advance. See .
Asymmetric encryption is also known as what?
Secret-key cryptography
Public-key cryptography
Stream cipher method
Block cipher encryption
Asymmetric encryption is commonly referred to as public-key cryptography because it uses a public key for encryption and a private key for decryption. This distinguishes it from secret-key (symmetric) cryptography that uses the same key for both processes. Public-key systems are foundational for secure internet protocols. See .
Which algorithm is an example of asymmetric encryption?
SHA
DES
RSA
AES
RSA (Rivest - Shamir - Adleman) is one of the earliest and most widely used asymmetric encryption algorithms. It relies on the difficulty of factoring large composite numbers. AES and DES are symmetric ciphers, and SHA is a hashing algorithm, not for encryption. See .
In asymmetric encryption, which key is kept secret?
Private key
Public key
Initialization vector
Session key
The private key in an asymmetric system must be secured and kept secret by its owner. It is used to decrypt data encrypted with the corresponding public key or to create digital signatures. If the private key is exposed, the system's security is compromised. See .
Which key is distributed publicly in asymmetric encryption?
Secret key
Public key
Shared key
Private key
The public key is intended for wide distribution and use by anyone who needs to send encrypted data or verify a signature. It does not need to be kept secret. Its mathematical link to the private key allows decryption or signature verification only by the private key holder. See .
What type of mathematical function is fundamental to asymmetric encryption?
Trapdoor one-way function
Pseudorandom generator
Hash function
Random oracle
Asymmetric encryption relies on trapdoor one-way functions that are easy to compute in one direction but infeasible to invert without special knowledge (the trapdoor). RSA uses integer factorization, and ECC uses discrete logarithms over elliptic curves. This asymmetry underpins key security. See One-way function.
Asymmetric encryption primarily provides what security service?
Integrity
Availability
Non-repudiation
Confidentiality
The core purpose of asymmetric encryption is to ensure confidentiality by allowing only the intended recipient (holding the private key) to decrypt the data. While it can also support non-repudiation via digital signatures, its main use is secure key exchange and encrypted communication. See .
Which asymmetric algorithm uses elliptic curve cryptography?
DSA
AES
RSA
ECC
ECC (Elliptic Curve Cryptography) is an asymmetric algorithm that uses properties of elliptic curves over finite fields for security. It achieves equivalent security to RSA with smaller key sizes. DSA can be implemented over elliptic curves (ECDSA), but ECC refers broadly to the curve-based approach. See .
What is the primary difference between symmetric and asymmetric encryption?
Symmetric uses same key for both processes; asymmetric uses different keys
Symmetric is slower; asymmetric is always faster
Symmetric uses larger keys; asymmetric uses smaller keys
Symmetric never uses algorithms, only hashes
Symmetric encryption uses the same key for encryption and decryption, requiring secure key distribution. Asymmetric encryption uses a public/private key pair, allowing secure communication without prior key sharing. This makes asymmetric systems more flexible but generally slower. See .
What type of function is used in asymmetric encryption that is easy to compute but hard to reverse?
Collision-resistant hash
Trapdoor one-way function
Symmetric cipher
Random oracle
Trapdoor one-way functions are easy to compute in one direction but difficult to invert without secret information. RSA's integer factorization and ECC's discrete logarithm problems are examples. These functions form the backbone of public-key security. See One-way function.
Which element is used to prevent replay attacks in asymmetric communication?
Nonce
Signature
Certificate
Salt
A nonce is a unique number used only once in a session to prevent replay attacks by ensuring that old communications cannot be reused. Combined with asymmetric protocols, nonces guarantee message freshness and authenticity. See .
Which standard defines the format for digital certificates used in asymmetric encryption?
PEM
PKCS#7
ISO 27001
X.509
The X.509 standard specifies the format for public key certificates, certificate revocation lists, and attribute certificates. It is widely used in SSL/TLS, S/MIME, and other PKI applications. PEM is a file encoding but not the certificate standard itself. See .
Which hashing algorithm is commonly paired with RSA for digital signatures?
Whirlpool
MD5
SHA-256
CRC32
SHA-256 is part of the SHA-2 family and is recommended for use with RSA digital signatures due to its strong collision resistance and widespread support. MD5 is deprecated due to vulnerabilities. Secure hash functions are crucial for pre-image resistance. See .
What does the acronym PKCS stand for?
Private Key Cryptography System
Public Key Certification Scheme
Private Key Control System
Public Key Cryptography Standards
PKCS stands for Public Key Cryptography Standards, a group of standards devised and published by RSA Laboratories for secure public key operations. They define formats for keys, certificates, and cryptographic messages. See .
Which of the following is a post-quantum asymmetric encryption algorithm?
RSA
McEliece
ECC
DSA
The McEliece cryptosystem, based on coding theory and the hardness of decoding random linear codes, is considered resistant to quantum attacks. RSA, ECC, and DSA rely on factoring or discrete logs, which are vulnerable to Shor's algorithm. See .
What term describes a related pair of keys in asymmetric cryptography?
Digital certificate
Shared secret
Key pair
Session key
In asymmetric cryptography, the two mathematically linked keys are referred to as a key pair: one public and one private. They are generated simultaneously and used for encryption/decryption or signing/verification. The private key must remain confidential. See .
In RSA, if the private exponent is too small, which attack may succeed?
Wiener attack
Replay attack
Bleichenbacher attack
Birthday attack
Wiener's attack exploits cases where the RSA private exponent is smaller than n^0.25 to recover the secret key using continued fractions. Ensuring sufficiently large private exponents mitigates this vulnerability. See .
What is the Chinese Remainder Theorem used for in RSA decryption?
Speed up decryption by working modulo prime factors
Generate public key
Hash messages
Prevent man-in-the-middle attacks
The Chinese Remainder Theorem (CRT) accelerates RSA decryption by performing modular exponentiation separately modulo each prime factor of n, then recombining results. It roughly quadruples decryption speed. Proper CRT implementation requires secure padding. See .
What vulnerability arises from using the same RSA modulus with different exponents?
Common modulus attack
Timing attack
Padding oracle attack
Birthday paradox attack
If two users share the same RSA modulus but have different public exponents, attackers can exploit the common modulus to recover plaintexts under certain conditions. Unique moduli per key pair prevent this attack. See .
Which padding scheme is recommended for RSA encryption?
ECB mode
GCM mode
OAEP
PKCS#1 v1.5
OAEP (Optimal Asymmetric Encryption Padding) provides semantic security and protects against chosen-ciphertext attacks in RSA. It is recommended by PKCS#1 version 2 and various standards. PKCS#1 v1.5 is now discouraged for new applications. See .
In ECC, what is the ratio of the size of the group to the size of a prime-order subgroup called?
Trace
Field order
Cofactor
Discriminant
The cofactor in elliptic curve cryptography is the ratio between the total number of points on the curve and the order of its large prime-order subgroup. Using low cofactors reduces risks of small-subgroup attacks. See .
Which group property is essential for the security of the Diffie-Hellman key exchange?
Non-abelian group
Cyclic group
Abelian group
Prime group
Diffie-Hellman requires a cyclic group where every element can be expressed as a power of a generator. The discrete logarithm problem in such groups is hard, ensuring shared secret security. While abelian groups are common, cyclic structure is the key requirement. See .
The MOV attack is associated with which cryptographic system?
McEliece
Elliptic curve cryptography
ElGamal
RSA
The Menezes - Okamoto - Vanstone (MOV) attack exploits certain weak elliptic curves by reducing the elliptic curve discrete logarithm problem to a finite field discrete logarithm, making it easier to solve. Secure ECC parameters avoid curves vulnerable to MOV. See .
Which hard lattice problem underpins the security of the NTRU encryption algorithm?
Shortest Vector Problem
Discrete Logarithm Problem
Graph Isomorphism Problem
Integer Factorization Problem
NTRU's security relies on the hardness of finding short vectors in a high-dimensional lattice (SVP). This lattice-based approach is believed to be resistant even to quantum attacks. It differs fundamentally from factorization and discrete logarithm-based systems. See .
Which algorithm can factor large integers in polynomial time on a quantum computer?
Grover's algorithm
Shor's algorithm
Diffie-Hellman protocol
RSA algorithm
Shor's algorithm efficiently factors integers in polynomial time on a quantum computer, threatening RSA and other factorization-based schemes. Grover's algorithm speeds brute-force search quadratically but does not factor. Quantum-resistant methods aim to mitigate Shor's impact. See .
In pairing-based cryptography, what is the embedding degree?
The size of the base field
The smallest positive integer k such that the group's order divides p^k - 1
The cofactor of the elliptic curve group
The number of bits in the public key
The embedding degree k is the smallest integer for which the order of the elliptic curve group divides p^k - 1, enabling efficient mapping to finite fields for pairings. It influences security against MOV-like attacks and optimal pairing selection. See .
What is the risk of using non-prime order subgroups in ECC?
Padding oracle attack
Side-channel attack
Small subgroup attack
Chosen-ciphertext attack
Non-prime order subgroups allow an attacker to force a shared secret into a small subgroup, revealing information about private keys through multiple protocol runs. Using prime-order subgroups or verifying point orders mitigates this risk. See .
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Study Outcomes

  1. Identify Which Two Items Are Used in Asymmetric Encryption -

    Recognize the distinct roles of public and private key encryption as the two essential asymmetric encryption items used to secure digital communications.

  2. Differentiate Asymmetric and Symmetric Encryption Items -

    Compare the key distribution, algorithm structures, and security properties that set asymmetric encryption items apart from symmetric methods.

  3. Analyze Public and Private Key Encryption Usage -

    Examine how public and private key pairs work together to encrypt and decrypt data, ensuring confidentiality, integrity, and authentication.

  4. Identify Common Security Threats -

    Learn to spot social engineering threats and assess physical security measures that can compromise key integrity in IT Essentials Chapter 10 security scenarios.

  5. Apply Knowledge in Quiz Scenarios -

    Use your understanding of asymmetric encryption items to confidently select the correct answers in our IT Essentials security quiz and reinforce retention through instant feedback.

Cheat Sheet

  1. Asymmetric Encryption Fundamentals -

    Asymmetric encryption relies on mathematically related key pairs, where one key encrypts and the other decrypts, leveraging hard problems like integer factorization (NIST SP 800-57). A handy mnemonic is "Lock-it-public, Unlock-it-private" to remember which key is shared openly. This approach provides confidentiality without pre-sharing a secret key.

  2. Public and Private Key Roles -

    In public and private key encryption, the public key is distributed freely to encrypt messages, while the private key is kept secret for decryption (RFC 8017). For example, in an email scenario anyone can encrypt a message using your public key but only you can decrypt it. Understanding this pair clarifies why "which two items are used in asymmetric encryption choose two" always points to public and private keys.

  3. Key Pair Generation Algorithms -

    Common algorithms like RSA generate key pairs by selecting two large primes p and q, computing n = p×q, and finding e and d such that e·d ≡ 1 mod φ(n) (RSA Laboratories). A simple rhyme "Pick p and q to get n; choose e and d to blend" helps recall the steps. Secure key sizes (e.g., 2048-bit RSA) ensure practical resistance to current attacks.

  4. Secure Key Distribution via PKI -

    Public Key Infrastructure (PKI) uses certificates signed by trusted Certificate Authorities (CAs) to bind public keys to identities (IEEE X.509 standard). This eliminates man-in-the-middle risks by verifying public keys before use, a key aspect in IT Essentials Chapter 10 security quiz scenarios. Always check certificate validity and revocation lists to maintain trust.

  5. Digital Signatures and Verification -

    Digital signatures flip encryption: you sign data with your private key and anyone can verify it using your public key, ensuring authenticity and integrity (ISO/IEC 14888). For instance, RSA signatures compute s = m^d mod n and verify via m = s^e mod n. Remember "Sign with private, verify with public" to distinguish signing from encryption.

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