1. What is the primary purpose of a digital signature?
A) Encrypting data for confidentiality
B) Authenticating the sender and ensuring data integrity
C) Compressing files for faster transmission
D) Masking IP addresses for anonymity
✅ Answer: B – A digital signature is primarily used for authentication and data integrity verification. It ensures that the sender is who they claim to be and that the document has not been altered.
2. Which cryptographic concept is used in digital signatures?
A) Symmetric encryption
B) Hash functions
C) Asymmetric encryption
D) Steganography
✅ Answer: C – Digital signatures use asymmetric encryption, where a private key signs the data and a public key verifies the signature.
3. What does a digital signature verify?
A) The physical identity of the sender
B) The authenticity and integrity of a message
C) The anonymity of the user
D) The presence of malware in a document
✅ Answer: B – A digital signature ensures that the document comes from the expected sender and that it hasn’t been tampered with.
4. Which cryptographic algorithm is commonly used for digital signatures?
A) AES
B) RSA
C) SHA-256
D) DES
✅ Answer: B – RSA (Rivest-Shamir-Adleman) is widely used for digital signatures, although DSA and ECDSA are also common.
5. A digital signature is created using which of the following?
A) The sender’s private key
B) The receiver’s private key
C) The sender’s public key
D) A shared symmetric key
✅ Answer: A – The sender signs the document using their private key, and the recipient verifies it using the sender’s public key.
6. Which component of a digital signature ensures that the document has not been altered?
A) Encryption key
B) Hash function
C) Steganography algorithm
D) File compression
✅ Answer: B – A hash function is applied to the document before signing. If any change occurs, the hash will be different, invalidating the signature.
7. If a digital signature is verified successfully, what does it mean?
A) The message has been encrypted
B) The message is from an authentic source and is unchanged
C) The message cannot be decrypted
D) The message was sent using a VPN
✅ Answer: B – Successful verification indicates that the message is authentic and has not been tampered with.
8. Which key is used to verify a digital signature?
A) Sender’s private key
B) Receiver’s private key
C) Sender’s public key
D) Receiver’s public key
✅ Answer: C – The sender’s public key is used to verify that the signature was created by their private key.
9. What will happen if a document is modified after being digitally signed?
A) The signature remains valid
B) The signature will become invalid
C) The modification is encrypted automatically
D) The document becomes password-protected
✅ Answer: B – Any modification to the document will alter its hash, causing the signature verification to fail.
10. Digital signatures rely on the security of which cryptographic principle?
A) One-time pad
B) Public-key cryptography
C) ROT13 encryption
D) XOR operations
✅ Answer: B – Digital signatures are based on public-key cryptography (asymmetric encryption).
11. What role does a certificate authority (CA) play in digital signatures?
A) Encrypts all data
B) Issues and verifies digital certificates
C) Provides VPN services
D) Stores all signed documents
✅ Answer: B – A Certificate Authority (CA) issues and verifies digital certificates to ensure authenticity.
12. Which digital signature algorithm is approved by NIST?
A) MD5
B) DSA
C) ROT13
D) Caesar Cipher
✅ Answer: B – DSA (Digital Signature Algorithm) is a NIST-approved standard for digital signatures.
13. In a digital signature scheme, what ensures non-repudiation?
A) Symmetric key encryption
B) The sender’s private key
C) The receiver’s public key
D) The sender’s public key
✅ Answer: B – Non-repudiation is ensured because only the sender’s private key could have generated the signature.
14. How does a digital signature provide integrity?
A) By encrypting the document
B) By using a hash function to detect changes
C) By using a VPN
D) By converting text to binary
✅ Answer: B – Hash functions generate a unique fingerprint of the document. Any modification results in a different hash, invalidating the signature.
15. What happens if an attacker alters a document with a digital signature?
A) The signature will still verify successfully
B) The signature verification will fail
C) The signature will be automatically updated
D) The document becomes unreadable
✅ Answer: B – Any alteration changes the document’s hash, causing the signature verification to fail.
16. Why is hashing important in digital signatures?
A) It compresses data
B) It encrypts the document
C) It ensures integrity by detecting changes
D) It masks IP addresses
✅ Answer: C – Hashing creates a unique representation of the data, ensuring that any modification is detected.
17. What is the primary difference between a digital signature and an electronic signature?
A) Digital signatures use cryptographic techniques; electronic signatures may not
B) Electronic signatures are more secure
C) Digital signatures can only be used in emails
D) Electronic signatures require a VPN
✅ Answer: A – Digital signatures use cryptographic authentication, while electronic signatures can be as simple as a typed name.
18. Which organization defines the standard for digital signatures?
A) IEEE
B) NIST
C) ICANN
D) IETF
✅ Answer: B – NIST (National Institute of Standards and Technology) defines standards for digital signatures, such as DSA.
19. If a hacker steals a private key, what can they do?
A) Modify documents and create fraudulent digital signatures
B) Decrypt all data
C) Change the public key
D) Make internet traffic anonymous
✅ Answer: A – If an attacker gains access to a private key, they can forge digital signatures.
20. How can organizations protect private keys used for digital signatures?
A) Store them in plaintext files
B) Use a Hardware Security Module (HSM)
C) Publish them on the internet
D) Store them in email attachments
✅ Answer: B – A Hardware Security Module (HSM) ensures secure storage and use of private keys.
21. Which of the following is NOT a feature of digital signatures?
A) Authentication
B) Integrity
C) Non-repudiation
D) Anonymity
✅ Answer: D – Digital signatures provide authentication, integrity, and non-repudiation, but they do not ensure anonymity. Instead, they establish identity.
22. Which of the following attacks specifically targets digital signatures?
A) Man-in-the-Middle (MitM) attack
B) Key Cloning Attack
C) Signature Spoofing Attack
D) Cross-Site Scripting (XSS)
✅ Answer: C – In a Signature Spoofing Attack, an attacker tries to generate a fake digital signature that appears valid.
23. If a public key is compromised, what should be done?
A) Nothing, as the private key is still secure
B) Revoke the corresponding certificate immediately
C) Share the private key with trusted parties
D) Use symmetric encryption instead
✅ Answer: B – If a public key is compromised, the corresponding certificate should be revoked to prevent misuse.
24. Which part of a digital signature ensures that no one can forge it without the sender’s private key?
A) The encryption algorithm
B) The hash of the message
C) The public key
D) The digital certificate
✅ Answer: B – The hash of the message ensures that even the smallest change in data invalidates the signature.
25. What does PKI stand for in digital signatures?
A) Public Key Infrastructure
B) Private Key Integration
C) Packet Key Identifier
D) Personal Key Interface
✅ Answer: A – Public Key Infrastructure (PKI) is the framework that manages digital certificates and key pairs.
26. Which type of digital signature uses elliptic curve cryptography for enhanced security?
A) RSA
B) DSA
C) ECDSA
D) MD5
✅ Answer: C – Elliptic Curve Digital Signature Algorithm (ECDSA) offers better security with shorter key lengths compared to RSA.
27. A timestamp in a digital signature is used to prevent which issue?
A) Signature forgery
B) Signature expiration or replay attacks
C) Key revocation
D) Public key distribution errors
✅ Answer: B – Timestamps prevent signature reuse (replay attacks) and verify that the document was signed before a key was revoked.
28. Which of the following statements about digital signatures is FALSE?
A) Digital signatures ensure the authenticity of a message.
B) Digital signatures require asymmetric encryption.
C) A digital signature proves the confidentiality of a message.
D) A valid digital signature means the data has not been altered.
✅ Answer: C – Digital signatures ensure authenticity, integrity, and non-repudiation, but they do not guarantee confidentiality. Encryption is needed for confidentiality.
29. What is the main weakness of digital signatures if the private key is stolen?
A) The public key becomes invalid
B) The signature algorithm stops working
C) The attacker can sign fraudulent documents
D) The digital signature process slows down
✅ Answer: C – If the private key is stolen, an attacker can generate valid-looking fraudulent signatures.
30. Which of the following is an industry-standard format for digital certificates?
A) PEM
B) X.509
C) JSON
D) XML
✅ Answer: B – X.509 is the most widely used format for digital certificates, ensuring standardization.
31. What is the purpose of a hash function in digital signatures?
A) Encrypt the message
B) Create a unique identifier for data
C) Replace the sender’s private key
D) Increase data storage capacity
✅ Answer: B – A hash function generates a unique representation of the data, making it easy to detect alterations.
32. Which of the following can be used to revoke a compromised digital certificate?
A) SSL Pinning
B) Certificate Revocation List (CRL)
C) VPN Encryption
D) SHA-256
✅ Answer: B – A Certificate Revocation List (CRL) is used to invalidate compromised or expired digital certificates.
33. What does a digital signature attach to a document?
A) The private key
B) A cryptographic hash of the document
C) The sender’s username
D) The certificate revocation list
✅ Answer: B – A digital signature attaches a cryptographic hash, which allows verification of the document’s integrity.
34. What is an alternative to CRL for checking revoked certificates?
A) TLS
B) OCSP (Online Certificate Status Protocol)
C) SSH
D) ROT13
✅ Answer: B – OCSP provides real-time status checking for revoked certificates.
35. What is the main reason organizations use digital signatures?
A) To prevent data compression
B) To verify the authenticity and integrity of digital documents
C) To hide the sender’s identity
D) To avoid encryption
✅ Answer: B – Digital signatures confirm authenticity and prevent unauthorized modifications.
36. Which of the following can compromise the security of a digital signature?
A) Using strong encryption
B) Using a revoked private key
C) Storing private keys in secure hardware
D) Using two-factor authentication
✅ Answer: B – If a revoked private key is used, the signature is no longer trustworthy.
37. How does a digital signature prevent data tampering?
A) By encrypting the message
B) By creating a hash that changes if the data is altered
C) By making the document read-only
D) By changing the sender’s IP address
✅ Answer: B – If data is tampered with, the hash changes, invalidating the signature.
38. Which regulatory framework requires digital signatures for secure electronic transactions?
A) GDPR
B) eIDAS
C) PCI-DSS
D) ISO 27001
✅ Answer: B – The eIDAS Regulation governs electronic signatures and trust services in the European Union.
39. What is a potential risk if an organization does not regularly update its digital signature algorithms?
A) Signature validation errors
B) Decreased data storage
C) Increased network speed
D) Higher power consumption
✅ Answer: A – Weak or outdated cryptographic algorithms may become vulnerable to attacks, causing signature validation failures.
40. Which of the following statements about digital signatures is TRUE?
A) A digital signature is the same as a handwritten signature.
B) Digital signatures provide authenticity, integrity, and non-repudiation.
C) A digital signature ensures absolute security.
D) Digital signatures use only symmetric encryption.
✅ Answer: B – Digital signatures provide authentication, integrity, and non-repudiation, but they do not guarantee absolute security.
41. Which type of attack attempts to generate two different messages with the same hash value?
A) Man-in-the-Middle attack
B) Collision attack
C) Replay attack
D) Dictionary attack
✅ Answer: B – A collision attack occurs when two different messages produce the same hash, which can undermine the security of digital signatures.
42. What happens if a digital certificate associated with a signature expires?
A) The signature remains valid indefinitely
B) The signature becomes invalid
C) The signature is automatically renewed
D) The signature can still be verified if timestamped correctly
✅ Answer: D – Timestamping allows verification of a signature even after the certificate expires, proving that the document was signed before expiration.
43. In which scenario would a digital signature NOT provide security benefits?
A) Signing an email to verify the sender’s identity
B) Ensuring a software package is authentic
C) Encrypting a confidential message
D) Verifying a digitally signed contract
✅ Answer: C – Digital signatures authenticate documents but do not provide encryption for confidentiality.
44. Which of the following is a trusted entity that issues digital certificates?
A) Certificate Authority (CA)
B) Cryptographic Algorithm Manager (CAM)
C) Public Key Repository (PKR)
D) Secure Hash Authority (SHA)
✅ Answer: A – A Certificate Authority (CA) is responsible for issuing and verifying digital certificates.
45. What is the main reason organizations use key pairs in digital signatures?
A) To reduce storage space
B) To allow public verification while keeping signing private
C) To speed up the signing process
D) To eliminate the need for encryption
✅ Answer: B – The private key is used for signing, while the public key allows verification.
46. How does a digital signature help detect a Man-in-the-Middle (MitM) attack?
A) By encrypting the message content
B) By ensuring the message hash is unchanged
C) By hiding the sender’s IP address
D) By detecting network latency changes
✅ Answer: B – If a MitM attacker alters the message, the signature verification will fail due to a mismatched hash.
47. What is the role of a digital certificate in digital signatures?
A) It contains the private key for signing
B) It verifies the authenticity of the public key
C) It generates the cryptographic hash
D) It encrypts the signed document
✅ Answer: B – A digital certificate, issued by a CA, verifies the authenticity of a public key.
48. Why should digital signatures use strong hash functions like SHA-256 instead of MD5?
A) MD5 is too slow for digital signatures
B) SHA-256 is required for legal compliance
C) MD5 is vulnerable to collision attacks
D) SHA-256 uses a shorter key size
✅ Answer: C – MD5 is insecure due to known collision vulnerabilities, making it unsuitable for digital signatures.
49. How does a digitally signed document help in legal disputes?
A) It proves the document was encrypted
B) It ensures confidentiality
C) It provides non-repudiation, meaning the signer cannot deny signing it
D) It guarantees the document has no malware
✅ Answer: C – Non-repudiation means that the signer cannot later deny signing the document.
50. What is an advantage of using ECDSA over RSA for digital signatures?
A) ECDSA is simpler to implement
B) ECDSA provides equivalent security with shorter key lengths
C) ECDSA does not require a private key
D) ECDSA eliminates the need for a Certificate Authority
✅ Answer: B – ECDSA achieves the same level of security as RSA but with shorter key lengths, making it more efficient.
51. Why do businesses use hardware security modules (HSMs) for digital signatures?
A) To speed up signing operations
B) To securely store and protect private keys
C) To replace the need for a public key
D) To eliminate the need for CAs
✅ Answer: B – HSMs provide secure storage for private keys and prevent unauthorized access.
52. Which security mechanism can strengthen digital signatures against private key theft?
A) Using VPNs
B) Multi-factor authentication (MFA) for private key access
C) Using weaker hashing algorithms
D) Removing the timestamp
✅ Answer: B – MFA adds an extra security layer to prevent unauthorized use of private keys.
53. What happens if the public key associated with a digital signature is lost?
A) The signature remains verifiable
B) The signature becomes unverifiable
C) The private key can regenerate the public key
D) The CA automatically replaces it
✅ Answer: B – Without the public key, the signature cannot be verified.
54. Which attack aims to trick a system into accepting a fraudulent digital signature?
A) Replay attack
B) Signature forgery attack
C) Brute-force attack
D) Phishing attack
✅ Answer: B – Signature forgery attacks try to generate fake digital signatures that appear legitimate.
55. What is the purpose of dual key pairs in advanced digital signature schemes?
A) One key pair for encryption and another for signing
B) One key pair for local storage and another for cloud backup
C) One key pair for authentication and another for hashing
D) One key pair for timestamping and another for validation
✅ Answer: A – Some security models use separate key pairs for encryption and digital signing.
56. Which of the following is an example of a trusted root CA?
A) Let’s Encrypt
B) SHA-256
C) AES-256
D) IPsec
✅ Answer: A – Let’s Encrypt is a widely recognized trusted root Certificate Authority.
57. How can digital signatures be protected against replay attacks?
A) Using a strong hash function
B) Implementing a timestamp with the signature
C) Encrypting the signature with AES
D) Using a VPN
✅ Answer: B – Timestamps prevent replay attacks by ensuring the signature is valid only for a specific time period.
58. What role does a CRL (Certificate Revocation List) play in digital signature security?
A) It helps revoke compromised or expired certificates
B) It encrypts the signature
C) It prevents key tampering
D) It verifies the document’s authenticity
✅ Answer: A – A CRL lists revoked certificates to prevent their continued use.
59. Which of the following is an attack that exploits weak random number generation in digital signature key creation?
A) Side-channel attack
B) Birthday attack
C) Predictable key attack
D) Known plaintext attack
✅ Answer: C – If an attacker can predict the random values used in key generation, they can forge signatures.
60. How do digital signatures enhance the security of software updates?
A) By encrypting the update files
B) By verifying that the update was not tampered with
C) By hiding the IP address of the update server
D) By preventing brute-force attacks
✅ Answer: B – Digitally signed software updates ensure that only authentic updates from trusted sources are installed.
61. What is the primary function of a Trusted Timestamping Authority (TSA) in digital signatures?
A) Encrypting the digital signature
B) Preventing key exposure
C) Certifying the time a document was signed
D) Replacing expired digital signatures
✅ Answer: C – A Trusted Timestamping Authority (TSA) ensures that a timestamped document was signed at a specific time, preventing backdating or future fraud.
62. Which of the following could compromise the validity of a digital signature?
A) Using a longer key size
B) A weak hash function vulnerable to collisions
C) Encrypting the signed document
D) Using multiple signatures
✅ Answer: B – A weak hash function (e.g., MD5, SHA-1) makes it easier for attackers to generate collisions, which can compromise the digital signature.
63. What is the main difference between digital signatures and digital certificates?
A) A digital certificate contains a public key; a digital signature authenticates a document
B) A digital certificate is used for encryption, while a digital signature is not
C) A digital signature replaces the need for a private key
D) A digital certificate is generated after signing
✅ Answer: A – A digital certificate is issued by a Certificate Authority (CA) and contains the public key, while a digital signature is used to authenticate documents.
64. What is an advantage of quantum-resistant digital signature algorithms?
A) They use shorter keys
B) They protect against future quantum computer attacks
C) They eliminate the need for hashing
D) They work faster on classical computers
✅ Answer: B – Quantum-resistant algorithms are designed to withstand quantum attacks that could break current asymmetric encryption schemes.
65. Why is a nonce (random number) sometimes used in digital signatures?
A) To prevent replay attacks
B) To replace the hash function
C) To make verification faster
D) To allow multiple users to sign the same document
✅ Answer: A – A nonce ensures that a digital signature cannot be reused in a replay attack.
66. What is the best way to store private keys securely for digital signing?
A) In plaintext on a hard drive
B) On a password-protected USB drive
C) Inside a Hardware Security Module (HSM)
D) In a public blockchain
✅ Answer: C – HSMs are the most secure method for storing private keys, protecting them from theft or unauthorized access.
67. Which type of certificate is specifically used for code signing?
A) SSL/TLS Certificate
B) Wildcard Certificate
C) Code Signing Certificate
D) Root Certificate
✅ Answer: C – Code Signing Certificates are used by developers to digitally sign software and ensure authenticity.
68. What is an example of a digital signature attack where an attacker tricks a system into accepting a fraudulent certificate?
A) Side-channel attack
B) Rogue Certificate Authority attack
C) Brute-force attack
D) Watermarking attack
✅ Answer: B – In a Rogue CA attack, an attacker compromises a Certificate Authority (CA) to issue fraudulent certificates.
69. Which of the following is NOT an application of digital signatures?
A) Electronic contracts
B) Secure software updates
C) Hiding IP addresses
D) Verifying email authenticity
✅ Answer: C – Digital signatures do not provide anonymity or hide IP addresses.
70. How does blockchain technology use digital signatures?
A) To encrypt all transactions
B) To verify transactions and authenticate users
C) To replace hashing algorithms
D) To generate public keys
✅ Answer: B – Blockchain transactions use digital signatures (typically ECDSA) to verify authenticity and prevent tampering.
71. What happens if a digital signature’s private key is leaked?
A) The signature becomes more secure
B) Anyone can forge digital signatures
C) The key automatically regenerates
D) The CA revokes the certificate
✅ Answer: B – Private key leakage allows an attacker to forge digital signatures, compromising security.
72. Which of the following is a post-quantum cryptographic digital signature algorithm?
A) ECDSA
B) Falcon
C) RSA
D) DSA
✅ Answer: B – Falcon is a post-quantum digital signature algorithm designed to resist quantum attacks.
73. Which law recognizes digital signatures as legally binding in the U.S.?
A) GDPR
B) DMCA
C) ESIGN Act
D) PCI-DSS
✅ Answer: C – The ESIGN Act (Electronic Signatures in Global and National Commerce Act) recognizes digital signatures as legally valid in the U.S.
74. What is the role of a signing authority in digital signatures?
A) It encrypts the signed document
B) It verifies the legitimacy of a signature
C) It replaces the need for public keys
D) It prevents all forms of hacking
✅ Answer: B – A Signing Authority (SA) validates and confirms the authenticity of digital signatures.
75. How can an organization ensure that its digital signatures remain valid even if its private key is compromised?
A) Using a timestamping service
B) Encrypting the public key
C) Increasing the key size
D) Avoiding key rotation
✅ Answer: A – Timestamping ensures that the signature is valid at the time of signing, even if the key is compromised later.
76. What is a cryptographic accumulator in digital signatures?
A) A method to store multiple signatures efficiently
B) A technique to replace hashing
C) A way to remove expired signatures
D) A type of brute-force protection
✅ Answer: A – A cryptographic accumulator allows multiple signatures or hashes to be stored and verified efficiently.
77. Which of these methods is used to verify a signature’s authenticity in a blockchain?
A) Trusted Third Party (TTP)
B) Decentralized Validation
C) Email Authentication
D) CAPTCHA
✅ Answer: B – Blockchain-based digital signatures use decentralized validation, removing the need for a trusted third party.
78. How do digital signatures help prevent document repudiation?
A) They provide cryptographic proof of signing
B) They make the document uneditable
C) They encrypt the signature with a symmetric key
D) They generate a unique password
✅ Answer: A – Non-repudiation means a signer cannot deny signing a document, as the digital signature is cryptographic proof.
79. What is an aggregate signature in cryptography?
A) A signature that combines multiple signers into one
B) A signature used only for certificates
C) A signature that is immune to hash collisions
D) A signature that encrypts email messages
✅ Answer: A – An aggregate signature allows multiple signatures to be combined into one compact signature, improving efficiency.
80. Which organization is responsible for setting cryptographic standards for digital signatures?
A) NIST
B) WHO
C) IMF
D) NATO
✅ Answer: A – The National Institute of Standards and Technology (NIST) defines digital signature standards such as FIPS 186-5.
81. Which of the following is a major disadvantage of RSA-based digital signatures?
A) They require symmetric key exchange
B) They require large key sizes for strong security
C) They do not provide integrity
D) They are not legally recognized
✅ Answer: B – RSA digital signatures require larger key sizes (e.g., 2048-bit or 4096-bit) for strong security, making them computationally expensive.
82. Which of the following organizations regulates digital signatures in the European Union?
A) PCI-DSS
B) NIST
C) eIDAS
D) W3C
✅ Answer: C – eIDAS (Electronic Identification, Authentication, and Trust Services) is the European regulatory framework for digital signatures.
83. What is the function of a root certificate in a Public Key Infrastructure (PKI)?
A) It signs all other certificates in a chain
B) It stores private keys securely
C) It replaces lost certificates
D) It encrypts all digital signatures
✅ Answer: A – A root certificate is the top-most certificate in a PKI hierarchy, and it is used to sign and verify all subordinate certificates.
84. What does an Extended Validation (EV) certificate provide that a standard SSL certificate does not?
A) A stronger hash function
B) Identity verification of the certificate owner
C) Unlimited key sizes
D) Encryption with a one-time pad
✅ Answer: B – Extended Validation (EV) certificates require rigorous identity verification of the certificate owner, providing higher trust.
85. What is the purpose of a signing key pair in digital signatures?
A) To store encrypted files
B) To allow one key to sign data and another to verify it
C) To replace passwords in authentication
D) To secure VPN connections
✅ Answer: B – A digital signature key pair consists of a private key for signing and a public key for verification.
86. Which cryptographic vulnerability can allow attackers to forge digital signatures?
A) Padding oracle attack
B) Session hijacking
C) Rainbow table attack
D) Clickjacking
✅ Answer: A – Padding oracle attacks exploit poor padding schemes in RSA signatures, allowing attackers to forge signatures.
87. How does forward secrecy impact digital signatures?
A) It prevents the reuse of private keys
B) It ensures old signatures remain valid even if keys are compromised
C) It prevents hash collisions
D) It eliminates the need for Certificate Authorities
✅ Answer: B – Forward secrecy ensures that previously signed documents remain valid even if the private key is later compromised.
88. What role does SHA-3 play in digital signatures?
A) It replaces RSA encryption
B) It is a post-quantum cryptographic algorithm
C) It provides a collision-resistant hash function for signing
D) It encrypts the digital signature
✅ Answer: C – SHA-3 is a cryptographic hash function that provides collision resistance, making digital signatures more secure.
89. Why are digital signatures not widely used in email communications?
A) Email servers do not support digital signatures
B) Users find the certificate management process complex
C) Digital signatures do not work with attachments
D) Email signatures cannot be verified
✅ Answer: B – Many users find digital certificate management (such as S/MIME or PGP) complex, limiting adoption in email security.
90. Which of the following digital signature schemes provides shorter signatures while maintaining high security?
A) RSA-2048
B) ECDSA
C) SHA-512
D) MD5
✅ Answer: B – ECDSA (Elliptic Curve Digital Signature Algorithm) provides shorter signatures compared to RSA while maintaining strong security.
91. What is a countermeasure against brute-force attacks on digital signatures?
A) Using stronger encryption algorithms
B) Storing private keys in plaintext
C) Using only symmetric cryptography
D) Reducing key sizes
✅ Answer: A – Stronger encryption (e.g., RSA-4096, ECDSA-521) makes brute-force attacks impractical.
92. What is an advantage of using post-quantum digital signature algorithms like Falcon or Dilithium?
A) They reduce the need for hashing
B) They resist attacks from quantum computers
C) They eliminate the need for Certificate Authorities
D) They allow unlimited key reuse
✅ Answer: B – Post-quantum algorithms like Falcon and Dilithium are designed to resist attacks from quantum computers, which could break RSA or ECDSA.
93. Which entity is responsible for managing and distributing digital certificates in an organization?
A) Hash Function Authority (HFA)
B) Certificate Authority (CA)
C) Digital Signature Trust (DST)
D) VPN Server
✅ Answer: B – Certificate Authorities (CAs) are responsible for issuing and managing digital certificates.
94. Which key should be kept secret in a digital signature scheme?
A) Public key
B) Private key
C) Hash function output
D) Timestamp
✅ Answer: B – The private key must be kept secret, as it is used for signing documents.
95. What is the purpose of hashing before applying a digital signature?
A) To compress the data
B) To reduce signature size and improve security
C) To encrypt the signature
D) To remove redundant data
✅ Answer: B – Hashing reduces data size and ensures that even a small change in data invalidates the signature.
96. What does a signature validation failure indicate?
A) The document was modified after signing
B) The encryption algorithm is outdated
C) The signature needs to be re-generated
D) The document is unreadable
✅ Answer: A – If signature validation fails, it means the document has been altered since it was signed.
97. Which key is used to verify a digital signature in a PKI system?
A) Sender’s private key
B) Receiver’s private key
C) Sender’s public key
D) Receiver’s public key
✅ Answer: C – The sender’s public key is used to verify the authenticity of a digital signature.
98. Which law mandates the use of digital signatures for government transactions in India?
A) HIPAA
B) IT Act, 2000
C) GDPR
D) FERPA
✅ Answer: B – India’s IT Act, 2000 mandates the use of digital signatures for government transactions.
99. How do timestamping services prevent backdating of digital signatures?
A) By encrypting the digital signature
B) By providing a verifiable third-party timestamp
C) By blocking expired certificates
D) By changing the private key regularly
✅ Answer: B – Trusted timestamping services ensure that a digital signature was generated at a specific time, preventing backdating fraud.
100. What is a side-channel attack in the context of digital signatures?
A) An attack exploiting weaknesses in the implementation rather than the algorithm itself
B) A brute-force attack on private keys
C) An attack where an attacker guesses the hash value
D) A network-layer attack that changes signatures
✅ Answer: A – A side-channel attack exploits timing, power consumption, or electromagnetic leaks rather than directly breaking cryptographic algorithms.
101. What is the primary function of a key pair in a digital signature system?
A) Encrypt and decrypt data
B) Sign and verify messages
C) Store data securely
D) Replace passwords
✅ Answer: B – A key pair (private and public key) is used for signing and verifying digital signatures.
102. Which of the following ensures that a digital signature remains valid even after the private key is compromised?
A) Encrypting the document
B) Using timestamping services
C) Increasing the key length
D) Using a blockchain ledger
✅ Answer: B – Timestamping services ensure that a signature remains valid even if the private key is compromised later.
103. Which digital signature standard is used in the United States for federal government communications?
A) X.509
B) ECDSA
C) DSA (Digital Signature Algorithm)
D) PKCS #7
✅ Answer: C – DSA (Digital Signature Algorithm) is a U.S. federal government standard for digital signatures, as specified in FIPS 186.
104. How does an attacker perform a certificate spoofing attack?
A) By modifying a digital signature
B) By using a fake certificate authority
C) By brute-forcing the public key
D) By injecting a virus into a signed document
✅ Answer: B – In a certificate spoofing attack, an attacker creates a fake CA to issue fraudulent certificates.
105. Which of the following best describes the principle of non-repudiation in digital signatures?
A) The sender cannot deny having signed a document
B) The document remains confidential
C) The public key is hidden from the recipient
D) The signature prevents phishing attacks
✅ Answer: A – Non-repudiation ensures that the signer cannot deny having signed the document.
106. Why is it recommended to rotate cryptographic keys used for digital signatures periodically?
A) To increase processing speed
B) To reduce the risk of key compromise
C) To replace public keys with private keys
D) To ensure signatures expire faster
✅ Answer: B – Key rotation reduces the risk of private key compromise and enhances security.
107. What is a digital signature collision attack?
A) When two different messages generate the same signature
B) When the private key is exposed
C) When the signature is encrypted twice
D) When a message is signed using an invalid algorithm
✅ Answer: A – A collision attack occurs when two different messages produce the same signature, making verification unreliable.
108. What is the role of a digital signature in secure email communication?
A) To encrypt the email
B) To authenticate the sender and ensure message integrity
C) To prevent spam
D) To mask the email’s metadata
✅ Answer: B – A digital signature authenticates the sender and ensures that the email content has not been altered.
109. Which of the following prevents an attacker from using a revoked digital certificate?
A) Blockchain verification
B) Certificate Revocation List (CRL)
C) Increasing key length
D) Using SHA-512 hashing
✅ Answer: B – A Certificate Revocation List (CRL) prevents the use of revoked certificates.
110. What is an advantage of using a cryptographic hardware module (HSM) for digital signatures?
A) It eliminates the need for asymmetric encryption
B) It securely stores and processes cryptographic keys
C) It makes signatures human-readable
D) It reduces the need for public keys
✅ Answer: B – A Hardware Security Module (HSM) securely stores and processes private keys, reducing exposure to attacks.
111. What is the role of a hash function in digital signatures?
A) To encrypt the document
B) To generate a unique fingerprint of the message
C) To replace the private key
D) To create a secure VPN connection
✅ Answer: B – Hash functions generate a unique fingerprint of the document to ensure integrity verification.
112. How does a digital signature help protect software downloads?
A) By encrypting the software
B) By verifying the authenticity and integrity of the software
C) By blocking malware automatically
D) By increasing download speed
✅ Answer: B – Digitally signing software ensures that it comes from a trusted source and has not been tampered with.
113. What is a wildcard certificate used for?
A) To sign documents automatically
B) To secure multiple subdomains under a single domain
C) To encrypt email messages
D) To create self-signed certificates
✅ Answer: B – A wildcard certificate allows securing multiple subdomains under one main domain.
114. How does a key escrow system work in digital signatures?
A) By encrypting signatures using multiple keys
B) By securely storing private keys for recovery purposes
C) By replacing the need for Certificate Authorities
D) By automatically revoking expired certificates
✅ Answer: B – A key escrow system securely stores private keys, allowing recovery in case of loss.
115. Which of the following hashing algorithms is considered weak and should NOT be used for digital signatures?
A) SHA-256
B) SHA-3
C) MD5
D) Blake2
✅ Answer: C – MD5 is vulnerable to collision attacks and should not be used for cryptographic security.
116. What is an advantage of using ECDSA instead of RSA for digital signatures?
A) ECDSA uses smaller key sizes for the same level of security
B) ECDSA does not require a private key
C) ECDSA eliminates the need for Certificate Authorities
D) ECDSA is faster at encrypting large files
✅ Answer: A – ECDSA provides the same security as RSA but with much shorter key sizes, making it more efficient.
117. Why is a private key required for generating a digital signature?
A) To securely verify the document
B) To prevent attackers from decrypting messages
C) To ensure only the signer can create the signature
D) To provide an additional layer of encryption
✅ Answer: C – The private key is used to generate the digital signature, ensuring that only the legitimate sender can sign documents.
118. What is the purpose of Online Certificate Status Protocol (OCSP)?
A) To provide real-time certificate revocation checks
B) To generate private keys for digital signatures
C) To encrypt digital signatures
D) To hash digital certificates
✅ Answer: A – OCSP provides real-time verification of a certificate’s revocation status.
119. What is a major benefit of using digital signatures in blockchain transactions?
A) They eliminate the need for miners
B) They verify the authenticity of transactions without a central authority
C) They speed up the blockchain network
D) They prevent all forms of cyber attacks
✅ Answer: B – Blockchain transactions use digital signatures to verify authenticity without requiring a central authority.
120. Which of the following is a quantum-resistant digital signature algorithm?
A) ECDSA
B) Falcon
C) RSA-2048
D) DSA
✅ Answer: B – Falcon is a quantum-resistant digital signature algorithm designed to withstand quantum computing attacks.
121. Which property of digital signatures ensures that a signed document cannot be altered without detection?
A) Non-repudiation
B) Integrity
C) Confidentiality
D) Anonymity
✅ Answer: B – Integrity ensures that a signed document cannot be modified without invalidating the signature.
122. What is the primary function of a message digest in a digital signature system?
A) To encrypt the message
B) To create a unique hash of the message for integrity verification
C) To replace public key cryptography
D) To store the digital signature
✅ Answer: B – A message digest is a unique hash output that helps verify the integrity of a signed message.
123. Which attack attempts to modify a document while keeping the same digital signature?
A) Birthday attack
B) Signature forgery attack
C) Man-in-the-Middle (MitM) attack
D) Key exchange attack
✅ Answer: A – A Birthday attack exploits hash function collisions to modify a document while maintaining the same digital signature.
124. How does using a stronger hash function improve digital signature security?
A) It speeds up the signing process
B) It makes brute-force attacks harder
C) It removes the need for a private key
D) It replaces asymmetric encryption
✅ Answer: B – Stronger hash functions (e.g., SHA-256, SHA-3) reduce the risk of collision attacks, making brute-force attempts impractical.
125. Which of the following is NOT a valid digital signature algorithm?
A) RSA
B) AES
C) DSA
D) ECDSA
✅ Answer: B – AES (Advanced Encryption Standard) is a symmetric encryption algorithm, not a digital signature algorithm.
126. Which entity is responsible for issuing and verifying digital certificates?
A) Internet Service Provider (ISP)
B) Certificate Authority (CA)
C) Domain Name System (DNS)
D) Secure Shell (SSH)
✅ Answer: B – A Certificate Authority (CA) issues and verifies digital certificates to establish trust.
127. What is a potential risk of using self-signed certificates for digital signatures?
A) They are expensive
B) They are difficult to generate
C) They may not be trusted by external parties
D) They require a separate key for signing
✅ Answer: C – Self-signed certificates are not issued by a trusted CA, making them less reliable for external verification.
128. What is the main reason for using hardware tokens in digital signatures?
A) To speed up signature verification
B) To store private keys securely
C) To replace hashing algorithms
D) To provide symmetric encryption
✅ Answer: B – Hardware tokens (e.g., USB security keys, HSMs) securely store private keys to prevent key compromise.
129. Which of the following is a disadvantage of using long key lengths in digital signatures?
A) Weaker encryption
B) Increased computational overhead
C) Reduced security
D) Higher risk of collisions
✅ Answer: B – Longer key lengths (e.g., RSA-4096) provide stronger security but increase processing time.
130. What is the main purpose of a digital signature in blockchain transactions?
A) To encrypt all blockchain data
B) To verify the authenticity of transactions
C) To create new cryptocurrency tokens
D) To replace hashing functions
✅ Answer: B – Digital signatures verify transaction authenticity in blockchain networks.
131. How does a digital signature provide authenticity?
A) By encrypting the document
B) By verifying the signer’s identity using a public key
C) By making the document read-only
D) By preventing malware infections
✅ Answer: B – Public key cryptography verifies the signer’s identity, ensuring authenticity.
132. What is an advantage of using quantum-resistant digital signatures?
A) They prevent all cyber attacks
B) They protect against future quantum computing threats
C) They remove the need for hashing
D) They eliminate private keys
✅ Answer: B – Quantum-resistant algorithms ensure security even when quantum computers become powerful enough to break traditional cryptography.
133. What is the role of a root certificate in a digital signature trust hierarchy?
A) It replaces private keys
B) It serves as the highest trust level for verifying digital certificates
C) It removes the need for hashing
D) It encrypts all signed documents
✅ Answer: B – A root certificate is the highest trust anchor in a certificate chain, verifying other certificates.
134. Which of the following is a common use case for code-signing certificates?
A) Encrypting emails
B) Signing software to verify authenticity
C) Storing passwords securely
D) Protecting against phishing attacks
✅ Answer: B – Code-signing certificates ensure software authenticity and integrity.
135. How does multi-signature technology improve digital signatures?
A) It allows multiple parties to sign a document
B) It eliminates the need for encryption
C) It speeds up hashing algorithms
D) It prevents certificate expiration
✅ Answer: A – Multi-signature (multi-sig) technology allows multiple signers to approve transactions or documents.
136. What is the main reason organizations use digital signatures for document signing?
A) To prevent email spam
B) To provide legal non-repudiation and integrity
C) To reduce internet traffic
D) To prevent server crashes
✅ Answer: B – Digital signatures ensure legal non-repudiation and document integrity.
137. Which of the following is an advantage of using an Online Certificate Status Protocol (OCSP) over a Certificate Revocation List (CRL)?
A) OCSP is faster for checking certificate revocation status
B) OCSP eliminates the need for encryption
C) OCSP prevents brute-force attacks
D) OCSP generates new keys automatically
✅ Answer: A – OCSP provides real-time revocation status, while CRLs require manual updates.
138. How can digital signatures protect against insider threats?
A) By detecting unauthorized document changes
B) By encrypting emails
C) By making data completely secure
D) By replacing firewalls
✅ Answer: A – Digital signatures detect tampering, helping identify insider threats.
139. Which of the following is an example of an advanced digital signature attack?
A) Simple brute-force attack
B) Hash length extension attack
C) VPN tunneling attack
D) Network latency attack
✅ Answer: B – A hash length extension attack exploits weak hash functions to create fraudulent digital signatures.
140. Why are blockchain-based digital signatures considered highly secure?
A) They use a decentralized verification process
B) They store private keys in the blockchain
C) They eliminate all security vulnerabilities
D) They do not require hashing
✅ Answer: A – Blockchain-based digital signatures rely on decentralized validation, making tampering extremely difficult.
141. What is a major security concern when using outdated digital signature algorithms?
A) They increase data redundancy
B) They may be vulnerable to cryptographic attacks
C) They consume more bandwidth
D) They eliminate the need for hashing
✅ Answer: B – Outdated digital signature algorithms (e.g., RSA-1024, SHA-1) are vulnerable to modern cryptographic attacks.
142. How does an attacker exploit weak entropy in key generation for digital signatures?
A) By forcing key expiration
B) By predicting private keys
C) By disabling signature verification
D) By encrypting the signature
✅ Answer: B – Weak entropy in key generation can lead to predictable private keys, allowing attackers to forge signatures.
143. What is the role of a cryptographic nonce in digital signatures?
A) It adds randomness to prevent replay attacks
B) It replaces hash functions
C) It encrypts the public key
D) It eliminates the need for timestamps
✅ Answer: A – A cryptographic nonce introduces randomness to prevent replay attacks.
144. What is a valid reason to revoke a digital certificate associated with a signature?
A) The public key was changed
B) The certificate has expired
C) The private key was compromised
D) The certificate was downloaded multiple times
✅ Answer: C – A compromised private key makes the digital signature untrustworthy, requiring certificate revocation.
145. Why is key length important in digital signature security?
A) Longer keys reduce signature size
B) Longer keys make brute-force attacks harder
C) Shorter keys improve security
D) Longer keys eliminate the need for hashing
✅ Answer: B – Longer keys (e.g., RSA-4096 vs. RSA-2048) increase resistance to brute-force attacks.
146. What is a limitation of using digital signatures for document authentication?
A) They cannot be used for emails
B) They require proper key management
C) They do not ensure integrity
D) They cannot be used in mobile devices
✅ Answer: B – Proper key management (e.g., protecting private keys, revoking compromised certificates) is essential for digital signature security.
147. How can a compromised CA impact digital signatures?
A) It allows the CA to change hash algorithms
B) It enables attackers to issue fraudulent certificates
C) It increases the speed of verification
D) It forces key expiration
✅ Answer: B – A compromised Certificate Authority (CA) can issue fraudulent certificates, undermining trust.
148. What is the purpose of dual-factor authentication (2FA) in digital signature systems?
A) To prevent key expiration
B) To add an extra layer of security for key usage
C) To replace public keys
D) To speed up encryption
✅ Answer: B – 2FA ensures that only authorized users can access and use private keys for digital signing.
149. What happens if a signer loses access to their private key?
A) The digital signature becomes invalid
B) The public key can regenerate the private key
C) The CA will automatically generate a new key
D) The signature remains valid indefinitely
✅ Answer: A – If a private key is lost, the signer cannot create new digital signatures.
150. How does an attacker exploit a hash collision attack on digital signatures?
A) By generating two different messages with the same hash
B) By brute-forcing the private key
C) By replacing the public key
D) By altering the certificate authority
✅ Answer: A – In a hash collision attack, an attacker finds two different inputs that produce the same hash, making forgery easier.
151. What is the benefit of using elliptic curve cryptography (ECC) in digital signatures?
A) It requires no hashing
B) It provides the same security as RSA with shorter key lengths
C) It eliminates public key encryption
D) It speeds up brute-force attacks
✅ Answer: B – ECC-based digital signatures (e.g., ECDSA) offer strong security with smaller key sizes.
152. What does a timestamp do in a digital signature?
A) Encrypts the signature
B) Provides proof of when the document was signed
C) Replaces hashing algorithms
D) Prevents malware infections
✅ Answer: B – Timestamps provide proof of signing time, preventing backdating fraud.
153. What is the difference between a digital signature and a handwritten signature?
A) Digital signatures use cryptographic techniques for security
B) Digital signatures require ink
C) Handwritten signatures are more secure
D) Digital signatures can be verified without encryption
✅ Answer: A – Digital signatures use cryptographic algorithms, making them more secure than handwritten signatures.
154. How does multi-party digital signing work?
A) It allows multiple users to sign the same document
B) It eliminates the need for hashing
C) It removes the need for a public key
D) It prevents certificate expiration
✅ Answer: A – Multi-party signing allows multiple users to add their digital signatures to a document.
155. What is a potential downside of self-signed digital certificates?
A) They expire faster
B) They are not automatically trusted by browsers and systems
C) They require additional encryption
D) They cannot be used in emails
✅ Answer: B – Self-signed certificates are not automatically trusted, requiring manual approval.
156. What is an example of a digital signature use case in financial transactions?
A) Signing electronic contracts
B) Encrypting credit card numbers
C) Preventing network congestion
D) Eliminating the need for passwords
✅ Answer: A – Digital signatures authenticate financial transactions, such as electronic contracts and agreements.
157. What makes quantum computers a threat to current digital signatures?
A) They generate longer key pairs
B) They can break traditional asymmetric encryption faster
C) They eliminate the need for hashing
D) They increase digital signature size
✅ Answer: B – Quantum computers could break RSA and ECDSA much faster, threatening current cryptographic security.
158. How does an attacker use a key substitution attack in digital signatures?
A) By replacing the public key with a fraudulent one
B) By changing the encryption algorithm
C) By modifying the message without detection
D) By blocking signature validation
✅ Answer: A – In a key substitution attack, an attacker replaces a legitimate public key with a fraudulent key, tricking users.
159. What is the role of a key escrow in digital signature management?
A) It securely stores private keys for recovery
B) It replaces hashing
C) It automatically renews expired certificates
D) It eliminates the need for encryption
✅ Answer: A – A key escrow securely stores private keys, ensuring they can be recovered if lost.
160. What is the difference between a basic and an advanced digital signature?
A) Advanced signatures require additional security features
B) Basic signatures are more secure
C) Advanced signatures use only symmetric encryption
D) Basic signatures are always legally recognized
✅ Answer: A – Advanced digital signatures require extra security measures (e.g., multi-factor authentication, trusted certificates).
161. Which of the following properties ensures that a digital signature remains unchanged and cannot be altered?
A) Encryption
B) Integrity
C) Confidentiality
D) Anonymity
✅ Answer: B – Integrity ensures that a digital signature remains unchanged and cannot be altered without detection.
162. How does a digital signature protect against replay attacks?
A) By encrypting the message
B) By using nonces and timestamps
C) By storing the signature in plaintext
D) By replacing hashing algorithms
✅ Answer: B – Nonces and timestamps ensure that a signature cannot be reused in a replay attack.
163. Which of the following is a legal framework recognizing digital signatures worldwide?
A) GDPR
B) eIDAS
C) ISO 9001
D) NIST SP 800-53
✅ Answer: B – eIDAS (Electronic Identification, Authentication, and Trust Services) is a legal framework for digital signatures in the European Union.
164. What is an ephemeral key in digital signature systems?
A) A key that is used only once and then discarded
B) A key that replaces public keys
C) A key that remains valid indefinitely
D) A key that eliminates encryption
✅ Answer: A – Ephemeral keys are temporary keys used once, reducing the risk of key compromise.
165. What is a rogue Certificate Authority (CA) attack?
A) When a CA issues fraudulent certificates
B) When a CA encrypts data incorrectly
C) When a CA replaces hashing algorithms
D) When a CA stops issuing certificates
✅ Answer: A – A rogue CA attack happens when a compromised CA issues fraudulent certificates, undermining trust.
166. Why is multi-factor authentication (MFA) recommended for private key protection?
A) To increase key length
B) To prevent unauthorized key usage
C) To speed up digital signing
D) To eliminate the need for encryption
✅ Answer: B – MFA adds an extra layer of security, ensuring that only authorized users can access private keys.
167. Which attack involves an attacker tricking a user into signing a different document than intended?
A) Signature substitution attack
B) Collision attack
C) Trojan horse attack
D) Key exchange attack
✅ Answer: A – In a signature substitution attack, an attacker manipulates the signing process to trick a user into signing a different document.
168. Why is SHA-1 no longer recommended for digital signatures?
A) It is too slow
B) It is vulnerable to collision attacks
C) It does not support asymmetric encryption
D) It replaces RSA
✅ Answer: B – SHA-1 is vulnerable to collision attacks, making it insecure for digital signatures.
169. What is the purpose of a trust anchor in a digital signature system?
A) To store private keys
B) To provide the highest level of trust in a PKI
C) To generate hashing algorithms
D) To encrypt digital signatures
✅ Answer: B – A trust anchor is a highly trusted certificate or authority used to verify other digital certificates.
170. How does a hybrid cryptographic system enhance digital signature security?
A) By combining symmetric and asymmetric encryption
B) By eliminating the need for hash functions
C) By using only symmetric encryption
D) By removing the need for public keys
✅ Answer: A – Hybrid cryptographic systems use asymmetric encryption for key exchange and symmetric encryption for data security.
171. What is a major limitation of a certificate revocation list (CRL)?
A) It does not prevent signature forgery
B) It requires frequent updates to remain effective
C) It replaces the need for digital certificates
D) It increases digital signature size
✅ Answer: B – CRLs must be updated frequently to remain effective, as revoked certificates can still be used until the list is updated.
172. What is a key-wrapping attack in digital signatures?
A) An attack that exploits weak key storage practices
B) An attack that replaces the digital signature with a forged one
C) An attack that corrupts public key certificates
D) An attack that prevents key exchange
✅ Answer: A – A key-wrapping attack exploits poor key storage or protection methods, potentially exposing private keys.
173. What is a chain of trust in digital signature verification?
A) A sequence of certificates used to verify authenticity
B) A hashing algorithm that improves verification speed
C) A method for encrypting digital signatures
D) A network-based signature verification system
✅ Answer: A – A chain of trust is a hierarchical system where each certificate is verified by the one above it, ensuring trust.
174. What is an advanced persistent threat (APT) targeting digital signatures?
A) A long-term, stealthy cyberattack focused on compromising cryptographic keys
B) A brute-force attack against private keys
C) A key exchange attack on SSL/TLS
D) A network flooding attack
✅ Answer: A – Advanced persistent threats (APTs) target digital signature keys to perform long-term cyber espionage.
175. Why is it important to renew digital certificates before they expire?
A) To prevent loss of trust in signed documents
B) To increase hashing speed
C) To reduce certificate size
D) To eliminate the need for public keys
✅ Answer: A – Expired digital certificates can cause loss of trust in signed documents.
176. What is an example of a cryptographic agility approach in digital signatures?
A) Allowing systems to switch to stronger encryption algorithms when needed
B) Using only one encryption algorithm permanently
C) Removing hash functions from digital signatures
D) Encrypting all digital signatures with the same key
✅ Answer: A – Cryptographic agility allows systems to adapt to newer, stronger algorithms as threats evolve.
177. What is a signature downgrade attack?
A) Forcing a system to use a weaker digital signature algorithm
B) Removing a digital signature from a document
C) Brute-forcing a private key
D) Encrypting the signature multiple times
✅ Answer: A – A signature downgrade attack forces a system to use a weaker digital signature algorithm, making it easier to break.
178. What is a blind signature?
A) A digital signature applied without knowing the content of the document
B) A signature that is only visible after decryption
C) A signature that does not require a private key
D) A signature that eliminates the need for hashing
✅ Answer: A – A blind signature is created without knowing the document’s content, commonly used in anonymous transactions.
179. What is a key-reuse attack in digital signatures?
A) Using the same key for multiple signatures, increasing vulnerability
B) Generating a new key for every signature
C) Replacing a public key with an invalid one
D) Encrypting a key using AES
✅ Answer: A – Key-reuse attacks occur when the same key is used for multiple signatures, making it a target for attacks.
180. How does forward secrecy enhance digital signature security?
A) It ensures past signatures remain secure even if private keys are compromised
B) It replaces the need for public keys
C) It eliminates the use of hashing
D) It prevents all cyberattacks
✅ Answer: A – Forward secrecy ensures that previously signed documents remain secure, even if private keys are later compromised.
181. Which of the following is a primary reason for using a cryptographic timestamp in digital signatures?
A) To verify when a document was signed
B) To encrypt the signature
C) To generate a new private key
D) To prevent certificate expiration
✅ Answer: A – Cryptographic timestamps help verify when a document was signed, ensuring it was signed before a certificate expired or was revoked.
182. What is the primary function of a root CA in a public key infrastructure (PKI)?
A) To issue and sign digital certificates
B) To store all signed documents
C) To generate private keys for users
D) To encrypt data at rest
✅ Answer: A – The root Certificate Authority (CA) is responsible for issuing and signing digital certificates, forming the trust anchor in a PKI system.
183. Which property of digital signatures ensures that the signer cannot deny signing a document?
A) Confidentiality
B) Anonymity
C) Non-repudiation
D) Encryption
✅ Answer: C – Non-repudiation ensures that a signer cannot deny having signed a document.
184. How can digital signatures improve email security?
A) By verifying the sender’s authenticity and email integrity
B) By encrypting the email contents
C) By blocking spam emails
D) By hiding email metadata
✅ Answer: A – Digitally signing emails ensures that the sender is authentic and the email has not been altered.
185. What is a cryptographic salt, and how does it enhance digital signatures?
A) It adds randomness to hashing to prevent precomputed attacks
B) It replaces public key encryption
C) It increases signature length
D) It generates private keys
✅ Answer: A – A cryptographic salt adds randomness to a hash function, making it harder for attackers to use precomputed hash attacks.
186. Which of the following is NOT a valid reason for a digital certificate to be revoked?
A) The certificate has expired
B) The private key has been compromised
C) The hash algorithm used in the certificate is outdated
D) The signer changes their email address
✅ Answer: D – A change in the signer’s email address does not necessarily require certificate revocation.
187. What role does key escrow play in digital signature management?
A) It securely stores private keys for recovery purposes
B) It encrypts digital signatures
C) It prevents key expiration
D) It eliminates the need for certificate authorities
✅ Answer: A – Key escrow is used to securely store private keys, ensuring they can be recovered if lost.
188. What is an air-gapped system, and why is it used for digital signatures?
A) A system completely isolated from networks to protect private keys
B) A system that encrypts digital signatures multiple times
C) A system that prevents hashing collisions
D) A system that automatically renews certificates
✅ Answer: A – Air-gapped systems are physically isolated from networks, protecting private keys from cyberattacks.
189. What is a cryptographic checksum, and how does it relate to digital signatures?
A) A hash-based value used to verify data integrity
B) A public key replacement method
C) A signature that does not expire
D) A form of asymmetric encryption
✅ Answer: A – A cryptographic checksum is a hash-based value that helps verify data integrity in digital signatures.
190. What is the purpose of digital signatures in electronic voting systems?
A) To ensure vote integrity and prevent tampering
B) To speed up vote counting
C) To make voting anonymous
D) To prevent all cyber threats
✅ Answer: A – Digital signatures ensure that electronic votes remain untampered, maintaining integrity and authenticity.
191. What is a quantum-resistant digital signature algorithm?
A) An algorithm designed to withstand quantum computing attacks
B) A signature that expires faster
C) A signature that does not require a private key
D) A signature that eliminates the need for a certificate authority
✅ Answer: A – Quantum-resistant digital signature algorithms (e.g., Dilithium, Falcon) are designed to resist quantum attacks.
192. What is the main advantage of a decentralized digital signature system, such as blockchain?
A) It removes the need for a central trusted authority
B) It increases the size of the digital signature
C) It requires more encryption keys
D) It speeds up hashing
✅ Answer: A – Decentralized digital signatures, such as those in blockchain, remove the need for a central trusted authority.
193. How does a hardware security module (HSM) enhance digital signature security?
A) By securely generating and storing cryptographic keys
B) By replacing public key infrastructure
C) By encrypting all signed documents
D) By reducing signature size
✅ Answer: A – HSMs securely generate and store cryptographic keys, reducing key exposure.
194. Which of the following attacks specifically targets digital signature key leakage?
A) Side-channel attack
B) Brute-force attack
C) SQL injection
D) Phishing attack
✅ Answer: A – A side-channel attack exploits physical characteristics (e.g., timing, power consumption) to extract cryptographic keys.
195. What is the benefit of using a post-quantum cryptographic (PQC) algorithm for digital signatures?
A) It resists attacks from quantum computers
B) It eliminates the need for hashing
C) It speeds up key exchange
D) It removes the need for encryption
✅ Answer: A – PQC algorithms (e.g., Falcon, Dilithium) ensure digital signatures remain secure against quantum computers.
196. Why is hashing necessary before applying a digital signature?
A) It reduces the size of the signed data
B) It increases encryption speed
C) It eliminates the need for public keys
D) It replaces certificate revocation lists
✅ Answer: A – Hashing reduces data size, making digital signatures more efficient while preserving integrity.
197. What is a threshold signature scheme?
A) A scheme where multiple parties contribute to generating a signature
B) A signature that expires after a set period
C) A method for encrypting digital signatures
D) A replacement for hashing algorithms
✅ Answer: A – A threshold signature scheme allows multiple parties to contribute to a single digital signature, enhancing security.
198. What is a major advantage of using elliptic curve digital signatures (ECDSA) over RSA?
A) ECDSA requires shorter key sizes for the same level of security
B) ECDSA eliminates the need for hashing
C) ECDSA encrypts data faster
D) ECDSA is not affected by quantum computing
✅ Answer: A – ECDSA provides the same security as RSA but with much shorter key lengths, making it more efficient.
199. What is the primary goal of a signature aggregation scheme?
A) To combine multiple signatures into a single, compact signature
B) To replace public key cryptography
C) To eliminate the need for private keys
D) To slow down brute-force attacks
✅ Answer: A – Signature aggregation combines multiple signatures into one compact signature, improving efficiency.
200. What is a potential risk of using weak random number generators in digital signature schemes?
A) Private keys may become predictable
B) Hash functions may fail
C) Signatures become larger
D) Public keys become invalid
✅ Answer: A – Weak random number generators can make private keys predictable, leading to digital signature compromise.