Digital signatures
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Questions and Answers

Which of the following is a requirement for a digital signature?

  • Compression of the message
  • Authentication of the author of the message (correct)
  • Decryption of the message
  • Encryption of the message

    • What is the purpose of non-repudiation in digital signatures?

  • To confirm the time of the message
  • To protect against forgery
  • To prevent the signer from denying they signed (correct)
  • To encrypt the message

    • What is the role of a hash function in digital signatures?

  • To confirm the time of the message
  • To encrypt the message
  • To produce a fixed-length message digest (correct)
  • To compress the message

    • Why was the first idea of signing a message not used in practice?

    <p>The signature was too long</p> Signup and view all the answers

    What is the advantage of using a hash function in digital signatures?

    <p>The signature is shorter than the message</p> Signup and view all the answers

    What is the disadvantage of using a poorly designed hash function in digital signatures?

    <p>The signature is vulnerable to attacks</p> Signup and view all the answers

    What is the purpose of the eIDAS EU regulation?

    <p>To establish the use of digital signatures as legal signatures</p> Signup and view all the answers

    Which of the following is a requirement for a digital signature?

    <p>Authentication of the author of the message</p> Signup and view all the answers

    What is non-repudiation in the context of digital signatures?

    <p>The ability to deny signing a message</p> Signup and view all the answers

    What is the purpose of a hash function in digital signatures?

    <p>To produce a fixed-length message digest</p> Signup and view all the answers

    What is the disadvantage of the first idea of signing a message using public key cryptography?

    <p>The signature is too long</p> Signup and view all the answers

    How is a message digest computed in the RSA signature scheme?

    <p>By applying a public hash function to the message</p> Signup and view all the answers

    What is the advantage of using a hash function in the RSA signature scheme?

    <p>The signature is shorter than the message</p> Signup and view all the answers

    What is the disadvantage of using a poorly designed hash function in the RSA signature scheme?

    <p>The signature is prone to attacks</p> Signup and view all the answers

    What is an example of a digital signature service?

    <p>DocuSign</p> Signup and view all the answers

    What is the purpose of a timestamp in a digital signature?

    <p>To confirm the time of the message</p> Signup and view all the answers

    What is the purpose of a public key in a digital signature scheme?

    <p>To verify the signature</p> Signup and view all the answers

    What is the purpose of a private key in a digital signature scheme?

    <p>To sign the message</p> Signup and view all the answers

    What is the difference between a digital signature and an electronic signature?

    <p>A digital signature relies on cryptographic mechanisms, while an electronic signature relies on a signing process</p> Signup and view all the answers

    What are the three requirements for a digital signature?

    <p>Authentication of the author, non-repudiation, and integrity.</p> Signup and view all the answers

    What is the disadvantage of the first idea of signing a message using public key cryptography?

    <p>The signature is as long as the message and vulnerable to attacks.</p> Signup and view all the answers

    What is the better solution for signing a message using public key cryptography?

    <p>Using a hash function to produce a fixed-length message digest.</p> Signup and view all the answers

    What is the advantage of using a hash function in digital signatures?

    <p>The signature has a small fixed length, regardless of the length of message.</p> Signup and view all the answers

    What is the potential disadvantage of using a poorly designed hash function in digital signatures?

    <p>It can introduce vulnerabilities to the signature scheme.</p> Signup and view all the answers

    What is the purpose of the eIDAS EU regulation?

    <p>To legally accept digital signatures as signatures.</p> Signup and view all the answers

    What is the example of a digital signature service mentioned in the text?

    <p>Adobe Digital signatures and DocuSign.</p> Signup and view all the answers

    What is the purpose of a message digest in the RSA signature scheme?

    <p>To produce a fixed-length value that can be signed using the private key.</p> Signup and view all the answers

    What is the formula used to compute the signature in the RSA signature scheme?

    <p>s = h^d mod n</p> Signup and view all the answers

    What is the formula used to verify the signature in the RSA signature scheme?

    <p>s^e mod n = h</p> Signup and view all the answers

    What is the advantage of using a hash function in the RSA signature scheme?

    <p>It produces a fixed-length message digest that can be signed using the private key.</p> Signup and view all the answers

    What is the potential disadvantage of using a poorly designed hash function in the RSA signature scheme?

    <p>It can introduce vulnerabilities to the signature scheme.</p> Signup and view all the answers

    What is the main purpose of a digital signature?

    <p>To authenticate the author of a message</p> Signup and view all the answers

    What is the main disadvantage of the first idea of signing a message using public key cryptography?

    <p>The signature is too long</p> Signup and view all the answers

    What is the purpose of a hash function in digital signatures?

    <p>To compress the message</p> Signup and view all the answers

    What is the main advantage of using a hash function in digital signatures?

    <p>The signature has a small fixed length</p> Signup and view all the answers

    What is the potential vulnerability introduced if the hash function used in a digital signature is not well designed?

    <p>The message digest can be easily manipulated</p> Signup and view all the answers

    What is the result of computing the signature of Bob for message m in the RSA signature scheme?

    <p>7</p> Signup and view all the answers

    What is the purpose of the eIDAS EU regulation?

    <p>To regulate the use of electronic signatures</p> Signup and view all the answers

    What is the main difference between a digital signature and an electronic signature?

    <p>A digital signature relies on cryptographic mechanisms, while an electronic signature relies on a signing process</p> Signup and view all the answers

    What is the main purpose of non-repudiation in digital signatures?

    <p>To prevent the author from denying that they signed the message</p> Signup and view all the answers

    What is the main requirement for a digital signature to protect against forgery?

    <p>The signature should be linked to the message</p> Signup and view all the answers

    What is the result of encrypting Bob's signature using his public key in the RSA signature scheme?

    <p>13</p> Signup and view all the answers

    What is the main disadvantage of using a poorly designed hash function in digital signatures?

    <p>The message digest can be easily manipulated</p> Signup and view all the answers

    What is the purpose of a digital signature?

    <p>To authenticate the author of a message</p> Signup and view all the answers

    What is the disadvantage of the first idea of signing a message using public key cryptography?

    <p>The signature is too long</p> Signup and view all the answers

    What is the disadvantage of using a poorly designed hash function in digital signatures?

    <p>The signature is not secure</p> Signup and view all the answers

    What is the advantage of using a hash function in digital signatures?

    <p>The signature is shorter</p> Signup and view all the answers

    What is non-repudiation in the context of digital signatures?

    <p>The signer cannot deny that they signed</p> Signup and view all the answers

    What is the role of a hash function in digital signatures?

    <p>To ensure the integrity of the message</p> Signup and view all the answers

    What is the purpose of the eIDAS EU regulation?

    <p>To regulate digital signatures</p> Signup and view all the answers

    What is an example of a digital signature service?

    <p>Adobe Digital Signatures</p> Signup and view all the answers

    What is the first idea for signing a message using public key cryptography?

    <p>To sign the message with a private key</p> Signup and view all the answers

    What is the better solution for signing a message using public key cryptography and a hash function?

    <p>To hash the message and sign the digest with a private key</p> Signup and view all the answers

    What is the disadvantage of using a poorly designed hash function in the RSA signature scheme?

    <p>The signature is not secure</p> Signup and view all the answers

    What is the purpose of authentication in digital signatures?

    <p>To protect against forgery</p> Signup and view all the answers

    What is the length of the signature using the first idea of signing a message with public key cryptography?

    <p>The length of the signature is as long as the message.</p> Signup and view all the answers

    What is the purpose of a hash function in digital signatures?

    <p>To produce a fixed-length message digest.</p> Signup and view all the answers

    What is the advantage of using a hash function in digital signatures?

    <p>The signature has a small fixed length.</p> Signup and view all the answers

    What is the disadvantage of using a poorly designed hash function in digital signatures?

    <p>The signature can be easily forged.</p> Signup and view all the answers

    What is the purpose of the eIDAS EU regulation?

    <p>To regulate the use of digital signatures in the EU.</p> Signup and view all the answers

    What is the difference between a digital signature and an electronic signature?

    <p>A digital signature relies on cryptographic mechanisms, while an electronic signature relies on the process of signing.</p> Signup and view all the answers

    What is the role of non-repudiation in digital signatures?

    <p>To ensure that the signer cannot deny that they signed.</p> Signup and view all the answers

    What is the role of authentication in digital signatures?

    <p>To provide a proof of the identity of the author.</p> Signup and view all the answers

    What is the role of integrity in digital signatures?

    <p>To prevent any change to the signed message without invalidating the signature.</p> Signup and view all the answers

    What is the first idea of signing a message using public key cryptography?

    <p>Bob decrypts the message with his private key.</p> Signup and view all the answers

    What is the second idea of signing a message using public key cryptography?

    <p>Bob applies a public hash function to his message.</p> Signup and view all the answers

    What is the formula for computing Bob's signature in the RSA signature scheme?

    <p>s = h7 mod 33</p> Signup and view all the answers

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