Suppose, Bob (the sender) wants to send a message to Alice. Before sending the message, Bob generates a digital signatur...
Suppose, Bob (the sender) wants to send a message to Alice. Before sending the message, Bob generates a digital signature. Assume that Bob and Alice use both of the public-key cryptography system and hash function when computing digital signatures. Say, the hash function used to compute and verify signatures is insecure, but the public-key cryptography system is secure. Show that Trudy can forge signatures.
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Suppose, Bob (the sender) wants to send a message to Alice. Before sending the message, Bob generates a digital signatur...
Suppose, Bob (the sender) wants to send a message to Alice. Before sending the message, Bob generates a digital signatur...
Suppose, Bob (the sender) wants to send a message to Alice. Before sending the message, Bob generates a digital signature. Assume that Bob and Alice use both of the public-key cryptography system and hash function when computing digital signatures. Say, the hash function used to compute and verify signatures is insecure, but the public-key cryptography system is secure. Show that Trudy can forge signatures.
Alice wants to send a secure email message m to Bob, such that confidentiality, sender authen...
Alice wants to send a secure email message m to Bob, such that confidentiality, sender authen tication, and message integrity are provided. Using block diagrams, explain how this can be achieved
Consider the following scenario: Alice receives a message, a digital signature and a certificate from Bob....
Consider the following scenario: Alice receives a message, a digital signature and a certificate from Bob. In order to verify the signature, Alice does the following: Hashes the received message using the same hash algorithm that Bob used, that's your calculated hash Decrypts the signature using the public key contained in the certificate, that your decrypted hash Compares the calculated hash and the decrypted hash Because the 2 hashes are identical, Alice goes on and: Checks the validity period on...
Q3: Suppose Bob wants to send an encrypted message to Alice. Which one of the followings...
Q3: Suppose Bob wants to send an encrypted message to Alice. Which one of the followings is correct? 1. Bob uses a shared secret key to encrypt the message. Alice uses Bob's public key to decrypt the encrypted message. 2. Bob uses Alice's private key to encrypt the message. Alice uses a shared secret key to decrypt the encrypted message. 3. Bob uses Alice's public key to encrypt the message digest. Alice uses Bob's public key to decrypt the encrypted...
Bob wants to send an encrypted message using public key cryptography to Alice. What key does...
Bob wants to send an encrypted message using public key cryptography to Alice. What key does he use for encryption? You need to be explicit whose key it is and what kind of key it is. 1 AB I
(Authentication with Alice cheating) Let’s assume Trudy is Alice’s little sister. Alice produces the message “Transfer...
(Authentication with Alice cheating) Let’s assume Trudy is Alice’s little sister. Alice produces the message “Transfer $100,000 from Bob to Trudy’s account” and appends it with a valid signature sign(x) of Bob. She then claims that she received this message from Bob. Can Bob prove that he could not have signed this message? 1. In this problem, we will compare the security services provided by Digital Signatures (DS) and Message Authentication Codes (MAC). We assume that Trudy is able to...
Alice intends to send a secure message to Bob. (i) What are the threats that Alice...
Alice intends to send a secure message to Bob. (i) What are the threats that Alice should be concerned about in sending messages to Bob? (ii) What information does Alice need if symmetric key encryption is used? (iii) What is needed if asymmetric key encryption is used? (iv) Is encryption alone sufficient to defend against these threats?
Alice wants to send a message m to Bob using Rabin Cryptosystem. Bob makes the public...
Alice wants to send a message m to Bob using Rabin Cryptosystem. Bob makes the public key n = 77 and sends it to Alice. By using Rabin Cryptosystem, a) Alice encrypts her message m and sends the encrypted message c to Bob. What are the encrypted messages if m = 8, 36, 41 and 69? b) Alice encrypts her message m = 6 and sends the encrypted message c to Bob. Bob decrypts the message. What are the possible...
Question 4 (5 points) Consider the following scenario: Alice wants to send Bill a message. Alice...
Question 4 (5 points)
Consider the following scenario: Alice wants to send Bill a
message. Alice encrypts some information using Bill's public key;
Bill decrypts the ciphertext using his private key. This is an
example of:
Question 4 options:
1)
symmetric encryption
2)
digital certificate
3)
asymmetric encryption
4)
digital signature
5. Consider the RSA encryption scheme, Alice wants to send a message to Bob. Both Alice...
5. Consider the RSA encryption scheme, Alice wants to send a message to Bob. Both Alice and Bob have p= 17,9 = 19. Alice has e=31 and Bob has e=29. a. What is the public key pair used in the transmission? 2 marks b. What is the secret key pair used in the transmission? 4 marks c. Encrypt the message m=111. 4 marks d. Decrypt the resulting ciphertext. 4 marks e. What's the security problem between Alice and Bob? How...
Alice wants to send a secure email message m to Bob, such that confidentiality, sender authen tication, and message integrity are provided. Using block diagrams, explain how this can be achieved
Q3: Suppose Bob wants to send an encrypted message to Alice. Which one of the followings is correct? 1. Bob uses a shared secret key to encrypt the message. Alice uses Bob's public key to decrypt the encrypted message. 2. Bob uses Alice's private key to encrypt the message. Alice uses a shared secret key to decrypt the encrypted message. 3. Bob uses Alice's public key to encrypt the message digest. Alice uses Bob's public key to decrypt the encrypted...
Bob wants to send an encrypted message using public key cryptography to Alice. What key does he use for encryption? You need to be explicit whose key it is and what kind of key it is. 1 AB I
Question 4 (5 points)
Consider the following scenario: Alice wants to send Bill a
message. Alice encrypts some information using Bill's public key;
Bill decrypts the ciphertext using his private key. This is an
example of:
Question 4 options:
1)
symmetric encryption
2)
digital certificate
3)
asymmetric encryption
4)
digital signature
5. Consider the RSA encryption scheme, Alice wants to send a message to Bob. Both Alice and Bob have p= 17,9 = 19. Alice has e=31 and Bob has e=29. a. What is the public key pair used in the transmission? 2 marks b. What is the secret key pair used in the transmission? 4 marks c. Encrypt the message m=111. 4 marks d. Decrypt the resulting ciphertext. 4 marks e. What's the security problem between Alice and Bob? How...
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