Alice wants to send a secure email message m to Bob, such that confidentiality, sender authen...
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.
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 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...
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?
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...
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...
Alice has a message M=51 to send to Bob securely using ElGamal encryption algorithm. Bob chooses p= 8167, g=4063, x=71. Alice chooses r=29. Show the encryption and decryption steps.
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
Suppose Alice has a and Bob has b. Alice and Bob also share a secure communication channel. Chris wants to compute S = a ⊕ b. Alice does not want Chris or Bob to learn a and Bob does not want Chris or Alice to learn b. How can this be done?
5. Alice wishes to send the message m4 to Bob using RSA encryption. She looks up Bob's public key and finds that it is (n-55. c= 3 (a) Specify exactly what information Alice sends to Bob (b) What is Bob's private key? Show how he would use it to recover Alice's message (c) Explain why Bob should never use this choice of public key in real life. 5. Alice wishes to send the message m4 to Bob using RSA encryption....