Consider the following plaintext message: THE SIXTEENTH PRESIDENT WAS ABRAHAM LINCOLN. (3 pts) If this message...
Consider the following plaintext message: THE SIXTEENTH PRESIDENT WAS ABRAHAM LINCOLN.
(3 pts) If this message is sent unencrypted and successfully received, what is its entropy? And why?
(3 pts) If this message is encrypted with DES using a random 56-bit key, what is the encrypted message’s entropy? And why
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Consider the following plaintext message: THE SIXTEENTH
PRESIDENT WAS ABRAHAM LINCOLN.
(3 pts) If this message...
Substitution Cipher Ke 1. Decipher the following ciphertext using the substitution cipher key shown above: (4 points) Ciphertext: DOVMYWOJAYJMYWZBAOXOADY!U I Plaintext: The following information was...
Substitution Cipher Ke 1. Decipher the following ciphertext using the substitution cipher key shown above: (4 points) Ciphertext: DOVMYWOJAYJMYWZBAOXOADY!U I Plaintext: The following information was extracted from The BLACK Chamber's Pigpen Cipher page. The content is available at https:/simonsingh net The_Black Chamber'pigpen html. "The Pigpen Cipher was used by Freemasons in the l8th Century to keep their records private. The cipher does not substitute one letter for another; rather it substitutes each letter for a symbol The aiphabet is written...
3) Out of the following, name which kind of attack you carried out in part 1...
3) Out of the following, name which kind of attack you carried out in part 1 and part2: a. ciphertext only, b. known plaintext, c. chosen plaintext, d. chosen ciphertext. Explain your answer Problem 3 10 points] A 4-bit long message was encrypted using one-time pad to yield a cipher-text “1010” Assuming the message space consists of all 4-bit long messages, what is the probability that the corresponding plaintext was “1001”? Explain your answer. Problem 4 Assume we perform a...
Consider the following scheme to provide message authentication. B gets a message supposedly from A, and...
Consider the following scheme to provide message authentication. B gets a message supposedly from A, and B wants to make sure that the message was sent by A and not modified by BG along the way. A generates a secret key K for DES, calculates C = E_K (M), and sends M, C, K to B. B checks it M = D_K (C) and if it is, accepts that M was sent by A. Is this is a good scheme?...
the w 2. This problem explores the use of a one-time pad version of t In...
the w 2. This problem explores the use of a one-time pad version of t In this scheme, the key is a stream of random numbers between 0 and example, if the key is 3 19 5..., then the first letter of plaintext is encrypted with a shift of 3 letters, the second with a shift of 19 letters, the third with a shift of 5 letters, and so on. a. Encrypt the plaintext sendmoremoney with the key stream 9...
Question 7 12.5 pts Recall that book ciphers do not necessarily require a full book to...
Question 7 12.5 pts Recall that book ciphers do not necessarily require a full book to decode, but instead any written text, such as the Declaration of Independence. For the example discussed in class (the second Beale cipher), we created the key by numbering words and taking the first letter. But we can also number characters themselves instead, making sure to skip spaces. The following is a message encrypted with a book cipher, using the text of this question as...
3. We have the following encryption algorithm: XOR with the HEX key AA, rotate 4 places...
3. We have the following encryption algorithm: XOR with the HEX key AA, rotate 4 places to the right, and XOR with the HEX key BC. Show your work for full marks. a. If we start with the bit pattern represented by the HEX number ACE1, what would the HEX number be that represents the encrypted bit pattern? b. Assume that we have intercepted a message that was encoded using the same algorithm. The encoded message as a HEX number...
(7) (2 pts) The simplified version of the handshaking procedure between a client and a bank...
(7) (2 pts) The simplified version of the handshaking procedure between a client and a bank server for establishing a secure connection is described below (just consider it identical to the SSL/TLS described in class): 1. A client connects to the TLS-enabled bank server requesting a secure connection, and presents a list of supported ciphers (RC4, DES, AES, etc) and hash functions (MD5, SHA-1, etc). 2. The server picks the strongest cipher and hash. It then server sends back its...
2. Use the 3-bit block cipher in the table below to answer the following. Suppose the...
2. Use the 3-bit block cipher in the table below to answer the following. Suppose the (a) Use the block cipher without cipher-block chaining (CBC) to encrypt the message (b) Suppose Trudy intercepts the ciphertext. Further suppose she knows that the text was plaintext is m 011011011. What is the resulting ciphertext? encrypted with a 3-bit block cipher without CBC, but she does not know the specific cipher. What can she determine about the original message? (c) Now use the...
1.Which of the following statements about asymmetric-key encryption is correct? a When using asym...
1.Which of the following statements about asymmetric-key encryption is correct? a When using asymmetric-key encryption method, a total of two keys are necessary in electronic communication between two parties. b Employees in the same company share the same public key. c Most companies would like to manage the private keys for their employees. d Most companies would like to use a Certificate Authority to manage the public keys of their employees. e Two of the above are correct. 2 Which...
2.Consider the following credit card numbers and tell me if they are valid or not. If...
2.Consider the following credit card numbers and tell me if they are valid or not. If a number is invalid, write the valid credit number by changing the “check” digit. Show your work for full marks. a. 4519 6731 6055 4166 b. 4515 1663 4722 3333 c. How many valid (according to the Luhn check) 16-digit credit card numbers are there that start with these 14 digits 4444 4444 4444 45? Give one of the valid credit card numbers. 3....
Substitution Cipher Ke 1. Decipher the following ciphertext using the substitution cipher key shown above: (4 points) Ciphertext: DOVMYWOJAYJMYWZBAOXOADY!U I Plaintext: The following information was extracted from The BLACK Chamber's Pigpen Cipher page. The content is available at https:/simonsingh net The_Black Chamber'pigpen html. "The Pigpen Cipher was used by Freemasons in the l8th Century to keep their records private. The cipher does not substitute one letter for another; rather it substitutes each letter for a symbol The aiphabet is written...
Consider the following scheme to provide message authentication. B gets a message supposedly from A, and B wants to make sure that the message was sent by A and not modified by BG along the way. A generates a secret key K for DES, calculates C = E_K (M), and sends M, C, K to B. B checks it M = D_K (C) and if it is, accepts that M was sent by A. Is this is a good scheme?...
the w 2. This problem explores the use of a one-time pad version of t In this scheme, the key is a stream of random numbers between 0 and example, if the key is 3 19 5..., then the first letter of plaintext is encrypted with a shift of 3 letters, the second with a shift of 19 letters, the third with a shift of 5 letters, and so on. a. Encrypt the plaintext sendmoremoney with the key stream 9...
Question 7 12.5 pts Recall that book ciphers do not necessarily require a full book to decode, but instead any written text, such as the Declaration of Independence. For the example discussed in class (the second Beale cipher), we created the key by numbering words and taking the first letter. But we can also number characters themselves instead, making sure to skip spaces. The following is a message encrypted with a book cipher, using the text of this question as...
(7) (2 pts) The simplified version of the handshaking procedure between a client and a bank server for establishing a secure connection is described below (just consider it identical to the SSL/TLS described in class): 1. A client connects to the TLS-enabled bank server requesting a secure connection, and presents a list of supported ciphers (RC4, DES, AES, etc) and hash functions (MD5, SHA-1, etc). 2. The server picks the strongest cipher and hash. It then server sends back its...
2. Use the 3-bit block cipher in the table below to answer the following. Suppose the (a) Use the block cipher without cipher-block chaining (CBC) to encrypt the message (b) Suppose Trudy intercepts the ciphertext. Further suppose she knows that the text was plaintext is m 011011011. What is the resulting ciphertext? encrypted with a 3-bit block cipher without CBC, but she does not know the specific cipher. What can she determine about the original message? (c) Now use the...
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