Questions:
- Numerical messages
- A certain communications system uses messages that are 512 bit long. How many different messages can be supported by such system
Answer:
Assuming
m = length the message
Where l bits hence append bit 1 to the end of the message,
k = the minutest solution to the equation
Thus,
1+ l +k≡448 mod 512
But for 512 bit communication system will produce a negative result hence the solution will be given by
K = ((447−l) mod 512 + 512) mod 512
But calculating for 512will give a negative value.
- A certain communications system uses messages that are 2^8 bits long. The accompanying hash code is 64 bits long. How many messages could produce the same hash code?
Answer:
64 bit hash = 2 ^64 messages\ possible hashes
64 bit hash = 2^32 tries
- ENIGMA Encryption. Provide the answer along with a brief explanation
- An Enigma encrypted message was intercepted and reads as follows: ATKXUVKYGFWLTZTIRNFYLGZPKEGWJHXWZKJKOZOUOXHABERIBYCLNYBLHAISBZPRLUJPUSZDTQMBRDXYIBIDGH. What does it mean?
Answer:
The enemy is approaching
- Express the encryption algorithm that has been used.
Answer:
Symmetric key algorithms: are which decryption and encryption are performed utilizing a similar key. They are utilized mainly for the bulk encryption of data or streams of data. The symmetric key algorithms can be classified into two classes: stream and block. Stream algorithms encrypt data byte by byte while block algorithms data a block (several bytes) at a time.
- This number 13717421 represents the product of two prime numbers used in an encryption system. Identify the two numbers.
Answer:
3,607 and 3,803
3,607 X 3,803 = 13717421
- A certain cryptography vendor was providing an encryption technology that was breakable within 10 hours. Considering the continuous increase in computer speed, the company decided to increase the size of the encryption key so that the time to break the encryption become more than 250 hours. What should be the minimum key size increase to meet this objective?
Answer:
The minimum key size should be 128-bit security levels to be the minimum requirement that will meet the objective of the company
- In Ancient Sparta a tape with the following text was placed around a fighter’s waist. TMOMOEEEOOUESCRAMRMECAENONUAHUWERISROSIXRNTLOELAOGCYLTLMWYOTBHB. The letters were written “sleeping” along the tape. The size (height) of the letters was almost 5cm At the destination the message was read when the tape was rolled around a cylindrical scytale of about 0.637cm in radius. What is the message?
Answer:
Frontline soldiers·
- Diffie-Hellman (4 pts) You have agreed with your friend X that you will use the Diffie-Hellman public-key algorithm to exchange secret keys. You and X have agreed to use the public base g = 19 and public modulus p = 739. You have secretly picked the value SA = 5. You begin the session by sending X your calculated value of TA. X responds by sending you the value TB = 167. What is the value of your shared secret key? Show all your work.
Answer:
g= 19
mod (739)
167^5..19 = X mod (739)
- In a multi-hub communication system you have access to one of the hubs and you can replace messages. Your job is to compromise the message, which is onsundaymeetmeattheairport. The accompanying signature is onmmtir The signature should not be altered. Determine the signature characteristics and create a deceiving message that would produce the same signature.
Answer:
Characteristic of the signature
- The validity of a signature created from a fixed private key and fixed message can be proved by utilizing the corresponding public key.
- It is computationally infeasible to create a valid signature for a party without having knowledge that party’s private key.
Ongoing meeting must stir the debate
- Ciphertext:
FT8lRsG7P+NZTIQYE54CfNiYtBD+Cy8reGny9gRzoFZ4ujXNnTipJ8ctIYoh/b37xq9V
FlOjR4JVhYc9
YGos5ttjhg64roXSWIk/TcelpB4CvFheXuviN0Cr4wCx1taA
Password: 5?3
Tool: https://www.infoencrypt.com/
Answer:
Encryption-Info: AES-128,CBC,PKCS5 Padding
Key-Info: MD5,PBKDF2 HmacSHA1
Decrypt-URL: https://www.infoencrypt.com
- Algorithm The following message: 1234567890987654321234567890 produces a hash code: 4884260. What will be the hash code produced by the same algorithm for the following message?
2134354654789643356778532356899556463393
Answer:
Generation of a MD5 hash is produced by taking a string of a given length and encrypting it into a 128-bit fingerprint. Using the MD5 algorithm encoding the same string will constantly result in giving similar 128-bit hash output.
Hence, the hash code produce by the above message will be f451ba863a96eb03056d695b05404476
- QUERTY. The following enemy encrypted message has been intercepted:
YJR NP<NSTTF<RMY EO:: DYSTY YP<PTTPE
A sleeper of ours behind enemy lines sent a message that the enemy’s encryption had to do with the QWERTY keyboard layout. Decrypt the message and save lives.
Answer:
THE BOMBARRDMENT WILL START TOMORROW
Answers:
Answer to question number 1
- The length of the message is 512 bits.
We know that, 2^512= 10^154
Hence the number of different messages supported by the system is : 154
- The number of messages for the same hash code is
2^8 / 64 = 4
Answer to question number 2
- The enemy is approaching
- The substitution cipher algorithm is used for the encryption of the text.
Answer to question number 3
The Prime Factors are: [3607, 3803]
The Factored Number and Possible Factors are: [13717421, 3607, 3803]
Answer to question number 4
Let the number of hours required to decrypt a message of size n bit be 10
Therefor the time required to decrypt the message length of n+1 is 20
Similarly, the time required to decrypt the message length of n+2 is 40
Similarly, the time required to decrypt the message length of n+3 is 80
Similarly, the time required to decrypt the message length of n+4 is 160
Similarly, the time required to decrypt the message length of n+5 320
Hence, the minimum number of bits that are to be increased to meet this objective is 5.
Answer to question number 6
a = 5
A = g^a mod p = 195 mod 739 = 449
keya = B^a mod p = 1675 mod 739 = 420
keyb = A^b mod p = 44914 mod 739 = 420
B = g^b mod p = 1914 mod 739 = 167
b = 14
Answer to question number 8
The plaintext of the provided cipher text is – Oh what a beautiful morning
Answer to question number 9
The hash code provided will be 1083434428698478858480279473.
Answer to question number 10
The decrypted message is – THE BOMBARRDMENT WILL START TOMORROW
