Question

A certain symmetric encrption system El uses the following secret key (KI) for confidential communication between A and B FEA01FAA3459012D (hex) A decides to deliver this secret key (K1) to B by transmitting it over the same insecure channel using a second encryption scheme E2 a- What method of encryption would you suggest for E2? b- Based on your suggestion, what would be the size in bits of the key (K2) used in encryption system E2? c- If a system of computers has the ability to try 64 keys every 100 microseconds in an effort to decipher the message encrypted by E1 by brute force, how long (on average) would it take to break the code? d- Is El computationally secure?

Answer 1

solution:

a).

Public - key cryptography is well suited for achieving a secure communication over an insecure channel. In public-key cryptography, each party will be having 2 pairs of keys. One public key and one private key. The public key is accessible and can be request from a central authority known as CA (Certification Authority). This CA rusted source whose data is not corrupted. We can use an RSA algorithm as the asymmetric key based encryption mechanism for sending the key over an insecure channel.

b).

The key length for an RSA encryption algorithm will range between 1024 to 4096 bits. Though the key size can vary based on our requirements, commonly used mechnisms have the key length between the above mentioned sizes.

c).

Assuming a consistent performance of carcking 64 keys for every 100 micro seconds, the system will take a total of
computations to perform a bruteforce attack. And given that, the system will crack 64 keys every 100 microseconds(0.0001 seconds):

rounds(each taking 100 micro seconds)

The above calculation turns out to be taking approximately 913,972 years to break in.

d).

Based on the bruteforce attack mentioned, it is computationally secure as long as the key is securely transmitted.

please give me thumb up