Lab 12 (17/05/2023)

Problems for lab session:

Practicals

Part 1

1. Implement RSA for ‘textual’ data encryption and decryption, keeping following instructions in account:

• Convert char. string to binary string before the encryption
• Unencrypted numbers (representing textual string block) should be represented in N-2 bits
• Encrypted numbers (representing ciphertext’s block) should be represented in N bits
• The ciphertext should be a binary string
• You must demonstrate the both encryption and decryption

* N represents the length of n in RSA key-pair.

Part 2

1. Diffie-Hellman key exchange algorithm

• Consider a prime number q
• Consider primitive root (generator) alpha of q such that alpha < q
• Take xPrv and find xMap = alpha ^ xPrv mod q. Similarly find yMap using yPrv.
• Find K1 such that K1 = yMap ^ xPrv mod q for user X. Similarly find K2
• Check for the equality of K1 and K2.

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