Added Lab2/Lab3 IS

IS/Lab/Lab3/RSA.py

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+from Crypto.PublicKey import RSA
+from Crypto.Cipher import PKCS1_OAEP
+import binascii
+
+def rsa_keygen(bits=2048):
+    key = RSA.generate(bits)
+    return key
+
+def rsa_en(ptext, pub_key):
+    cipher = PKCS1_OAEP.new(pub_key)
+    ctext = cipher.encrypt(ptext.encode('utf-8'))
+    return ctext
+
+def rsa_de(ctext, priv_key):
+    cipher = PKCS1_OAEP.new(priv_key)
+    decrypted = cipher.decrypt(ctext)
+    return decrypted.decode('utf-8')
+
+def main():
+    print("Welcome to RSA")
+    ptext = input("Enter plaintext: ")
+
+    # RSA key pair
+    key = rsa_keygen()
+    pub_key = key.publickey()
+    priv_key = key
+
+    print("\nPublic Key (n, e):")
+    print("n =", hex(pub_key.n))
+    print("e =", pub_key.e)
+
+    ctext = rsa_en(ptext, pub_key)
+    print("\nYour ciphertext (hex):", binascii.hexlify(ctext).decode())
+
+    decrypted = rsa_de(ctext, priv_key)
+    print("Your decrypted plaintext:", decrypted)
+
+if __name__ == '__main__':
+    main()