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Author: Jivan052

Day15.py

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+import random
+
+def is_prime(n):
+    if n <= 1:
+        return False
+    elif n <= 3:
+        return True
+    elif n % 2 == 0 or n % 3 == 0:
+        return False
+    i = 5
+    while i * i <= n:
+        if n % i == 0 or n % (i + 2) == 0:
+            return False
+        i += 6
+    return True
+
+def generate_prime(bits):
+    while True:
+        num = random.getrandbits(bits)
+        if is_prime(num):
+            return num
+
+def gcd(a, b):
+    while b != 0:
+        a, b = b, a % b
+    return a
+
+def multiplicative_inverse(e, phi):
+    d = 0
+    x1, x2 = 0, 1
+    y1, y2 = 1, 0
+    temp_phi = phi
+
+    while e > 0:
+        temp1 = temp_phi // e
+        temp2 = temp_phi - temp1 * e
+        temp_phi = e
+        e = temp2
+
+        x = x2 - temp1 * x1
+        y = y2 - temp1 * y1
+
+        x2 = x1
+        x1 = x
+        y2 = y1
+        y1 = y
+
+    if temp_phi == 1:
+        d = y2 + phi
+
+    return d % phi
+
+def generate_keypair(bits):
+    p = generate_prime(bits)
+    q = generate_prime(bits)
+    n = p * q
+    phi = (p - 1) * (q - 1)
+    
+    while True:
+        e = random.randrange(2, phi)
+        if gcd(e, phi) == 1:
+            break
+    
+    d = multiplicative_inverse(e, phi)
+    return ((e, n), (d, n))
+
+def encrypt(public_key, plaintext):
+    e, n = public_key
+    encrypted_msg = [pow(ord(char), e, n) for char in plaintext]
+    return encrypted_msg
+
+def decrypt(private_key, ciphertext):
+    d, n = private_key
+    decrypted_msg = [chr(pow(char, d, n)) for char in ciphertext]
+    return ''.join(decrypted_msg)
+
+#input
+public_key, private_key = generate_keypair(16)
+message = "Hello, RSA!"
+print("Original message:", message)
+encrypted_message = encrypt(public_key, message)
+print("Encrypted message:", encrypted_message)
+decrypted_message = decrypt(private_key, encrypted_message)
+print("Decrypted message:", decrypted_message)
+