Create RSA.py

Project finally resurrected after 10 years. #2015-2025

Author: Compulytics

RSA.py

@@ -0,0 +1,97 @@
+from random import randint, randrange
+import base64
+
+def is_prime(n, k=10):
+    def check(a, s, d, n):
+        x = pow(a, d, n)
+        if x == 1 or x == n - 1:
+            return True
+        for _ in range(s - 1):
+            x = pow(x, 2, n)
+            if x == n - 1:
+                return True
+        return False
+
+    if n < 2:
+        return False
+    if n in (2, 3):
+        return True
+    if n % 2 == 0:
+        return False
+
+    s = 0
+    d = n - 1
+    while d % 2 == 0:
+        d >>= 1
+        s += 1
+
+    for _ in range(k):
+        a = randrange(2, n - 1)
+        if not check(a, s, d, n):
+            return False
+    return True
+
+def keygen():
+    key_p = randint(2**1023, 2**1024)
+    while not is_prime(key_p):
+        key_p = randint(2**1023, 2**1024)
+
+    key_q = randint(2**1023, 2**1024)
+    while not is_prime(key_q):
+        key_q = randint(2**1023, 2**1024)
+
+    key_n = key_p * key_q
+    phi_n = (key_p - 1) * (key_q - 1)
+
+    key_e = randint(2, phi_n - 1)
+    while not is_prime(key_e):
+        key_e = randint(2, phi_n - 1)
+
+    old_r, r = key_e, phi_n
+    old_s, s = 1, 0
+
+    while r != 0:
+        quotient = old_r // r
+        old_r, r = r, old_r - quotient * r
+        old_s, s = s, old_s - quotient * s
+
+    key_d = old_s % phi_n
+
+    return key_n, key_e, key_d
+
+def encrypt(msg: str, key_n: int, key_e: int) -> str:
+    msg_bytes = msg.encode('utf-8')
+    msg_int = int.from_bytes(msg_bytes, 'big')
+    if msg_int >= key_n:
+        raise ValueError("Message too large for the key size.")
+    cipher_int = pow(msg_int, key_e, key_n)
+    cipher_bytes = cipher_int.to_bytes((cipher_int.bit_length() + 7) // 8, 'big')
+    return base64.b64encode(cipher_bytes).decode('utf-8')
+
+def decrypt(cipher_b64: str, key_n: int, key_d: int) -> str:
+    cipher_bytes = base64.b64decode(cipher_b64.encode('utf-8'))
+    cipher_int = int.from_bytes(cipher_bytes, 'big')
+    msg_int = pow(cipher_int, key_d, key_n)
+    msg_bytes = msg_int.to_bytes((msg_int.bit_length() + 7) // 8, 'big')
+    return msg_bytes.decode('utf-8')
+
+def main():
+    print("Generating RSA keypair...")
+    key_n, key_e, key_d = keygen()
+    print("Key generation successful!")
+    
+    print(f"Key D: {key_d}")
+    print(f"Key N: {key_n}")
+    print(f"Key E: {key_e}")
+    
+    message = "Whatup?"
+    print(f"Original Message: {message}")
+
+    cipher_b64 = encrypt(message, key_n, key_e)
+    print(f"Encrypted (base64): {cipher_b64}")
+
+    plaintext = decrypt(cipher_b64, key_n, key_d)
+    print(f"Decrypted Message: {plaintext}")
+
+if __name__ == "__main__":
+    main()