Create homomorphic_encryption.py

src/security/homomorphic_encryption.py

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+import numpy as np
+
+class Paillier:
+    def __init__(self, p, q):
+        self.p = p
+        self.q = q
+        self.n = p * q
+        self.n_squared = self.n ** 2
+        self.g = self.n + 1
+        self.lambda_ = (p - 1) * (q - 1)
+
+    def encrypt(self, plaintext):
+        r = np.random.randint(1, self.n)
+        ciphertext = (pow(self.g, plaintext, self.n_squared) * pow(r, self.n, self.n_squared)) % self.n_squared
+        return ciphertext
+
+    def decrypt(self, ciphertext):
+        u = pow(ciphertext, self.lambda_, self.n_squared)
+        plaintext = (u - 1) // self.n % self.n
+        return plaintext
+
+    def add_encrypted(self, c1, c2):
+        return (c1 * c2) % self.n_squared
+
+# Example usage
+if __name__ == "__main__":
+    p = 11
+    q = 13
+    paillier = Paillier(p, q)
+
+    plaintext1 = 5
+    plaintext2 = 7
+
+    encrypted1 = paillier.encrypt(plaintext1)
+    encrypted2 = paillier.encrypt(plaintext2)
+
+    encrypted_sum = paillier.add_encrypted(encrypted1, encrypted2)
+    decrypted_sum = paillier.decrypt(encrypted_sum)
+
+    print(f"Encrypted 1: {encrypted1}")
+    print(f"Encrypted 2: {encrypted2}")
+    print(f"Decrypted Sum: {decrypted_sum}")