From 6c265f902cc9ad407e20adf7e948fa9d3c6645d4 Mon Sep 17 00:00:00 2001
From: brunombpereira <brunoborlido@gmail.com>
Date: Tue, 16 May 2023 18:31:08 +0100
Subject: [PATCH] [LABI] tema01: added encrypt_decrypt_RSA.py

---
 .../labi/tema01/src/encrypt_decrypt_RSA.py    | 97 +++++++++++++++++++
 1 file changed, 97 insertions(+)
 create mode 100644 1ano/2semestre/labi/tema01/src/encrypt_decrypt_RSA.py

diff --git a/1ano/2semestre/labi/tema01/src/encrypt_decrypt_RSA.py b/1ano/2semestre/labi/tema01/src/encrypt_decrypt_RSA.py
new file mode 100644
index 0000000..a788416
--- /dev/null
+++ b/1ano/2semestre/labi/tema01/src/encrypt_decrypt_RSA.py
@@ -0,0 +1,97 @@
+import os
+import sys
+import hashlib
+from Crypto.Cipher import AES, PKCS1_OAEP
+from Crypto.PublicKey import RSA
+
+BLOCK_SIZE = 16
+
+
+def generate_key(key):
+    if len(key) < BLOCK_SIZE:
+        # Gerar uma síntese de chave com SHA-256
+        key = hashlib.sha256(key.encode('utf-8')).digest()
+    else:
+        # Usar apenas os primeiros 256 octetos
+        key = key[:BLOCK_SIZE].encode('utf-8')
+    return key
+
+
+def pad_data(data):
+    pad_len = BLOCK_SIZE - (len(data) % BLOCK_SIZE)
+    padding = bytes([pad_len] * pad_len)
+    return data + padding
+
+
+def unpad_data(data):
+    pad_len = data[-1]
+    return data[:-pad_len]
+
+
+def encrypt_file(file_path, key, output_path):
+    with open(file_path, 'rb') as file:
+        data = file.read()
+
+    # Gerar chave simétrica aleatória
+    symmetric_key = os.urandom(BLOCK_SIZE)
+
+    # Cifrar dados do arquivo
+    cipher = AES.new(symmetric_key, AES.MODE_EAX)
+    ciphertext, tag = cipher.encrypt_and_digest(pad_data(data))
+
+    # Cifrar chave simétrica com chave pública RSA
+    with open(key, 'rb') as key_file:
+        recipient_key = RSA.import_key(key_file.read())
+    cipher_rsa = PKCS1_OAEP.new(recipient_key)
+    encrypted_symmetric_key = cipher_rsa.encrypt(symmetric_key)
+
+    # Concatenar nonce, tag, chave cifrada e dados cifrados em um único arquivo
+    with open(output_path, 'wb') as output_file:
+        output_file.write(cipher.nonce)
+        output_file.write(tag)
+        output_file.write(encrypted_symmetric_key)
+        output_file.write(ciphertext)
+
+
+def decrypt_file(file_path, key, output_path):
+    with open(file_path, 'rb') as file:
+        data = file.read()
+
+    # Separar nonce, tag, chave cifrada e dados cifrados
+    nonce = data[:16]
+    tag = data[16:32]
+    encrypted_symmetric_key = data[32:288]
+    ciphertext = data[288:]
+
+    # Decifrar chave simétrica com chave privada RSA
+    with open(key, 'rb') as key_file:
+        private_key = RSA.import_key(key_file.read(), passphrase=input("Enter passphrase for private key: "))
+    cipher_rsa = PKCS1_OAEP.new(private_key)
+    symmetric_key = cipher_rsa.decrypt(encrypted_symmetric_key)
+
+    # Descriptografar arquivo
+    cipher = AES.new(symmetric_key, AES.MODE_EAX, nonce=nonce)
+    plaintext = cipher.decrypt_and_verify(ciphertext, tag)
+
+    # Remover padding
+    plaintext = unpad_data(plaintext)
+
+    # Escrever arquivo decifrado
+    with open(output_path, 'wb') as output_file:
+        output_file.write(plaintext)
+
+
+if __name__ == '__main__':
+    if len(sys.argv) != 5:
+        print('Usage: python3 encrypt_decrypt_file.py encrypt|decrypt file key output_file', file=sys.stderr)
+        sys.exit(1)
+
+    action = sys.argv[1]
+    file_path = sys.argv[2]
+    key = sys.argv[3]
+    output_path = sys.argv[4]
+
+    if action == 'encrypt':
+        encrypt_file(file_path, key, output_path)
+    elif action == 'decrypt':
+        decrypt_file(file_path, key, output_path)