Integrates encryption/decryption within the Cryptographer. Close #63

Includes unittests. Also reformats test_inspector to avoid using cli functions

common/cryptographer.py

@@ -3,30 +3,68 @@ from binascii import unhexlify, hexlify
 from cryptography.exceptions import InvalidTag
 from cryptography.hazmat.primitives.ciphers.aead import ChaCha20Poly1305
 
+from common.tools import check_sha256_hex_format
+
 from pisa.logger import Logger
 
 logger = Logger("Cryptographer")
 
 
 class Cryptographer:
+    @staticmethod
+    def check_data_key_format(data, key):
+        if len(data) % 2:
+            error = "Incorrect (Odd-length) value."
+            logger.error(error, data=data)
+            raise ValueError(error)
+
+        if not check_sha256_hex_format(key):
+            error = "Key must be a 32-byte hex value (64 hex chars)."
+            logger.error(error, key=key)
+            raise ValueError(error)
+
+        return True
+
+    @staticmethod
+    def encrypt(blob, key, rtype="hex"):
+        if rtype not in ["hex", "bytes"]:
+            raise ValueError("Wrong return type. Return type must be 'hex' or 'bytes'")
+
+        Cryptographer.check_data_key_format(blob.data, key)
+
+        # Transaction to be encrypted
+        # FIXME: The blob data should contain more things that just the transaction. Leaving like this for now.
+        tx = unhexlify(blob.data)
+
+        # sk is the H(txid) (32-byte) and nonce is set to 0 (12-byte)
+        sk = sha256(unhexlify(key)).digest()
+        nonce = bytearray(12)
+
+        logger.info("Encrypting blob.", sk=hexlify(sk).decode(), nonce=hexlify(nonce).decode(), blob=blob.data)
+
+        # Encrypt the data
+        cipher = ChaCha20Poly1305(sk)
+        encrypted_blob = cipher.encrypt(nonce=nonce, data=tx, associated_data=None)
+
+        if rtype == "hex":
+            encrypted_blob = hexlify(encrypted_blob).decode("utf8")
+
+        return encrypted_blob
+
     @staticmethod
     # ToDo: #20-test-tx-decrypting-edge-cases
     def decrypt(encrypted_blob, key, rtype="hex"):
         if rtype not in ["hex", "bytes"]:
             raise ValueError("Wrong return type. Return type must be 'hex' or 'bytes'")
 
-        if len(encrypted_blob.data) % 2:
-            logger.info(
-                "Incorrect (Odd-length) value to be decrypted.", encrypted_blob=encrypted_blob.data, dispute_txid=key
-            )
-            return None
+        Cryptographer.check_data_key_format(encrypted_blob.data, key)
 
         # sk is the H(txid) (32-byte) and nonce is set to 0 (12-byte)
         sk = sha256(unhexlify(key)).digest()
         nonce = bytearray(12)
 
         logger.info(
-            "Creating new blob.",
+            "Decrypting Blob.",
             sk=hexlify(sk).decode(),
             nonce=hexlify(nonce).decode(),
             encrypted_blob=encrypted_blob.data,