Add methods encrypt_bulk, decrypt_bulk, and derive_path_key

nkms/crypto/keyring.py

@@ -1,6 +1,8 @@
 import sha3
 from nacl.utils import random
 from nkms.crypto.keypairs import SigningKeypair, EncryptingKeypair
+from nkms.crypto import (default_algorithm, pre_from_algorithm,
+                         symmetric_from_algorithm)
 
 
 class KeyRing(object):
@@ -15,6 +17,8 @@ class KeyRing(object):
         """
         self.sig_keypair = SigningKeypair(sig_privkey)
         self.enc_keypair = EncryptingKeypair(enc_privkey)
+        self.pre = pre_from_algorithm(default_algorithm)
+        self.symm = symmetric_from_algorithm(default_algorithm)
 
     @property
     def sig_pubkey(self):
@@ -96,3 +100,42 @@ class KeyRing(object):
         :return: Secure random generated bytestring of <length> bytes
         """
         return random(length)
+
+    def derive_path_key(self, path, is_pub=True):
+        """
+        Derives a key for the specific path.
+
+        :param bytes path: Path to generate the key for
+        :param bool is_pub: Is the derived key a public key?
+
+        :rtype: bytes
+        :return: Derived key
+        """
+        key = sha3.keccak_256(self.enc_privkey + path).digest()
+        return self.pre.priv2pub(key) if is_pub else key
+
+    def encrypt_bulk(self, data, key):
+        """
+        Encrypt bulk of the data with nacl's SecretBox.
+
+        :param bytes data: Data to encrypt
+        :param bytes key: Symmetric key
+
+        :rtype: bytes
+        :return: Ciphertext of encrypted data
+        """
+        cipher = self.symm(key)
+        return cipher.encrypt(data)
+
+    def decrypt_bulk(self, ciphertext, key):
+        """
+        Decrypts bulk of the data with nacl's SecretBox.
+
+        :param bytes ciphertext: Ciphertext to decrypt
+        :param bytes key: Symmetric key
+
+        :rtype: bytes
+        :return: Plaintext decrypted from ciphertext
+        """
+        cipher = self.symm(key)
+        return cipher.decrypt(ciphertext)