Refactored fernet to token

README.md

@@ -325,12 +325,12 @@ In the default installation configuration, the `X25519`, `Ed25519` and
 (via the [PyCA/cryptography](https://github.com/pyca/cryptography) package).
 The hashing functions `SHA-256` and `SHA-512` are provided by the standard
 Python [hashlib](https://docs.python.org/3/library/hashlib.html). The `HKDF`,
-`HMAC`, `Fernet` primitives, and the `PKCS7` padding function are always
+`HMAC`, `Token` primitives, and the `PKCS7` padding function are always
 provided by the following internal implementations:
 
 - [HKDF.py](RNS/Cryptography/HKDF.py)
 - [HMAC.py](RNS/Cryptography/HMAC.py)
-- [Fernet.py](RNS/Cryptography/Fernet.py)
+- [Token.py](RNS/Cryptography/Token.py)
 - [PKCS7.py](RNS/Cryptography/PKCS7.py)
 
 

RNS/Cryptography/Token.py

@@ -27,7 +27,7 @@ from RNS.Cryptography import HMAC
 from RNS.Cryptography import PKCS7
 from RNS.Cryptography.AES import AES_128_CBC
 
-class Fernet():
+class Token():
     """
     This class provides a slightly modified implementation of the Fernet spec
     found at: https://github.com/fernet/spec/blob/master/Spec.md
@@ -37,7 +37,7 @@ class Fernet():
     not relevant to Reticulum. They are therefore stripped from this
     implementation, since they incur overhead and leak initiator metadata.
     """
-    FERNET_OVERHEAD  = 48 # Bytes
+    TOKEN_OVERHEAD  = 48 # Bytes
 
     @staticmethod
     def generate_key():

RNS/Cryptography/__init__.py

@@ -5,7 +5,7 @@ from .Hashes import sha256
 from .Hashes import sha512
 from .HKDF import hkdf
 from .PKCS7 import PKCS7
-from .Fernet import Fernet
+from .Token import Token
 from .Provider import backend
 
 import RNS.Cryptography.Provider as cp

RNS/Destination.py

@@ -26,7 +26,7 @@ import time
 import threading
 import RNS
 
-from RNS.Cryptography import Fernet
+from RNS.Cryptography import Token
 from .vendor import umsgpack as umsgpack
 
 class Callbacks:
@@ -525,8 +525,8 @@ class Destination:
             raise TypeError("A single destination holds keys through an Identity instance")
 
         if self.type == Destination.GROUP:
-            self.prv_bytes = Fernet.generate_key()
+            self.prv_bytes = Token.generate_key()
-            self.prv = Fernet(self.prv_bytes)
+            self.prv = Token(self.prv_bytes)
 
     def get_private_key(self):
         """
@@ -556,7 +556,7 @@ class Destination:
 
         if self.type == Destination.GROUP:
             self.prv_bytes = key
-            self.prv = Fernet(self.prv_bytes)
+            self.prv = Token(self.prv_bytes)
 
     def load_public_key(self, key):
         if self.type != Destination.SINGLE:

RNS/Identity.py

@@ -31,7 +31,7 @@ import threading
 from .vendor import umsgpack as umsgpack
 
 from RNS.Cryptography import X25519PrivateKey, X25519PublicKey, Ed25519PrivateKey, Ed25519PublicKey
-from RNS.Cryptography import Fernet
+from RNS.Cryptography import Token
 
 
 class Identity:
@@ -66,7 +66,7 @@ class Identity:
     """
 
     # Non-configurable constants
-    FERNET_OVERHEAD           = RNS.Cryptography.Fernet.FERNET_OVERHEAD
+    TOKEN_OVERHEAD            = RNS.Cryptography.Token.TOKEN_OVERHEAD
     AES128_BLOCKSIZE          = 16          # In bytes
     HASHLENGTH                = 256         # In bits
     SIGLENGTH                 = KEYSIZE     # In bits
@@ -646,8 +646,8 @@ class Identity:
                 context=self.get_context(),
             )
 
-            fernet = Fernet(derived_key)
+            token = Token(derived_key)
-            ciphertext = fernet.encrypt(plaintext)
+            ciphertext = token.encrypt(plaintext)
             token = ephemeral_pub_bytes+ciphertext
 
             return token
@@ -684,8 +684,8 @@ class Identity:
                                     context=self.get_context(),
                                 )
 
-                                fernet = Fernet(derived_key)
+                                token = Token(derived_key)
-                                plaintext = fernet.decrypt(ciphertext)
+                                plaintext = token.decrypt(ciphertext)
                                 if ratchet_id_receiver:
                                     ratchet_id_receiver.latest_ratchet_id = ratchet_id
                                 
@@ -709,8 +709,8 @@ class Identity:
                             context=self.get_context(),
                         )
 
-                        fernet = Fernet(derived_key)
+                        token = Token(derived_key)
-                        plaintext = fernet.decrypt(ciphertext)
+                        plaintext = token.decrypt(ciphertext)
                         if ratchet_id_receiver:
                             ratchet_id_receiver.latest_ratchet_id = None
 

RNS/Link.py

@@ -21,7 +21,7 @@
 # SOFTWARE.
 
 from RNS.Cryptography import X25519PrivateKey, X25519PublicKey, Ed25519PrivateKey, Ed25519PublicKey
-from RNS.Cryptography import Fernet
+from RNS.Cryptography import Token
 from RNS.Channel import Channel, LinkChannelOutlet
 
 from time import sleep
@@ -61,7 +61,7 @@ class Link:
     ECPUBSIZE         = 32+32
     KEYSIZE           = 32
 
-    MDU = math.floor((RNS.Reticulum.MTU-RNS.Reticulum.IFAC_MIN_SIZE-RNS.Reticulum.HEADER_MINSIZE-RNS.Identity.FERNET_OVERHEAD)/RNS.Identity.AES128_BLOCKSIZE)*RNS.Identity.AES128_BLOCKSIZE - 1
+    MDU = math.floor((RNS.Reticulum.MTU-RNS.Reticulum.IFAC_MIN_SIZE-RNS.Reticulum.HEADER_MINSIZE-RNS.Identity.TOKEN_OVERHEAD)/RNS.Identity.AES128_BLOCKSIZE)*RNS.Identity.AES128_BLOCKSIZE - 1
 
     ESTABLISHMENT_TIMEOUT_PER_HOP = RNS.Reticulum.DEFAULT_PER_HOP_TIMEOUT
     """
@@ -188,7 +188,7 @@ class Link:
             self.prv     = X25519PrivateKey.generate()
             self.sig_prv = Ed25519PrivateKey.generate()
 
-        self.fernet  = None
+        self.token  = None
         
         self.pub = self.prv.public_key()
         self.pub_bytes = self.pub.public_bytes()
@@ -979,14 +979,14 @@ class Link:
 
     def encrypt(self, plaintext):
         try:
-            if not self.fernet:
+            if not self.token:
                 try:
-                    self.fernet = Fernet(self.derived_key)
+                    self.token = Token(self.derived_key)
                 except Exception as e:
-                    RNS.log("Could not instantiate Fernet while performin encryption on link "+str(self)+". The contained exception was: "+str(e), RNS.LOG_ERROR)
+                    RNS.log("Could not instantiate token while performing encryption on link "+str(self)+". The contained exception was: "+str(e), RNS.LOG_ERROR)
                     raise e
 
-            return self.fernet.encrypt(plaintext)
+            return self.token.encrypt(plaintext)
 
         except Exception as e:
             RNS.log("Encryption on link "+str(self)+" failed. The contained exception was: "+str(e), RNS.LOG_ERROR)
@@ -995,10 +995,10 @@ class Link:
 
     def decrypt(self, ciphertext):
         try:
-            if not self.fernet:
+            if not self.token:
-                self.fernet = Fernet(self.derived_key)
+                self.token = Token(self.derived_key)
                 
-            return self.fernet.decrypt(ciphertext)
+            return self.token.decrypt(ciphertext)
 
         except Exception as e:
             RNS.log("Decryption failed on link "+str(self)+". The contained exception was: "+str(e), RNS.LOG_ERROR)

RNS/Packet.py

@@ -95,7 +95,7 @@ class Packet:
     # With an MTU of 500, the maximum of data we can
     # send in a single encrypted packet is given by
     # the below calculation; 383 bytes.
-    ENCRYPTED_MDU  = math.floor((RNS.Reticulum.MDU-RNS.Identity.FERNET_OVERHEAD-RNS.Identity.KEYSIZE//16)/RNS.Identity.AES128_BLOCKSIZE)*RNS.Identity.AES128_BLOCKSIZE - 1
+    ENCRYPTED_MDU  = math.floor((RNS.Reticulum.MDU-RNS.Identity.TOKEN_OVERHEAD-RNS.Identity.KEYSIZE//16)/RNS.Identity.AES128_BLOCKSIZE)*RNS.Identity.AES128_BLOCKSIZE - 1
     """
     The maximum size of the payload data in a single encrypted packet 
     """

docs/source/understanding.rst

@@ -868,13 +868,17 @@ both on general-purpose CPUs and on microcontrollers. The necessary primitives a
 
 * HKDF for key derivation
 
-* Modified Fernet for encrypted tokens
+* Encrypted tokens are based on the Fernet spec
 
-  * AES-128 in CBC mode
+  * Ephemeral keys derived from an ECDH key exchange on Curve25519
 
-  * HMAC for message authentication
+  * AES-128 in CBC mode with PKCS7 padding
 
-  * No Version and Timestamp metadata included
+  * HMAC using SHA256 for message authentication
+
+  * IVs are generated through os.urandom()
+
+  * No Fernet version and timestamp metadata fields
 
 * SHA-256
 
@@ -884,12 +888,12 @@ In the default installation configuration, the ``X25519``, ``Ed25519`` and ``AES
 primitives are provided by `OpenSSL <https://www.openssl.org/>`_ (via the `PyCA/cryptography <https://github.com/pyca/cryptography>`_
 package). The hashing functions ``SHA-256`` and ``SHA-512`` are provided by the standard
 Python `hashlib <https://docs.python.org/3/library/hashlib.html>`_. The ``HKDF``, ``HMAC``,
-``Fernet`` primitives, and the ``PKCS7`` padding function are always provided by the
+``Token`` primitives, and the ``PKCS7`` padding function are always provided by the
 following internal implementations:
 
 - ``RNS/Cryptography/HKDF.py``
 - ``RNS/Cryptography/HMAC.py``
-- ``RNS/Cryptography/Fernet.py``
+- ``RNS/Cryptography/Token.py``
 - ``RNS/Cryptography/PKCS7.py``