Add Python 3+ support

Dockerfile

@@ -2,7 +2,10 @@ FROM node
 
 # Install pip
 RUN apt-get update && apt-get install -y \
-    python-pip
+    python python-dev && \
+    curl https://bootstrap.pypa.io/pip/2.7/get-pip.py -o get-pip.py && \
+    python get-pip.py && \
+    rm get-pip.py
 
 
 # Create app dir

README.md

@@ -67,9 +67,9 @@ in the project root
 Before you can run the application, make sure that you have the following software installed:
 
 - Node.js (at least version 8, as the `async` `await` syntax is used)
-- Python 2.7 with the following `pip` packages installed:
+- Python 2.7 or Python 3+ with the following `pip` packages installed:
   - `websocket-client` and `git+https://github.com/dpallot/simple-websocket-server.git` for acting as WebSocket server and client.
-  - `curve25519-donna` and `pycrypto` for the encryption stuff.
+  - `curve25519-donna` and `pycryptodome` for the encryption stuff.
   - `pyqrcode` for QR code generation.
   - `protobuf` for reading and writing the binary conversation format.
 - Note: On Windows `curve25519-donna` requires [Microsoft Visual C++ 9.0](http://aka.ms/vcpython27) and you need to copy [`stdint.h`](windows) into `C:\Users\YOUR USERNAME\AppData\Local\Programs\Common\Microsoft\Visual C++ for Python\9.0\VC\include`.

backend/utilities.py

@@ -1,54 +1,57 @@
-from __future__ import print_function;
+from __future__ import print_function
+import sys
+import time
 
-import sys;
-import time;
 
+def eprint(*args, **kwargs):  # from https://stackoverflow.com/a/14981125
+    print(*args, file=sys.stderr, **kwargs)
 
 
-def eprint(*args, **kwargs):							# from https://stackoverflow.com/a/14981125
-	print(*args, file=sys.stderr, **kwargs);
-
 def getTimestamp():
-	return int(time.time());
+    return int(time.time())
+
 
 def getTimestampMs():
-	return int(round(time.time() * 1000));
+    return int(round(time.time() * 1000))
 
 
+def mergeDicts(x, y):  # from https://stackoverflow.com/a/26853961
+    if x is None and y is None:
+        return
+    z = (y if x is None else x).copy()
+    if x is not None and y is not None:
+        z.update(y)
+    return z
 
-def mergeDicts(x, y):									# from https://stackoverflow.com/a/26853961
-	if x is None and y is None:
-		return;
-	z = (y if x is None else x).copy();
-	if x is not None and y is not None:
-		z.update(y);
-	return z;
 
 def getAttr(obj, key, alt=None):
-	return obj[key] if isinstance(obj, dict) and key in obj else alt;
+    return obj[key] if isinstance(obj, dict) and key in obj else alt
+
 
 def filterNone(obj):
-	if isinstance(obj, dict):
-		return dict((k, filterNone(v)) for k, v in obj.iteritems() if v is not None);
-	elif isinstance(obj, list):
-		return [filterNone(entry) for entry in obj];
-	else:
-		return obj;
+    if isinstance(obj, dict):
+        return dict((k, filterNone(v)) for k, v in obj.iteritems() if v is not None)
+    elif isinstance(obj, list):
+        return [filterNone(entry) for entry in obj]
+    else:
+        return obj
+
 
 def getNumValidKeys(obj):
-	return len(filter(lambda x: obj[x] is not None, list(obj.keys())));
+    return len(filter(lambda x: obj[x] is not None, list(obj.keys())))
+
 
 def encodeUTF8(s):
-	if not isinstance(s, str):
-		s = strng.encode("utf-8");
-	return s;
+    if not isinstance(s, str):
+        s = s.encode("utf-8")
+    return s
 
 
+def ceil(n):  # from https://stackoverflow.com/a/32559239
+    res = int(n)
+    return res if res == n or n < 0 else res + 1
 
-def ceil(n):											# from https://stackoverflow.com/a/32559239
-	res = int(n);
-	return res if res == n or n < 0 else res+1;
 
 def floor(n):
-	res = int(n);
-	return res if res == 0 or n >= 0 else res-1;
+    res = int(n)
+    return res if res == 0 or n >= 0 else res - 1