The RobotDyn Joystick shield has the XBee TX / RX lines switched to D0 and D1 or completely disconnected

RobotDyn offers a well-manufactured Joystick and XBee shield for the Arduino Uno which I am currently using for some IEEE 802.15.4-related experiments.

However, as it is not mentioned in any official documentation, I want to document here that the XBee TX / RX lines are connected to the Arduino D1 and D0 lines respectively and can only be disconnected via the “USB sketch update / Wireless” hardware switch at the top left:

The D0 and D1 lines are of course also connected to the Arduino’s main serial interface and connection to the host computer. This is why the switch has to be on “USB sketch update” when you program the board.

Unfortunately, this also means that it won’t be possible to send debug output from the Arduino to the host machine’s serial monitor when the XBee is active, i.e. the switch is in “wireless” mode. This is especially problematic when writing and debugging new programmes that use the XBee radio module.

With the SparkFun XBee Shield, one can switch the mounted XBee to use either pins 0 and 1, or pins 2 and 3 (see the section named “UART/SoftwareSerial Switch”), neatly solving this problem. It would have been great if the RobotDyn unit had done something similar, but keeping cost under control probably played a role.

Driving the Dell U2713HM at 2650×1440 from the HDMI output of the HyperDrive USB-c dock with macOS SwitchResX

In a post from 2014, I showed how to drive the sub-standard HDMI input of the Dell U2713HM 27″ UltraSharp at a resolution of 2560×1440 from the HDMI 1.3 output of a Linux-running laptop.

Fast forward 3 years, and I found myself having to drive the exact same monitor at its native resolution via its (sub-standard) HDMI input from a 2017 MacBook Pro through the brilliant HyperDrive USB-C dock.

(Apple, USB-C is nice, but you really pushed it too far this time.)

Fortunately, using a shareware tool called SwitchResX and information from one of the comments on my previous post, this is possible.

Although one can import Linux ModeLine timings into SwitchResX, the previous timings refused to work. It looks like this is due to macOS refusing to apply monitor timings which exceed the EDID-reported maximum pixel clock of 170 MHz.

Fortunately, SwitchResX is able to generate new timings for reduced blanking (this is crucial to be able to drive this monitor at its full resolution in spite of its HDMI port technically not supporting this) given the resolution and the refresh rate.

Setting the refresh rate to 42 yields a pixel clock of 162 MHz. This screenshot shows you how:

43Hz was probably also possible, but 42 is the answer to life the universe and everything, so there’s that.

To be able to setup these custom timings, you have to disable System Integrity Protection temporarily by booting into the recovery partition.

Extracting the Jaxx 12-word wallet backup phrase.


Because this matter is still ongoing (Jaxx does not seem to want to fix this vulnerability), I have moved the updates here to the front. The original post is below.

2017-08-08 18:42 UTC

I have added the exact filesystem locations / paths to the relevant Jaxx local storage file to the demonstration section.

2017-06-20 07:51 UTC

Since the first publication of this post, Jaxx has publically stated several times that storing our wallets unsecurely is not a problem.

If that is indeed the case, why do all other reputable desktop wallets perform this encryption in the correct manner, thus safeguarding our wallets, and only Jaxx does not?

  • Desktop wallets that DO CORRECTLY ENCRYPT your wallet: Exodus, MyEtherWallet, geth, parity, electrum.
  • Desktop wallets that DO NOT CORRECTLY ENCRYPT your wallet: Jaxx.

(Jaxx “encrypts” the wallet seed, but with a hard-coded and easily extracted key, which means this is not encryption but rather obfuscation, which is not much better than no encryption.)

2017-06-13 10:14 UTC

Reader Imed reports in the comments below that the 4-digit user PIN is stored as an unsalted sha256 hash, which can easily be reversed using rainbow tables, for example via sites like CrackStation.

I have just confirmed with a test Jaxx installation that I am able to extract a configured PIN from the local storage database without Jaxx running of course.

2017-06-11 10:08 UTC

Daira Hopwood correctly points out in the comments that encrypting using the PIN would be too easily brute-forced. I have updated the post in two places to indicate that instead Jaxx does in fact need to implement support for a strong password. One can discuss whether to do this differently for the desktop (no sandboxing) than for mobile devices (usually good sandboxing).

2017-06-10 20:19 UTC

Based on this response by the Jaxx CTO on reddit, they are not planning to fix this vulnerability. If that is the case, I strongly recommend that you avoid the Jaxx wallet.


I was curious how easy it would be to extract the 12-word wallet backup phrase from a Jaxx cryptocurrency wallet desktop app / chrome extension install.

After an hour or two of analysis, I can conclude that this is unfortunately far too easy.

Jaxx Chrome extension Eth UI. Throw-away address, don’t use.

Even when your Jaxx has a security PIN configured, anyone with 20 seconds of (network) access to your PC can extract your 12 word backup phrase and copy it down. Jaxx does not have to be running for this to happen.

With the 12 word backup phrase, they can later restore your wallet, including all of your private keys, on their own computers, and then proceed to transfer away all of your cryptocurrency.

The main problem is that the Jaxx software encrypts the mnemonic using a hard-coded encryption key, instead of making use of a strong user-supplied password. (As Daira Hopwood points out in the comments, using the PIN would not be sufficient.)

This means we can easily read and decrypt the full recovery phrase from local storage using sqlite3 and some straight-forward code.

I successfully tested this vulnerability on the Jaxx Chrome extension v1.2.17 and the Jaxx Linux desktop app 1.2.13.


To test this proof of concept, you will need node.js installed. Ensure that your Jaxx is PIN protected, just for fun. It won’t help.

On Linux or Mac, open the Jaxx local storage file using the sqlite3 tool, or if you prefer GUIs you can use sqlitebrowser. You can find this file at the following locations depending on your operating system, and whether you’re using the desktop app or the chrome extension:

  • Linux desktop: $HOME/.config/Jaxx/Local\ Storage/file__0.localstorage
  • Linux chrome extension: $HOME/.config/google-chrome/Default/Local Storage/chrome-extension_ancbofgphhmhcchnaognahmjfajaecmo_0.localstorage
  • macOS desktop: /Users/[username]/Library/Application Support/Jaxx/Local Storage/file__0.localstorage, thanks to Manuel in the comments;
  • Windows desktop: C:\Users\<Your Computer's User Name>\AppData\Roaming\Jaxx\Local Storage
  • Windows chrome extension: C:\Users\<Your Computer's User Name>\Local\Google\Chrome\User Data\Default\Local Storage\chrome-extension_ancbofgphhmhcchnaognahmjfajaecmo_0.localstorage

At the sqlite3 prompt, do the following:

sqlite> select value from ItemTable where key="mnemonic";

(If you opted for sqlitebrowser, just copy out the value of the mnemonic key.)

Note the returned value down. This is Jaxx’s encrypted mnemonic which we shall decrypt into your 12 word backup phrase.

(If the returned string is too short in your case, try sqlitebrowser instead. In my case, sqlite3 works perfectly for the desktop Jaxx, but not the Chrome Jaxx, where I use either the chrome Dev Tools or sqlitebrowser to extract the string.)

Install crypto-js version 3.1.2 by doing either npm install crypto-js@3.1.2 or yarn add crypto-js@3.1.2, and then run the following code using node, after substituting the mnemonicEncrypted variable value with the one you extracted using sqlite3:

// Jaxx recovery phrase extraction by 2017

// you need v3.1.2 (same as latest jaxx) else you'll get invalid UTF-8 error
var CryptoJS = require('crypto-js');
var _key = "6Le0DgMTAAAAANokdfEial"; //length=22
var _iv  = "mHGFxENnZLbienLyALoi.e"; //length=22

var mnemonicEncrypted="ofvoUNhkw+zBN+nvxd1GoL/u1Stn1hyXChD9JvCVkNZgpp19mWY595fbiFjjRPNbw5xxNtzAJGUchr3mImHCsLqSx7aQxcCbo+VrqxBJ5+4=";

var _keyB;
var _ivB;

// js/vault/vault.js
function decryptSimple(encryptedTxt) {
    // not sure why jaxx does  this inside the function
    _keyB = CryptoJS.enc.Base64.parse(_key);
    _ivB = CryptoJS.enc.Base64.parse(_iv);    
    var decrypted = CryptoJS.AES.decrypt(encryptedTxt, _keyB, { iv: _ivB });
    var decryptedText = decrypted.toString(CryptoJS.enc.Utf8);
    return decryptedText;


This should print out your 12 word backup phrase, in the case of this dummy setup I’m seeing “snake purity emerge blue subway lab loyal timber depth leg federal work” which is indeed correct.

How can we fix this?

The thing is, Jaxx is unfortunately one of the better cross-platform multi-currency wallets. Although it has a great UI, I personally don’t like Exodus, because they don’t let me manage more than one Ethereum address.

To mitigate the Jaxx security issue discussed here, keep the Jaxx desktop app’s local storage directory on an encrypted filesystem which you only mount when you’re using Jaxx, and unmount directly afterwards. This is what I’m currently doing using encfs.

If you prefer using the Chrome extension, you can try symlinking just the extension’s local storage file as it lives in Chrome’s global Local Storage directory.

Importantly, keep on encouraging Jaxx support to add support for using a strong user-supplied password as part of the encryption key (just like Exodus) with which they encrypt your mnemonic (recovery phrase) and all other sensitive values in local storage. Refer them to this post for more details. (See Daira Hopwood’s comment, using the PIN for encryption is not sufficient.)


If this helped you, and you like sending ethereum around, feel free to send some to address 0xA3448C2e3F22F58759fd5dD14BE76269034d440E also known as the following QR code:


Adding page sidebar to WordPress Twenty Seventeen theme.

The WordPress Twenty Seventeen theme was exactly what I needed to update the look and feel of the Visible Orbit project website, except for one thing: No sidebar on pages, only posts. For  the Visible Orbit website, having the site information and navigation visible on the page-heavy site is quite important:

Getting the sidebar to show on pages seems to be a popular question online. Besides just hacking the source, the only nicely packaged solution is this plugin by Joachim Jensen. However, for that to render correctly, you have to set page layout to “one column”, but that setting is exposed only if your front page is static, which is not the case for the Visible Orbit site.

Enter Twenty Seventeen VisOrb, a super simple child theme I made for the project which is able to fix this issue even for sites with “latest posts” as the front page, the WordPress default. Simply unpack the whole twentyseventeen-visorb directory in your wp-content/themes folder, and select the theme from the Appearance – Themes menu.


Setting up FastCGI apps on WebFaction

For the high-resolution orbital slice viewer on the Visible Orbit website, I had to setup wlziipsrv, a fork of the iipsrv large tiled image server. This is a FastCGI app, which means that, unlike a normal CGI which is started up for each request, one runs a number of these processes in daemon mode, and the front-end webserver communicates with them using the fastcgi protocol.

The end-result is this web-based high-resolution image viewer, which you can use to explore several thousands of microsocopic slices of human eyes. This is slice 41 of the S2897L registered set:


To make a long story short, there was no documentation on how to do this on a WebFaction shared host, a problem this post will try to remedy.

The main idea of the solution is to compile and run the lighttpd web server as a custom app, and then to map the fastcgi URL to that app. You can then configure lighttpd to run your fastcgi app. In the following sections, I show you how to do this.

Configure custom app

Using the webfaction panel, create a custom app as shown in the following screenshot.


Note down the port number that webfaction has allocated for this app. We will setup lighttpd to listen at this port for local access by the frontend webfaction webserver.

Using the website configuration screen of the webfaction panel, associate your new custom app to the fastcgi URL that will be requested. In my case, I have configured the front-end code to invoke the wlziipsrv fastcgi by going to /cgi-bin/wlziipsrv.fcgi. The configuration looks like this:


Here you are telling webfaction that if any client requests /cgi-bin/wlziipsrv.fcgi, it should connect them with whatever’s running behind the specially allocated custom app port. Next we will make sure that lighttpd will answer those requests.

Configure lighttpd

After building lighttpd with:

cd lighttpd_source_dir
./configure --prefix=$HOME/opt
make install

I created a config file such as the following one in the new custom app directory. Most important is that server.port matches the port number webfaction assigned. I also gave the file a name which will probably not be used by other lighttpd users on the system, namely visorb-lighttpd.conf.

server.document-root = "/home/myusername/webapps/wp_visorb_2017/"

server.port = 22430

server.modules += ( "mod_fastcgi" )

var.mypath = "/home/myusername/webapps/visorb_iipsrv/"

# uncomment this and start with -D to debug requests as they
# come in
#debug.log-request-handling = "enable"

mimetype.assign = (
  ".html" => "text/html", 
  ".txt" => "text/plain",
  ".jpg" => "image/jpeg",
  ".png" => "image/png" 

# webfaction frontend strips away the path; we end up here with only /
# however, we KNOW it must be /cgi-bin/wlziipsrv.fcgi
fastcgi.server = ( "/" =>
  (( "socket" => var.mypath + "wlziipsrv-fastcgi.socket",
     "check-local" => "disable",
     "min-procs" => 1,
     "max-procs" => 1,
     "bin-path" => "/home/myusername/build/WlzIIPSrv/src/wlziipsrv.fcgi",
     "bin-environment" => (
        "LOGFILE" => var.mypath + "iipsrv.log",
        "VERBOSITY" => "5",
        "MAX_IMAGE_CACHE_SIZE" => "10",
        "FILENAME_PATTERN" => "_pyr_",
        "JPEG_QUALITY" => "50",
        "MAX_CVT" => "3000"

Test lighttpd by doing:

~/opt/bin/lighttpd -t -f visorb-lighttpd.conf
~/opt/bin/lighttpd -D -f visorb-lighttpd.conf

This last command will keep lighttpd running in the foreground just so you can see any log messages. Press Ctrl-C to exit.

Setup cron to keep lighttpd running

Next we need to ensure that lighttpd is kept running. On webfaction, it seems that the only way to do this, is with a cronjob.

I made the following bash script that we will configure cron to invoke every 10 minutes. The script will start lighttpd if it is not already running.


VO_RUNNING=$(ps ax | grep visorb-lighttpd | grep -v grep)

if [ -z "$VO_RUNNING" ];
then $HOME/opt/sbin/lighttpd -f $HOME/webapps/visorb_iipsrv/visorb-lighttpd.conf;

I installed the script using crontab -e, adding the following line:

*/10 * * * * /home/myusername/webapps/visorb_iipsrv/


Using this method, you can reroute any fastcgi request to a custom app handled by lighttpd, and then have lighttpd manage the fastcgi processes.

For now this does exactly what I want. However, I can easily map multiple URLs to the same lighttpd using the webfaction panel. Ideally, I would then have the single lighttpd reroute to different fastcgi apps.

However, it seems that webfaction strips away the URL path information before passing the request on to lighttpd (this is what I saw in debug mode), which is why I currently have to map / to the wlziipsrv.fcgi in the lighttpd configuration. Fortunately, lighttpd is super light-weight (currently 1.4MB RSS), and having a separate lighttpd process per type of fastcgi application is more robust in any case.