Julian Yap
    FRIDAY, 4 JULY 2014

    GNU Privacy Guard (GPG) examples using Golang

    Someone wrote to me today that they found some of my public Github Gists “public_key_decrypt encrypt_gpg_base64.go and encrypt_decrypt_gpg_armor.go - incredibly helpful! Thanks for sharing those. I’m using the latter for storing bitcoin private keys.”

    I originally wrote them as there weren’t any good examples on the web that ran through different scenarios.

    As part of the process I wrote a program called Jaeger which is a JSON encoded GPG encrypted key value store. It is useful for generating and keeping configuration files secure.

    Here is a compilation of my code examples.

    THURSDAY, 3 JULY 2014

    Enhancing security through signed Mac Wallet builds

    Presently the vast majority of cryptocurrency Mac Wallet applications are distributed in an insecure fashion which opens end users up to potential security issues such as malware.

    Trust is essential when using cryptocurrency wallet applications as reducing your operating system’s security settings and allowing yourself to install a software application from an unverified source could have disastrous effects. It is quite feasible that a wallet application you install today may contain “malware that steals Bitcoins”:http://www.darkreading.com/attacks-breaches/more-than-100-flavors-of-malware-are-stealing-bitcoins/d/d-id/1141396.

    One way to combat this in the Mac OS X system is to use “code signing”:https://developer.apple.com/library/mac/documentation/Security/Conceptual/CodeSigningGuide/CodeSigningGuide.pdf.

    From the “Wikipedia”:http://en.wikipedia.org/wiki/Code_signing entry:

    Code signing is the process of digitally signing executables and scripts to confirm the software author and guarantee that the code has not been altered or corrupted since it was signed by use of a cryptographic hash.

    I have started a “Signed Mac Wallet Builds Program”:http://julianyap.com/pages/macwalletbuilds.html which provides coins the service of having their Mac Wallets built and signed by me. Please note that there is nothing preventing coin developers from directly signing up for an Apple Mac developer account, going through the verification process and providing this service themselves.

    I encourage all coins which believe in the longevity and public trust of their coin to provide signed Mac Wallets. You owe it to your users and the community.

    I encourage all cryptocurrency users to demand signed Mac Wallet builds from their coin developers. In order for alt coins to compete on the same level as Bitcoin, they must offer the same if not better level of trustworthiness.

    I have discussed this program with Pinkcoin and Razorcoin who have agreed to be apart of the launch of this program. The “signed Pinkcoin wallet”:http://crypto.pink/wallet/ and the “signed Razorcoin wallets”:http://razorco.in are both available for immediate download.

    Here is a screen shot of the signed Pinkcoin Mac Wallet along with my developer ID verified by Apple:


    Please read my “Signed Mac Wallet Builds Program”:http://julianyap.com/pages/macwalletbuilds.html page which goes into more detail.

    UPDATE, July 9 2014: The “Nautiluscoin”:http://www.nautiluscoin.com Mac Wallet is now signed.

    UPDATE, July 29 2014: The “Sync”:http://www.synclub.net Mac Wallet is now signed.


    Digital Ocean - First impressions

    I signed up for Digital Ocean the other day since I was planning on using it for some online services. I also felt the service had reached a point of growth and maturity where it felt like they were “sticking around”.

    Here are some first impressions.

    You can choose to create a virtual machine (a “droplet”) in 1 of 4 data centers (a “region”). Only the “New York 2” data center supports Private Networking so for example if you create a VM in “San Francisco 1”, the VM will only have a public IP interface. If you are thinking of deploying a permanent system which will use N+1 servers then deploying to the “New York 2” data center is your only option so you don’t need to expose services on a public IP just to talk to another one of your servers. When creating a VM, “New York 2” is the default data center selected.

    Ubuntu 12.04 x32 is the default distribution selected when creating a VM. You should change this to a 64-bit distribution so that you have less hassles in case you want to resize your VM. I had initially installed an Ubuntu 13.04 x64 VM but I had issues starting up the IPTables firewall and noticed that all of the documentation refers to 12.04 which would then be considered their best supported and maintained Ubuntu distribution version.

    You should add a SSH key first in the web console so that you can select this during the install. The installer only installs with a ‘root’ user and emails you the created password. Having your SSH key pre-installed means you can automate additional install process items such creating another user account and disabling remote ‘root’ access. Digital Ocean also has a nice REST API which spits back JSON.

    On the default Ubuntu 12.04 x64 install there was no firewall installed by default. You should definitely install UFW and implement a security policy for SSH access at a bare minimum.

    I ran some quick tests and benchmarks and Digital Ocean lives up to the hype. Performance is fast and consistent.

    The main issue I have with VM online providers is inconsistent performance, be it disk, CPU or network IO. Inconsistent performance means you need to implement less than ideal workarounds such as overprovisioning your servers or performing workarounds like implementing software RAID 10.

    Imagine: The flexibility of virtual machines with the predictability of bare metal.

    Another thing I see myself doing is spinning up a VM just for quick testing. Creating a VM literally takes a minute.

    Digital Ocean looks to have a great differentiator with SSD disks, pricing and overall impressive virtual machine performance. At this early stage I can definitely recommend checking them out.

    Here is a quick ApacheBench test of a Go application serving up a static template.

    # sysctl -w net.netfilter.nf_conntrack_max=131072
    # ab -n 20000 -c 20 http://myserver/new/
    This is ApacheBench, Version 2.3 <$Revision: 655654 $>
    Document Path:          /new/
    Document Length:        4022 bytes
    Concurrency Level:      20
    Time taken for tests:   29.186 seconds
    Complete requests:      20000
    Failed requests:        0
    Write errors:           0
    Total transferred:      82740000 bytes
    HTML transferred:       80440000 bytes
    Requests per second:    685.27 [#/sec] (mean)
    Time per request:       29.186 [ms] (mean)
    Time per request:       1.459 [ms] (mean, across all concurrent requests)
    Transfer rate:          2768.51 [Kbytes/sec] received
    Connection Times (ms)
                  min  mean[+/-sd] median   max
    Connect:        0    0   0.1      0       5
    Processing:     2   29   3.0     29      53
    Waiting:        0   29   3.0     29      53
    Total:          2   29   3.0     29      53
    Percentage of the requests served within a certain time (ms)
      50%     29 
      66%     30 
      75%     31 
      80%     31 
      90%     32 
      95%     33 
      98%     34 
      99%     35 
     100%     53 (longest request)

    Here is a test of downloading a 100MB file from various locations from a VM created at the “San Francisco 1” data center.

    # curl -O http://speedtest.fremont.linode.com/100MB-fremont.bin
      % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                     Dload  Upload   Total   Spent    Left  Speed
    100  100M  100  100M    0     0  44.7M      0  0:00:02  0:00:02 --:--:-- 51.2M
    # curl -O http://speedtest.tokyo.linode.com/100MB-tokyo.bin
      % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                     Dload  Upload   Total   Spent    Left  Speed
    100  100M  100  100M    0     0  12.5M      0  0:00:07  0:00:07 --:--:-- 16.4M
    # curl -O http://speedtest.london.linode.com/100MB-london.bin
      % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                     Dload  Upload   Total   Spent    Left  Speed
    100  100M  100  100M    0     0  8459k      0  0:00:12  0:00:12 --:--:-- 10.0M
    # curl -O http://speedtest.dallas.linode.com/100MB-dallas.bin
      % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                     Dload  Upload   Total   Spent    Left  Speed
    100  100M  100  100M    0     0  21.9M      0  0:00:04  0:00:04 --:--:-- 22.8M


    Using Anonymous Structs to pass data to templates in GoLang

    One thing that is quite common with Python web frameworks like Django, Flask or Bottle is passing multiple objects to a view.

    Something like this in Django is common where a context dictionary with multiple objects is passed back to the template for rendering:

    from django.shortcuts import render
    def my_view(request):
            context = {'poll': p, 'error_message': "You didn't select a choice.",}
            return render(request, 'polls/detail.html', context)

    While reading through some examples in GoLang is seemed strange that all the tutorials and examples only passed a single object back to the template.

    Here is an example:

    package main
    import (
    type Paste struct {
        Expiration string
        Content    []byte
        UUID       string
    func pasteHandler(w http.ResponseWriter, r *http.Request) {
        paste_id := strings.TrimPrefix(r.URL.Path, "/paste")
        paste := &Paste{UUID: paste_id}
        data := paste
        t, _ := template.ParseFiles("templates/paste.html")
        t.Execute(w, data)

    Your template code would then look something like this:

    Expiration: {{ .Expiration }}
    UUID: {{ .UUID }}

    What if we want to pass multiple objects to the template?

    A really clean solution I found was to use an anonymous struct.

    In the following example, we are now modifying the pasteHandler function in the above example to pass extra boolean flags to the template.

    func pasteHandler(w http.ResponseWriter, r *http.Request) {
        paste_id := strings.TrimPrefix(r.URL.Path, "/paste")
        paste := &Paste{UUID: paste_id}
        keep_alive := false
        burn_after_reading := false
        data := struct {
            Paste *Paste
            KeepAlive bool
            BurnAfterReading bool
        } {
        t, _ := template.ParseFiles("templates/paste.html")
        t.Execute(w, data)

    We then need to modify out template code to access the objects like this:

    Expiration: {{ .Paste.Expiration }}
    UUID: {{ .Paste.UUID}}
    {{ if .BurnAfterReading }}
    BurnAfterReading: True
    {{ else }}
    BurnAfterReading: False
    {{ end }}

    TUESDAY, 26 MARCH 2013

    Setting up a Ruby rbenv environment on OS X

    rbenv is the best way to set up a Ruby environment. It’s pretty essential since you can test your stack against different versions of Ruby and gems such as Rails.

    … It’s pretty much like virtualenv for Python.

    I don’t always use Ruby but when I do I use rbenv (said in the Dos Equis man voice).

    Install rbenv and ruby-build via brew

    brew update
    brew install rbenv
    brew install ruby-build

    Add rbenv init to your shell to enable shims and autocompletion.

    echo 'eval "$(rbenv init -)"' >> ~/.bash_profile

    Select the version of Ruby to install. First list all the available versions

    rbenv install -l

    For example, let’s install the latest version in the 1.9.3 branch

    export VERSION=1.9.3-p392

    Build and install Ruby without documentation (saves time)

    CONFIGURE_OPTS="--disable-install-doc" rbenv install $VERSION

    Set the global Ruby version

    rbenv global $VERSION

    Disable ri and rdoc documentation for Gems. Add to ~/.gemrc

    install: --no-rdoc --no-ri
    update: --no-rdoc --no-ri


    cat << EOT > ~/.gemrc
    install: --no-rdoc --no-ri
    update: --no-rdoc --no-ri

    Bonus points. Install Rails

    gem install rails


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