In
a
previous post I have talked a little about where I prefer to buy SSL
certificates. Comodo Group have this site called
www.instantssl.com that is
- Cheap.
- Fast.
- Good service.
I renewed my company's certificate for our mail server yesterday. This is a
trivial task and I could not see any challenges with this task.
Oh I was wrong. Our Windows Mobile cell phones did not handle this so well.
How does certificates work?
A
certificate is a proof of something. All certificates needs to be issued by
a known authority. Common well-known certificates are:
- Drivers license.
- Passport.
- Your identity card.
But how do you validate certificates you do not know? In the computer world
we have something called a root certificate store. This store is a list
of all issuers that we trust. Unfortunately, this list is maintained separately
by each application or vendor. Here are some examples of different applications:
- Opera web browser
- Nokia cell phones
- Sony Ericsson cell phones
- FireFox browser
- Internet Explorer
- Windows CE (with variations; Windows Mobile and SmartPhone). CE does not
share root certificate store with Windows. And it can be hard to add new
root certificates.
A root certificate is the same as the
certificate authority or issuing certificate.
The root certificate store in Microsoft Windows is updated by Windows Update
and contains lots of issuers. Some applications, many from Microsoft, are using
Microsoft Cryptography Services and benefit from the same root store.
Why the certificate issuer is important
The issuer of the certificate is important, because you need that issuer
supported on your target device. On most devices you can add a new root
certificate yourself, but if you have 100 devices from 10 vendors this task is
time-consuming. And many SmartPhones are restricted from doing so. I came across
some HTC phones the other day shipped from Dangaard. If I want to add my own
root certificate they have to sign a
deployment file. And they will charge me about €500 for the job. Easy money?
:)
You should check your target applications for compatibility before
you purchase a certificate!
Comodo and InstantSSL
Comodo does not have their own root certificate. Or at least - they are not
using it. But they have access to many root certificates via their own
intermediate issuing certificates. In the past Comodo have issued certificates
from GTE CyberTrust Global Root, but recently they have changed to
AddTrust External CA Root. They claim to have 99.3% browser compatibility.
AddTrust is not support out of the box on Windows CE, and we have lots cell
phones based on this operating system...
I called their technical support and asked what to do. They told me to create
a support ticket on the web and make a new CSR. I did so and within a few hours
they gave me a new certificate with GTE CyberTrust Global Root as the issuing
certificate. This is the first time I used their support but it worked out well
in the end!
References
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