Help - Answered Questions

What is it for?

The purpose of digital signing is to prove, electronically, one's identity. You see this all the time on the Internet - every time you go to a secure page on a web site, for example to enter personal details, or to make a purchase, every day you browse web sites that have been digitally signed by a Certificate Authority that is accepted as having the authority to sign it. This is all invisible to the user, except that you may be aware that you are entering a secure zone (e.g. SSL and HTTPS).

Your browser includes special digital (root) certificates from a number of these 'Certificate Authorities' by default, and all web sites use certificates that are validated by one of these companies, which you as a user implicitly trust every time you go to the secure part of a web site. (You might ask, who validates the security of the Certificate Authorities, and why should you trust them?!.... Good question.)

Digital signing thus provides security on the Internet.

Why digitally sign your own emails?! (weirdo..)

Emails are not secure. In fact emails are VERY not secure!

To get from computer Internet User A to Internet User B an email may pass through tens of anonymous computers on the Internet. These 'Internet infrastructure' computers are all free to inspect and change the contents of your email as they see fit. Governments systematically browse the contents of all emails going in/out/within their country, e.g. the UK Government has done this since the year 2000. (How it prepares us to protect our freedom). Ever requested a password that you lost to be emailed to you? That password was wide open to inspection by potential crackers.

As anyone who has received an email containing a virus from a strange address knows, emails can be easily spoofed. The identity of the sender is very easy to forge via email. Thus a great advantage is that digital signing provides a means of ensuring that an email is really from the person you think it is. If everyone digitally signed their emails, it would be much easier to know whether an email is legitimate and unchanged and to the great relief of many, spamming would be much easier to control, and viruses that forge the sender's address would be obvious and therefore easier to control.

How it prepares us to protect our freedom

But perhaps, fundamentally, the most important reason for digital signing is awareness and privacy. It creates awareness of the (lack of) security of the Internet, and the tools that we can arm ourselves with to ensure our personal security. And in sensitising people to digital signatures, we become aware of the possibility of privacy and encryption.

Most people would object if they found that all their postal letters are being opened, read and possibly recorded by the Government before being passed on to the intended recipient, resealed as if nothing had happened. And yet this is what happens every day with your emails (in the UK). There are some who have objected to this intrusion of privacy, but their voices are small and fall on deaf ears. However the most effective way to combat this intrusion is to seal the envelope shut in a miniature bank vault, i.e. encrypt your email. If all emails were encrypted, it would be very hard for Government, or other organisations/individual crackers, to monitor the general public. They would only realistically have enough resources to monitor those they had reason to suspect. Why? Because encryption can be broken, but it takes a lot of computing power and there wouldn't be enough to monitor the whole population of any given country.

The reason digital signatures prepare us for encryption is that if everyone were setup to be able to generate their own digital signatures, it would be technically very easy to make the next step from digital signatures to encryption. And that would be great for privacy, the fight against spamming, and a safer Internet.

Why isn't it being adopted by everyone?

Of the biggest reasons why most people haven't started doing this, apart from being slightly technical, the reason is financial. You need your own certificate to digitally sign your emails. And the Certificate Authorities charge money to provide you with your own certificate. Need I say more. Dosh = no thanks I'd rather walk home. But organisations are emerging to provide the common fool in the street with a free alternative. However, given the obvious lack of funding and the emphasis on money to get enrolled, these organisations do not yet have the money to get themselves established as trusted Certificate Authorities. Thus it is currently down to trust. The decision of the individual to trust an unknown Certificate Authority. However once you have put your trust in a Certificate Authority you can implicitly trust the digital signatures generated using their certificates. In other words, if you trust (and accept the certificate of) the Certificate Authority that I use, you can automatically trust my digital signature. Trust me!

Why is the digital signature described as 'not valid/not trusted'?

To fully understand, read the section directly above. I am using a free Certificate Authority to provide me with the ability to digitally sign my emails. As a result, this Certificate Authority is not (yet) recognised by your email software as it is a new organisation that is not yet fully established, although it is probably being included in the Mozilla browser. If you choose to, you can go the their site at to install the root certificate. You may be told that the certificate is untrusted - that is normal and I suggest that you continue installation regardless. Be aware that this implies your acceptance that you trust their secure distribution and storing of digital signatures, such as mine. (You already do this all the time). The root certificate will then automatically provide the safe validation of my digital signature, which I have entrusted to them. Or you can simply decide that you've wasted your time reading this and do nothing (humbug!). Shame on you! :-)

But, er, is this really proof of your email identity?

Security is a serious matter. For a digital certificate with full rights to be issued to an individual by a Certificate Authority, stringent tests must be conducted, including meeting the physical person to verify their identity. At the current moment in time, my physical identity has not been verified by, but they have verified my email address. Installing their root certificate (see above) will thus automatically allow you to validate my digital signature. You can then be confident of the authenticity of my email address - only I have the ability to digitally sign my emails using my certificate, so if you get an email that I digitally signed and which is validated by your email software using the root certificate that you installed, you know it's from me. (Visually you get a simple indication that my email is signed and trusted). Technically, they haven't verified that I really am me! But you have the guarantee that emails from my address are sent by the person who physically administers that address, i.e. me! The only way that someone could forge my digital signature would be if they logged on to my home computer (using the password) and ran my email software (using the password) to send you a digitally signed email from my address. Although I have noticed the cats watching me logon...

Cool man! How do I create my own digital signature?!

Easy. Ish. Go to, install their root certificate and then follow their joining instructions. Once you have joined, request a certificate from the menu. You will receive an email with a link to the certificate. Click on the link from your email software, and hopefully it will be seamlessly installed. Next find the security section of the settings in your email software and configure digital signatures using the certificate you just downloaded. Hmm. Call me if you want, I'll guide you through it.

I can't wait to start sending encrypted emails!

There's nothing to it. I mean literally, you can already start sending your emails encrypted. Assuming of course you have your own digital signature certificate (e.g. as per above), and the person you want to send an encrypted email to also has a digital signature certificate, and has recently sent you a digitally signed email with it. If all these conditions hold, you just have to change the settings in your email software to send the email encrypted and hey presto! Your email software (probably Outlook I guess) should suss out the rest.

Notes for the strangely curious

You are putting your trust in people you don't know! One assumes that if a site has an SSL certificate (that's what enables secure communication, for exchanging personal details, credit card numbers, etc. and gives the 'lock' icon in the browser) that they have obtained that certificate from a reliable source (a Certificate Authority), which has the appropriate stringent credentials for issuing something so vital to the security of the Internet, and the security of your communications. You have probably never even asked yourself the question of who decided to trust these Certificate Authorities, because your browser comes with their (root) certificates pre-installed, so any web site that you come across that has an SSL certificate signed by one of them, is automatically accepted (by your browser) as trustworthy.

Thus, having now asked the question, you suppose that it's the people who make the browser software that have carefully decided who is a trustworthy Certificate Authority. Funnily enough, the mainstream browsers have not, historically, had public policies on how they decide whether a Certificate Authority gets added to their browser. All of the Certificate Authorities that have found themselves in the browser software, are big names, probably with big profits (so they must be doing a good job!).

That situation has changed, and Internet Explorer, being the most obvious example, now insists that any Certificate Authorities are 'audited' by an 'independent' organisation, the American Institute for Certified Public Accountant's (AICPA). So now, if you have the money needed (from US$75000 up to US$250000 and beyond) you can get these accountants, who clearly know a lot about money, to approve you as having the required technical infrastructure and business processes to be a Certificate Authority. And they get a nice wad of money for the pleasure. And the Certificate Authorities, having a kind of monopoly as a result, charge a lot for certificates and also get a nice wad of money. And everyone's happy.

But, with all this money, and all this responsibility, they must be taking a lot of care to ensure the Certificate Authorities do their jobs well, and keep doing their jobs well, right? Well right?!

And they are making mistakes

So if you don't pass the audit, you don't get to be a Certificate Authority. And to pass the audit, well, you've got to show that you can do a good job issuing certificates. That they're secure, you only give them to the right people, etc. So what happens when you make a mistake and you erroneously issue a certificate that risks the entire Internet browsing population, like Verisign did? Well, er, nothing actually. They already paid for their audit, and damn it, they're so big now, we couldn't possibly revoke their Certificate Authority status. (There's too much money at stake!)

So, dammit, what's the point of all this then?

The point is, as the current situation holds, you should be wary of anyone making decisions for you (i.e. pre-installed certificates in your browser), and you should be weary of anyone else's certificates that you install. But at the end of the day, it all boils down to trust. If an independent Certificate Authority seems to be reputable to you, and you can find evidence to support this claim, there's no reason why you shouldn't trust it any less than you implicitly trust the people who have already made mistakes.


Ten Risks of PKI: What You're not Being Told about Public Key Infrastructure -

WebTrust for Certification Authorities -

Erroneous Verisign Issued Digital Certificates Pose Spoofing Hazard -

Microsoft Root Certificate Program -

The Regulation of Investigational Powers Act (RIPA) ('Snooping Bill' official gov site, UK) -

U.K. e-mail snooping bill passed (UK) -

Disclaimer : These are the author's opinions, but they should not be considered 'truth' without personal verification. The author may have made mistakes and any mistakes will be willingly rectified by contacting the administrator of, contact details available from the normal domain registration information services (e.g. No recommendation to install a Certificate Authority's root certificate is either intended nor implied.

The page has been reproduced on with explicit permission from the author with the information being copyrighted to the author (name with held by request)

HELP/2 (last edited 2011-05-09 13:27:35 by UlrichSchroeter)