How to Encrypt Your Traffic

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This is the how to guide for making your Apache httpd use encryption to transfer + data between you and your visitors. Instead of http: links, your site will use + https: ones and, if everything is setup correctly, people visiting your site will + have their privacy better protected. +

+ This How-To is intended for people that are not really into SSL/TLS and ciphers + and all this crypto techno-babble (We are joking, it's a serious field with + serious experts and real problems to solve - but it sounds like techno-babble to + anyone not intimate with it). People who have heard that their http: server is + not really secure enough nowadays. That spies and bad guys are listening. That even + legitimate corporations are inserting data into their web pages and selling + profiles of visitors. +

+ This guide wants to help you migrate your httpd server from serving insecure http: links + to encrypted https: ones, without you becoming a SSL expert first. You might get + fascinated by all this crypto things and study it more and become a real expert. But + you also might not, run a reasonably secure web server nevertheless and do other + things good for mankind with your time. +

+ You will get a rough idea what roles these mysterious things called "certificate" and + "private key" play and how they are used to let your visitors be sure they are talking + to your server. You will not be told how this works, just how it + is used: it's basically about passports. +

A short Introduction Certificates, e.g. Internet Passports
Buy a Certificate
Get a Free Certificate

A short Introduction Certificates, e.g. Internet Passports

+ +

+ The TLS protocol (formerly known as SSL) is a way a client and a server + can talk to each other without anyone else listening, or better understanding + a thing. It is what your browser uses when you open a https: link. +

+ In addition to having a private conversation with a server, your browser also needs + to know that it really talks to the server - and not someone else acting like it. That, + next to the encryption, is the other part of the TLS protocol. +

+ In order to do that, your server does not only need the software for TLS, e.g. the + mod_ssl module, but some sort of identity proof + on the Internet. This is commonly referred to as a certificate. Basically, everyone + has the same mod_ssl and can encrypt, but only your have your certificate + and with that, you are you. +

+ A certificate is the digital equivalent of a passport. It contains two things: a stamp + of approval from the people issuing the passport and a reference to your digital + fingerprints, e.g. what is called a private key in encryption terms. +

+ When you configure your Apache httpd for https: links, you need to give it the certificate and + the private key. If you never give the key to anyone else, only you will be able to prove + to visitors that the certificate belongs to you. That way, a browser talking to your + server a second time will be sure that it is indeed the very same server it talked + to before. +

+ But how does it know that it is the real server, the first time it starts talking to + someone? Here, the digital rubber stamping comes into play. The rubber stamp is done + by someone else, using her own private key. That person has also a certificate, e.g. + her own passport. The browser can make sure that this passport is based on the same + key that was used to rubber stamp your server passport. Now, instead of making sure + that your passport is correct, it must make sure that the passport of the person that + says your passport is correct, is correct. +

+ And that passport is also rubber stamped digitally, by someone else with a key and a + certificate. So the browser only needs to make sure that that one is correct + that says it is correct to trust the one that says your server is correct. This trusting + game can go to a few or many levels (usually less than 5). +

+ In the end, the browser will encounter a passport that is stamped by its own key. It's + a Gloria Gaynor certificate that says "I am what I am!". The browser then either trust + this Gloria or not. If not, your server is also not trusted. Otherwise, it is. Simple. +

+ The trust check for the Gloria Gaynors of the Internet is easy: your browser (or your + operating system) comes with list of Gloria passports to trust, pre-installed. If it + sees a Gloria certificate, it is either in this list or not to be trusted. +

+ This whole thing works as long as everyone keeps his private keys to himself. Anyone copying + such a key can impersonate the key owner. And if the owner can rubber stamp passports, the + impersonator can also do that. And all the passports stamped by an impersonator, + all those certificates will look 100% valid, indistinguishable from the "real" ones. +

+ So, this trust model works, but it has its limits. That is why browser makers are so keen + on having the correct Gloria Gaynor lists and threaten to expel anyone from it that + is careless with her keys. +

Buy a Certificate

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+ Well, you can buy one. There are a lot of companies selling Internet Passports as a service. In + this list + from Mozilla you find all companies that the Firefox browser trusts. Pick one, visit their + website and they will tell you what it costs. And how you need to prove that you are who + you claim to be so they can rubber stamp your passport with confidence. +

+ They all have their own methods, also depending on what kind of passport you apply for, and + it's probably some sort of click web interface in a browser. They may send you an email that + you need to answer or do something else. In the end, they will show you how to generate + your own, unique private key and issue you a stamped passport matching it. +

+ You then place the key in one file, the certificate in another. Put these on your server, make + sure that only a trusted user can read the key file and add it to your httpd configuration. + This is extensively covered in the SSL How-To. +

Get a Free Certificate

+ +

+ There are also companies that offer certificates for web servers free of charge. The pioneer + in this is Let's Encrypt which is a service of the + Internet Security Research Group (ISRG), a not-for-profit organization to + "reduce financial, technological, and education barriers to secure communication over the + Internet." +

+ They not offer free certificates, they also developed a interface that can be used by + your Apache httpd to get one. This is where mod_md + comes in. +

+ (zoom out the camera on how to configure mod_md and virtual host...) +

How to Encrypt Your Traffic

See also

A short Introduction Certificates, e.g. Internet Passports

Buy a Certificate

Get a Free Certificate

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