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Note this question is related, except this one is about free SSL certs.

There are providers who are offering totally free entry-level SSL certs (like StartSSL). I was wondering if they are technically the same thing as the paid ones (at least with the entry-level SSL certs like RapidSSL and PositiveSSL)? I do understand that extended/organization SSL is a different category, but if you only need entry-level SSL certs, are the free ones technically the same as the paid entry-level variants?

Moreover, if they are technically the same, why would you want to pay for something that's available free?

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I think 2 of the main differences are the way it is checked that you actually own the domain and the trustworthiness of the SSL provider. Other facts are how many browsers can recognize and trust the root CA. Not 100% sure about this fact tough – Goez Aug 20 '12 at 14:46
A somebody who is going to visit a website, any website that uses a free SSL certificate is a website I won't visit, because lets face it there is no way to verify the certificate is actually theirs. – Ramhound Aug 20 '12 at 15:06
@Ramhound "Free certificate" as in "free beer" (one certificate, gratis), not free as in "free speech"! It's a certificate for a very low price: 0 $. – curiousguy Aug 20 '12 at 15:31
@Ramhound - as curiousguy said free SSL certificates are different than self-signed certificates. A CA still validates your class-1 identity (that is to an individual; you can get emails at or similar) before giving out the certificate, they just don't charge for this automated service. (The idea being you start using them and then pay them for a premium product once you do purchase a product). – dr jimbob Aug 20 '12 at 22:07
Try lets encrypt first !!!!!!!!! – user115563 Jun 25 at 14:34
up vote 35 down vote accepted

At the byte level, X.509 is X.509 and there is no reason why the free SSL certificates would be any better or worse than the non-free -- the price is not written in the certificate. Any certificate provider can fumble the certificate generation, regardless of whether he gets paid for it or not.

The hard part of a certificate is outside of it: it is in the associated procedures, i.e. everything that is in place to manage the certificates: how the key holder is authenticated by the CA, how revocation can be triggered and corresponding information propagated, what kind of legal guarantee is offered by the CA, its insurance levels, its continuity plans...

For the certificate buyer, the big value in a particular CA is where the CA succeeded in placing its root key (browsers, operating systems...). The vendors (Microsoft, Mozilla...) tend to require quite a lot of administrativia and legal stuff from the CA before accepting to include the CA root key in their products, and such things are not free. Therefore, a CA which could get its root key distributed but emits certificates for free has a suspicious business plan. This is why the free-cert dealers also offer paid certificates with some extra characteristics (certs which last longer, certs with wildcard names, extra authentication procedures...): at some point, the CA operators must have an incoming cash flow. But, ultimately, that's the CA problem, not yours. If they are willing to give away certificates for free and Microsoft is OK with including their root key as a "trusted by default key" then there is no problem for you in using such certificates.

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I've been using startssl for free certificate for a for about a year and half now with only very tiny issues

They were:

  • Only class-1 validation are free. That is I can have a certificate that validates my identity, e.g., I control the email address for the administrative contact of the domain that I purchased. However, it cannot validate that I the admin of is am in way affiliated with My Organization, a well-known trusted business. That is someone could purchase get a class-1 SSL as the domain owner of despite having no ties to My Organization.

  • Initial misconfuguration on my end. Be sure to test in multiple browsers; you have to add the intermediary certificate (when I initially set up; had an issue as I believe chrome could find and pull the intermediate CA certificates in the chain); firefox could not and said it was untrusted.

  • I didn't get a reminder email when the certificate expired. I only found out I needed to renew based on the certificate stopped working. (Though possibly I used a little used email address for the signup and they did send out reminders).

  • Having to renew the certificate every year. You have to pay if you want to only set this up less frequently.

  • A certificate is only valid for one domain is quite limiting. Every different subdomain needs its own certificate; they can't use UCC or wildcards. This may get complicated quickly.

  • They have you manage your keys based on an installed client certificate in your browser. This can be an issue if you say change computers or upgrade your OS and didn't keep a backup of installed client certificates. (However, I didn't have an issue just creating a new class-1 validation and generating a new certificate as the old one had expired).

But other than those issues which were mostly a result of mismanagement on my end or not paying for better features (ability to sign object code, ability to use in S/MIME, extended validation, etc) there's no real downside.

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The main technical disadvantage would only be that if a free CA is not widely accepted by browser or operating system makers, then the certificates they generate may also not be trusted. Also, if there are any issues with the CA that cause their root certificate to be invalidated, then you could run in to issues. That said, you could potentially run in to the same issues with any CA and it isn't necessarily really a technical issue directly.

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There are no technical disadvantages of using any free SSL certificates. SSL technology and protocol insures that the handshake between the client and server generates robust and secure session keys to thwart spoofing of data and man in the middle attacks. You need to ensure that your free SSL provider provide real time certificate status using either OCSP or CRL without fail.

If you are able to tell the end users to trust your SSL certificate by any means or medium everything should be fine.

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What about if someone creates a new certificate for free with your domain. Can they still do a man in the middle attack? Lets assume that the free SSL has trusted CA root certificate in all major browsers, it just started so your current one is not revoked. – over_optimistic Dec 21 '14 at 23:51
If an attacker can persuade a CA to issue them a cert for your domain then (assuming the client doesn't have any key pins for your domain) they can mitm your clients. Whether the CA the attacker used charged the attacker money for the misissued cert is irrelevent. Whether the CA you used charged you money for your legitimate cert is also irrelevent. – Peter Green Nov 14 '15 at 15:25

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