1

What is the relationship between letsencrypt and DANE TLSA?

Can or should letsencrypt be used together with DANE TLSA?

Is DANE TLSA a full replacement for letsencrypt [and any certificate authority (CA) based]?

When letsencrypt is used together with DANE TLSA, can or should two different SSL certificates be used?

1

What is the relationship between letsencrypt and DANE TLSA?

None in particular, and at least nothing different from any other CA and DANE. Why do you think there would be a specific relationship?

Can or should letsencrypt be used together with DANE TLSA?

You can, but should you, that is a lot of another matter, and you are giving no details on your situation to know what would be best. Note that TLSA records are mostly used by email systems currently, not very much by browsers.

However, by default, certbot uses a new public key at each certificate renewal. This is good hygiene for cryptographic material, however if you use the certificate in some TLSA records it means you will need to change those records, and carefully, considering various caches. The alternative is to instruct certbot or equivalent, to renew the certificate but use the same public key. It won't be wise however to never change the key.

After that, again, your question is the same for any CA, why do you specifically pick Let's Encrypt?

Is DANE TLSA a full replacement for letsencrypt [and any certificate authority (CA) based]?

No, or not fully. Did you read at least some introductory material on DANE?

There are multiple usages:

  • PKIX-TA: you publish the CA certificate for a given service and connection can proceed only if the certificate presented by server is from this given CA.
  • PKIX-EE: you publish the certificate that the client is expected to see from the server, but usual PKIX validation must occur (the certificate needs to have a valid trust path until a root certificate)
  • DANE-TA: the certificate that will be used is chained to the one published here, and no PKIX validation is necessary (that means basically anyone can be its own CA)
  • DANE-EE: the certificate is self signed and published in the DNS, it should be the one seeing when connecting.

On top of the above, you can publish either the certificate or the public key, and when you do the certificate it can be the certificate itself or a fingerprint.

This is all detailed in the Wikipedia entry on DANE, you should have a look at it.

When letsencrypt is used together with DANE TLSA, can or should two different SSL certificates be used?

First, do not say "SSL certificates", as this is doubly wrong:

  1. SSL died 20 years ago because in 1999 TLS was invented and it is its successor. No sane people would today still run SSL versions...
  2. You can use TLS without certificates (TLS works as well with a shared key), and you can use those certificates outside TLS (ex: S/MIME)

So you are dealing with "X.509 certificates" if you want to be precise, but otherwise certificate is enough in this context everyone understand which kind of certificates you are talking about.

Now, why 2 certificates? With Let's Encrypt you can generate as many you want if you like (until you reach their rate limits), and you can have multiple TLSA records.

Hence you can have 2 certificates if you want. Or 1. Or 3. Or 10. "It depends". Your questions at this stage are far too vague/generic. Where do they come from to have this shape?

PS1: you should also look at CAA records if you are serious about handling your certificates. All known public CAs have to use them, and hence you can restrict which CA can deliver certificates for the domains you maintain.

PS2: and of course if you are really serious, if you use TLSA or CAA records, you need to use DNSSEC.

| improve this answer | |
  • No, or not fully. Did you read at least some introductory material on DANE? Yes, but it seemed to me when using DANE-EE (the certificate is self signed and published in the DNS, it should be the one seeing when connecting.), i.e. using own TLS certificate signed by DNSSEC "more end to end" why keep the middle man (CA)? you should also look at CAA records if you are serious about handling your certificates. Got that already. Same as above. With "DNSCRYPT-to-end" signed certificates, I wouldn't know why keep the CA. – adrelanos May 24 at 9:18
  • Why one would keep both certificates (CA and TLSA)? Well, I've seen these screenshots such as this one. Basically saying "The remote server certificate, DNS, TLSA, DNSSEC all good. But all I saw who previously blogged about enabling TLSA for their domain nowadays result to Firefox show Firefox saying: Verified by: Let's Encrypt. At the same time online TLSA verification tools say their TLSA record is still good. Therefore I wondered the status of TLSA. If (Firefox) browser support was removed. – adrelanos May 24 at 9:23
  • Why did I ask specifically about the lets encrypt CA? Because 1) I am already using that CA. 2) there are many lengthy blog posts about lets encrypt CA in combination with TLSA such as this and many lengthy, highly technical lets encrypt forum discussions. – adrelanos May 24 at 9:31
  • Note that TLSA records are mostly used by email systems currently, not very much by browsers. Are you sure? There are TLSA screenshots from 2013 for Firefox, Chrome and Internet Explorer. Even if these where alpha/beta screenshots, I assume that feature should be now 7 years later in stable for sure. Perhaps the TLSA browser message is only shown when a server is only using TLSA and does not have a CA configured? – adrelanos May 24 at 9:37
  • "there are many lengthy blog posts about lets encrypt CA in combination with TLSA" Because Let's Encrypt is not the only one but the most known CA using the ACME protocol that allows for fully automated certificates issuance and renewals. – Patrick Mevzek May 24 at 17:14

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.