Shortening the Let’s Encrypt Chain of Belief

When Let’s Encrypt first launched, we wanted to make sure that our certificates have been extensively trusted. To that finish, we organized to have our intermediate certificates cross-signed by IdenTrust’s DST Root CA X3. This meant that every one certificates issued by these intermediates could be trusted, even whereas our personal ISRG Root X1 wasn’t but. Throughout subsequent years, our Root X1 turned widely trusted by itself. 

Come late 2021, our cross-signed intermediates and DST Root CA X3 itself have been expiring. And whereas all up-to-date browsers at the moment trusted our root, over a third of Android devices have been nonetheless operating previous variations of the OS which might all of a sudden cease trusting web sites utilizing our certificates. That breakage would have been too widespread, so we organized for a brand new cross-sign – this time directly onto our root reasonably than our intermediates – which might outlive DST Root CA X3 itself. This stopgap allowed these previous Android units to proceed trusting our certificates for 3 extra years.

On September thirtieth, 2024, that cross-sign too will expire.

Within the final three years, the share of Android units which belief our ISRG Root X1 has risen from 66% to 93.9%. That share will enhance additional over the subsequent 12 months, particularly as Android releases model 14, which has the flexibility to update its trust store without a full OS update. As well as, dropping the cross-sign will scale back the variety of certificates bytes despatched in a TLS handshake by over 40%. Lastly, it’s going to considerably scale back our working prices, permitting us to focus our funding on persevering with to enhance your privateness and safety.

For these causes, we won’t be getting a brand new cross-sign to increase compatibility any additional.

The transition will roll out as follows:

• On Thursday, Feb eighth, 2024, we’ll cease offering the cross-sign by default in requests made to our /acme/certificates API endpoint. For many Subscribers, which means your ACME consumer will configure a sequence which terminates at ISRG Root X1, and your webserver will start offering this shorter chain in all TLS handshakes. The longer chain, terminating on the soon-to-expire cross-sign, will nonetheless be accessible as an alternate chain which you’ll configure your consumer to request.

• On Thursday, June sixth, 2024, we’ll cease offering the longer cross-signed chain solely. That is simply over 90 days (the lifetime of 1 certificates) earlier than the cross-sign expires, and we want to ensure subscribers have had at the very least one full issuance cycle emigrate off of the cross-signed chain.

• On Monday, September thirtieth, 2024, the cross-signed certificates will expire. This needs to be a non-event for most individuals, as any consumer breakages ought to have occurred over the previous six months.

Should you use Android 7.0 or earlier, you could have to take motion to make sure you can nonetheless entry web sites secured by Let’s Encrypt certificates. We advocate putting in and utilizing Firefox Mobile, which makes use of its personal belief retailer as an alternative of the Android OS belief retailer, and subsequently trusts ISRG Root X1.

If you’re a website operator, you must control your web site utilization statistics and lively user-agent strings throughout Q2 and Q3 of 2024. Should you see a sudden drop in visits from Android, it’s probably as a result of you may have a big inhabitants of customers on Android 7.0 or earlier. We encourage you to offer the identical recommendation to them as we supplied above.

If you’re an ACME consumer writer, please make it possible for your consumer accurately downloads and installs the certificates chain supplied by our API throughout each certificates issuance, together with renewals. Failure modes we’ve got seen previously embrace a) by no means downloading the chain in any respect and solely serving the end-entity certificates; b) by no means downloading the chain and as an alternative serving a hard-coded chain; and c) solely downloading the chain at first issuance and never re-downloading throughout renewals. Please be sure that your consumer doesn’t fall into any of those buckets.

We respect your understanding and assist, each now and within the years to come back as we offer secure and safe communication to everybody who makes use of the net. You probably have any questions on this transition or any of the opposite work we do, please ask on our community forum.

We’d wish to thank IdenTrust for his or her years of partnership. They performed an necessary position in serving to Let’s Encrypt get to the place we’re at the moment and their willingness to rearrange a stopgap cross sign up 2021 demonstrated a real dedication to making a safe Net. 

We rely on contributions from our supporters in an effort to present our providers. If your organization or group may also help our work by changing into a sponsor of Let’s Encrypt please e-mail us at sponsor@letsencrypt.org. We ask that you simply make an individual contribution whether it is inside your means.