In mid-November 2020, Certificate Authority (CA) Let’s Encrypt warned before the expiration of that root certificate from Idtrust, with the own free X.509 certificates are crossed. Instead of creating the problem with a new cross-signature from the world, the CA wanted to set the CA in favor of more independence on the own root certificate ISRG Root X1.
For Android devices with operating system versions before 7.1.1 had that means that apps and internal browsers can no longer have access to servers with Certificates of Let’s Encrypt. At least not without manual “dislocations”, because with these versions Let’s Encrypt’s own root certificate not included in the memory of the root certificates. Already from the beginning of the transition to ISRG Root X1 to 11. January 2021 caused error messages in the appelling of many websites – because an alternative “Intermediate Certificate”, which the previous root certificate “DST Root X3” from Idtrust still up to its expiration on 21. September 2021 uses, had been explicitly requested by server operators.
A comprehensive solution for the problem was probably missing. But now Let’s Encrypt’s Idtrust convinced how to continue to act as a Certificate Authority and to provide the new root certificate ISRG Root X1 for three more years with a cross signature. Thus, the compatibility ies fired from January are logged up, enters a current blog entry of Let’s Encrypt.
DST Root X3 long term as an anchor certificate
Already at the basic of LET’s Encrypt almost five years ago, Idtrust came up with the root certificate DST Root X3 as a partner, because this was already established in the tone-wide web browsers as well as under Windows, Mac OS X, iOS and Android. The transverse signature ensured that these systems and browsers also familiar from the beginning LET’s Encrypt, whose own root certificate ISRG Root X1 was largely unknown.
Current browsers and systems know this certificate now, but old Android versions whose certificate memory can not be updated from Google. Let’s Encrypt will therefore continue to provide a certificate chain containing its own ISR root X1 with a cross signature on Identrusts DST Root X3.
Since the terms of DST Root X3 occurs in September 2021, this is an unusual action, so let’s encrypt. As an anchor certificate, it is then not worthless, as specifically, these basic root certificates under Android is not assigned an expiration date – they remain unlimited on this platform. Other operating systems and browsers ignore the cross signature because of the expiration date, but are already satisfied with the current ISRG Root X1 anyway.
But no completely independence
The consortium ISRG (Internet Security Research Group) behind Let’s Encrypt as well as identtrust have obtained the confirmation on the part of the auditors that this procedure continues to comply with the guidelines of the CA / Browser Forum. As a high instance and merger of CAS, browser manufacturers and developer companies, it is monitoring the procurement practice of recognized X.509 certificates.
For Idtrust, this step means continuing part of the responsibility for Let’s Encrypt. And for the free provider, it remains a dependency, from which Let’s Encrypt really wanted to liberate the opinion updated now. The need to continue to serve the still widespread ages Android versions, we ultimately heavier than the desired independence over the own root certificate.
Longer runtime, Longer certificate chain
The change to the new, continued to be exhausted compatible certificate chain as standard is planned to be originally planned on the 11. January 2021 now in Spade January or Fruben February 2021 take place.
The new certificate chain with two Intermediate Certificates (Mitte) remain for old Antdroid versions continues the DST Root X3 from Idtrust as Cross Signature.
For server operators and visitors nothing else and there are no further actions than the full-time certificate renewal with one of the Let”s Encrypt clients. However, the provider points out that the client used must be up-to-date to use the last version of the ACME (Automatic Certificate Management Environment) used to domain validation. Let”s Encrypt offers the official client”s own Certbot written in Python, but also maintain a list of compatible clients in other languages.
For the connection with servers and services with Certificates by Let’s Encrypt, the longest certificate chain with the additional intermediate certificate means more effort at the TLS handshake, as the server presents two certificates. Let’s Encrypt wants to make the handshake more efficient in the future and therefore plans in the coming year ECDSA-based root and intermediate certificates, which fail significantly short than the existing RSA-based certificates.