But, as warned by security researcher Scott Helme, the root certificate that Let’s Encrypt currently uses - the IdentTrust DST Root CA X3 - was set to expire on September 30. Millions of websites alone rely on Let’s Encrypt. Let’s Encrypt, a free-to-use nonprofit, issues certificates that encrypt the connections between your devices and the wider internet, ensuring that nobody can intercept and steal your data in transit. One of the largest providers of HTTPS certificates, Let’s Encrypt, saw its root certificate expire this week - meaning you might need to upgrade your devices to prevent them from breaking.