The objective of Let’s Encrypt and the ACME protocol is to make it possible to set up an HTTPS server and have it automatically obtain a browser-trusted certificate, without any human intervention.
First, the agent proves to the CA that the web server controls a domain.
Then, the agent can request, renew, and revoke certificates for that domain.
The first time the agent software interacts with Let’s Encrypt, it generates a new key pair and proves to the Let’s Encrypt CA that the server controls one or more domains.
The Let’s Encrypt CA will look at the domain name being requested and issue one or more sets of challenges
different ways that the agent can prove control of the domain
Once the agent has an authorized key pair, requesting, renewing, and revoking certificates is simple—just send certificate management messages and sign them with the authorized key pair.
A
certificate is considered a duplicate of an earlier certificate if they contain
the exact same set of hostnames, ignoring capitalization and ordering of
hostnames.
We also have a Duplicate Certificate limit of 5 certificates per week.
a
Renewal Exemption to the Certificates per Registered Domain limit.
The Duplicate Certificate limit and the Renewal Exemption ignore the public key
and extensions requested
You can issue 20 certificates in
week 1, 20 more certificates in week 2, and so on, while not interfering with
renewals of existing certificates.
Revoking certificates does not reset rate limits
If you’ve hit a rate limit, we don’t have a way to temporarily reset it.
get a list of certificates
issued for your registered domain by searching on crt.sh
Revoking certificates does not reset rate limits
If you have a large number of pending authorization objects and are getting a
rate limiting error, you can trigger a validation attempt for those
authorization objects by submitting a JWS-signed POST to one of its challenges, as
described in the
ACME spec.
If you do not
have logs containing the relevant authorization URLs, you need to wait for the
rate limit to expire.
having a large number of pending authorizations is generally the
result of a buggy client