Automatic Certificate Management Environment (ACME)


ACME 1) is a protocol that a certification authority (CA) and an applicant can use to automate the process of verification and issuance of domain validated certificate

ACME is simple (It has almost been implemented in pure Bourne shell).


ACME challenges 2) are intended to verify your ownership of a domain.

There are mainly three (excluding preauthorization) where you need to set a token.

Challenge Description Secure
tls-http-01 3) Token under /.well-known/acme-challenge and serve it on 80/tcp
tls-dns-01 4) Token to put in a TXT record in the DNS zone
tns-sni-01 Token to embed in the SAN of a certificate you serve to TLS clients who request it through TLS SNI No, due to shared hosting 5)


ACME / Let's encrypt client:

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