Challenge Types - Lets Encrypt When you get a certificate from Let’s Encrypt, our servers validate that you control the domain names in that certificate using “challenges,” as defined by the ACME standard
Challenge–response authentication - Wikipedia In computer security, challenge–response authentication is a family of protocols in which one party presents a question ("challenge") and another party must provide a valid answer ("response") to be authenticated
Challenge-Response Protocol - Glossary | CSRC The verifier can independently verify the response generated by the claimant (e g , by recomputing the hash of the challenge and the shared secret and comparing it to the response or performing a public-key operation on the response) and establish that the claimant possesses and controls the secret
HTTP Domain Validation (http-01) - Certify The Web Docs When the Certificate Authority performs domain validation over http (known as an http-01 challenge) they ask for a randomly named text file to be presented in the well-known acme-challenge path of your website
(Advanced) Custom Challenge Validation - Posh-ACME Normally the challenge specific details are buried a bit deeper in a challenges property, but Posh-ACME tries to help by surfacing the commonly used challenge details on the root object