HTTP Public Key Pinning (HPKP) is a security mechanism which allows HTTPS websites to resist impersonation by attackers using mis-issued or otherwise fraudulent certificates. (For example, sometimes attackers can compromise certificate authorities, and then can mis-issue certificates for a web origin.).
The HTTPS web server serves a list of public key hashes, and on subsequent connections clients expect that server to use one or more of those public keys in its certificate chain. Deploying HPKP safely will require operational and organizational maturity due to the risk that hosts may make themselves unavailable by pinning to a set of public key hashes that becomes invalid. With care, host operators can greatly reduce the risk of man-in-the-middle (MITM) attacks and other false authentication problems for their users without incurring undue risk.
Before implement HPKP please read this https://www.chromestatus.com/feature/5903385005916160.
|pin-sha256=”<sha256>”||The quoted string is the Base64 encoded Subject Public Key Information (SPKI) fingerprint. It is possible to specify multiple pins for different public keys. Some browsers might allow other hashing algorithms than SHA-256 in the future.|
|max-age=SECONDS||The time, in seconds, that the browser should remember that this site is only to be accessed using one of the pinned keys.|
|includeSubDomains||If this optional parameter is specified, this rule applies to all of the site’s subdomains as well.|
|report-uri=”<URL>”||If this optional parameter is specified, pin validation failures are reported to the given URL.|
Public-Key-Pins: pin-sha256="d6qzRu9zOECb90Uez27xWltNsj0e1Md7GkYYkVoZWmM="; pin-sha256="E9CZ9INDbd+2eRQozYqqbQ2yXLVKB9+xcprMF+44U1g="; report-uri="http://example.com/pkp-report"; max-age=10000; includeSubDomains
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