Geekspeak I don't understand

Peter Sommer peter at
Wed May 13 07:25:53 BST 2015

 From the Mozilla wiki:

Public Key Pinning is a mechanism for sites to specify which certificate 
authorities have issued valid certs for that site, and for user-agents 
to reject TLS connections to those sites if the certificate is not 
issued by a known-good CA. Public key pinning prevents man-in-the-middle 
attacks due to rogue CAs not on the site's list (see the Diginotar 
attack which Chrome detected and we did not:

The feature binds a set of hashes public keys to a domain name such that 
when connecting to a site using TLS the browser ensures that there is an 
intersection between the public keys in the computed trust chain and the 
set of fingerprints associated with that domain. This check is done 
during the certificate verification phase of the connection, before any 
data is sent or processed by the browser. In particular we are pinning 
the sha256 digest of the der encoded subject public key info. In order 
to reduce rejections, Firefox computes all potential trust chains before 
deciding that are no valid pins.

But it's interesting that this affects Facebook....

Peter Sommer

On 12/05/2015 21:02, Roland Perry wrote:
> Can anyone tell me what this really means, and what might have gone 
> wrong, or what's amiss in 'my setup'?
> "An error occurred during a connection to The server 
> uses key pinning (HPKP) but no trusted certificate chain could be 
> constructed that matches the pinset. Key pinning violations cannot be 
> overridden. (Error code: mozilla_pkix_error_key_pinning_failure)
>     The page you are trying to view cannot be shown because the
>     authenticity of the received data could not be verified.
>     Please contact the website owners to inform them of this problem."

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