# Noise NK1 pattern identity hiding

In the official documentation for the Noise Framework there is a section with an overview of the identity hiding for each pattern. The numbering of properties there, obviously, from weaker properties to strong ones, and the last property is:

1. An active attacker who pretends to be the initiator and records a single protocol run can then check candidates for the responder's public key.

The NK1 pattern has this property.

NK1 pattern itself
<- s
...
-> e
<- e, ee, es
->


What does this property mean?

• What mean check candidates for the responder's public key?
• How can recording a single run of a protocol help this? (preferably with an example)
• Why is this property the latest in the list (i.e. supposedly the strongest)?

(here is not any tag related to Noise Framework, this is strange)