What is an "Obfuscation key" in SQL Server?
I would guess they mean rows created for symmetric keys.

create symmetric key KeyTest with 
  algorithm = aes_128, 
  identity_value = '123456'
  encryption by password = '123456!Q';

go

-- Needs a DAC connection    
select *
from sys.sysclsobjs
where Name = 'KeyTest'


Result:

class id    name      status  type intprop  created                 modified
----- ----- --------- ------- ---- -------- ----------------------- -----------------------
56    259   KeyTest   0       A1   128      2017-12-22 08:43:33.170 2017-12-22 08:43:33.170