anchor.diff:  The HMAC authentication hash is sent in a header and has the format of
   
   ...................................
  -`X-Auth-Scan: 566ab2a7601c7cf18b52d07cddf5bc3ea63b1352649f6c324f62431d0cd80506;date=Tue, 25 Nov 2014 16:31:11 GMT`
  +`X-Auth-Scan: 566ab2a7601c7cf18b52d07cddf5bc3ea63b1352649f6c324f62431d0cd80506; date=Tue, 25 Nov 2014 16:31:11 GMT`
   ...................................
   
   .A Computed Hash
  
positive.code: |     Syntax|`AuthScanGracePeriod`
  |    Default|300 (5 minutes).
  |    Context|Any
  |Cardinality|0..n
  |     Module|authscan
  |    Version|0.12
  |===============================================================================
  
negative.code: |     Syntax|`AuthScanRequestHeader`
  |    Default|X-Auth-Scan
  |    Context|Any
  |Cardinality|0..1
  |     Module|authscan
  |    Version|0.12
  |===============================================================================
  