anchor.diff:  details.
   
   === YubiKey 2.3 firmware and above
  -[−]*use-numeric-keypad*::
  +[-]*use-numeric-keypad*::
   
   Send scancodes for numeric keypad keypresses when sending digits - helps
   with some keyboard layouts. This option is only valid for the 2.x
   firmware line.
   
  -[−]*fast-trig*::
  +[-]*fast-trig*::
   
   Faster triggering when only configuration 1 is available. This option is
   always in effect on firmware versions 3.0 and above.
   
  -[−]*allow-update*::
  +[-]*allow-update*::
   
   Allow updating (or swapping) of certain parameters in a configuration at
   a later time.
   
  -[−]*dormant*::
  +[-]*dormant*::
   
   Hides/unhides a configuration stored in a YubiKey.
   
   
   === YubiKey 2.4/3.1 firmware and above
  -[−]*led-inv*::
  +[-]*led-inv*::
   
   Inverts the behaviour of the led on the YubiKey.
   
  
positive.code: a qwerty keyboard. This mode sends raw scan codes, so output will differ
  between keyboard layouts.
  
  [−]*strong-pw1*::
  
  Upper-case the two first letters of the output string. This is for
  compatibility with legacy systems that enforce both uppercase and
  lowercase characters in a password and does not add any security.
  
  [−]*strong-pw2*::
  
  Replace the first eight characters of the modhex alphabet with the
  numbers 0 to 7. Like **-ostrong-pw1**, this is intended to support
  legacy systems.
  
  [−]*man-update*::
  
  Enable user-initiated update of the static password. Only makes sense
  with the *-ostatic-ticket* option. This is only valid for firmware 2.x.
  
  === YubiKey 2.1 firmware and above
  [−]*oath-hotp8*::
  
  When set, generate an 8-digit HOTP rather than a 6-digit one.
  
  [−]*oath-fixed-modhex1*::
  
  When set, the first byte of the fixed part is sent as modhex.
  
  [−]*oath-fixed-modhex2*::
  
  When set, the first two bytes of the fixed part is sent as modhex.
  
  [−]*oath-fixed-modhex*::
  
  When set, the fixed part is sent as modhex.
  
  
negative.code: 
  
  === YubiKey 2.2 firmware and above
  [-]*chal-yubico*::
  
  Yubico OTP challenge-response mode.
  
  [-]*chal-hmac*::
  
  Generate HMAC-SHA1 challenge responses.
  
  [-]*hmac-lt64*::
  
  Calculate HMAC on less than 64 bytes input. Whatever is in the last byte
  of the challenge is used as end of input marker (backtracking from end
  of payload).
  
  [-]*chal-btn-trig*::
  
  The YubiKey will wait for the user to press the key (within 15 seconds)
  before answering the challenge.
  
  [-]*serial-btn-visible*::
  
  The YubiKey will emit its serial number if the button is pressed during
  power-up. This option is only valid for the 2.x firmware line.
  
  [-]*serial-usb-visible*::
  
  The YubiKey will indicate its serial number in the USB iSerial field.
  This option is not available in the 3.0 and 3.1 firmwares.
  
  [-]*serial-api-visible*::
  
  The YubiKey will allow its serial number to be read using an API call.
  
  