One Preferred Embodiment of Disavowal.

The morning started off with a read of the non-precedential CAFC ruling in Data Encryption v. Microsoft & Dell.  The best part was that it’s non-precedential, for as such, it does not add to the murky matter of ‘apparent’ disavowal of claim scope.

One claim at issue recited no limitation on “maintaining” data in encrypted, or in unencryted format, in a buffer.  The CAFC agreed that “it is true that claim 5 makes no mention of how data is maintained in” the buffer.  Even so, by definitional fiat, the “maintaining” element was added to claim 5, then defined so narrowly that the claim was not infringed.  It’s not what you said, it how you didn’t say it.

The claim scope was disavowed by a sentence, taken IMO out of context, from the specification.  There described was “all” data in the buffer being “maintained” in encrypted form.  From that, a disavowal was imposed as to systems where data in the buffer is unencrypted.  Thus, the defendants did not infringe.

One bromide commonly recommended to treat disavowal, or its symptoms, was to add “in the preferred embodiment” to every statement in the specification that containing a limiting term, such as all, or every, or always, or only.  Turns out, that remedy has a limitation similar to sunscreen – if you miss a place, that’s where you get burned.  In the 200 or so words that precede the disavowal sentence in the Data Encryption patent, there is repeated use of “in the preferred embodiment.”  The disavowing sentence was “All data subject to encryption by operation of the present invention is maintained in an encrypted state in the buffer pool.”  Within a dozen or so sentences preceding that, the specification states:

“In accordance with the preferred embodiment of the present invention, data is encrypted in individual blocks corresponding to the smallest buffered block size.

“In the preferred embodiment, as is typical of standard Unix operating system variants, the minimum buffered block size is 256 bytes.

“The actual data value being written is utilized, in the preferred embodiment of the present invention, as…
In accordance with the preferred embodiment of the present invention the unencrypted and encrypted blocks 82 and 88 are one and the same.”


One wonders whether the claim construction inquiry is “informed by” references from the specification, or are express elements instantiated by examples gleaned therefrom.  The implied disclaimer rule works likes the small-print terms on the back of a triplicate carbon form contract, which rear up with ugliness later.