Obfuscating document stylometry

• US 20070288458A1
• Filed: 06/13/2006
• Published: 12/13/2007
• Est. Priority Date: 06/13/2006
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Gamon, Michael, Kacmarcik, Gary J.
• Granted Patent: US 7,627,562 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 40/253 Grammatical analysis; Style critique

Abstract

A new system has been invented that can obfuscate the stylometry of a document. This may be used to anonymize a document and make it resistant to forensic stylometry analysis, or to mimic the style of an existing set of documents, for example. A system may compare indicators of distinctive stylometry in a document with corresponding indicators of distinctive stylometry in a stylometric reference, and provide one or more alterations to the document that alter the indicators of distinctive stylometry compared to the stylometric reference, according to one illustrative embodiment.

Claims

1. A method, implementable at least in part by a computing device, comprising:

comparing indicators of distinctive stylometry in a document with corresponding indicators of stylometry in a stylometric reference; and

providing one or more alterations to the document that alter the indicators of distinctive stylometry compared to the stylometric reference.

2. The method of claim 1, wherein altering the indicators of distinctive stylometry comprises reducing the distinctiveness of the indicators compared to the stylometric reference to increase anonymity of the document.

3. The method of claim 1, wherein altering the indicators of distinctive stylometry comprises mimicking stylometric indicators in the stylometric reference.

4. The method of claim 3, wherein the stylometric reference is an anonymized corpus.

5. The method of claim 3, wherein the stylometric reference is a sample of writing by a target author or a set of references corresponding to a set of target authors.

6. The method of claim 1, wherein the alterations are provided automatically.

7. The method of claim 1, wherein the alterations are provided as options selectable by a user.

8. The method of claim 7, further comprising:

providing an updated gauge of total stylometric distinctiveness of the document after each of the alterations;

wherein the options selectable by the user at each of the indicators further comprise an option to finish altering the indicators of distinctive stylometry in the document.

9. The method of claim 1, further comprising:

ranking one or more of the indicators of distinctive stylometry;

wherein the alterations to the document are provided in order from an indicator having the highest ranked stylometric distinctiveness, and progressing through indicators having the successively next highest ranked stylometric distinctiveness.

10. The method of claim 9, wherein the alterations are provided automatically, and the alterations are automatically finished once a gauge of total stylometric distinctiveness of the document reaches a pre-selected threshold.

11. The method of claim 9, wherein the alterations are provided as options selectable by a user, the method further comprising:

providing an updated gauge of total stylometric distinctiveness of the document after each of the alterations;

wherein the options selectable by the user at each of the indicators further comprise an option to finish altering the indicators of distinctive stylometry in the document.

12. The method of claim 1, wherein comparing the indicators of distinctive stylometry comprises measuring values of selected features in the document, and comparing the values of the selected features with values of the selected features in a stylometric reference.

13. The method of claim 12, wherein comparing the values of the selected features with the values of the selected features in the stylometric reference comprises:

determining whether each of one or more of the selected features is above or below a threshold value determined from the stylometric reference; and

determining by what percentage each of the selected features is above or below the threshold value determined from the stylometric reference.

14. The method of claim 12, wherein the selected features comprise words.

15. The method of claim 12, wherein the selected features comprise at least one measurable linguistic feature selected from a group consisting of tokens, function words, function word distances, letter metrics, feature length metrics, part-of-speech trigrams, parse tree segments, logical forms, lexical N-gram features, morphological inflections, honorific suffixes, minority dialect features, minority spellings, spelling errors, and grammar errors.

16. The method of claim 12, wherein measuring values of selected features comprises measuring a frequency of vocabulary originating from a lingua franca register compared with a frequency of vocabulary originating from a vernacular register.

17. The method of claim 1, further comprising:

ranking the indicators of distinctive stylometry in an order of distinctiveness;

removing the indicators of distinctive stylometry that have been subject to the alterations from the document, along with the corresponding indicators of stylometry from the stylometric reference, in order of the ranking, from highest distinctiveness to lower distinctiveness; and

measuring a rate at which a total stylometric distinctiveness between the document and the stylometric reference changes, as the indicators are removed.

18. A method, implementable at least in part by a computing device, comprising:

measuring a value of one or more linguistic features in a target corpus;

measuring a value of one or more linguistic features in an input document;

comparing the value of the linguistic features in the target corpus with the value of the linguistic features in the input document; and

replacing one or more of the linguistic features in the input document with one or more of the linguistic features in the target corpus.

19. The method of claim 18, further comprising:

ranking the linguistic features in order of greater to lesser difference in the value between the target corpus and the input document;

replacing one or more of the linguistic features in the input document with one or more of the linguistic features in the target corpus, following the ranked order, beginning with the linguistic features ranked with greater difference in the value; and

gauging a total remaining stylometric distinctiveness between the input document and the target corpus after each replacing of one of the linguistic features in the input document with one of the linguistic features in the target corpus.

20. A medium, readable by a computing device and comprising executable instructions that are executable by the computing device, wherein the executable instructions enable a computing device to:

evaluate linguistic features in a document compared with a reference corpus;

determine one or more of the linguistic features in the document that are stylometrically distinctive relative to the reference corpus; and

modify one or more of the linguistic features in the document to make them less stylometrically distinctive relative to the reference corpus.