Changes between Version 5 and Version 6 of Fingerprinting


Ignore:
Timestamp:
Mar 17, 2011 8:32:00 AM (11 years ago)
Author:
robert@roberthogan.net
Comment:

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  • Fingerprinting

    v5 v6  
    169169=== iii. Window object ===
    170170
     171See [https://www.torproject.org/torbutton/en/design/#fingerprinting] for an introduction and links to the sort of information about the user that can be gleaned from the Window and Screen object :
     172
     173  "For illustration, let's perform a back-of-the-envelope calculation on the number of anonymity sets for just the resolution information available in the window and window.screen objects. Browser window resolution information provides something like (1280-640)*(1024-480)=348160 different anonymity sets. Desktop resolution information contributes about another factor of 5 (for about 5 resolutions in typical use). In addition, the dimensions and position of the desktop taskbar are available, which can reveal hints on OS information. This boosts the count by a factor of 5 (for each of the major desktop taskbars - Windows, OSX, KDE and Gnome, and None). Subtracting the browser content window size from the browser outer window size provide yet more information. Firefox toolbar presence gives about a factor of 8 (3 toolbars on/off give 23=8). Interface effects such as titlebar fontsize and window manager settings gives a factor of about 9 (say 3 common font sizes for the titlebar and 3 common sizes for browser GUI element fonts). Multiply this all out, and you have (1280-640)*(1024-480)*5*5*8*9 ~= 229, or a 29 bit identifier based on resolution information alone."
     174
     175
    171176You have two choices here:
    172 - restrict the layout of the actual browser window to three or four
    173 predetermined-sizes, and return those.
    174 - return values that do not reflect the real size of the browser window.
     177 * restrict the layout of the actual browser window to three or four predetermined-sizes, and return those.
     178 * return values that do not reflect the real size of the browser window.
    175179
    176180The properties you need to override are at least: