User Tools

Site Tools


sql-derivative-sensitivity-analyser_advanced

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revision Previous revision
Next revision
Previous revision
Next revision Both sides next revision
sql-derivative-sensitivity-analyser_advanced [2018/11/26 10:09]
alisa
sql-derivative-sensitivity-analyser_advanced [2018/11/26 11:44]
alisa
Line 37: Line 37:
 </​code>​ </​code>​
  
-The line ''​u = lp 2.0 latitude longitude;''​ combines latitude and longitude to define Euclidean distance (i.e l<​sub>​2</​sub>​-norm). We may scale the distances, and 0.2 in the line ''​z = scaleNorm 0.2 u''​means that we conceal changes in location up to 1/0.2 = 5 units. Finally, ''​return linf z;''​ shows how the distance between the tables is computed from the distances between their rows, and ''​linf''​ means that we take the maximum row distance (i.e l<​sub>​∞</​sub>​-norm),​ so DP conceals the change even if all sensitive rows change by a unit.+The line ''​u = lp 2.0 latitude longitude;''​ combines latitude and longitude to define Euclidean distance (i.e l<​sub>​2</​sub>​-norm). We may scale the distances, and 0.2 in the line ''​z = scaleNorm 0.2 u;''​ means that we conceal changes in location up to 1 / 0.2 = 5 units. Finally, ''​return linf z;''​ shows how the distance between the tables is computed from the distances between their rows, and ''​linf''​ means that we take the maximum row distance (i.e l<​sub>​∞</​sub>​-norm),​ so DP conceals the change even if all sensitive rows change by a unit.
  
 === Combined sensitivity === === Combined sensitivity ===
  
-TODOexplain shortly what combined sensitivity ​is and how to use it+In the previous section, we considered differential privacy w.r.t. change in some particular cells of the data tables. The number of rows was considered immutable. To achieve a more traditional differential privacy, which considers addition or deletion of a row as a unit change, we need to define a cost of such operation, expressed by the line ''​G1.0 ;''​. It is possible to combine these two distances. 
 + 
 +<​code>​ 
 +rows: all ; 
 +cols: latitude longitude ; 
 +G: 1.0 ; 
 +</​code>​ 
 + 
 +Intuitively,​ this means that both types of changes are allowed. In this example, differential privacy conceals the facts that a row has been added or removed, as well as that the latitude or longitude have been changed by a unit. More precisely, we define the distance between two tables as a //table edit distance// (analogous to string edit distance) that uses the following operations:​ 
 +  * the cost of row insertion/​deletion (defined by the line ''​G:''​). 
 +  * the cost of cell modification (defined by the line ''​cols:'' ​and the possible extension). 
 + 
 +Table edit distance is defined as the minimal cost of operations required ​to transform one table into the other.
sql-derivative-sensitivity-analyser_advanced.txt · Last modified: 2019/12/13 16:54 by alisa