Method and apparatus for managing access to a database

1. A method for managing access to a database, comprising:

receiving a database query;

executing the query on the database to obtain a result;

determining a sensitivity of the received database query, wherein the sensitivity of the received database query comprises a maximum value of a L1 norm of the difference in query result caused by the presence or absence of a single database element;

generating a noise value from a bimodal probability distribution having a minimum probability at zero noise, wherein the bimodal probability distribution is a u-quadratic probability distribution, and wherein generating the noise value comprises scaling the bimodal probability distribution according to the determined sensitivity;

perturbing the result with the generated noise value; and

outputting the perturbed result.

2. The method as claimed in claim 1 , wherein the bimodal probability distribution is bounded.

3. The method as claimed in claim 1 , wherein the bimodal probability distribution has a mean at zero noise.

4. The method as claimed in claim 1 , wherein perturbing the result with the generated noise value comprises adding the noise value to the generated result.

5. The method as claimed in claim 1 , further comprising retrieving a utility parameter, and wherein generating the noise value comprises scaling the bimodal probability distribution according to the retrieved utility parameter.

6. The method as claimed in claim 5 , wherein scaling according to sensitivity and utility parameter comprises equating a vertical scale parameter of the bimodal probability distribution to a combination of the sensitivity and the utility parameter.

7. The method as claimed in claim 6 , wherein the combination of sensitivity and utility parameter comprises the square of a term formed by dividing the utility parameter by the sensitivity.

8. An access management processing element for a database, comprising:

a memory; and

a processor, the processor coupled to the memory and configured to:

receive a database query;

execute the query on the database to obtain a result;

determine a sensitivity of the received database query, wherein the sensitivity of the received database query comprises a maximum value of a L1 norm of the difference in query result caused by the presence or absence of a single database element;

generate a noise value from a bimodal probability distribution having a minimum probability at zero noise, wherein the bimodal probability distribution is a u-quadratic probability distribution, and wherein generating the noise value comprises scaling the bimodal probability distribution according to the determined sensitivity;

perturb the result with the generated noise value; and

output the perturbed result.

9. The access management processing element as claimed in claim 8 , wherein the bimodal probability distribution is bounded.

10. The access management processing element as claimed in claim 8 , wherein the bimodal probability distribution has a mean at zero noise.

11. The access management processing element as claimed in claim 8 , wherein the processor is further configured to perturb the result with the generated noise value by adding the noise value to the generated result.

12. The access management processing element as claimed in claim 8 , wherein the processor is further configured to retrieve a utility parameter, and scale the bimodal probability distribution according to the retrieved utility parameter.

13. The access management processing element as claimed in claim 12 , wherein the processor is further configured to equate a vertical scale parameter of the bimodal probability distribution to a combination of the sensitivity and the utility parameter.

14. The access management processing element as claimed in claim 13 , wherein the combination of sensitivity and utility parameter comprises the square of a term formed by dividing the utility parameter by the sensitivity.