Secure private database querying system with content hiding bloom filters

1. method performed by a server for secure private database querying by a client on a database for a query having a formula evaluation on at least two keywords A and B, comprising:

receiving a Bloom filter tree comprised of encrypted Bloom filters of encrypted keywords from the database, wherein each Bloom filter in the Bloom filter tree is separately masked by a random mask pad P;

receiving an encrypted version of the at least two keywords A and B from the client;

evaluating bit positions of the keywords A and B in the Bloom filter to obtain masked Bloom filter indices for the keywords A and B;

participating in Secure Function Evaluation (SFE) with the client, wherein the Secure Function Evaluation employs at least one garbled circuit representing the formula, wherein the server has an input comprising the masked Bloom filter indices for the at least two keywords A and B and wherein the client has an input comprising the random mask pad P and wherein the Secure Function Evaluation performed by the server with the client comprises the following steps:

removing the random mask pad P from the masked Bloom filter indices input by the server;

determining when there is a matching Bloom filter for each of the at least two keywords A and B;

applying the formula evaluation to determine when the formula is satisfied; and

generating a result, wherein the result does not reveal whether each term of the formula is matched by the Bloom filter tree.

2. The method of claim 1 , wherein each of the Bloom filters in the Bloom filter tree is separately masked by a random mask pad P based on a node index of the Bloom filter.

3. The method of claim 1 , wherein the step of removing the random mask pad P from the masked Bloom filter indices input by the server further employs an XOR function.

4. The method of claim 1 , wherein the step of removing the random mask pad P from the masked Bloom filter indices input by the server further comprises applying an XOR function to the masked indices for the at least two keywords A and B and separate indices for the at least two keywords A and B.

5. A tangible machine-readable recordable storage medium for secure private database querying by a client on a database for a query having a formula evaluation on the at least two keywords A and B, wherein one or more software programs when executed by one or more processing devices implement the steps of the method of claim 1 .

6. A method performed by a client for secure private database querying with a server on a database for a query having a formula evaluation on at least two keywords A and B, comprising:

providing an encrypted version of the at least two keywords A and B to the server, wherein the server represents the database as a Bloom filter tree comprised of encrypted Bloom filters of encrypted keywords from the database, wherein each Bloom filter in the Bloom filter tree is separately masked by a random mask pad P;

participating in Secure Function Evaluation (SFE) with the server, wherein the Secure Function Evaluation employs at least one garbled circuit representing the formula, wherein the server evaluates bit positions of the at least two keywords A and B in the Bloom filter to obtain an input comprising masked Bloom filter indices for the at least two keywords A and B from the Bloom filter tree and wherein the client has an input comprising the random mask pad P and wherein the Secure Function Evaluation performed by the client with the server comprises the following steps:

removing the random mask pad P from the masked Bloom filter indices input by the server;

determining when there is a matching Bloom filter for each of the at least two keywords A and B;

applying the formula evaluation to determine when the formula is satisfied; and

generating a result, wherein the result does not reveal whether each term of the formula is matched by the Bloom filter tree.

7. The method of claim 6 , wherein each of the Bloom filters in the Bloom filter tree is separately masked by a random mask pad P based on a node index of the Bloom filter.

8. The method of claim 6 , wherein the step of removing the random mask pad P from the masked Bloom filter indices input by the server further employs an XOR function.

9. The method of claim 6 , wherein the step of removing the random mask pad P from the masked Bloom filter indices input by the server further comprises applying an XOR function to the masked indices for the at least two keywords A and B and separate indices for the at least two keywords A and B.

10. A tangible machine-readable recordable storage medium for secure private database querying with a server on a database for a query having a formula evaluation on the at least two keywords A and B, wherein one or more software programs when executed by one or more processing devices implement the steps of the method of claim 6 .

11. A server system for secure private database querying by a client on a database for a query having a formula evaluation on at least two keywords A and B, comprising:

a memory; and

at least one hardware device, coupled to the memory, operative to:

receive a Bloom filter tree comprised of encrypted Bloom filters of encrypted keywords from the database, wherein each Bloom filter in the Bloom filter tree is separately masked by a random mask pad P;

receive an encrypted version of the at least two keywords A and B from the client;

evaluate bit positions of the keywords A and B in the Bloom filter to obtain masked Bloom filter indices for the at least two keywords A and B;

participate in Secure Function Evaluation (SFE) with the client, wherein the Secure Function Evaluation employs at least one garbled circuit representing the formula, wherein the server has an input comprising the masked Bloom filter indices for the at least two keywords A and B and wherein the client has an input comprising the random mask pad P and wherein the Secure Function Evaluation performed by the server with the client comprises the following steps:

removing the random mask pad P from the masked Bloom filter indices input by the server;

determining when there is a matching Bloom filter for each of the at least two keywords A and B;

applying the formula evaluation to determine when the formula is satisfied; and

generating a result, wherein the result does not reveal whether each term of the formula is matched by the Bloom filter tree.

12. The server system of claim 11 , wherein each of the Bloom filters in the Bloom filter tree is separately masked by a random mask pad P based on a node index of the Bloom filter.

13. The server system of claim 11 , wherein the random mask pad P is removed from the masked Bloom filter indices input by the server using an XOR function.

14. The server system of claim 11 , wherein the random mask pad P is removed from the masked Bloom filter indices input by applying an XOR function to the masked indices for the at least two keywords A and B and separate indices for the at least two keywords A and B.

15. A client system for secure private database querying by a client on a database for a query having a formula evaluation on at least two keywords A and B, comprising:

a memory; and

at least one hardware device, coupled to the memory, operative to:

provide an encrypted version of the at least two keywords A and B to the server, wherein the server represents the database as a Bloom filter tree comprised of encrypted Bloom filters of encrypted keywords from the database, wherein each Bloom filter in the Bloom filter tree is separately masked by a random mask pad P;

participate in Secure Function Evaluation (SFE) with the server, wherein the Secure Function Evaluation employs at least one garbled circuit representing the formula, wherein the server evaluates bit positions of the at least two keywords A and B in the Bloom filter to obtain an input comprising masked Bloom filter indices for the at least two keywords A and B from the Bloom filter tree and wherein the client has an input comprising the random mask pad P and wherein the Secure Function Evaluation performed by the client with the server comprises the following steps:

removing the random mask pad P from the masked Bloom filter indices input by the server;

determining when there is a matching Bloom filter for each of the at least two keywords A and B;

applying the formula evaluation to determine when the formula is satisfied; and

generating a result, wherein the result does not reveal whether each term of the formula is matched by the Bloom filter tree.

16. The client system of claim 15 , wherein each of the Bloom filters in the Bloom filter tree is separately masked by a random mask pad P based on a node index of the Bloom filter.

17. The client system of claim 15 , wherein the random mask pad P is removed from the masked Bloom filter indices input by the server using an XOR function.

18. The client system of claim 15 , wherein the random mask pad P is removed from the masked Bloom filter indices input by applying an XOR function to the masked indices for the at least two keywords A and B and separate indices for the at least two keywords A and B.