Probabilistic set membership using partial prefix matching

1. A method for locating user credentials in databases, the method being performed by one or more computing devices with each computing device comprising at least one processor, the method comprising:

enabling a user to generate remotely a truncated length first cryptographic hash of a user credential of the user, the user credential comprising a user name or a password, or both, associated with the user;

receiving a portion of the first cryptographic hash from the user;

comparing the portion of the first cryptographic hash with each of a plurality of cryptographic hashes of user credentials stored at a database;

determining whether a match exists between the portion of the first cryptographic hash and at least one of the plurality of cryptographic hashes stored at the database;

determining a false positive error rate based at least in part on determining the portion of the first cryptographic hash matches at least one of the plurality of cryptographic hashes;

transmitting a notification to the user indicating the determined false positive error rate and whether the user credential is stored at the database based at least in part on a result of the comparing.

2. The method of claim 1 , further comprising:

enabling the user to generate remotely an increased length cryptographic hash of the user credential to lower the false positive error rate; and

determining a quantity of the plurality of cryptographic hashes stored at the database, wherein the notification includes an indication of the false positive error rate.

3. The method of claim 2 , wherein the determined false positive error rate is based at least in part on a number of bits associated with the portion of one or more of the first cryptographic hash and the increased length cryptographic hash.

4. The method of claim 1 , wherein the portion of the first cryptographic hash comprises a subset of a predetermined maximum number of bits for each cryptographic hash.

5. The method of claim 1 , wherein a location of the portion of the first cryptographic hash is selected by the user.

6. The method of claim 5 , wherein the selected location includes at least one of a beginning portion of the first cryptographic hash, a middle portion of the first cryptographic hash, or an ending portion of the first cryptographic hash, or any combination thereof.

7. The method of claim 1 , wherein the truncated length first cryptographic hash includes a non-contiguous portion of bits of an untruncated version of the first cryptographic hash.

8. The method of claim 1 , wherein a size or location, or both size and location, of the portion of the first cryptographic hash is selected randomly by a computing device.

9. The method of claim 1 , wherein the first cryptographic hash and each of the plurality of cryptographic hashes comprise at least 128 bits.

10. The method of claim 1 , wherein only the user has access to an untruncated version of the first cryptographic hash.

11. A computing device configured for locating user credentials in databases, comprising:

a processor;

memory in electronic communication with the processor, wherein the memory stores computer executable instructions that when executed by the processor cause the processor to perform the steps of:

enable a user to generate remotely a truncated length first cryptographic hash of a user credential of the user, the user credential comprising a user name or a password, or both, associated with the user;

receive a portion of the first cryptographic hash from the user;

compare the portion of the first cryptographic hash with each of a plurality of cryptographic hashes of user credentials stored at a database;

determine whether a match exists between the portion of the first cryptographic hash and a portion of at least one of the plurality of cryptographic hashes stored at the database;

determine a false positive error rate based at least in part on determining the portion of the first cryptographic hash matches at least one of the plurality of cryptographic hashes;

transmit a notification to the user indicating the determined false positive error rate and whether the user credential is stored at the database based at least in part on a result of the comparing.

12. The computing device of claim 11 , wherein the instructions are executable by the processor to:

enable the user to generate remotely an increased length cryptographic hash of the user credential to lower the false positive error rate; and

determining a quantity of the plurality of cryptographic hashes stored at the database, wherein the notification includes an indication of the false positive error rate.

13. The computing device of claim 12 , wherein the determined false positive error rate is based at least in part on a number of bits associated with the portion of one or more of the first cryptographic hash and the increased length cryptographic hash.

14. The computing device of claim 11 , wherein the portion of the first cryptographic hash comprises a subset of a predetermined maximum number of bits for each cryptographic hash.

15. The computing device of claim 11 , wherein a location, of the portion of the first cryptographic hash is selected by the user.

16. The computing device of claim 15 , wherein the selected location includes at least one of a beginning portion of the first cryptographic hash, a middle portion of the first cryptographic hash, or an ending portion of the first cryptographic hash, or any combination thereof.

17. The computing device of claim 11 , wherein the truncated length first cryptographic hash includes a non-contiguous portion of bits of an untruncated version of the first cryptographic hash.

18. The computing device of claim 11 , wherein a size or location, or both size and location, of the portion of the first cryptographic hash is selected randomly by the computing device.

19. The computing device of claim 11 , wherein the first cryptographic hash and each of the plurality of cryptographic hashes comprise at least 128 bits.

20. A non-transitory computer-readable storage medium storing computer executable instructions that when executed by a processor cause the processor to perform the steps of:

enabling a user to generate remotely a truncated length first cryptographic hash of a user credential of the user, the user credential comprising a user name or a password, or both, associated with the user;

receiving a portion of the first cryptographic hash from the user;

comparing the portion of the first cryptographic hash with each of a plurality of cryptographic hashes of user credentials stored at a database;

determining whether a match exists between the portion of the first cryptographic hash and at least one of the plurality of cryptographic hashes stored at the database;

determining a false positive error rate based at least in part on determining the portion of the first cryptographic hash matches at least one of the plurality of cryptographic hashes;

transmitting a notification to the user indicating the determined false positive error rate and whether the user credential is stored at the database based at least in part on a result of the comparing.