Password checking

• US 8,539,247 B2
• Filed: 06/22/2010
• Issued: 09/17/2013
• Est. Priority Date: 06/22/2010
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: McGrew, David A., Persaud, Andrew D.
• Primary Examiner(s): Zand, Kambiz
• Assistant Examiner(s): KAPLAN, BENJAMIN A
• Application Number:
  US12/821,082
• Publication Number:
  US 20110314294A1
• Time in Patent Office: 1,183 Days
• Field of Search: 713/182, 713/183
• US Class Current: 713/183
• CPC Class Codes: G06F 21/31 User authentication
• CPC Class Codes: G06F 21/46 by designing passwords or checking the strength of passwords

Abstract

A method is disclosed for password checking. After input is received, a proposed password included in the input is parsed into symbols. At least one of the symbols includes two or more characters. A probably metric is determined based on a sequence of symbols. The probability metric is used to determine whether or not the password is secure.

Claims

1. A computer-implemented method, comprising:

receiving a proposed password;

parsing the proposed password into two or more symbols, wherein a first symbol of the two or more symbols comprises one or more characters, and a second symbol of the two or more symbols comprises two or more characters;

wherein the parsing the proposed password into two or more symbols comprises determining a number of characters for each symbol, and finding a longest possible matching symbol, from the two or more symbols, that matches a character string, from a plurality of character strings, in a database source;

based at least in part on a sequence of the first and second symbols and the plurality of strings in the database source, determining one or more probabilities and storing in a first probability metric those probabilities from the one or more probabilities that exceed a threshold value and indicate not uncommon character strings;

based at least in part on the first probability metric, determining whether the proposed password is secure;

wherein the method is performed by one or more computing devices.

2. The method of claim 1, wherein the first probability metric measures, based on a data source of passwords, a likelihood that the second symbol will follow the first symbol.

3. The method of claim 1, further comprising:

based at least in part on the sequence of the first and second symbols, determining a second probability metric;

based at least in part on the second probability metric, determining whether the proposed password is secure;

wherein the first probability metric is based on a first data source and the second probability metric is based on a second data source.

4. The method of claim 1, further comprising:

determining a complexity metric for the proposed password;

based at least in part on the complexity metric, determining whether the proposed password is secure.

5. The method of claim 4, wherein determining a complexity metric comprises performing a Lempel-Ziv complexity check.

6. The method of claim 1, further comprising applying one or more character transformations to the password, wherein the password comprises a plurality of characters and applying a character transformation includes substituting a first character of the plurality of characters with a second character that is different than the first character.

7. The method of claim 1, wherein a third symbol of the set of symbols comprises one or more characters;

and further comprising;

based at least in part on a sequence of the second and third symbols, determining a second probability metric;

based at least in part on the second probability metric, determining whether the proposed password is secure.

8. The method of claim 7, wherein the second probability metric is based at least in part on the first symbol.

9. The method of claim 1, comprising receiving the proposed password in a request to set or change a password.

19. The method of claim 1, wherein the database source comprises one or more dictionaries, each of the one or more dictionaries having a weight indicating whether the dictionary comprises words that are less commonly used to create passwords.

10. A computer-readable non-transitory storage medium storing instructions which, when executed, cause one or more processors to perform:

receiving a proposed password;

parsing the proposed password into two or more symbols, wherein a first symbol of the two or more symbols comprises one or more characters, and a second symbol of the two or more symbols comprises two or more characters;

wherein the instructions that cause the parsing the proposed password into two or more symbols further comprise instructions which, when executed, cause determining a number of characters for each symbol, and finding a longest possible matching symbol, from the two or more symbols, that matches a character string, from a plurality of character strings, in a database source;

based at least in part on a sequence of the first and second symbols and the plurality of strings in the database source, determining one or more probabilities and storing in a first probability metric those probabilities from the one or more probabilities that exceed a threshold value and indicate not uncommon characters strings;

based at least in part on the first probability metric, determining whether the proposed password is secure.

11. The computer-readable non-transitory storage medium of claim 10, wherein the first probability metric measures, based on a data source of passwords, a likelihood that the second symbol will follow the first symbol.

12. The computer-readable non-transitory storage medium of claim 10, wherein the instructions further include instructions for:

based at least in part on the sequence of the first and second symbols, determining a second probability metric;

based at least in part on the second probability metric, determining whether the proposed password is secure;

wherein the first probability metric is based on a first data source and the second probability metric is based on a second data source.

13. The computer-readable non-transitory storage medium of claim 10, wherein the instructions further include instructions for:

determining a complexity metric for the proposed password;

based at least in part on the complexity metric, determining whether the proposed password is secure.

14. The computer-readable non-transitory storage medium of claim 13, wherein determining a complexity metric comprises performing a Lempel-Ziv complexity check.

15. The computer-readable non-transitory storage medium of claim 10, wherein the instructions further include instructions for applying one or more character transformations to the password, wherein the password comprises a plurality of characters and applying a character transformation includes substituting a first character of the plurality of characters with a second character that is different than the first character.

16. The computer-readable non-transitory storage medium of claim 10, wherein a third symbol of the set of symbols comprises one or more characters;

and wherein the instructions further include instructions for;

based at least in part on a sequence of the second and third symbols, determining a second probability metric;

based at least in part on the second probability metric, determining whether the proposed password is secure.

17. The computer-readable non-transitory storage medium of claim 16, wherein the second probability metric is based at least in part on the first symbol.

18. The computer-readable non-transitory storage medium of claim 10, wherein the instructions further include instructions for receiving the proposed password in a request to set or change a password.

20. The computer-readable non-transitory storage medium of claim 10, wherein the database source comprises one or more dictionaries, each of the one or more dictionaries having a weight indicating whether the dictionary comprises words that are less commonly used to create passwords.