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Overload of web passwords leads to insecure coping techniques. This talk presents approaches to password management, including our secure construction and comparison with other methods. Learn about password generators, the concept of Master Password, and how to thwart brute force attacks. Our construction allows for easy access to passwords from anywhere without server-side changes and offers a high level of security.
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A Convenient Method for Securely Managing Passwords J. Alex Halderman Princeton Brent Waters Stanford Edward W. Felten Princeton
****ing Passwords! • Web site password overload Generating, keeping secret, and recalling passwords for scores of sites • Leads to insecure coping techniques • Writing passwords down • Reusing same passwords • Difficult to enforce better behavior We need to make password security easy
In This Talk • Approaches to password management • Our construction and its security • Comparison with other techniques • Demonstration of our implementation • Future work and conclusions
Approaches to Password Mgmt • Local encrypted storage e.g., Password Safe (1998) • Cumbersome to access from multiple locations • Centralized remote authentication e.g., Microsoft Passport (1999) • Needs server-side changes, trusted third party • Cryptographic password generation e.g., LPWA (1997), PwdHash (2004), our scheme (2004)
Password Generators • E.g.: LPWA, PwdHash • Client software derives individual site passwords using deterministic one-way function • Users sets all site passwords to function output • Only need to remember master password to recreate all site passwords—highly transportable! Master Password “amazon.com” Hash() “wrbPzdqS” Use as your Amazon password A simple idea, but hard to get right!
Stealing the Master Password Password Guess “spot” “yahoo.com” “lassie” “rover” “spot” “fido” Hash() “RWwsYlTi” “H2VeusSq” “CJPZfAKx” “LZIniBNd” amazon.com wrbPzdqS gmail.com obIDmogl citibank.com sX4rLlO1 == =? “LZIniBNd” “LZIniBNd” Adversary learns password from low-security site Dictionary attack to learn master password Can access all otherpassword-managedsites Easy to execute because scheme use fast hashes
Thwarting Brute Force Attacks attack cost = ½ × dictionary size × cost per guess • Hard to increase dictionary size User habits hard to change, limits on human memory • Increase cost per guess by using slower hash • Used elsewhere to protect password verification routines (UNIX crypt) • Our approach: iterated hash • Security vs. usability tradeoff User has to wait too! — Cache intermediate results
Our Construction Master password “MyD06ReX” User identity “jhalderm@princeton.edu” Initialization Phase (k1 >> k2) Hk1() Local Cache Target site “amazon.com” Hk2() Master password (again) Generation Phase Mapping User’s site passwordfor “amazon.com” “wrb8zdqS”
Security Analysis Four attack scenarios: • No information • Stolen site password • Stolen cache data • Stolen cache + site password Primary concern is offline attacks. Increasing external difficulty ? ? ?
Equivalent Password Length ********* ******** ****
Password Multiplier • Extension for Mozilla Firefox Windows, Mac OS X, and Linux • Tightly integrated with browser Double-click any password field to fill in • Balanced security and convenience • Initialization — 108 iterations, ~100 seconds(Onlyonce per installation) • Password generation — 105 iterations, ~0.1 secs(Before every password operation)
Future Improvements • Flexible password formatting Cope with sites that require numbers, punctuation, special patterns • Easier password changes Manually and at regular intervals • Improved anti-spoofing Adopt techniques from PwdHash • Port to Internet Explorer, others Require additional “state”
Summary — Our scheme: • Provides password access from anywhere our software can be executed • Asks user to remember only one short password • Requires no server-side changes • Does not require trusting a third-party service • Nearly as secure as independent random pwds • Likely much more secure than what you do now • Is practical, available today, and free http://www.cs.princeton.edu/~jhalderm/projects/password/
A Convenient Method for Securely Managing Passwords J. Alex Halderman Princeton Brent Waters Stanford Edward W. Felten Princeton