Graduate School and Research Center in Digital Sciences

Password strength : an empirical analysis

Dell Amico, Matteo;Michiardi, Pietro;Roudier, Yves

INFOCOM 2010, 29th Conference on Computer Communications, March 14-19, 2010, San Diego, USA

It is a well known fact that user-chosen passwords are somewhat predictable: by using tools such as dictionaries or probabilistic models, attackers and password recovery tools can drastically reduce the number of attempts needed to guess a password. Quite surprisingly, however, existing literature does not provide a satisfying answer to the following question: given a number of guesses, what is the probability that a state-of-the-art attacker will be able to break a password? To answer the former question, we compare and evaluate the effectiveness of currently known attacks using various datasets of known passwords. We find that a "diminishing returns" principle applies: in the absence of an enforced password strength policy, weak passwords are common; on the other hand, as the attack goes on, the probability that a guess will succeed decreases by orders of magnitude. Even extremely powerful attackers won't be able to guess a substantial percentage of the passwords. The result of this work will help in evaluating the security of authentication means based on user- chosen passwords, and our methodology for estimating password strength can be used as a basis for creating more effective proactive password checkers for users and security auditing tools for administrators.

Document Doi Arxiv Bibtex

Title:Password strength : an empirical analysis
City:San Diego
Department:Digital Security
Eurecom ref:2910
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Bibtex: @inproceedings{EURECOM+2910, doi = { }, year = {2010}, title = {{P}assword strength : an empirical analysis}, author = {{D}ell {A}mico, {M}atteo and {M}ichiardi, {P}ietro and {R}oudier, {Y}ves}, booktitle = {{INFOCOM} 2010, 29th {C}onference on {C}omputer {C}ommunications, {M}arch 14-19, 2010, {S}an {D}iego, {USA}}, address = {{S}an {D}iego, {UNITED} {STATES}}, month = {03}, url = {} }
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