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1. An Analysis of Password Managers’ Password Checkup Tools

   https://doi.org/10.1145/3613905.3650741  

   Hutchinson, Adryana; Munyendo, Collins W; Aviv, Adam J; Mayer, Peter (May 2024, ACM)
2. Password Strength Signaling: A Counter-Intuitive Defense Against Password Cracking

   https://doi.org/10.1007/978-3-030-90370-1_18  

   Bai, Wenjie; Blocki, Jeremiah; Harsha, Ben. (October 2021, Decision and Game Theory for Security: 12th International Conference, GameSec 2021)

   We introduce password strength signaling as a potential defense against password cracking. Recent breaches have exposed billions of user passwords to the dangerous threat of offline password cracking attacks. An offline attacker can quickly check millions (or sometimes billions/trillions) of password guesses by comparing a candidate password’s hash value with a stolen hash from a breached authentication server. The attacker is limited only by the resources he is willing to invest. We explore the feasibility of applying ideas from Bayesian Persuasion to password authentication. Our key idea is to have the authentication server store a (noisy) signal about the strength of each user password for an offline attacker to find. Surprisingly, we show that the noise distribution for the signal can often be tuned so that a rational (profit-maximizing) attacker will crack fewer passwords. The signaling scheme exploits the fact that password cracking is not a zero-sum game i.e., it is possible for an attacker to increase their profit in a way that also reduces the number of cracked passwords. Thus, a well-defined signaling strategy will encourage the attacker to reduce his guessing costs by cracking fewer passwords. We use an evolutionary algorithm to compute the optimal signaling scheme for the defender. We evaluate our mechanism on several password datasets and show that it can reduce the total number of cracked passwords by up to 12% (resp. 5%) of all users in defending against offline (resp. online) attacks. While the results of our empirical analysis are positive we stress that we view the current solution as a proof-of-concept as there are important societal concerns that would need to be considered before adopting our password strength signaling solution. 

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3. Password-Protected Threshold Signatures

   https://doi.org/10.1007/978-981-96-0891-1_6  

   Dziembowski, Stefan; Jarecki, Stanislaw; Kedzior, Pawel; Krawczyk, Hugo; Ngo, Chan Nam; Xu, Jiayu (December 2024, Springer Nature Singapore)

   Chung, KM; Sasaki, Y (Ed.)

   We witness an increase in applications like cryptocurrency wallets, which involve users issuing signatures using private keys. To protect these keys from loss or compromise, users commonly outsource them to a custodial server. This creates a new point of failure, because compromise of such a server leaks the user’s key, and if user authentication is implemented with a password then this password becomes open to an offline dictionary attack (ODA). A better solution is to secret-share the key among a set of servers, possibly including user’s own device(s), and implement password authentication and signature computation using threshold cryptography. We propose a notion of augmented password-protected threshold signature (aptSIG) scheme which captures the best possible security level for this setting. Using standard threshold cryptography techniques, i.e. threshold password authentication and threshold signatures, one can guarantee that compromising up to t out of n servers reveals no information on either the key or the password. However, we extend this with a novel property, that compromising even all n servers also does not leak any information, except via an unavoidable ODA attack, which reveals the key only if the attacker guesses the password. We define aptSIG in the Universally Composable (UC) framework and show that it can be constructed very efficiently, using a black-box composition of any UC threshold signature [13] and a UC augmented Password-Protected Secret Sharing (aPPSS), which we define as an extension of prior notion of PPSS [30]. As concrete instantiations we obtain secure aptSIG schemes for ECDSA (in the case of t=n-1) and BLS signatures with very small overhead over the respective threshold signature. Finally, we note that both the notion and our generic solution for augmented password-protected threshold signatures can be generalized to password-protecting MPC for any keyed functions. 

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4. DALock: Password Distribution-Aware Throttling

   Blocki, Jeremiah; Zhang, Wuwei. (January 2022, Proceedings on Privacy Enhancing Technologies)

   Large-scale online password guessing attacks are widespread and pose a persistant privacy and security threat to users. The common method for mitigating the risk of online cracking is to lock out the user after a fixed number ($$K$$) of consecutive incorrect login attempts. Selecting the value of $$K$$ induces a classic security-usability trade-off. When $$K$$ is too large, a hacker can (quickly) break into a significant fraction of user accounts, but when $$K$$ is too low, we will start to annoy honest users by locking them out after a few mistakes. Motivated by the observation that honest user mistakes typically look quite different from an online attacker's password guesses, we introduce $$\DALock$$, a {\em distribution-aware} password lockout mechanism to reduce user annoyance while minimizing user risk. As the name suggests, $$\DALock$$ is designed to be aware of the frequency and popularity of the password used for login attacks. At the same time, standard throttling mechanisms (e.g., $$K$$-strikes) are oblivious to the password distribution. In particular, $$\DALock$$ maintains an extra ``hit count" in addition to ``strike count" for each user, which is based on (estimates of) the cumulative probability of {\em all} login attempts for that particular account. We empirically evaluate $$\DALock$$ with an extensive battery of simulations using real-world password datasets. In comparison with the traditional $$K$$-strikes mechanism, {our simulations indicate that} $$\DALock$$ offers a superior {simulated} security/usability trade-off. For example, in one of our simulations, we are able to reduce the success rate of an attacker to $$0.05\%$ (compared to $$1\%$$ for the $$3$$-strikes mechanism) whilst simultaneously reducing the unwanted lockout rate for accounts that are not under attack to just $$0.08\%$$ (compared to $$4\%$$ for the $$3$$-strikes mechanism). 

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5. Password-Authenticated Public-Key Encryption

   https://doi.org/10.1007/978-3-030-21568-2_22  

   Bradley, Tatiana; Camenisch, Jan; Jarecki, Stanislaw; Lehmann, Anja; Neven, Gregory; Xu, Jiayu (June 2019, Applied Cryptography and Network Security - 17th International Conference, ACNS 2019)

   Deng, Robert H; Gauthier, Valerie; Ochoa, Martin; Yung, Moti (Ed.)