Anna Gerchanovsky | Searcharxiv

arXiv2026

MindReader: Using LLMs to Encourage Memorable and Secure Password Replacement

We report on the design and evaluation of MindReader, a tool that helps a user replace her password when she is required to do so. Left to their own devices, users tend to replace their previous passwords with predictable variations of the original ones. MindReader leverages LLMs to suggest password variations that are chosen to be easy for the user to remember but harder for an attacker to predict. To do this, MindReader infers the meaning behind original password components and then suggests semantically related (yet syntactically unrelated) components for the new password. In a user study, passwords created using MindReader were more secure than both replacement passwords created without using MindReader and original passwords. In particular, MindReader replacement passwords were harder to guess in an online attack than alternative replacement passwords even by an attacker with knowledge of the original password and full knowledge of the tool implementation. Passwords created with MindReader were also comparably memorable to alternative replacement passwords and original passwords, as measured by the ability of users to successfully log in a week after creating their password.

cs.CR↗

arXiv2024

LLM Whisperer: An Inconspicuous Attack to Bias LLM Responses

Writing effective prompts for large language models (LLM) can be unintuitive and burdensome. In response, services that optimize or suggest prompts have emerged. While such services can reduce user effort, they also introduce a risk: the prompt provider can subtly manipulate prompts to produce heavily biased LLM responses. In this work, we show that subtle synonym replacements in prompts can increase the likelihood (by a difference up to 78%) that LLMs mention a target concept (e.g., a brand, political party, nation). We substantiate our observations through a user study, showing that our adversarially perturbed prompts 1) are indistinguishable from unaltered prompts by humans, 2) push LLMs to recommend target concepts more often, and 3) make users more likely to notice target concepts, all without arousing suspicion. The practicality of this attack has the potential to undermine user autonomy. Among other measures, we recommend implementing warnings against using prompts from untrusted parties.

cs.CR↗