LLM-Generated Passphrases That Are Secure and Easy to Remember

Jie S. Li, Jonas Geiping, Micah Goldblum, Aniruddha Saha, Tom Goldstein


Abstract
Automatically generated passwords and passphrases are a cornerstone of IT security. Yet, these passphrases are often hard to remember and see only limited adoption. In this work, we use large language models to generate passphrases with rigorous security guarantees via the computation of the entropy of the output as a metric of the security of the passphrase. We then present a range of practical methods to generate language model outputs with sufficient entropy: raising entropy through in-context examples and generation through a new top-q truncation method. We further verify the influence of prompt construction in steering the output topic and grammatical structure. Finally, we conduct user studies to determine the adoption rates for these LLM-generated passphrases in practice.
Anthology ID:
2025.findings-naacl.290
Volume:
Findings of the Association for Computational Linguistics: NAACL 2025
Month:
April
Year:
2025
Address:
Albuquerque, New Mexico
Editors:
Luis Chiruzzo, Alan Ritter, Lu Wang
Venue:
Findings
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
5216–5234
Language:
URL:
https://preview.aclanthology.org/fix-sig-urls/2025.findings-naacl.290/
DOI:
Bibkey:
Cite (ACL):
Jie S. Li, Jonas Geiping, Micah Goldblum, Aniruddha Saha, and Tom Goldstein. 2025. LLM-Generated Passphrases That Are Secure and Easy to Remember. In Findings of the Association for Computational Linguistics: NAACL 2025, pages 5216–5234, Albuquerque, New Mexico. Association for Computational Linguistics.
Cite (Informal):
LLM-Generated Passphrases That Are Secure and Easy to Remember (Li et al., Findings 2025)
Copy Citation:
PDF:
https://preview.aclanthology.org/fix-sig-urls/2025.findings-naacl.290.pdf