[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"detail-sidebar-cat-0-en-105":3,"doc-seo-503594-105":59,"doc-detail-503594-en":130},{"code":4,"msg":5,"data":6},0,"success",[7,13,18,23,28,33,38,43,48,51,55],{"id":8,"doc_module":4,"doc_module_name":9,"category_name":10,"show_sort_weight":11,"slug":12},1,"Document","Story & Novel",90,"story-novel",{"id":14,"doc_module":4,"doc_module_name":9,"category_name":15,"show_sort_weight":16,"slug":17},2,"Literature",80,"literature",{"id":19,"doc_module":4,"doc_module_name":9,"category_name":20,"show_sort_weight":21,"slug":22},4,"Exam",70,"exam",{"id":24,"doc_module":4,"doc_module_name":9,"category_name":25,"show_sort_weight":26,"slug":27},5,"Comic",60,"comic",{"id":29,"doc_module":4,"doc_module_name":9,"category_name":30,"show_sort_weight":31,"slug":32},6,"Technology",50,"technology",{"id":34,"doc_module":4,"doc_module_name":9,"category_name":35,"show_sort_weight":36,"slug":37},7,"Healthcare",40,"healthcare",{"id":39,"doc_module":4,"doc_module_name":9,"category_name":40,"show_sort_weight":41,"slug":42},8,"Research & Report",30,"research-report",{"id":44,"doc_module":4,"doc_module_name":9,"category_name":45,"show_sort_weight":46,"slug":47},9,"Religion & Spirituality",20,"religion-spirituality",{"id":46,"doc_module":4,"doc_module_name":9,"category_name":49,"show_sort_weight":46,"slug":50},"World Cup","world-cup",{"id":52,"doc_module":4,"doc_module_name":9,"category_name":53,"show_sort_weight":52,"slug":54},10,"Lifestyle","lifestyle",{"id":56,"doc_module":4,"doc_module_name":9,"category_name":57,"show_sort_weight":24,"slug":58},19,"General","general",{"code":4,"msg":60,"data":61},"ok",{"site_id":62,"language":63,"slug":64,"title":65,"keywords":66,"description":67,"schema_data":68,"social_meta":123,"head_meta":125,"extra_data":127,"updated_unix":129},105,"en","detecting-compromise-of-passkey-storage-on-the-cloud-paper","Detecting Compromise of Passkey Storage on the Cloud - Paper","","FIDO synced passkeys solve account recovery by backing up users’ FIDO2 private signing keys to the cloud storage of passkey management services (PMS). This also creates a serious threat: attackers may steal passkeys via PMS cloud-storage breaches and use them for unauthorized account takeovers. Existing defenses cannot remove this risk without reintroducing recovery challenges or harming daily login flows. The paper introduces CASPER, a passkey-breach detection framework for detecting abusive use of leaked passkeys.",{"@graph":69,"@context":122},[70,84,105],{"@type":71,"itemListElement":72},"BreadcrumbList",[73,77,79,82],{"item":74,"name":75,"@type":76,"position":8},"https://docshare.wps.com","Home","ListItem",{"item":78,"name":9,"@type":76,"position":14},"https://docshare.wps.com/document/",{"item":80,"name":30,"@type":76,"position":81},"https://docshare.wps.com/document/technology/",3,{"item":83,"name":65,"@type":76,"position":19},"https://docshare.wps.com/document/detecting-compromise-of-passkey-storage-on-the-cloud-paper/503594/",{"url":83,"name":65,"@type":85,"image":86,"author":91,"headline":65,"publisher":94,"fileFormat":97,"inLanguage":63,"description":67,"dateModified":98,"datePublished":99,"encodingFormat":97,"isAccessibleForFree":100,"interactionStatistic":101},"DigitalDocument",{"url":87,"@type":88,"width":89,"height":90},"https://docshare.wps.com/thumbnails/detecting-compromise-of-passkey-storage-on-the-cloud-paper/503594.png","ImageObject",300,407,{"name":92,"@type":93},"8796093062539","Person",{"url":74,"name":95,"@type":96},"DocShare","Organization","application/pdf","2026-10-20","2026-10-03",true,{"@type":102,"interactionType":103,"userInteractionCount":52},"InteractionCounter",{"@type":104},"ViewAction",{"@type":106,"mainEntity":107},"FAQPage",[108,114,118],{"name":109,"@type":110,"acceptedAnswer":111},"What security risk does the paper identify with cloud-synced passkeys?","Question",{"text":112,"@type":113},"It explains that attackers can steal users’ passkeys when they breach a PMS cloud storage, and then use the stolen keys to take over accounts at relying parties.","Answer",{"name":115,"@type":110,"acceptedAnswer":116},"How does CASPER detect passkey compromise attempts?",{"text":117,"@type":113},"CASPER uses a decoy-based technique that hides the real passkey among indistinguishable decoy passkeys, causing abuse attempts to trigger breach detection at the relying party with high probability.",{"name":119,"@type":110,"acceptedAnswer":120},"What design goals does the paper emphasize for usability and deployment?",{"text":121,"@type":113},"CASPER is designed to avoid false detections (including denial-of-service-driven false alarms), minimize user-secret management burdens, and integrate into existing backup/synchronization/authentication with minimal impact on user experience and performance.","https://schema.org",{"og:url":83,"og:type":124,"og:title":65,"og:site_name":95,"og:description":67},"article",{"robots":126,"canonical":83},"index,follow",{"doc_id":128,"site_id":62},503594,1791426635,{"code":4,"msg":5,"data":131},{"doc_id":128,"user_id":132,"nickname":92,"user_avatar":66,"doc_module":4,"category_id":29,"category_name":30,"doc_title":65,"doc_description":67,"doc_content":133,"file_id":134,"file_url":135,"file_type":136,"file_size":137,"view_count":52,"is_deleted":4,"is_public":8,"is_downloadable":8,"audit_status":8,"page_count":138,"language":139,"language_code":63,"site_id":62,"html_lang":63,"table_of_contents":140,"faqs":141,"seo_title":142,"seo_description":67,"update_tm":143,"read_time":144},8796093062539,"Detecting Compromise of Passkey Storage on the Cloud Mazharul Islam, University of Wisconsin—Madison; Sunpreet S. Arora, Visa Research; Rahul Chatterjee, University of Wisconsin—Madison; Ke Coby Wang, Visa Research  \n[https://www.usenix.org/conference/usenixsecurity25/presentation/islam](https://www.usenix.org/conference/usenixsecurity25/presentation/islam)  \nThis paper is included in the Proceedings of the 34th USENIX Security Symposium .  \nAugust 13–15, 2025 • Seattle, WA, USA  \n978-1-939133-52-6  \nOpen access to the Proceedings of the 34th USENIX Security Symposium is sponsored by USENIX.  \nDetecting Compromise of Passkey Storage on the Cloud  \nMazharul Islam∗3, Sunpreet S. Arora‡, Rahul Chatterjee3 , Ke Coby Wang† ‡  \n3 University of Wisconsin—Madison, ‡Visa Research  \nAbstract  \nFIDO synced passkeys address account recovery challenges by enabling users to back up their FIDO2 private signing keys to the cloud storage of passkey management services (PMS) . However, it introduces a serious security risk—attackers can steal users’ passkeys through breaches of PMS’s cloud storage. Unfortunately, existing defenses cannot eliminate this risk without reintroducing account recovery challenges or disrupting users’ daily account login routines. In this paper, we present CASPER, the first passkey breach detection framework that enables web service providers to detect the abuse of passkeys leaked from PMS for unauthorized login attempts. Our analysis shows that CASPER provides compelling detection effectiveness, even against knowledgeable attackers who strategically optimize their attacks to evade CASPER’s detection. We also show how CASPER can be seamlessly integrated into the existing passkey backup, synchronization, and authentication processes, with only minimal impact on user experience, negligible performance overhead, and minimum deployment and storage complexity for the participating parties.  \n1 Introduction  \nFIDO2-based user authentication has compelling security guarantees which allows users to log into their web service accounts with device-bound private keys. While they are promising at (finally) replacing passwords, recovering accounts in the event of device loss remains a significant challenge preventing the adoption of FIDO2 . To address this challenge and accelerate the adoption of FIDO2-based passwordless user authentication, Microsoft, Apple, and Google announced passkeys [1], which enables cloud backup and multi-device synchronization of FIDO2 private keys. Today, there are many passkey management services (PMS) that allow passkey backup, e.g., iCloud Keychain from Apple [14], Google Password Manager [12], Password Monitor from Microsoft [11], 1Password  [5], LastPass [4], and DashLane [3] .  \n∗ Work partially done during a research internship at Visa Research.  \n†Corresponding author: [coby.wang@visa.com](coby.wang@visa.com)  \nWhile synced passkeys address the account recovery concern, backing up passkeys to a centralized cloud server poses a serious security risk: attackers can steal users’ passkeys through PMS breaches and use them to take over users’ web service accounts. The breach can happen when an attacker compromises a user’s PMS account (possibly by guessing the account password) or when an insider attacker gains access to the cloud backup storage [27, 82]. Unfortunately, existing passkey backup and synchronization implementations lack the capability to detect unauthorized access to users’ passkeys stored at the PMS.  \nIn this paper, we address this problem by proposing CASPER 1 , which, to the best of our knowledge, is the first framework to detect the abuse of passkeys leaked from PMS. Underlying CASPER is a decoy-based detection technique [30, 50, 75]: it hides the real passkey within a list of decoy passkeys that are indistinguishable from the real one. As a result, an attacker who steals the passkeys from PMS and attempts to use them to log into the user’s account at a relying party (RP), e.g., a we","cbCaijS8fb6cdvRR","https://ap.wps.com/l/cbCaijS8fb6cdvRR","pdf",823009,21,"English","# Abstract\n# 1 Introduction\n## Threat model and problem statement\n## CASPER decoy-based detection approach\n## Passkey backup and restoration protocol (BnR)\n## Compromise detection algorithm (CD)","[{\"question\":\"What security risk does the paper identify with cloud-synced passkeys?\",\"answer\":\"It explains that attackers can steal users’ passkeys when they breach a PMS cloud storage, and then use the stolen keys to take over accounts at relying parties.\"},{\"question\":\"How does CASPER detect passkey compromise attempts?\",\"answer\":\"CASPER uses a decoy-based technique that hides the real passkey among indistinguishable decoy passkeys, causing abuse attempts to trigger breach detection at the relying party with high probability.\"},{\"question\":\"What design goals does the paper emphasize for usability and deployment?\",\"answer\":\"CASPER is designed to avoid false detections (including denial-of-service-driven false alarms), minimize user-secret management burdens, and integrate into existing backup/synchronization/authentication with minimal impact on user experience and performance.\"}]","Detecting Compromise of Passkey Storage on the Cloud - Paper | PDF",1791058520,53]