BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//pretalx//cfp.dragonsec.si//dctf26//8HHRCJ
BEGIN:VTIMEZONE
TZID:CET
BEGIN:STANDARD
DTSTART:20001029T040000
RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10
TZNAME:CET
TZOFFSETFROM:+0200
TZOFFSETTO:+0100
END:STANDARD
BEGIN:DAYLIGHT
DTSTART:20000326T030000
RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=3
TZNAME:CEST
TZOFFSETFROM:+0100
TZOFFSETTO:+0200
END:DAYLIGHT
END:VTIMEZONE
BEGIN:VEVENT
UID:pretalx-dctf26-QWPGK3@cfp.dragonsec.si
DTSTART;TZID=CET:20260321T153000
DTEND;TZID=CET:20260321T155500
DESCRIPTION:Anonymous credentials are a critical building block for privacy
 -preserving systems\, from EU digital wallets to privacy-respecting authen
 tication schemes. At the IETF\, however\, they address efficient rate limi
 ting in the presence of CAPTCHA-based human verification.\nCurrent rate li
 miting systems use blind signatures or OPRFs to issue batches of rate-limi
 ting tokens post-CAPTCHA. While cryptographically sound\, this approach in
 curs communication complexity linear in the number of tokens issued\, a si
 gnificant bottleneck when handling large token batches.\nThe talk presents
  two proposals to reduce the token issuance to constant-size communication
  regardless of batch size\, and shows how to combine them to get parallel\
 , revocable tokens \nThe talk will cover the cryptographic foundations\, d
 iscuss trade-offs between revocation expressiveness and issuance efficienc
 y\, and examine deployment challenges. We'll also explore an interesting s
 econdary application: extending rate limiting to adaptive systems (LLMs\, 
 bots) that must solve CAPTCHAs\, where the same credential mechanism enabl
 es fine-grained behavioral constraints beyond simple token budgets.
DTSTAMP:20260501T111301Z
LOCATION:PA
SUMMARY:Anonymous Credentials for Next-Generation Rate Limiting: From Linea
 r to Constant-Size Issuance - Lena Heimberger
URL:https://cfp.dragonsec.si/dctf26/talk/QWPGK3/
END:VEVENT
END:VCALENDAR