BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:Majority is not Enough: Bitcoin Mining is Vulnerable - Ittay Eyal\
 , Cornell University
DTSTART:20140709T100000Z
DTEND:20140709T110000Z
UID:TALK53263@talks.cam.ac.uk
CONTACT:Microsoft Research Cambridge Talks Admins
DESCRIPTION:The Bitcoin cryptocurrency records its transactions in a publi
 c log called the blockchain. Its security rests critically on the distribu
 ted protocol that maintains the blockchain\, run by participants called mi
 ners. Conventional wisdom asserts that the mining protocol is incentive-co
 mpatible and secure against colluding minority groups\, that is\, it incen
 tivizes miners to follow the protocol as prescribed. \n\nWe show that the 
 Bitcoin mining protocol is not incentive-compatible. We present an attack 
 with which colluding miners obtain a revenue larger than their fair share.
  This attack can have significant consequences for Bitcoin: Rational miner
 s will prefer to join the selfish miners\, and the colluding group will in
 crease in size until it becomes a majority. At this point\, the Bitcoin sy
 stem ceases to be a decentralized currency. \n\nUnless certain assumptions
  are made\, selfish mining may be feasible for any group size of colluding
  miners. We propose a practical modification to the Bitcoin protocol that 
 protects Bitcoin in the general case. It prohibits selfish mining by pools
  that command less than 1/4 of the resources. This threshold is lower than
  the wrongly assumed 1/2 bound\, but better than the current reality where
  a group of any size can compromise the system.
LOCATION:Auditorium\, Microsoft Research Ltd\, 21 Station Road\, Cambridge
 \, CB1 2FB
END:VEVENT
END:VCALENDAR