the eternity service - university of illinois at chicagospopuri/eternity_presentation.pdf ·...
TRANSCRIPT
Today ' s p resenta t ion
●Based on two papers:●“The Eternity Service” by Ross J. Anderson●“Protecting Free Expression Online with Freenet” by Ian Clarke, Theodore W. Hong, and Oscar Sandberg.
What i s i t about
● Internet Censorship ● Privacy● Freedom of expression● Availability of electronic data
knowledge == power
● Bibles were kept chained up during medieval times
● Until.. the printing press came by.● After that, censorship became *very*
expensive!
Pr ivacy and Censorsh ip
● Back to square one with 'electronic publishing'
● Digital copies of data can be annihilated● People handling it can be tracked, sued
and threatened● Privacy? what privacy ????
Anderson ' s p roposa l (1996)
● The Eternity Service – A resilient distributed file store.
● Keeps your files 'eternally alive'● No one (including you) can delete all
copies of it!● Draws from principles of the Internet
Anderson ' s “s imp le” des ign
● Host data on Multiple servers● Use tamper proof hardware● Principles from fault tolerance● Indexing● Payments● Accuracy of measuring time
Mul t ip le se rvers
● Pay multiple “Eternity Service” providers
● “Forget” most of their names and locations
● Use the “Perjury trap”– “System admin shall not log on under
duress”
The E te rn i ty Serv i ce
Tamper p roo f ha rdware (? )
● Trusted computing modules ?● Mix nets● “Security Servers”
Etern i ty A rch i tec tu re
Security Server
Security Server
File servers File servers
Math o r meta l ?
● Byzantine fault tolerance– If n copies out of m are destroyed can we
make a full recovery ?● Cryptography
– Encrypt, sign files– Eternity service will NOT identify users– (Hence) No confidentiality
I ndex ing
● Directory is a file on the system● Logical name + tags/keywords● Local caching
Payments
● Anonymous payments by digital cash● How to account for taxes?● How to ensure QOS ?
T ime
● Reliable time service is needed● NTP should be safe from being
manipulated!
The F reenet P ro jec t
Freenet – A modern Eternity like Service
Freenet – An imp lementa t ion
● A peer to peer system● Pools free disk space across peers to
form a collaborative virtual file system● Participants can turn malicious/fail
without warning at any time!● A free service (no payments required)
Freenet A rch i tec tu re
File
ab
c
e
f
Freenet A rch i tec tu re
● Uses a distributed hash table● GUID keys
– a Content Hash Key (CHK)– Signed Subspace Key (SSK)
● CHK == inodes (system usable)● SSK == file names (human usable)
Freenet GU ID keys
● CHK used by system to locate files● SSK used by users to setup personal
namespaces● SSK(file) = hash( hash(public_key) +
hash(text_description))● File can then be signed to provide
integrity
S igned Subspace Keys
politics/us/pentagonpapers
AF5EC2
SSK gen
Public key+
Key c lus te r ing
politics/us/pentagonpapers
AF5EC2
SSK gen AF5EC2AF5EC3AF5EC7
....
....
....
Node
Pr ivacy in F reenet
● Similar to Tor network● Employs mixnet schemes● Each node knows only about its
neighbours● Nodes do NOT have to talk to non-
participating servers like in the Tor case.
Rout ing quer ies
a bc
e
fd
requester
holder
A compar i son
● Centralized● Commercial
service● Indexing by
directories
● Peer to Peer● Free (voluntary)
service● Indexing by
Signed namespaces
Quest ions