wuala, p2p online storage
DESCRIPTION
Speaker: Dominik GrolimundTRANSCRIPT
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Web 2.0 Expo Berlin, 2007Dominik Grolimund
P2P Online Storagehttp://wua.la
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large, reliable, and securedistributed online storage
harness idle resources of participating computers
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old dream of computer science
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“The design of a world-wide, fully transparent distributed file system for simultaneous use by millions of mobile and frequently disconnected
users is left as an exercise for the reader.”
A. Tanenbaum, Distributed Operating System, 1995
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lots of research projects
OceanStore (UC Berkeley)Past (Microsoft Research)
CFS (MIT)
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we were inspired by them
wanted to make it work
first step: closed alpha
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upload any file in any size
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upload any file in any size
access from anywhere
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upload any file in any size
access from anywhereshare with friends and groups
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upload any file in any size
access from anywhereshare with friends and groups
publish to the world
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free and simple application
(Win, Mac, and soon Linux)
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free and simple application
(Win, Mac, and soon Linux)
start with 1 GB of storage
provided by us
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free and simple application
(Win, Mac, and soon Linux)
start with 1 GB of storage
provided by us
if you want more, you can
trade local disk space for more
online storage
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online storage
with the “power of P2P”
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online storage
with the “power of P2P”
fast downloads
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online storage
with the “power of P2P”
fast downloads
no file size limit
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online storage
with the “power of P2P”
fast downloads
no file size limit
no traffic limit
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privacy
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privacy
all files are encrypted on your computer
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privacy
all files are encrypted on your computer
your password never leaves your computer
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privacy
all files are encrypted on your computer
your password never leaves your computer
so no one, not even we, can see your files
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screens
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screens
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screens
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screens
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how does it work?
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data stored in the p2p network
users’s computer can be offline
how to ensure availability
(persistent storage)?
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two approaches
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two approaches
1. make sure the data is always
in the network
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two approaches
1. make sure the data is always
in the networkmove the data when a computer goes offline
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two approaches
1. make sure the data is always
in the networkmove the data when a computer goes offline
bad idea for lots of data and high churn rate
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two approaches
1. make sure the data is always
in the networkmove the data when a computer goes offline
bad idea for lots of data and high churn rate
2. introduce redundancy
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redundany = replication?
p = node availability
k = redundancy factor
prep = file availability
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redundany = replication?
example
p = 0.25
k = 5
prep = 0.763 not enough
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redundany = replication?
example
p = 0.25
k = 24
prep = 0.999
unrealistic
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erasure codes
encode m fragments into n
need any m out of n to reconstruct
reed-solomon (optimal codes)
RAID storage systems
(vs. low-density-parity-check need (1+e) * m,
where e is a fixed, small constant)
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availability
p = 0.25
m = 100, n = 517, k = n/m = 5.17
pec = 0.999k = n/m = 5.17 vs. k = 24 using replication
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x
y d points
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polynomial of degree d
x
y d points
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polynomial of degree d
any d points
x
y d points
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alice stores a file
roadtrip.mpg
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alice drags roadtrip.mpg into wuala
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1. encrypted on alice’s computer (128 bit AES)
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1. encrypted on alice’s computer (128 bit AES)
2. encoded into redundant fragments
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1. encrypted on alice’s computer (128 bit AES)
2. encoded into redundant fragments
3. uploaded into the p2p network
p2p network
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1. encrypted on alice’s computer (128 bit AES)
2. encoded into redundant fragments
3. uploaded into the p2p network
p2p network
4. m fragments
uploaded onto our
servers (boostrap,
backup)
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alice shares the file with bob
alice and bob have friendship key
alice encrypts file key and exchanges it with bob
bob wants to download the file
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p2p network
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1. download subset of fragments (m)
p2p network
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1. download subset of fragments (m)
p2p network
if necessary, get
the remaining
fragments from
our servers
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1. download subset of fragments (m)
p2p network
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2. decode the file
1. download subset of fragments (m)
p2p network
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3. decrypt the file
2. decode the file
1. download subset of fragments (m)
p2p network
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bob plays roadtrip.mpg
2. decode the file
1. download subset of fragments (m)
p2p network
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p2p network
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maintenance
p2p network
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maintenance
alice’s computer checks and maintains her files
p2p network
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maintenance
alice’s computer checks and maintains her filesif necessary, it constructs new fragments and uploads them
p2p network
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maintenance
alice’s computer checks and maintains her filesif necessary, it constructs new fragments and uploads them
p2p network
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maintenance
alice’s computer checks and maintains her filesif necessary, it constructs new fragments and uploads them
p2p network
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p2p network
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p2p network
put
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p2p network
getput
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distributed hash table (DHT)
p2p network
getput
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super nodes
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storage nodes
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client nodes
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get
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get
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get
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get
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get
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download of fragments (in parallel)
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routing
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routing
napster: centralized :-(
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routing
napster: centralized :-(gnutella: flooding :-(
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routing
napster: centralized :-(gnutella: flooding :-(
chord, tapestry: structured overlay networks
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routing
napster: centralized :-(gnutella: flooding :-(
chord, tapestry: structured overlay networksO(log n) hops :-)
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routing
napster: centralized :-(gnutella: flooding :-(
chord, tapestry: structured overlay networksO(log n) hops :-)
n = # super nodes
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routing
napster: centralized :-(gnutella: flooding :-(
chord, tapestry: structured overlay networksO(log n) hops :-)
n = # super nodes
vulnerable to attacks (partitioning) :-(
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super node
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super nodeconnected to direct neighbors
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super nodeconnected to direct neighbors
plus some random links
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super nodeconnected to direct neighbors
plus some random links
random links?
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super nodeconnected to direct neighbors
plus some random links
random links? piggy-pack routing information
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number of hops depends on
![Page 103: Wuala, P2P Online Storage](https://reader034.vdocument.in/reader034/viewer/2022051514/54b94af24a7959e2078b45ff/html5/thumbnails/103.jpg)
number of hops depends on
size of the network (n)
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number of hops depends on
size of the network (n)size of the routing table (R)
![Page 105: Wuala, P2P Online Storage](https://reader034.vdocument.in/reader034/viewer/2022051514/54b94af24a7959e2078b45ff/html5/thumbnails/105.jpg)
number of hops depends on
size of the network (n)size of the routing table (R)
which itself depends on the traffic
![Page 106: Wuala, P2P Online Storage](https://reader034.vdocument.in/reader034/viewer/2022051514/54b94af24a7959e2078b45ff/html5/thumbnails/106.jpg)
number of hops depends on
size of the network (n)size of the routing table (R)
which itself depends on the trafficwe have lots of traffic due to erasure coding
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simulation results
![Page 109: Wuala, P2P Online Storage](https://reader034.vdocument.in/reader034/viewer/2022051514/54b94af24a7959e2078b45ff/html5/thumbnails/109.jpg)
simulation results
n = 106
![Page 110: Wuala, P2P Online Storage](https://reader034.vdocument.in/reader034/viewer/2022051514/54b94af24a7959e2078b45ff/html5/thumbnails/110.jpg)
simulation results
n = 106
R = 1,000: < 3 hops
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simulation results
n = 106
R = 1,000: < 3 hopsR = 100: ~5 hops
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simulation results
n = 106
R = 1,000: < 3 hopsR = 100: ~5 hops
reasonable already with moderate traffic
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small world effects(see milgram, watts & strogatz, kleinberg)
regular graph
high diameter :-(high clustering :-)
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small world effects(see milgram, watts & strogatz, kleinberg)
regular graph
high diameter :-(high clustering :-)
random graph
low diameter :-)low clustering :-(
![Page 115: Wuala, P2P Online Storage](https://reader034.vdocument.in/reader034/viewer/2022051514/54b94af24a7959e2078b45ff/html5/thumbnails/115.jpg)
small world effects(see milgram, watts & strogatz, kleinberg)
regular graph
high diameter :-(high clustering :-)
random graph
low diameter :-)low clustering :-(
mix
low diameter :-)high clustering :-)
![Page 116: Wuala, P2P Online Storage](https://reader034.vdocument.in/reader034/viewer/2022051514/54b94af24a7959e2078b45ff/html5/thumbnails/116.jpg)
routing tablen = 109, R = 10,000
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incentives, fairness
![Page 119: Wuala, P2P Online Storage](https://reader034.vdocument.in/reader034/viewer/2022051514/54b94af24a7959e2078b45ff/html5/thumbnails/119.jpg)
incentives, fairness prevent free-riding
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incentives, fairness prevent free-riding
local disk space
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incentives, fairness prevent free-riding
local disk spaceonline time
![Page 122: Wuala, P2P Online Storage](https://reader034.vdocument.in/reader034/viewer/2022051514/54b94af24a7959e2078b45ff/html5/thumbnails/122.jpg)
incentives, fairness prevent free-riding
local disk spaceonline time
upload bandwidth
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online storage = local disk space * online time
![Page 125: Wuala, P2P Online Storage](https://reader034.vdocument.in/reader034/viewer/2022051514/54b94af24a7959e2078b45ff/html5/thumbnails/125.jpg)
online storage = local disk space * online timeexample: 10 GB disk space, 70% online --> 7 GB
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online storage = local disk space * online timeexample: 10 GB disk space, 70% online --> 7 GB
we have different mechanisms to measure
![Page 127: Wuala, P2P Online Storage](https://reader034.vdocument.in/reader034/viewer/2022051514/54b94af24a7959e2078b45ff/html5/thumbnails/127.jpg)
online storage = local disk space * online timeexample: 10 GB disk space, 70% online --> 7 GB
we have different mechanisms to measure and check these two variables
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trading storage
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trading storage
only if you want to (you start with 1 GB)
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trading storage
only if you want to (you start with 1 GB)
you must be online at least 17% of the time
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trading storage
only if you want to (you start with 1 GB)
you must be online at least 17% of the time(⋲ 4 hours a day, running average)
![Page 133: Wuala, P2P Online Storage](https://reader034.vdocument.in/reader034/viewer/2022051514/54b94af24a7959e2078b45ff/html5/thumbnails/133.jpg)
trading storage
only if you want to (you start with 1 GB)
you must be online at least 17% of the time(⋲ 4 hours a day, running average)
storage can be earned on multiple computers
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upload bandwidth
the more upload bandwidth you provide,the more download bandwidth you get
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“client” storage node
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“client” storage node
asymmetric interest
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“client” storage node
asymmetric interesttit-for-tat doesn’t work :-(
![Page 138: Wuala, P2P Online Storage](https://reader034.vdocument.in/reader034/viewer/2022051514/54b94af24a7959e2078b45ff/html5/thumbnails/138.jpg)
“client” storage node
asymmetric interesttit-for-tat doesn’t work :-(
believe the software? hack it (kazaa lite) :-(
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distributed reputation systemthat is not susceptible to false reports
and other forms of cheating
Havelaar, NetEcon 2006
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distributed reputation systemthat is not susceptible to false reports
and other forms of cheating
Havelaar, NetEcon 2006
must scale well with number of transactionswe have lots of small transactions due to erasure coding
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Havelaar, NetEcon 2006
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Havelaar, NetEcon 2006
1. lots of transactions“observations”
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Havelaar, NetEcon 2006
2. every round (e.g., a week)send observations to
pre-determined neighbors (hash code)
1. lots of transactions“observations”
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Havelaar, NetEcon 2006
2. every round (e.g., a week)send observations to
pre-determined neighbors (hash code)
3. discard ego-reports, median, etc.
1. lots of transactions“observations”
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Havelaar, NetEcon 2006
2. every round (e.g., a week)send observations to
pre-determined neighbors (hash code)
3. discard ego-reports, median, etc.
4. next round, aggregate
1. lots of transactions“observations”
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Havelaar, NetEcon 2006
2. every round (e.g., a week)send observations to
pre-determined neighbors (hash code)
3. discard ego-reports, median, etc.
4. next round, aggregate
5. update reputationof storage nodes
1. lots of transactions“observations”
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Havelaar, NetEcon 2006
2. every round (e.g., a week)send observations to
pre-determined neighbors (hash code)
3. discard ego-reports, median, etc.
4. next round, aggregate
5. update reputationof storage nodes
rewarding: upload bandwidth
proportionalto reputation
1. lots of transactions“observations”
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Havelaar, NetEcon 2006
local approximation of contribution
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“client” storage node
![Page 150: Wuala, P2P Online Storage](https://reader034.vdocument.in/reader034/viewer/2022051514/54b94af24a7959e2078b45ff/html5/thumbnails/150.jpg)
“client” storage node
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“client” storage node
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“client” storage node
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“client” storage node
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“client” storage node
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“client” storage node
“flash crowd”
![Page 156: Wuala, P2P Online Storage](https://reader034.vdocument.in/reader034/viewer/2022051514/54b94af24a7959e2078b45ff/html5/thumbnails/156.jpg)
content distributionsimilar to bittorrent
tit-for-tat
some differences due toerasure codes
“client”
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encryption
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encryption
128 bit AES for encryption
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encryption
128 bit AES for encryption2048 bit RSA for authentication
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encryption
128 bit AES for encryption2048 bit RSA for authentication
all data is encrypted (file + meta data)
![Page 162: Wuala, P2P Online Storage](https://reader034.vdocument.in/reader034/viewer/2022051514/54b94af24a7959e2078b45ff/html5/thumbnails/162.jpg)
encryption
128 bit AES for encryption2048 bit RSA for authentication
all data is encrypted (file + meta data)all cryptographic operations performed locally
(i.e., on your computer)
![Page 163: Wuala, P2P Online Storage](https://reader034.vdocument.in/reader034/viewer/2022051514/54b94af24a7959e2078b45ff/html5/thumbnails/163.jpg)
Cryptree, SRDS 2006
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access control
Cryptree, SRDS 2006
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access control
cryptographic tree structure
Cryptree, SRDS 2006
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access control
cryptographic tree structureuntrusted storage
Cryptree, SRDS 2006
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access control
cryptographic tree structureuntrusted storage
doesn’t reveal who has access
Cryptree, SRDS 2006
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access control
cryptographic tree structureuntrusted storage
doesn’t reveal who has accessvery efficient for typical operations
Cryptree, SRDS 2006
![Page 169: Wuala, P2P Online Storage](https://reader034.vdocument.in/reader034/viewer/2022051514/54b94af24a7959e2078b45ff/html5/thumbnails/169.jpg)
access control
cryptographic tree structureuntrusted storage
doesn’t reveal who has accessvery efficient for typical operations
(grant access, move, etc.)
Cryptree, SRDS 2006
![Page 170: Wuala, P2P Online Storage](https://reader034.vdocument.in/reader034/viewer/2022051514/54b94af24a7959e2078b45ff/html5/thumbnails/170.jpg)
Cryptree, SRDS 2006
alice
videos
vacation roadtrip.mpg
switzerland.mpg
europe.mpg
root
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Cryptree, SRDS 2006
alice
videos
vacation roadtrip.mpg
switzerland.mpg
europe.mpg
root
claire
bob
bob doesn’t see thatclaire has also access
and vice versa
![Page 172: Wuala, P2P Online Storage](https://reader034.vdocument.in/reader034/viewer/2022051514/54b94af24a7959e2078b45ff/html5/thumbnails/172.jpg)
Cryptree, SRDS 2006
alice
videos
vacation roadtrip.mpg
switzerland.mpg
europe.mpg
root
garfield
granting access to this and all subfolders takes
just one operationall subkeys can be derived from that
parent keyclaire
bob
bob doesn’t see thatclaire has also access
and vice versa
![Page 173: Wuala, P2P Online Storage](https://reader034.vdocument.in/reader034/viewer/2022051514/54b94af24a7959e2078b45ff/html5/thumbnails/173.jpg)
demo
![Page 174: Wuala, P2P Online Storage](https://reader034.vdocument.in/reader034/viewer/2022051514/54b94af24a7959e2078b45ff/html5/thumbnails/174.jpg)
thank you!
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