Transcript ppt - cryptic6

6° of Darkness
or
Using Webs of Trust to Solve
the Problem of Global Indexes
The problem
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Most P2P networks are insecure
Thus they are susceptible to lawsuits
Napster
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Centralized servers
Easily taken down
Gnutella
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Decentralized
Still possible to glean IP addresses of the
individual nodes
KaZaA
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Much more efficient
Uses supernodes to route traffic
Hundred of users have been sued
Direct Connect
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Uses hubs and has large minimum share
sizes
Bittorrent
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Each file must be hosted by a tracker and
then is forwarded though a chain of
downloaders/uploaders
Bittorrent
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If the tracker goes down, the other nodes
have no way of finding each other
The IP address of the tracker is easily traced
WASTE
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A truly secure network with rings of
encryption
WASTE
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The problem is that these two networks
cannot communicate with each other
WASTE
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The reason why other P2P networks are so
popular is because you can share files with
people you don't personally know
A New Network
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What is needed is a network that will allow
you to share files with people you don't know,
without revealing your identity to them.
A little history
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In 1967 Stanly Milgrim published an article
entitled “The Small World Phenomenon” in
Psychology Today
A little history
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In 1967 Stanly Milgrim published an article
entitled “The Small World Phenomenon” in
Psychology Today
He concluded that most people in the world
were connected to each other by a chain of
six friends
A little history
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In 1967 Stanly Milgrim published an article
entitled “The Small World Phenomenon” in
Psychology Today
He concluded that most people in the world
were connected to each other by a chain of
six friends
It was from this and later studies that the
popular idea of Six Degrees of separation
came from
A little history
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There has been some debate about whether
the average of six connections between any
two people holds true throughout the world,
but physiologists agree that are a lot of
subnetworks with people being connected by
an average of six or even fewer friends
Six Degrees
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It may be possible to create a secure
anonymous network on this principle
Six Degrees
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Instead of sharing files with anyone who asks
for them you will only reveal what files you
are sharing to your trusted friends
Six Degrees
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In turn they will let others know about these
files, but not reveal your IP address
So How does this Work?
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The base of the network is similar to WASTE,
and the entire protocol depends on Public
Key Cryptography
Public Key Cryptography
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Each connection in this darknet represents
an exchange of public keys
Here is my public Key
A
B
Public Key Cryptography
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If Bob put Alice's public key in his list of
trusted users (Bob has decided to trust
Alice), Alice will be able to download files
from Bob
Bob: I'll trust this key
A
B
Public Key Cryptography
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All the files Bob send to Alice will be
encrypted with Alice's public key, and no one
will be able to read them but Alice.
A
B
E
I can't read this!
Public Key Cryptography
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Assuming that Alice is kind enough to return
the favor and trust Bob, they will both be able
to access each other's files, and Eve will not
be able to eavesdrop at all.
A
B
E
I still can't read this!
Public Key Cryptography
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Supposing that Carol has a file that Alice
wants.
A
B
E
C
Public Key Cryptography
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Alice does not trust Carol, more importantly
Carol does not trust Alice, so there is no way
for Alice to know that Carol has the file
A
B
E
C
Public Key Cryptography
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If Carol trusts Bob, she will tell him what files
she has, and in turn, Bob can tell Alice
A
B
E
C
Public Key Cryptography
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Alice will then request the file from Bob, and
Bob will request the file from Carol
A
B
E
C
Public Key Cryptography
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Bob will act as proxy between Carol and
Alice, so that Carol does not have to reveal
her IP address to Alice
A
B
E
C
Public Key Cryptography
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All the while, Eve who had been trying to
eavesdrop on this transfer, can read none of
the file.
A
B
E
C
Six Degrees
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This method can scale to many users each
who only trust a few people, yet can access
the entire network
C
A
D
B
F
E
G
H
I
Six Degrees
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Of course the more people you trust (more
correctly the more people you can convince
to trust you) the faster your downloads will
be.
C
A
D
B
F
E
G
H
I
C
D
A
B
F
E
H
G
I
Problems
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If Bob is the only link between a lot of people,
file transfers between them will be very slow
C
A
B
D
F
E
G
H
I
Problems
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Bob can help solve this problem by
convincing more of his friends to trust each
other
C
A
B
D
F
E
G
H
I
C
D
A
B
F
E
H
G
I