Nym: An anonymous, secure, peertopeer instant messenger

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Nym An anonymous, secure, peer-to-peer instant
messenger

• By Seth Cooper, Adam Hoel, Elliott Hoel, Jeff
  Holschuh, and Hilde Schmitt

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AOL Instant Messenger
AOL
IP Addresses
Dan Rather 162.27.1.102 Bill OReilly
24.26.105.25 John Doe 137.22.4.60
Server
Dan Rather 162.27.1.102
John Doe 137.22.4.60
Bill OReilly 24.26.105.25
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AOL Instant Messenger
AOL
IP Addresses
Dan Rather 162.27.1.102 Bill OReilly
24.26.105.25 John Doe 137.22.4.60
Server
Confidential Information
Dan Rather
John Doe
Bill OReilly
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AOL Instant Messenger
AOL
IP Addresses
Dan Rather 162.27.1.102 Bill OReilly
24.26.105.25 John Doe 137.22.4.60
Server
Confidential Information
Dan Rather
John Doe
Bill OReilly
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AOL Instant Messenger
Lawsuit
Big Tobacco
AOL
IP Addresses
Dan Rather 162.27.1.102 Bill OReilly
24.26.105.25 John Doe 137.22.4.60
Server
Dan Rather
John Doe
Bill OReilly
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AOL Instant Messenger
Big Tobacco
AOL
IP Addresses
Dan Rather 162.27.1.102 Bill OReilly
24.26.105.25 John Doe 137.22.4.60
Server
John Doe 137.22.4.60
Dan Rather
John Doe
Bill OReilly
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AOL Instant Messenger
Big Tobacco
AOL
IP Addresses
Dan Rather 162.27.1.102 Bill OReilly
24.26.105.25 John Doe 137.22.4.60
Server
Lawsuit and job loss
Dan Rather
John Doe
Bill OReilly
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Nym Not just another AIM
John Doe
Dan Rather
Amy Csizmar Dalal
Jeff Ondich
Bill OReilly
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Nym Not just another AIM
John Doe 137.22.4.60
Dan Rather 162.27.1.102
Amy Csizmar Dalal 207.251.23.142
Jeff Ondich 82.65.100.55
Bill OReilly 24.26.105.25
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Nym Not just another AIM
John Doe john_doe
Dan Rather dan_rather
Amy Csizmar Dalal amy_csizmar_dalal
Jeff Ondich jeff_ondich
Bill OReilly bill_oreilly
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Nym Not just another AIM
John Doe john_doe
Dan Rather dan_rather
Confidential Information
To dan_rather
To bill_oreilly
Bill OReilly bill_oreilly
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Nym Not just another AIM
John Doe john_doe
Dan Rather dan_rather
Confidential Information
To bill_oreilly
Bill OReilly bill_oreilly
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Nym Not just another AIM
John Doe john_doe
Dan Rather dan_rather
Big Tobacco
Job Safe
Lawsuit
?
Bill OReilly bill_oreilly
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Goals

• Implement a peer-to-peer network that provides
• Decentralization
• Anonymity
• Security
• Reliability
• Scalability

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Decentralization

• Significantly minimize the applications reliance
  on a central server
• Peer-to-peer communication
• Normally centralized tasks are distributed among
  nodes

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Decentralization in Nym

• Message routing, searching, presence updates and
  text messaging functionality occurs between peers
  without the help of any central servers.
• However, on first launch a client connects to a
  node that caches the IP addresses of other Nym
  clients.

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Anonymity

• Anonymity is the state of having an undisclosed
  identity.
• On a network, anonymous communication must ensure
  that information related to the source of a
  message (e.g. the originating machines IP
  address) cannot be determined.

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Why is anonymity important?

• According to the Electronic Frontier Foundation
• Anonymity is a shield from the tyranny of the
  majority...It thus exemplifies the purpose behind
  the Bill of Rights, and of the First Amendment in
  particular to protect unpopular individuals from
  retaliationat the hand of an intolerant society.

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Anonymity in Nym

• Pseudonyms
• Virtual addressing
• Decentralization
• Security
• Nondeterministic/probabilistic routing

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Routing Demo
Node B
Nym Network
Node A John Doe
Node D Dan Rather
Node C
Node E Bill O'Reilly
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Routing Demo
Node As Channel List Bill Dan
Node B
Nym Network
Node A John Doe
Node D Dan Rather
Node C
Node E Bill O'Reilly
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Routing Demo
Node As Channel List Bill Dan
Node B
Packet sent
Broadcast
Nym Network
Node A John Doe
Packet sent
Node D Dan Rather
Node C
Node E Bill O'Reilly
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Routing Demo
Node As Channel List Bill Dan
Broadcast
Packet sent
Node B
Packet sent
Broadcast
Nym Network
Node A John Doe
Packet sent
Broadcast
Node D Dan Rather
Packet sent
Node C
Node E Bill O'Reilly
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Routing Demo
Node As Channel List Bill Dan
Broadcast
Packet sent
Node B
Packet sent
Broadcast
Nym Network
Node A John Doe
Packet received
Packet sent
Broadcast
Node D Dan Rather
Packet sent
Node C
Node E Bill O'Reilly
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Routing Demo
Node As Channel List Bill Dan
Node B
Nym Network
Response packet sent
Node A John Doe
Node D Dan Rather
Node C
Node E Bill O'Reilly
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Routing Demo
Node As Channel List Bill Dan
Packet sent
Node B
Nym Network
Response packet sent
Node A John Doe
Node D Dan Rather
Node C
Node E Bill O'Reilly
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Routing Demo
Node As Channel List Bill Dan
Packet sent
Packet sent
Node B
Nym Network
Response packet sent
Node A John Doe
Node D Dan Rather
Node C
Node E Bill O'Reilly
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Routing Demo
Node As Channel List Bill Dan B
Packet sent
Packet sent
Node B
Nym Network
Packet received
Response packet sent
Node A John Doe
Node D Dan Rather
Node C
Node E Bill O'Reilly
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Routing Demo
Node As Channel List Bill Dan B
Node B
Nym Network
Node A John Doe
Node D Dan Rather
Node C
Node E Bill O'Reilly
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Routing Demo
Node As Channel List Bill Dan B
Node B
Nym Network
Packet sent
Node A John Doe
Node D Dan Rather
Node C
Node E Bill O'Reilly
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Routing Demo
Node As Channel List Bill Dan B
Node B
Nym Network
Packet sent
Node A John Doe
Node D Dan Rather
Packet sent
Node C
Node E Bill O'Reilly
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Routing Demo
Node As Channel List Bill Dan B
Node B
Nym Network
Packet sent
Node A John Doe
Packet sent
Node D Dan Rather
Packet sent
Node C
Node E Bill O'Reilly
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Routing Demo
Node As Channel List Bill Dan B C
Node B
Nym Network
Packet received
Packet sent
Node A John Doe
Packet sent
Node D Dan Rather
Packet sent
Node C
Node E Bill O'Reilly
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Routing Demo
Node As Channel List Bill Dan B C
Node B
Packet sent
Broadcast
Nym Network
Node A John Doe
Packet sent
Node D Dan Rather
Node C
Node E Bill O'Reilly
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Routing Demo
Node As Channel List Bill Dan B C
Broadcast
Packet sent
Node B
Packet sent
Broadcast
Nym Network
Node A John Doe
Packet sent
Broadcast
Node D Dan Rather
Packet sent
Node C
Packet received
Node E Bill O'Reilly
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Routing Demo
Node As Channel List Bill Dan B C
Node B
Nym Network
Node A John Doe
Node D Dan Rather
Response packet sent
Node C
Node E Bill O'Reilly
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Routing Demo
Node As Channel List Bill Dan B C
Node B
Nym Network
Node A John Doe
Node D Dan Rather
Packet sent
Response packet sent
Node C
Node E Bill O'Reilly
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Routing Demo
Node As Channel List Bill Dan B C
Node B
Nym Network
Node A John Doe
Packet sent
Node D Dan Rather
Packet sent
Response packet sent
Node C
Node E Bill O'Reilly
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Routing Demo
Node As Channel List Bill Dan C B C
Node B
Nym Network
Packet received
Node A John Doe
Packet sent
Node D Dan Rather
Packet sent
Response packet sent
Node C
Node E Bill O'Reilly
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Routing Demo
Node As Channel List Bill Dan C B C
Node B
Nym Network
Node A John Doe
Node D Dan Rather
Node C
Node E Bill O'Reilly
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The channel list builds up
Node As Channel List Bill Dan C B B
C C C B C
Node B
Nym Network
Node A John Doe
Node D Dan Rather
Node C
Node E Bill O'Reilly
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Now, we can route!
Node As Channel List Bill Dan C B B
C C C B C
Node B
Nym Network
Node A John Doe
Node D Dan Rather
Node C
Node E Bill O'Reilly
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Now, we can route!
Node As Channel List Bill Dan C B B
C C C B C
Select a node at random from the Dan column
Node B
Nym Network
Node A John Doe
Node D Dan Rather
Node C
Node E Bill O'Reilly
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Now, we can route!
Node As Channel List Bill Dan C B B
C C C B C
So send to node C
Node B
Nym Network
Node A John Doe
Node D Dan Rather
Node C
Node E Bill O'Reilly
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Note that there is a natural weighting of nodes
in the list
Node As Channel List Bill Dan C B B
C C C B C
This means that there are preferred routes.
Node B
Nym Network
Node A John Doe
Node D Dan Rather
Node C
Node E Bill O'Reilly
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Sometimes, we pick at random from an unweighted
channel list
Node As Channel List Bill Dan C B B
C C C B C
This prevents any routing patterns that may occur.
Node B
Nym Network
Node A John Doe
Node D Dan Rather
Node C
Node E Bill O'Reilly
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Security

• Confidentiality
• Information should be kept secret from
  unauthorized parties.
• Integrity
• Information should be tamper evident.
• The authenticity of the source of information
  should be verifiable.
• Availability
• Services should be resilient to malicious attacks

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Security in Nym

• Link-to-link encryption
• Digital signing and verifying of text messages

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Link-to-link versus end-to-end

• Link-to-link encryption
• Messages are encrypted and decrypted at each node
  in the network
• Messages intercepted by parties outside the
  network will be unable to read the encrypted text
• End-to-end encryption
• Messages are encrypted with a secret key by the
  sender and are not decrypted until they reach the
  recipient

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The Man-in-the-Middle

• Secure end-to-end encryption is impossible in an
  anonymous network
• An intermediary node between the sender and
  recipient can easily intercept a key exchange.
• Link-to-link encryption
• More robust against man in the middle attacks

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Link to link (Symmetric key)

• A 56-bit DES key is generated and exchanged when
  a connection is made with a neighbor
• Both parties share this key, but no one else
  knows it
• Much quicker than asymmetric encryption

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RSA public/private key pair

• RSA key pair is generated from username and
  password
• Public key is essentially the virtual address
• Asymmetric key pair is only used for digital
  signatures
• To send a message to someone, sign it with your
  private key
• The recipient uses your public key to validate it

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Digital Signatures

• Allow us to verify
• who a message is from
• that the message has not been changed since it
  was sent
• Use the SHA-1 hash algorithm
• Takes the message (under 264 bits)
• Returns 160 bit message digest
• Use RSA key pair

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How digital signatures work
At Login
User A
User B
Public Key A
Public Key B
Username A
Username B
Private Key A
Private Key B
Password A
Password B
Virtual Address A
Virtual Address B
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How digital signatures work
User A
User B
Public Key A
Private Key A
Private Key B
Public Key B
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How digital signatures work
User A
User B
Message text
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How digital signatures work
User A
User B
Message text
SHA-1
Message digest
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How digital signatures work
User A
User B
Message text
SHA-1
Encrypt with Private key A
Message digest
Digital signature
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How digital signatures work
User A
User B
Message
Message text
SHA-1
Encrypt with Private key A
Message digest
Digital signature
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How digital signatures work
User A
User B
Message
Digital signature
Message text
Message
Message text
SHA-1
Encrypt with Private key A
Message digest
Digital signature
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How digital signatures work
User A
User B
Message
Digital signature
Message text
Message
Message text
SHA-1
SHA-1
Message digest
Encrypt with Private key A
Message digest
Digital signature
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How digital signatures work
User A
User B
Message
Digital signature
Message text
Decrypt with Public key A
Message
Message text
SHA-1
SHA-1
Message digest
Message digest
Encrypt with Private key A
Message digest
Digital signature
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How digital signatures work
User A
User B
Message
Digital signature
Message text
Decrypt with Public key A
Message
Message text
SHA-1
SHA-1
Message digest
Message digest
Encrypt with Private key A
Message digest
Digital signature
Compare
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Instant Messaging

• Text communication
• Presence notification
• Contact list maintenance
• Distributed search
• User friendly interface

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DEMO
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Tradeoffs and Limitations

• Anonymity
• Statistical analysis
• Textual analysis
• Accidental disclosure
• Scalability
• Test results and predictions
• Reliability
• Routing loop avoidance

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Extensions

• Increased fault tolerance for dropped packets and
  routing loops
• Group chat
• Testing and research on anonymity scheme

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Acknowledgements

• Amy Csizmar Dalal and the CS department for
  guidance and support
• Michael N. Tie and ITS for helping make our
  equipment work
• MUTE and Jason Rohrer
• Our friends and family for putting up with us
• You all for being here today

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References

• Rohrer, Jason. MUTE Technical Details
  http//mute-net.sourceforge.net/technicalDetails.s
  html
• http//www.bouncycastle.org/
• Sun Microsystems http//java.sun.com
• Freenet http//freenet.sourceforge.net
• RFC 3921 XMPP http//www.xmpp.org
• The Gnutella Protocol Specification v0.4
  http//www9.limewire.com/developer/gnutella_protoc
  ol_0.4.pdf