projecttox: free as in freedom skype replacement

ProjectTox Free as in freedom Skype

replacement

Wei-Ning Huang (AZ)

About the Speaker • 正在水深火熱中的碩二學生

• 熱愛Python及Open Source

• Involved open source projects: o Gummi LaTeX Editor

o cppman

o PyTox

o ProjectTox-Core

o Toxic

o jToxcore

o …

• More info: http://azhuang.me

http://azhuang.me/

http://azhuang.me/

Outline • What is Tox?

• Functionality

• Architecture and Design

• Pitfalls and Solutions

• In Progress Features

• Client and Bindings

• Live Demo

What is anyway?

What is anyway? • FOSS messaging network, supports A/V (GPLv3)


• Decentralized architecture



• End-to-end encryption




• Configuration free (does not require registration)





• Secure and easy to use





• Secure and easy to use

• A Skype replacement

Why are we doing this?

Why are we doing this? 4chan/g/


馬卡茸表示：如果沒做錯事，就不用怕監聽!

圖片來自插畫家謝立聖




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憲法第十二條：「人民有祕密通訊之自由」

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Why are we doing this? • We want a free(as in Freedom) and secure

alternative for , since it is “Microsofted”....



• "We don't want to be the next secure chatting program, we want to be the next secure chatting program that people actually use." - Someone on IRC



• "We don't want to be the next secure chatting program, we want to be the next secure chatting program that people actually use." - Someone on IRC

• Current secure chat programs aren't easy to use, at least not for our parents and grandparents normal people

Who started this?

Who started this? • irungentoo

o Real identity is a mystery :P

o Most of the code is implemented by him




• Project started up Jun 23, 2013




• Project started up Jun 23, 2013

• There are currently about 10 active tox.im developers, including me.

Architecture and Design

Architecture and Design • Separated core and client, Tox is a library.


• Current implemented features in core:


• Current implemented features in core: o Text messages

• Read receipt

• Typing status



• Read receipt

• Typing status

o File transfer (way faster than Skype)



• Read receipt

• Typing status


o Group chat (IRC-like, currently invitation only)



• Read receipt

• Typing status



o Audio / Video call support

• Currently only 1-to-1 call supported

• 1-to-many and many-to-many support on the way!



• Read receipt

• Typing status



o Audio / Video call support

• Currently only 1-to-1 call supported

• 1-to-many and many-to-many support on the way!

o All communication between clients are encrypted.

DHT • Distributed Hash Table similar to BitTorrent


• Hash table contains ID to IP-Port mapping


• Hash table contains ID to IP-Port mapping

Bootstrap Server

Client

NAT

Client Client

LAN Discovery

Client

Client Boostrap

Hole punching

NAT

Friend Requests

Friend Requests • Friend requests are routed between clients


• Client list or a list of clients whose ID are mathematically (XOR) closest to us


• Client list or a list of clients whose ID are mathematically (XOR) closest to us

Alice

Jack

Lucy

Bob

Request

Request

Got Alice’s IP_Port

Using the UDP Protocal • Using UDP, easier for hole punching


• A Lossless UDP protocol on top of UDP



• Allow packet drop for A/V data packet



• Allow packet drop for A/V data packet

• NAT Traversal: Most NAT works, but symmetric NAT are problematic for now

Encryption • Using Elliptic Curve Cryptography

o Short key length, but still secure



• Using NaCl (Networking and Cryptography library)



• Using NaCl (Networking and Cryptography library) o libsodium is prefered




o crypto_box: curve25519xsalsa20poly1305

• curve25519 for Key exchange

• xsalsa20 for encryption

• poly1305 for message authentication




o crypto_box: curve25519xsalsa20poly1305

• curve25519 for Key exchange

• xsalsa20 for encryption

• poly1305 for message authentication

• ID == Public Key o Example ID:

4E9D1B82DEE3BD3D4DDA62190873EA40737251A43445E4D517E66230BC4507233533EDD01F24

Pitfalls and Solutions

Pitfalls and Solutions • Attack against DHT

o Sybil attacks: attacker with large resource (e.g. governments) can create a large number of pseudo nodes that does nothing or disrupt network.



• Metadata Leaking o When routing friend requests, nodes leaks information

about the request’s ID and IP mapping.

o Possible to identify a users’s real identity with IP



• Metadata Leaking o When routing friend requests, nodes leaks information

about the request’s ID and IP mapping.

o Possible to identify a users’s real identity with IP

• How do we safely exchange ID (Public Key) o Key being swap by a MITM?

Solutions • Attack against DHT

o Periodically check all client’s behavior to see if it’s a bad node.

o The criteria of a good node is strict.




• Metadata Leaking o Don’t use their long term keypair in DHT, generate a

temporary one when sending friend requests.

o Onion routing for friend requests




• Metadata Leaking o Don’t use their long term keypair in DHT, generate a

temporary one when sending friend requests.

o Onion routing for friend requests

• How do we safely exchange ID (Public Key) o DNS lookup!

DNS User Discovery

mailto:[email protected]

DNS User Discovery • Use DNS TXT record to store the ID, for example:

o tox://[email protected] will be mapped to at TXT record ‘tox1._tox.azhuang.me’




o ‘v=tox1;id=4E9D1B82DEE3BD3D4DDA62190873EA40737251A43445E4D517E66230BC4507233533EDD01F24’





• To prevent DNS poisoning or MITM, use the tox2 protocol (requires a extra pin): o 'v=tox2;pub=4E9D1B82DEE3BD3D4DDA62190873EA407372

51A43445E4D517E66230BC450723;check=1F24‘





• To prevent DNS poisoning or MITM, use the tox2 protocol (requires a extra pin): o 'v=tox2;pub=4E9D1B82DEE3BD3D4DDA62190873EA407372

51A43445E4D517E66230BC450723;check=1F24‘

• tox.se will be available for the public


In Progress Features

In Progress Features • DHT Hardening

o Research for more attach patterns



• TCP Server o Route traffic for clients behind symmetric NAT or

enterprise firewalls

o Act like a “Super node” in the Skype network



• TCP Server o Route traffic for clients behind symmetric NAT or

enterprise firewalls

o Act like a “Super node” in the Skype network

• A/V improvements o Congestion control and variable bitrate support

o A/V synchronization

Clients and Bindings

Clients and Bindings • Support most platforms


o Windows, Linux, Mac

• Toxic (Ncurses CLI), has audio call support

• Venom (Vala with GTK+)

• Poison (MacOS only)






o Mobile

• AnTox (Android), supports QR code scanning

• Toxicity (iOS)






o Mobile

• AnTox (Android), supports QR code scanning

• Toxicity (iOS)

• Language bindings: o Python: PyTox (full A/V support)

o jTorecore: used in Antox

How to use? • Just launch any client, and it will generate a

public/private key pair for you



• No login required




• Send your public key to you friends





• Add you friends with their public key





• Add you friends with their public key

• Start chatting!

PyTox • CDD (Conference Driven Developemnt)


• No A/V support 2 days ago… o The video implementation in core even has some critical

bugs



bugs

• Full A/V support implemented before OSDC.tw!



bugs

• Full A/V support implemented before OSDC.tw!

• Leverage the power of Python o An EchoBot can be implement in less than 50 lines of

Python code

o SyncBot: a PoC of PyTox, syncing messages between Tox groupchat and freenode #tox-ontopic

Live Demo

Join Us! • Wiki:

o http://wiki.tox.im/

• Github: o ProjectTox-Core:

https://github.com/irungentoo/ProjectTox-Core

o PyTox: https://github.com/aitjcize/PyTox

• Freenode IRC o #tox, #tox-dev, #tox-ontopic

http://wiki.tox.im/

http://wiki.tox.im/

http://wiki.tox.im/









https://github.com/aitjcize/PyTox






projecttox: free as in freedom skype replacement

Technology