mirror of https://gitlab.com/yawning/obfs4
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49 lines
1.8 KiB
Markdown
49 lines
1.8 KiB
Markdown
## obfs4 - The obfourscator
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#### Yawning Angel (yawning at torproject dot org)
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### What?
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This is a look-like nothing obfuscation protocol that incorporates ideas and
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concepts from Philipp Winter's ScrambleSuit protocol. The obfs naming was
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chosen primarily because it was shorter, in terms of protocol ancestery obfs4
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is much closer to ScrambleSuit than obfs2/obfs3.
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The notable differences between ScrambleSuit and obfs4:
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* The handshake always does a full key exchange (no such thing as a Session
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Ticket Handshake).
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* The handshake uses the Tor Project's ntor handshake with public keys
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obfuscated via the Elligator 2 mapping.
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* The link layer encryption uses NaCl secret boxes (Poly1305/XSalsa20).
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As an added bonus, obfs4proxy also supports acting as an obfs2/3 client and
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bridge to ease the transition to the new protocol.
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### Why not extend ScrambleSuit?
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It's my protocol and I'll obfuscate if I want to.
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Since a lot of the changes are to the handshaking process, it didn't make sense
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to extend ScrambleSuit as writing a server implementation that supported both
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handshake variants without being obscenely slow is non-trivial.
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### Dependencies
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Build time library dependencies are handled by go get automatically but are
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listed for clarity.
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* Go 1.2.0 or later. Debian stable packages Go 1.0.2 which is missing several
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things obfs4 depends on like SHA256.
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* go.crypto (https://code.google.com/p/go.crypto)
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* go.net (https://code.google.com/p/go.net)
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* ed25519/extra25519 (https://github.com/agl/ed25519/extra25519)
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* SipHash-2-4 (https://github.com/dchest/siphash)
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* goptlib (https://git.torproject.org/pluggable-transports/goptlib.git)
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### Thanks
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* David Fifield for goptlib.
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* Adam Langley for his Elligator implementation.
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* Philipp Winter for the ScrambleSuit protocol which provided much of the
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design.
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