Carrier obfuscation

By default the UDP payload on the wire is the bare salt ++ AEAD envelope. The optional obfs field shapes that payload so it doesn't read as an opaque random-looking UDP blob, to evade naive protocol classification. It is selected with the obfs config field and both ends must agree — a mismatched peer just sees its traffic dropped.

Cosmetic framing only

This adds no security. The AEAD envelope underneath is unchanged, and a wrong/absent obfuscation simply fails to decode (the packet is dropped before decryption).

Modes

obfs	On the wire	Note
none	the plain salt ++ AEAD datagram (default)	—
quic	each datagram is wrapped as a QUIC 1-RTT short-header packet, so it reads as HTTP/3	adds a few header bytes; self-describing decode
base64	each datagram is standard base64, so the UDP payload is printable ASCII	~33% larger — size the mtu down to compensate

Configuration

Set it in both config files (it has no CLI flag):

{
  "server": "vpn.example.com:8388",
  "password": "correct horse battery staple",
  "obfs": "quic"
}

The server logs the active mode in its startup banner. The wire formats are documented in src/obfs.rs.

Impact on throughput

Negligible for quic framing at broadband rates — see the benchmarks, which include a chacha20-poly1305 / quic row within noise of the unobfuscated run. base64 grows the payload ~33%, so lower the tunnel mtu to keep the outer datagram under the path MTU.