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Wi-Fi bulk transport: AWDL data plane for large media with BLE fallback

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BLE stays the control plane: a sender with a queued file > 64 KiB to a
directly connected peer advertising the wifiBulk capability sends a
bulkTransferOffer (0x04) inside the established Noise session — transferID,
file size, payload SHA-256, a fresh 32-byte token, and a random per-transfer
Bonjour instance name. The receiver answers bulkTransferResponse (0x05) with
its own token half, then both sides meet on a per-transfer
_bitchat-bulk._tcp channel over peer-to-peer Wi-Fi (AWDL).

The TCP stream is secured independently of TLS: both tokens traveled inside
Noise, so only the two peers can derive the ChaChaPoly channel key
(HKDF-SHA256, domain "bitchat-bulk-v1", transferID as salt). Frames are
length-prefixed sealed boxes with structured direction+counter nonces; the
first frame must prove knowledge of the key or the client is disconnected,
and the final hash is verified against the offer before delivery.

Decline, timeout, or any mid-transfer error falls back to BLE fragmentation
exactly once, driving the same TransferProgressManager stream so the UI is
unchanged. Wi-Fi-negotiated transfers may carry up to 8 MiB (new
FileTransferLimits.maxWifiBulkPayloadBytes, enforced by the receiver from
the accepted offer); the BLE path keeps its existing caps.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
This commit is contained in:
jack
2026-07-06 20:35:40 +02:00
co-authored by Claude Fable 5
parent 688b954fb8
commit e4b3cff5fa
21 changed files with 2614 additions and 21 deletions
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bitchat/Protocols/BitchatProtocol.swift
+6 -1
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@@ -72,15 +72,20 @@ enum NoisePayloadType: UInt8 {
case privateMessage = 0x01 // Private chat message
case readReceipt = 0x02 // Message was read
case delivered = 0x03 // Message was delivered
// Wi-Fi bulk transport negotiation (AWDL data plane for large media)
case bulkTransferOffer = 0x04 // Offer to move a large file over peer-to-peer Wi-Fi
case bulkTransferResponse = 0x05 // Accept/decline reply to a bulk transfer offer
// Verification (QR-based OOB binding)
case verifyChallenge = 0x10 // Verification challenge
case verifyResponse = 0x11 // Verification response
var description: String {
switch self {
case .privateMessage: return "privateMessage"
case .readReceipt: return "readReceipt"
case .delivered: return "delivered"
case .bulkTransferOffer: return "bulkTransferOffer"
case .bulkTransferResponse: return "bulkTransferResponse"
case .verifyChallenge: return "verifyChallenge"
case .verifyResponse: return "verifyResponse"
}