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Encrypted peer-to-peer messaging over Bluetooth mesh networks.

No internet. No servers. No carrier. No account. Just radios talking to radios.

Overview

Hoppr is a messaging platform engineered for environments where internet access is unavailable, degraded, or untrusted. Messages propagate device-to-device through a Bluetooth Low Energy mesh, requiring no centralized infrastructure, accounts, or identifiers.

Vision

Decentralisation has come in layers. Each one removed a dependency.

2009Bitcoinmoney without banks
2022Nostrspeech without platforms
2026Hopprmessaging without the internet

Bitcoin freed value from custodians. Nostr freed identity and publication from centralised hosts. Hoppr removes the last assumption: that a network has to exist at all. A phone without service, a city under blackout, a protest, a festival, a desert. The mesh still carries.

The same Bluetooth radio your device already has, used the way radios were always meant to be used: direct, local, and unowned.

Architecture

Devices within Bluetooth range establish peer sessions automatically.
Messages are relayed hop-by-hop through intermediate nodes toward the recipient.
All traffic is end-to-end encrypted using the Noise XX handshake pattern with Curve25519, ChaCha20-Poly1305, and Ed25519 signatures.

Reach Analysis

In a mesh of N devices with average node degree d, a gossip packet propagates to all peers in expected O(log_d N) hops. Under an asynchronous flood at uniform density, the expected number of devices reached after h hops is bounded by:

E[R(h)]  =  min( N ,  d · (d−1)^h−1 )

Field example. Five peers on average within Bluetooth Low Energy range (d = 5), default TTL of seven hops (h = 7):

E[R]  =  min( N ,  5 · 4⁶ )  =  20 480 devices

Duplicate packets are suppressed per device by a bounded LRU cache of 1000 recent message identifiers with a five-minute expiry. Lookups are O(1) and deterministic. To reconcile missed messages between peers on reconnection, each node exchanges a 400-byte Golomb-Coded Set summarising what it has seen. For a GCS encoding n elements at target false-positive rate p, the expected bits per element is:

bits / element  ≈  log₂( 1 / p )  +  1 / ln 2

Field example. With n = 200 recent identifiers and p = 0.01, each device advertises roughly 200 · 8 ≈ 1600 bits of state, or about 200 B encoded. Under 1% false-positive pressure, a 400-byte summary carries on the order of 400 message identifiers before a peer must ask for the full set.

In practical terms: a packet released into a moderately dense mesh reaches thousands of devices within seconds of radio time, while each individual device rejects duplicates exactly, and missed messages are healed on reconnection through a sync envelope smaller than a single TCP segment.

Capabilities

Mesh-first architecture. Built on the transport layer. Social graphs, feeds, and recommendation systems are absent by design.
End-to-end encryption. 1:1 direct messages use a Noise XX handshake. Mesh broadcasts are signed packets. Nostr fallback uses NIP-17 gift-wrap.
Dual transport. Automatic fallback to Nostr relays routed over the Tor network (via Arti) when mesh connectivity is unavailable.
Adaptive relay control. Seven-hop default TTL with probabilistic forwarding at elevated peer density to conserve battery without reducing reach.
GCS gossip sync. A 400-byte Golomb-Coded Set reconciles missed messages between peers on reconnection at a 1% false-positive rate.
QR peer verification. On-device live-camera scan compares Ed25519 and Noise identity fingerprints before a session is trusted.
Geohash channels. Location-scoped public rooms and location notes ride the Nostr transport.
Panic wipe. A single gesture destroys keys, message caches, and identity state on the device.
Slash commands. IRC-style controls: /who, /fav, /block, /unblock, /me, /slap, /help.
Payment chip detection. Lightning bolt11, LNURL, and Cashu tokens are recognised inline and tappable to open a wallet. Sending is not yet implemented.
iOS Share Extension. Share text and links from Safari or any app directly into the mesh.
Native macOS app. Same codebase. Shipping since v1.5.
Efficient runtime. Approximately 12 MB installed footprint. Cold launch under 400 ms on iPhone 12.
Data minimization. No telemetry, crash reports, or advertising identifiers are transmitted from client devices.

Roadmap

v1.6Settings screen with opt-in light mode and Tor-enforce toggle.2 to 3 days
v1.7Reactions via NIP-25 and a new Noise payload type.1 week
v1.8Reply threads. Groundwork for moderated groups.1 to 2 weeks
v1.9Disappearing DMs with per-peer TTL and NIP-40 support.1 week
v2.0NIP-57 zaps, receive path first.1 to 2 weeks
v2.1Voice notes and images in Nostr DMs and geohash channels.2 to 3 weeks
v2.2NIP-47 Nostr Wallet Connect for Lightning send.2 to 3 weeks

Every release is signed. Pre-release builds are not distributed outside of closed testing programmes.

Technical Specifications

Transport: Bluetooth Low Energy mesh
1:1 DMs: Noise XX handshake
Mesh packets: Signed broadcast
Key agreement: X25519 (Curve25519)
Encryption: ChaCha20-Poly1305
Signing: Ed25519. secp256k1 Schnorr for Nostr
Hashing: SHA-256
TTL: 7 hops default. Fragment-relay cap 5
Dedup cache: LRU 1000 entries. 5 min expiry
Gossip sync: 400 B Golomb-Coded Set. 1% FPR
Voice codec: AAC. M4A. 16 kHz mono 16 kbps
Online relay: Nostr via Tor (Arti)

Availability

iOS . App Store coming soon
iPadOS . universal iOS binary coming soon
macOS . App Store coming soon
macOS . direct download coming soon