Using Bitcoin Without the Internet

How to use Bitcoin without the Internet: physical bitcoins, eCash and mesh networks decrypted and explained!

Transcript

1. Bitcoin Paris Montmartre Meetup - June 17, 2026 Using Bitcoin Without the Internet Renaud Lifchitz IoT & cybersecurity Expert
2. Table of Contents 1. Why Go Without the Internet? 2. Physical Bitcoins 3. eCash 4. Mesh Networks 5. Focus on Reticulum 6. Conclusion Using Bitcoin Without the Internet - June 17, 2026 - Renaud Lifchitz 2
3. Why Go Without the Internet? Using Bitcoin Without the Internet - June 17, 2026 - Renaud Lifchitz 3
4. Why Go Without the Internet? (1/2) ▪ Billions of people live off-grid worldwide (including in France) ▪ Extreme centralisation of the Internet in the USA: ▪ DNS servers ▪ Domain names ▪ GAFAM ▪ 75% of certificate authorities: Rank Issuer Usage Market share 1 Let’s Encrypt 60.6% 64.1% 2 GlobalSign 22.3% 23.6% 3 Sectigo 5.7% 6.0% 4 GoDaddy group 3.7% 3.9% 5 DigiCert group 1.8% 1.9% (source: https://en.wikipedia.org/wiki/Certificate_authority) Using Bitcoin Without the Internet - June 17, 2026 - Renaud Lifchitz 4
5. Why Go Without the Internet? (2/2) Increasing threats to Internet neutrality: ▪ “Lying” DNS: download sites, online gambling sites ▪ IP filtering: ARCOM with IPTV during Roland-Garros and the 2026 FIFA World Cup ▪ KYC for social networks, adult sites, VPNs, … Relative fragility of the Internet, numerous outages of essential services in the last 12 months: ▪ Google Cloud / Cloudflare — June 2025 ▪ Cloudflare (DNS resolver 1.1.1.1) — July 2025 ▪ Amazon Web Services (AWS) — October 2025 ▪ Microsoft Azure (Front Door) — October 2025 ▪ Cloudflare — November 2025 ▪ YouTube / Google — December 2025 ▪ X (Twitter) — January 2026 ▪ Google Gemini — June 2026 ▪ Meta — June 2026 ▪ Microsoft Teams — June 2026 (today! 😅 ) Using Bitcoin Without the Internet - June 17, 2026 - Renaud Lifchitz 5
6. Physical Bitcoins Using Bitcoin Without the Internet - June 17, 2026 - Renaud Lifchitz 6
7. Physical Bitcoins Name Type Indicative price URL Photo Casascius (discontinued) coin ~ https://www.casascius.com/ Offline Cash NFC note ~ https://offline.cash/ Opendime USB stick €35 https://opendime.com/ Satodime NFC card €25 https://satochip.io/fr/la-carte-satodime-expliquee/ Satscard NFC card €15 https://satscard.com/ ⚠️ Legal issue for sale if pre-loaded Using Bitcoin Without the Internet - June 17, 2026 - Renaud Lifchitz 7
8. eCash Using Bitcoin Without the Internet - June 17, 2026 - Renaud Lifchitz 8
9. eCash - Principles ▪ Bearer electronic currency: tokens work like digital cash. Whoever holds the token holds the value, with no named account ▪ Privacy through blind signatures: thanks to the Chaumian protocol (David Chaum, 1980s), the issuer signs tokens without being able to link them to transactions, guaranteeing payment anonymity ▪ Backed by Bitcoin / Lightning: eCash tokens represent deposited sats. You deposit bitcoins to “mint” tokens, and redeem them to get your sats back ▪ Instant and near-free transactions: token exchanges are local and do not touch the blockchain, so they are fast and fee-free. ▪ Use cases: micro-payments, community economies, financial inclusion, and privacy preservation against traceable payments. Using Bitcoin Without the Internet - June 17, 2026 - Renaud Lifchitz 9
10. eCash - Usage This currency can be exchanged: ▪ physically (token written on paper / printed note) ▪ optically (QR code scan) ▪ via wireless networks (NFC — “tap to pay”, Bluetooth, peer-to-peer Wi-Fi, …) ▪ via the Internet, normally Using Bitcoin Without the Internet - June 17, 2026 - Renaud Lifchitz 10
11. Cashu (1/2) ▪ ⚠️ Single mint: each mint is operated by a single entity, with no distribution of trust. ▪ Lightweight and simple: minimalist protocol, easy to deploy and integrate into applications. ▪ Explicitly custodial: the user fully trusts the mint operator with their funds. ▪ Open ecosystem: multiple interoperable wallets and mints (Nutshell, Cashu.me, etc.), with a standardised protocol (NUTs). ▪ Ideal for: micro-payments, tips, Nostr integration, and rapid experimentation. Using Bitcoin Without the Internet - June 17, 2026 - Renaud Lifchitz 11
12. Cashu (2/2) Application Compatible OS URL eNuts Android, iOS https://enuts.cash Minibits Android https://www.minibits.cash Macadamia iOS https://macadamia.cash Sovran iOS https://sovran.money Cashu.me Web / Mobile (PWA) https://cashu.me Nutstash Web / Mobile (PWA) https://nutstash.app Using Bitcoin Without the Internet - June 17, 2026 - Renaud Lifchitz 12
13. Cashu with TEE Avoids “rugpulls” with recent developments that shift trust away from the mint operator ▪ The TEE solution: a mint that can neither be spied on nor tampered with ▪ A TEE (“Trusted Execution Environment”) provides an isolated, encrypted CPU zone that protects the container, code, and data against any unauthorised access, including that of cloud providers and cluster administrators ▪ Remote attestation is the key mechanism: before executing any image or delivering secrets, it verifies the integrity of the environment, confirms the TEE has not been tampered with, and that it is running the expected configuration. This allows users to verify that the mint is running precise, unmodified code. ▪ Implementations: ▪ Nutshell in Azure TEE: https://github.com/aljazceru/nutshell-azure-tee ▪ Agicash: https://agi.cash/ cf.: https://github.com/cashubtc/awesome-cashu Using Bitcoin Without the Internet - June 17, 2026 - Renaud Lifchitz 13
14. Fedimint (1/2) ▪ Federated custody (multisig): funds are collectively controlled by multiple guardians via a signature threshold. ▪ Increased resilience: no single actor can run off with the funds; majority collusion is required. ▪ Extensible modules: modular architecture allowing additional services to be added (Lightning, accounts, etc.). ▪ Community approach: designed for local communities that collectively manage their Bitcoin treasury. ▪ Ideal for: families, villages, associations seeking shared custody and distributed trust. Using Bitcoin Without the Internet - June 17, 2026 - Renaud Lifchitz 14
15. Fedmint (2/2) Application Compatible OS URL Fedi Android, Web (PWA), macOS https://www.fedi.xyz Conduit Wallet Android, iOS https://conduit.cash Ecash App Android, Desktop https://github.com/fedimint/ecash-app Vipr Wallet Web / Mobile (PWA) https://vipr.cash Harbor Desktop only https://harbor.cash Using Bitcoin Without the Internet - June 17, 2026 - Renaud Lifchitz 15
16. Mesh Networks Using Bitcoin Without the Internet - June 17, 2026 - Renaud Lifchitz 16
17. What Are They? ▪ Radio networks with medium (Bluetooth, Wi-Fi) or long range (LoRa) ▪ Peer-to-peer network ▪ Each user can act as a routing node and in turn extend the network (“network effect”) ▪ No or minimal personal identifiers (IP, IMEI, IMSI, MAC, …) ▪ Usable offline without the Internet by sending: ▪ eCash tokens: ~ 300 bytes ▪ seed phrases (intermediate temporary on-chain wallet): ~ 80 bytes ▪ pre-signed Bitcoin transactions (“PSBT”): ~ 200 bytes Using Bitcoin Without the Internet - June 17, 2026 - Renaud Lifchitz 17
18. Comparison of LoRa Mesh Networks Meshtastic Meshcore Reticulum Automatic fragmentation No Limited Yes Packet reordering No Limited Yes Encryption Optional Mandatory Mandatory Offline delivery Optional, requires a dedicated router node Yes Yes (LXMF) Maximum payload size per packet ~ 237 ~ 237 Near unlimited Radio/internet routing Optional (MQTT) Not standardised Native cf. my article “Why the Meshcore mesh network is not suitable for Bitcoiners?”: https://hackmd.io/@rlifchitz/bitcoin-meshcore-en Using Bitcoin Without the Internet - June 17, 2026 - Renaud Lifchitz 18
19. Focus on Reticulum Using Bitcoin Without the Internet - June 17, 2026 - Renaud Lifchitz 19
20. Focus on Reticulum Usable on autonomous devices (example: Lilygo T-Deck Plus) or companion (keyboard and screen offloaded to a smartphone or PC), connected via USB or Bluetooth (example: Heltec LoRa 32 V4) Using Bitcoin Without the Internet - June 17, 2026 - Renaud Lifchitz 20
21. Hosting Content on Reticulum - Nomadnet bd5f6e706ff2996c4c686eb2a6796dec:/page/index.mu Using Bitcoin Without the Internet - June 17, 2026 - Renaud Lifchitz 21
22. Reticulum Clients My preferences (far more feature-rich than Bitchat!): Mobile clients with Bluetooth mesh support in particular: ▪ Ratspeak: https://ratspeak.org/ ▪ Columba: https://columba.network/ Desktop client: ▪ MeshChatX: https://meshchatx.com/ Flash devices online without any installation: https://liamcottle.github.io/rnode-flasher/ Using Bitcoin Without the Internet - June 17, 2026 - Renaud Lifchitz 22
23. LoRa Radio Configuration ▪ There are no official recommended LoRa parameters for Reticulum ▪ Here is what I recommend for use in Europe: ▪ Centre frequency: 869.525 MHz (middle of sub-band P, allows a 10% duty cycle instead of 1%, and up to 500 mW for gateways to increase range) ▪ Other parameters (also known as “Long Fast”): ▪ BW: 250 kHz (sub-band P limit) ▪ CR: 4/5 (more error-resilient) ▪ SF: 11 (nearly the same range as SF12 but twice the throughput) ▪ power for clients: 22 dBm Using Bitcoin Without the Internet - June 17, 2026 - Renaud Lifchitz 23
24. A Bitcoin Reticulum Bridge (1/2) Using Bitcoin Without the Internet - June 17, 2026 - Renaud Lifchitz 24
25. A Bitcoin Reticulum Bridge (2/2) Bitcoin without the Internet, confidential and sovereign over Reticulum, open source code: https://github.com/nono2357/reticulum-bitcoin-bot Using Bitcoin Without the Internet - June 17, 2026 - Renaud Lifchitz 25
26. Conclusion Using Bitcoin Without the Internet - June 17, 2026 - Renaud Lifchitz 26
27. Conclusion ▪ The Internet is already greatly threatened, filtered, and fragile ▪ As is often the case, we need to prepare alternative tools BEFORE experiencing the problems — afterwards it will be too late ▪ Many individual solutions available at low cost (though heterogeneous) — let’s take advantage of them! ▪ Graphical interfaces and tutorials still need improvement Find me on Nostr: nono2357@nostr.fr 👉 Questions & discussion! Using Bitcoin Without the Internet - June 17, 2026 - Renaud Lifchitz 27