rns-covert-transport 0.1.3

Reticulum Network Stack interfaces for censorship-resistant communication over everyday services

rns-covert-transport

Reticulum Network Stack interfaces for censorship-resistant communication over everyday services.

When internet access is restricted to a whitelist of state-approved services, when VPNs are blocked, when DPI is deployed at every ISP, and when the authorities hold a kill switch for the entire network, people still need a way to communicate securely. This project provides that way.

rns-covert-transport implements custom interfaces for the Reticulum Network Stack that tunnel encrypted packets through ordinary services -- services that censors cannot easily block without disrupting the economy.

Inspired by Delta Chat, which turns email into a messenger.

How It Works

Reticulum encrypts all traffic by default. No unencrypted packets can exist on the network. Forward secrecy is standard. Packets carry no source addresses.

This project takes those encrypted packets and disguises them as normal service traffic:

Reticulum packet (encrypted, fixed-size, no source address)
    -> HDLC frame
    -> pad to fixed size (every packet identical length)
    -> send as email attachment / API message / cloud file
    -> peer polls, extracts, unpads, deframes
    -> Reticulum processes the packet

An observer sees ordinary emails between two accounts. The attachments are opaque binary blobs, indistinguishable from compressed archives, scanned documents, or backup files. Every attachment is exactly the same size. Subject lines, filenames, and body text are generated from pools of locale- appropriate correspondence patterns.

Available Transports

Transport	Protocol	Tested With	Status
MailInterface	IMAP/SMTP	Yandex Mail, Gmail	Working, tested

The MailInterface works with any email provider that supports standard IMAP and SMTP over SSL. Additional transports (VKontakte, Yandex.Disk, cloud storage APIs) can be built on the same base class. See CONTRIBUTING.md.

Requirements

• Python 3.8+
• Reticulum Network Stack (rns package)
• Two email accounts on the target service (one per node)

Installation

pip install rns-covert-transport

Or from source:

git clone https://github.com/TechVoid-Co/rns-covert-transport
cd rns-covert-transport
pip install -e .

Quick Start

1. Create two email accounts

Use any provider with IMAP/SMTP support. Dedicated accounts only -- do not use personal email.

Tested providers:

• Yandex Mail (mail.yandex.ru) -- enable IMAP in settings
• Gmail (gmail.com) -- generate app password at myaccount.google.com/apppasswords
• Mail.ru, Outlook, or any standard IMAP/SMTP server

2. Install the interface

mkdir -p ~/.reticulum/interfaces
cp rns_covert/interfaces/MailInterface.py ~/.reticulum/interfaces/

3. Configure Node A

Edit ~/.reticulum/config:

[reticulum]
  enable_transport = no
  share_instance = yes

[interfaces]
  [[Mail Transport]]
    type = MailInterface
    enabled = yes
    account = [e-mail]
    password = app_password_here
    peer_address = [e-mail]
    imap_host = imap.yandex.ru
    smtp_host = smtp.yandex.ru
    locale = ru
    encoding = blob
    inner_size = 1280
    poll_interval = 30
    max_sends_per_hour = 30
    batch_window = 5

4. Configure Node B

Same configuration with account and peer_address swapped.

5. Start both nodes

rnsd -v

Use Sideband, LXMF, rncp, rnprobe, or any Reticulum application to communicate.

Configuration Reference

Option	Default	Description
account	(required)	Email address for this node
password	(required)	App-specific password
peer_address	(required)	Email address of the peer node
imap_host	(required)	IMAP server hostname
smtp_host	(required)	SMTP server hostname
imap_port	993	IMAP port (SSL)
smtp_port	465	SMTP port (SSL)
locale	ru	Email camouflage language: ru, en, neutral
encoding	blob	blob (binary attachment) or base64 (text body)
inner_size	1280	Fixed payload size in bytes. Both peers must match.
poll_interval	30	Seconds between inbox checks
max_sends_per_hour	30	Rate limit for outbound emails
batch_window	5	Seconds to collect packets before sending one email
cleanup	yes	Move processed emails to subfolder
retry_delay	60	Seconds before reconnection attempt after failure

Locale Reference

Locale	Language	Subject/filename examples
ru	Russian	"Счёт-фактура №А-4821", "договор_1234.docx"
en	English	"Invoice #4821", "contract_1234.docx"
neutral	ASCII-only	"Re: #4821", "doc_1234.pdf"

Provider Quick Reference

Provider	imap_host	smtp_host	Notes
Yandex	imap.yandex.ru	smtp.yandex.ru	Enable IMAP in settings. 500 emails/day.
Gmail	imap.gmail.com	smtp.gmail.com	App password required. 500 emails/day.
Mail.ru	imap.mail.ru	smtp.mail.ru	Enable IMAP in settings.
Outlook	outlook.office365.com	smtp.office365.com	App password required. Port 587 for SMTP.

Architecture

rns_covert/
  base.py                   Base class for all covert interfaces.
                            HDLC framing, fixed-size padding, packet
                            batching, rate limiting, poll loops,
                            error recovery.

  locale.py                 Email camouflage locales (ru, en, neutral).

  encoding/
    strategies.py           Encoding strategies (blob, base64).

  interfaces/
    mail.py                 IMAP/SMTP transport implementation.
    MailInterface.py        Drop-in for ~/.reticulum/interfaces/

Security Properties

Provided by Reticulum (not this project):

• End-to-end encryption (X25519 + AES-256)
• Forward secrecy (ephemeral keys)
• No source addresses on any packet
• Unforgeable delivery proofs

Provided by this project:

• Fixed-size padding: every email attachment is identical in size regardless of payload. Traffic analysis based on packet length is not possible.
• Locale-appropriate camouflage: email subjects, filenames, and body text are drawn from pools of realistic correspondence patterns for the configured language.
• Rate limiting and batching: traffic patterns are controlled to stay within provider limits and avoid triggering spam detection.
• Idle silence: no traffic is generated when there is nothing to send.

Not provided (known limitations):

• Timing analysis is possible for an adversary with access to both mail servers.
• Email metadata (headers, timestamps, routing) is visible to the mail server operator.
• Sustained high-volume communication between two accounts is detectable regardless of content.

See SECURITY.md for the full threat model.

License

Apache-2.0 License. See LICENSE.

Related Projects

• Reticulum -- Cryptography-based networking stack
• Delta Chat -- Messenger over email
• LXMF -- Delay-tolerant messaging over Reticulum
• Sideband -- Reticulum messenger application