# SooSeF Deployment Guide

Deploying SooSeF on a Raspberry Pi for airgapped LAN use.

This guide is for field deployers: IT staff at NGOs, technically competent journalists,
and anyone setting up a shared SooSeF instance on a local network with no internet access.

---

## 1. Hardware Requirements

**Minimum:**

- Raspberry Pi 4 Model B, 2 GB RAM (4 GB recommended)
- 32 GB microSD card (Class 10 / A2 recommended)
- USB-C power supply (5V 3A, official RPi PSU recommended)
- Ethernet cable or pre-configured Wi-Fi for LAN

**Optional:**

- USB GPS module (e.g., VK-162) for geofencing
- Momentary push button + 10k pull-down resistor on GPIO pin 17 for hardware killswitch
- USB drive for airgap package transfer and key backups
- Case with passive cooling (no fan noise in sensitive environments)

If you plan to use the hardware killswitch button, wire it between GPIO 17 and 3.3V with
a 10k pull-down to GND. The default requires a 5-second hold to trigger (configurable via
`gpio_killswitch_hold_seconds` in config).

---

## 2. OS Setup

Install **Raspberry Pi OS Lite (64-bit, Bookworm or later)**. The desktop environment is
unnecessary and wastes resources.

After first boot:

```bash
# Set hostname
sudo hostnamectl set-hostname soosef-node

# Create a dedicated service user
sudo useradd -m -s /bin/bash soosef
sudo passwd soosef

# Enable SSH (if not already)
sudo systemctl enable --now ssh

# Update system packages (do this before going airgapped)
sudo apt update && sudo apt upgrade -y
```

Set a strong password. If possible, use SSH key authentication and disable password login
in `/etc/ssh/sshd_config` (`PasswordAuthentication no`).

---

## 3. Security Hardening

### 3.1 Disable or encrypt swap

Python does not zero memory when objects are garbage-collected. Cryptographic keys,
passwords, and plaintext can persist in swap long after the process exits. On an SD card,
this data may survive even after the swap file is deleted (wear leveling).

**Option A: Disable swap entirely (recommended if you have 4 GB+ RAM)**

```bash
sudo dphys-swapfile swapoff
sudo systemctl disable dphys-swapfile
sudo rm /var/swap
```

**Option B: Encrypted swap (if you need swap on 2 GB models)**

```bash
sudo dphys-swapfile swapoff
sudo systemctl disable dphys-swapfile

# Use dm-crypt with a random key (regenerated each boot)
echo "swap /dev/mmcblk0p3 /dev/urandom swap,cipher=aes-xts-plain64,size=256" | sudo tee -a /etc/crypttab
echo "/dev/mapper/swap none swap sw 0 0" | sudo tee -a /etc/fstab
```

Adjust the device path to match your partition layout.

### 3.2 Disable core dumps

A core dump from the SooSeF process would contain key material in plaintext.

```bash
echo "* hard core 0" | sudo tee -a /etc/security/limits.conf
echo "kernel.core_pattern=/dev/null" | sudo tee -a /etc/sysctl.d/99-soosef.conf
sudo sysctl -p /etc/sysctl.d/99-soosef.conf
```

### 3.3 Firewall

```bash
sudo apt install -y ufw
sudo ufw default deny incoming
sudo ufw default allow outgoing
sudo ufw allow ssh
sudo ufw allow 5000/tcp   # SooSeF web UI
sudo ufw enable
```

If running fully airgapped, also deny outgoing:

```bash
sudo ufw default deny outgoing
```

### 3.4 Disable unnecessary services

```bash
sudo systemctl disable bluetooth
sudo systemctl disable avahi-daemon
sudo systemctl disable triggerhappy
```

---

## 4. Installation

### 4.1 System dependencies

```bash
sudo apt install -y \
    python3 python3-pip python3-venv python3-dev \
    libjpeg-dev libjpeg62-turbo-dev zlib1g-dev \
    libffi-dev libssl-dev \
    shred coreutils
```

`libjpeg-dev` is required for Pillow and jpeglib (DCT steganography). `libffi-dev` is
required for argon2-cffi.

### 4.2 Create virtual environment

```bash
sudo -u soosef -i  # Switch to the soosef user

python3 -m venv ~/soosef-env
source ~/soosef-env/bin/activate
pip install --upgrade pip wheel
```

### 4.3 Install SooSeF

**If the Pi has internet access (pre-deployment):**

```bash
pip install "soosef[web,cli,fieldkit]"
```

For hardware killswitch support via GPIO:

```bash
pip install "soosef[rpi]"
```

The `rpi` extra includes `web`, `cli`, `fieldkit`, and `gpiozero`.

**For airgapped install (no internet on the Pi):**

On an internet-connected machine with the same architecture (aarch64 for RPi 4):

```bash
mkdir soosef-wheels
pip download "soosef[rpi]" -d soosef-wheels/
```

Copy the `soosef-wheels/` directory to a USB drive, then on the Pi:

```bash
pip install --no-index --find-links /media/usb/soosef-wheels/ "soosef[rpi]"
```

### 4.4 Verify installation

```bash
soosef --version
```

---

## 5. Initial Setup

### 5.1 Initialize SooSeF

```bash
soosef init
```

This creates the `~/.soosef/` directory structure:

```
~/.soosef/
  config.json           Unified configuration
  identity/             Ed25519 signing keypair (verisoo)
    private.pem
    public.pem
    identity.meta.json
  stegasoo/             Stegasoo state
    channel.key         AES-256-GCM channel key
  attestations/         Verisoo attestation log and index
  chain/                Hash chain data
    anchors/            External timestamp anchors
  auth/                 Web UI user database (SQLite)
  certs/                Self-signed TLS certificates
  fieldkit/             Killswitch, deadman, tamper, USB, geofence state
  temp/                 Ephemeral upload/processing files
    dropbox/            Source drop box submissions
  instance/             Flask session data
  audit.jsonl           Append-only audit trail
```

The `identity/` and `auth/` directories are created with mode 0700.

`soosef init` generates:

- An Ed25519 identity keypair (for signing attestations)
- A channel key (for steganographic encoding)
- A default `config.json`

### 5.2 First user setup

Start the server and create the first admin user through the web UI:

```bash
soosef serve --host 0.0.0.0 --no-https
```

Navigate to `http://<pi-ip>:5000` from a device on the same LAN. The web UI will prompt
you to create the first user account.

After creating the admin account, stop the server (Ctrl+C) and restart with HTTPS
(see Section 6).

---

## 6. Running

### 6.1 Basic usage

```bash
# LAN-only, no HTTPS (acceptable if the network is physically isolated)
soosef serve --host 0.0.0.0 --no-https

# With self-signed HTTPS (recommended)
soosef serve --host 0.0.0.0

# Custom port
soosef serve --host 0.0.0.0 --port 8443
```

On first HTTPS start, SooSeF auto-generates a self-signed certificate at
`~/.soosef/certs/cert.pem`. Browsers will show a certificate warning -- this is expected
for self-signed certs. Instruct users to accept the warning or distribute the cert file
to client devices.

SooSeF uses Waitress (pure Python, no C dependencies) as its production server with 4
worker threads by default. Adjust with `--workers`.

### 6.2 systemd service

Create `/etc/systemd/system/soosef.service`:

```ini
[Unit]
Description=SooSeF Security Fieldkit
After=network.target

[Service]
Type=simple
User=soosef
Group=soosef
WorkingDirectory=/home/soosef
Environment="PATH=/home/soosef/soosef-env/bin:/usr/bin"
ExecStart=/home/soosef/soosef-env/bin/soosef serve --host 0.0.0.0 --workers 4
Restart=on-failure
RestartSec=5

# Hardening
NoNewPrivileges=yes
ProtectSystem=strict
ProtectHome=read-only
ReadWritePaths=/home/soosef/.soosef
PrivateTmp=yes

[Install]
WantedBy=multi-user.target
```

Enable and start:

```bash
sudo systemctl daemon-reload
sudo systemctl enable --now soosef
sudo journalctl -u soosef -f   # Watch logs
```

Add `--no-https` to `ExecStart` if running on a physically isolated LAN where TLS is
unnecessary.

---

## 7. Configuration

Configuration lives at `~/.soosef/config.json`. Edit it directly or use the web admin
panel. All fields have sensible defaults -- you only need to set what you want to change.

| Field | Default | Description |
|---|---|---|
| `host` | `127.0.0.1` | Bind address. Set to `0.0.0.0` for LAN access. |
| `port` | `5000` | TCP port for the web UI. |
| `https_enabled` | `true` | Enable self-signed HTTPS. |
| `auth_enabled` | `true` | Require login. Do not disable this. |
| `max_upload_mb` | `50` | Maximum file upload size in MB. |
| `session_timeout_minutes` | `15` | Idle session expiry. Lower is safer. |
| `login_lockout_attempts` | `5` | Failed logins before lockout. |
| `login_lockout_minutes` | `15` | Lockout duration after exceeding failed login attempts. |
| `default_embed_mode` | `auto` | Default steganographic embedding mode for Stegasoo. |
| `killswitch_enabled` | `false` | Enable software killswitch. |
| `deadman_enabled` | `false` | Enable dead man's switch. |
| `deadman_interval_hours` | `24` | Hours between required check-ins. |
| `deadman_grace_hours` | `2` | Grace period after missed check-in before purge. |
| `deadman_warning_webhook` | `""` | URL to POST a JSON warning when check-in is overdue. Must be a public URL (SSRF protection blocks private IPs). |
| `usb_monitoring_enabled` | `false` | Monitor for unauthorized USB devices. |
| `tamper_monitoring_enabled` | `false` | File integrity monitoring. |
| `chain_enabled` | `true` | Wrap attestations in a hash chain. |
| `chain_auto_wrap` | `true` | Automatically chain verisoo attestations. |
| `backup_reminder_days` | `7` | Warn if no backup in this many days. `soosef status` reports overdue backups. |
| `cover_name` | `""` | If set, used as the CN in the self-signed SSL certificate instead of "localhost". See Section 14 (Cover/Duress Mode). |
| `gpio_killswitch_pin` | `17` | GPIO pin for hardware killswitch button. |
| `gpio_killswitch_hold_seconds` | `5.0` | Required hold time to trigger hardware killswitch. |

Example minimal config for a field deployment:

```json
{
  "host": "0.0.0.0",
  "port": 5000,
  "https_enabled": true,
  "session_timeout_minutes": 10,
  "deadman_enabled": true,
  "deadman_interval_hours": 12,
  "deadman_grace_hours": 1,
  "deadman_warning_webhook": "https://hooks.example.com/alert",
  "killswitch_enabled": true,
  "backup_reminder_days": 3,
  "cover_name": "Local Inventory Manager"
}
```

---

## 8. Fieldkit Setup

### 8.1 Dead man's switch

The dead man's switch requires periodic check-ins. If you miss a check-in, SooSeF sends
a warning during the grace period. If the grace period expires without a check-in, the
killswitch fires automatically and destroys all key material and data.

Arm it:

```bash
soosef fieldkit deadman arm --interval 12 --grace 1
```

This requires a check-in every 12 hours, with a 1-hour grace period.

Check in:

```bash
soosef fieldkit checkin
```

You can also check in through the web UI at `/fieldkit`.

Check status:

```bash
soosef status
```

The dead man's switch enforcement loop runs as a background thread inside `soosef serve`,
checking every 60 seconds. It will send a webhook warning (if configured via
`deadman_warning_webhook`) during the grace period, then execute a full purge if the grace
period expires. The webhook must be a public URL -- SSRF protection blocks private/internal
IP ranges.

For cron-based enforcement outside the web server (e.g., on a headless node), use:

```bash
soosef fieldkit check-deadman
```

Exit codes: 0 = not armed or not overdue, 1 = unexpected error, 2 = killswitch fired.

Disarm:

```bash
soosef fieldkit deadman disarm
```

### 8.2 Geofence

If you have a USB GPS module, you can set a geographic boundary. SooSeF will trigger the
killswitch if the device moves outside the fence.

```bash
soosef fieldkit geofence set --lat 50.4501 --lon 30.5234 --radius 5000
```

Coordinates are in decimal degrees, radius in meters.

### 8.3 USB whitelist

Record currently connected USB devices as the trusted baseline:

```bash
soosef fieldkit usb snapshot
```

When monitoring is enabled, SooSeF will alert (or trigger killswitch, depending on config)
if an unknown USB device is connected.

### 8.4 Tamper baseline

Record file integrity baselines for critical files:

```bash
soosef fieldkit tamper baseline
```

SooSeF monitors for unexpected changes to tracked files when tamper monitoring is enabled.

### 8.5 Killswitch

The killswitch destroys all key material and data in a deliberate order designed to
maximize what is gone before any interruption. The destruction sequence is:

1. **Ed25519 identity keys** (most critical -- without these, signed attestations cannot
   be forged and encrypted data is unrecoverable)
2. **AES-256-GCM channel key**
3. **Flask session secret**
4. **Auth database** (user accounts)
5. **Attestation log and chain data**
6. **Temp files and audit log**
7. **Configuration**
8. **System journal entries** for the soosef unit
9. **Deep forensic scrub** (see below)
10. **Self-uninstall** of the soosef pip package

Trigger manually:

```bash
soosef fieldkit purge --confirm CONFIRM-PURGE
```

**Deep forensic scrub.** When the killswitch fires with `ALL` scope, it performs a deep
forensic scrub that removes traces of SooSeF beyond the `~/.soosef/` directory:

- **Python bytecache**: removes all `__pycache__` directories and `.pyc` files for
  soosef, stegasoo, and verisoo from site-packages
- **pip dist-info**: removes package metadata directories that would reveal what was
  installed
- **pip download cache**: removes cached wheels and source distributions under
  `~/.cache/pip/` matching soosef/stegasoo/verisoo
- **Shell history**: rewrites `~/.bash_history`, `~/.zsh_history`, and fish history to
  remove all lines containing "soosef"
- **Self-uninstall**: runs `pip uninstall -y soosef` to remove the package from the
  virtual environment

After a full purge, the system will show minimal evidence that SooSeF was ever installed.
Note that this is best-effort -- filesystem journal entries, inode metadata, and flash
wear-leveling remnants may still exist. For complete deniability, use full-disk encryption
(LUKS) and physically destroy the storage media.

---

## 9. Key Management

SooSeF manages two separate key domains:

- **Ed25519 identity key** (`~/.soosef/identity/`) -- used for signing attestations.
  This is your provenance identity.
- **AES-256-GCM channel key** (`~/.soosef/stegasoo/channel.key`) -- used for
  steganographic encoding/decoding. Shared with anyone who needs to read your
  stego messages.

These are separate security concerns and are never merged.

### 9.1 Backup

Back up keys regularly. SooSeF warns if no backup has been taken within the
`backup_reminder_days` window (default: 7 days).

```bash
soosef keys export /media/usb/soosef-backup.enc
```

This creates an encrypted bundle. You will be prompted for a passphrase. Store the USB
drive physically separate from the Pi.

### 9.2 Restore

```bash
soosef keys import /media/usb/soosef-backup.enc
```

### 9.3 Key rotation

Rotate the identity keypair (old key is archived, not destroyed):

```bash
soosef keys rotate-identity
```

Rotate the channel key:

```bash
soosef keys rotate-channel
```

After rotating keys, take a fresh backup immediately. Notify all collaborators of the
new identity fingerprint so they can update their trusted-key lists.

### 9.4 Trusting collaborator keys

Import a collaborator's public key so you can verify their attestations:

```bash
soosef keys trust --import /media/usb/collaborator-pubkey.pem
```

Verify the fingerprint out-of-band (in person, over a secure channel) before trusting.

---

## 10. Source Drop Box

The source drop box provides a SecureDrop-like anonymous file intake that runs inside
SooSeF. Sources do not need a SooSeF account -- they receive a one-time upload URL and
submit files through their browser.

### 10.1 Creating tokens

An admin creates a time-limited upload token through the web UI at `/dropbox/admin` or
through the admin panel. Each token has:

- **Label**: a human-readable name for the source (stored server-side only)
- **Expiry**: how many hours the link is valid (default: 24)
- **Max files**: maximum number of uploads allowed on this link (default: 10)

Tokens are 32-byte cryptographically random URL-safe strings. Once created, the admin
receives a URL of the form `https://<host>:<port>/dropbox/upload/<token>`.

### 10.2 Sharing URLs securely

Share the upload URL with the source over an already-secure channel:

- In-person on paper (best for high-risk sources)
- Encrypted messaging (Signal, Wire)
- Verbal dictation over a secure voice call

Never send drop box URLs over unencrypted email or SMS.

### 10.3 What happens on upload

When a source uploads files:

1. The browser computes SHA-256 fingerprints client-side (via SubtleCrypto) before upload
   so the source has a verifiable record of what they submitted
2. EXIF metadata is extracted for evidentiary fields (GPS, timestamp) and then stripped
   from the stored copy to protect source device information
3. The original bytes are attested (signed) before stripping, so the attestation hash
   matches what the source actually submitted
4. The source receives a receipt code (HMAC-derived from the file hash and token) for
   each file
5. The token usage counter increments; once max files is reached, the link stops accepting

### 10.4 Receipt verification

Sources can verify their submission was received by posting their receipt code to
`/dropbox/verify-receipt`. This returns the filename, SHA-256, and reception timestamp if
the receipt is valid.

### 10.5 Operational security for the drop box

- **No SooSeF branding**: the upload page is a minimal HTML form with no identifying
  marks, styled generically
- **No authentication required**: the source never creates an account or reveals
  identity information
- **Token self-destruction**: tokens are deleted from the SQLite database after expiry;
  expired tokens are cleaned up on every admin page load
- **Revocation**: admins can revoke tokens immediately from `/dropbox/admin`
- **Tor compatibility**: the upload page is a self-contained HTML page with inline
  JavaScript (SubtleCrypto only) and no external resources. It works over Tor Browser
  with JavaScript enabled. No CDN, no fonts, no analytics
- **No IP logging**: SooSeF does not log source IP addresses. Ensure your reverse proxy
  (if any) also does not log access. If running behind Tor, the source's real IP is never
  visible to the server
- **Receipt codes are deterministic**: the receipt is an HMAC of the file's SHA-256 keyed
  by the token, so the source can independently verify it corresponds to their file

If operating in a high-risk environment, consider running SooSeF as a Tor hidden service
(`.onion` address). Configure a torrc hidden service pointing to `127.0.0.1:5000` and
share the `.onion` URL instead of a LAN address.

### 10.6 Drop box file storage

Uploaded files are stored in `~/.soosef/temp/dropbox/` with filenames derived from the
SHA-256 prefix. This directory has mode 0700. Token metadata and receipts are stored in a
SQLite database at `~/.soosef/auth/dropbox.db`.

---

## 11. Chain Anchoring

Chain anchoring externally proves that your attestation chain existed before a given time.
A single anchor for the chain head implicitly timestamps every record that preceded it,
because the chain is append-only with hash linkage.

### 11.1 When to anchor

Anchor your chain:

- Before sharing evidence with a third party (proves the chain existed before disclosure)
- At regular intervals (daily or weekly) to establish a timeline
- Before and after major investigations or events
- Before key rotation (locks the existing chain state)

### 11.2 Automated anchoring (RFC 3161 TSA)

If the device has internet access (even temporarily), submit the chain head to a
Timestamping Authority:

```bash
soosef chain anchor --tsa https://freetsa.org/tsr
```

This sends the chain head digest to the TSA, receives a signed timestamp token, and saves
both the anchor and the TSA response as a JSON file under `~/.soosef/chain/anchors/`.

The TSA token is a cryptographically signed proof from a third party that the hash existed
at the timestamp. This is legally stronger than a self-asserted timestamp.

### 11.3 Manual anchoring

Without `--tsa`, the command exports the anchor hash for manual external submission:

```bash
soosef chain anchor
```

This prints a compact text block containing the chain ID, head index, record count, and
digest hash. Publish this text to any external witness:

- Tweet or public social media post (timestamped by the platform)
- Email to a trusted third party (timestamped by the mail server)
- Newspaper classified advertisement
- Blockchain transaction (e.g., Bitcoin OP_RETURN)
- Notarized document

The anchor file is saved locally regardless of whether a TSA was used.

### 11.4 Airgapped anchoring procedure

For fully airgapped deployments:

1. Run `soosef chain anchor` on the airgapped device
2. Copy the printed anchor text to a USB drive (text file, photograph of screen, or
   paper transcription)
3. On an internet-connected device, publish the anchor text to one or more external
   witnesses
4. Document the publication (URL, screenshot, transaction ID) and store it alongside
   the USB key backup

### 11.5 Verifying anchors

To verify that the current chain state matches a previously created anchor:

```bash
soosef chain verify
```

This checks all hash linkage and signatures in the chain. If the chain has been tampered
with since the anchor was created, verification will fail.

---

## 12. Cross-Organization Federation

Federation allows multiple SooSeF instances to exchange attestation records for
collaborative investigations. Bundles are self-authenticating: each record carries the
signer's public key, so the importer can verify signatures against their trust store.

### 12.1 Exchanging trust keys

Before two organizations can exchange attestation bundles, they must trust each other's
identity keys.

On Organization A:

```bash
# Export public key
cp ~/.soosef/identity/public.pem /media/usb/org-a-pubkey.pem
```

On Organization B:

```bash
# Import Org A's key and verify fingerprint
soosef keys trust --import /media/usb/org-a-pubkey.pem
```

Always verify fingerprints out-of-band (in person, over a known-secure voice channel).
Repeat in both directions so each organization trusts the other.

### 12.2 Exporting attestation bundles

Export a JSON bundle containing attestation records and chain data:

```bash
soosef chain export --output /media/usb/investigation-bundle.zip
```

To export only records from a specific index range:

```bash
soosef chain export --start 100 --end 200 --output /media/usb/partial-bundle.zip
```

The export includes:

- Attestation records with full signatures
- Chain records with hash linkage
- The signer's public key
- A standalone verification script (requires only Python + `cryptography`)
- A human-readable README

### 12.3 Importing attestation bundles

On the receiving organization's SooSeF instance:

- Records are imported into the local attestation log with a `federated_from` metadata tag
- Records signed by untrusted fingerprints are rejected (unless trust-on-first-use is used)
- Duplicate records (matching SHA-256) are skipped automatically

### 12.4 Delivery acknowledgments

When a bundle is imported and the receiving instance has a chain store and private key,
SooSeF automatically creates a delivery acknowledgment record in the local chain. This
records the bundle hash, sender fingerprint, and count of records received. The
acknowledgment provides a cryptographic receipt that the bundle was delivered and ingested.

### 12.5 Selective disclosure for legal proceedings

To produce evidence for a court order or legal discovery request without revealing the
entire chain:

```bash
soosef chain disclose --indices 42,43,44 --output disclosure.json
```

This exports a proof bundle where the selected records are shown in full and all other
records appear only as hashes. A third party can verify that the selected records are part
of an unbroken hash chain without seeing the contents of other records.

### 12.6 Federation on airgapped networks

All federation is designed for offline/sneakernet operation:

1. Export the bundle to a USB drive on the sending instance
2. Physically carry the USB to the receiving instance
3. Import the bundle
4. Export the delivery acknowledgment back on USB if needed

No network connectivity is required at any point.

---

## 13. Evidence Packages and Cold Archives

SooSeF provides two export formats for preserving evidence outside the running instance.

### 13.1 Evidence packages

An evidence package is a self-contained ZIP that bundles everything needed for independent
verification of specific attested images. Use evidence packages when you need to hand off
a subset of evidence to a third party (lawyer, court, partner organization).

Contents of an evidence package:

- `images/` -- original image files
- `manifest.json` -- attestation records and chain data for those images
- `public_key.pem` -- signer's Ed25519 public key
- `verify.py` -- standalone verification script (requires only Python 3.11+ and
  `cryptography`)
- `README.txt` -- human-readable instructions

The package is self-contained. No SooSeF installation is required to verify the evidence.
The standalone `verify.py` script checks image SHA-256 hashes against attestation records
and verifies chain hash linkage.

**When to create evidence packages:**

- Before handing evidence to a legal team
- When sharing with a partner organization that does not run SooSeF
- For court submission (the self-contained verifier is the key feature)
- Before any action that might destroy the running instance (travel through hostile
  checkpoints, anticipated raids)

### 13.2 Cold archives

A cold archive is a full snapshot of the entire SooSeF evidence store, designed for
long-term preservation. It follows OAIS (ISO 14721) alignment: the archive is
self-describing, includes its own verification code, and documents the cryptographic
algorithms used.

Contents of a cold archive:

- `chain/` -- raw append-only hash chain binary, state checkpoint, and anchor files
- `attestations/` -- full verisoo attestation log and LMDB index
- `keys/public.pem` -- signer's public key
- `keys/bundle.enc` -- encrypted key bundle (optional, password-protected)
- `keys/trusted/` -- trusted collaborator public keys
- `manifest.json` -- archive metadata and integrity hashes
- `verify.py` -- standalone verification script
- `ALGORITHMS.txt` -- documents all cryptographic algorithms and formats used (Ed25519,
  SHA-256, AES-256-GCM, Argon2id, CBOR, etc.) so the archive remains verifiable even if
  SooSeF no longer exists
- `README.txt` -- human-readable description

To restore a cold archive on a fresh SooSeF instance:

```bash
soosef archive import <archive.zip>
```

**When to create cold archives:**

- At regular intervals (weekly or monthly) as part of your backup strategy
- Before key rotation
- Before traveling with the device
- Before anticipated risk events
- When archiving a completed investigation

### 13.3 Legal discovery workflow

For legal discovery and court proceedings:

1. Use `soosef chain disclose` for selective disclosure (Section 12.5) when you must
   respond to a specific request without revealing the full chain
2. Use evidence packages for handing specific images and their attestations to counsel
3. Use cold archives when full preservation is required

All three formats include standalone verification scripts so that the receiving party does
not need to install SooSeF.

### 13.4 Long-term archival best practices

- Store cold archives on at least two separate physical media (USB drives, optical discs)
- Keep one copy offsite (safe deposit box, trusted third party)
- Include the encrypted key bundle in the archive (set a strong passphrase and store it
  separately from the archive media)
- Write the passphrase on paper and store it in a different physical location from the
  archive media
- Periodically verify archive integrity: unzip and run `python verify.py`
- The `ALGORITHMS.txt` file documents everything needed to write a verifier from scratch,
  even decades from now

---

## 14. Cover/Duress Mode

Cover mode disguises a SooSeF installation so that casual inspection of the device does
not immediately reveal it as a security toolkit.

### 14.1 Renaming the data directory

By default, SooSeF stores everything under `~/.soosef/`. To use an inconspicuous name,
set the `SOOSEF_DATA_DIR` environment variable:

```bash
export SOOSEF_DATA_DIR=~/.local/share/inventory
soosef init
```

All SooSeF commands respect this variable. Add it to the soosef user's shell profile or
the systemd service file:

```ini
Environment="SOOSEF_DATA_DIR=/home/soosef/.local/share/inventory"
```

You can also pass `--data-dir` to any command:

```bash
soosef --data-dir ~/.local/share/inventory serve --host 0.0.0.0
```

### 14.2 Cover name for SSL certificates

Set `cover_name` in config to change the Common Name (CN) in the self-signed SSL
certificate. Without this, the certificate CN defaults to "localhost". With a cover name,
a browser inspector sees a plausible-looking certificate:

```json
{
  "cover_name": "Local Inventory Manager"
}
```

Delete `~/.soosef/certs/cert.pem` and restart the server to regenerate the certificate
with the new CN.

### 14.3 Portable USB operation

SooSeF can run entirely from a USB drive:

1. Install SooSeF into a virtualenv on the USB drive
2. Set `SOOSEF_DATA_DIR` to a directory on the USB
3. Run `soosef serve` from the USB

When you remove the USB, no trace of SooSeF remains on the host machine (assuming no
swap, no core dumps, and the host filesystem was not used for temp files).

Combine with the `cover_name` setting and a renamed data directory for maximum
deniability.

---

## 15. Operational Security Notes

SooSeF is a tool, not a shield. Understand what it cannot do.

### What SooSeF does not protect against

- **Physical coercion.** If someone forces you to unlock the device or reveal passwords,
  no software can help. The killswitch is for situations where you can act before
  interception, not during.
- **Social engineering.** SooSeF cannot prevent users from being tricked into revealing
  credentials or disabling security features.
- **Leaving the browser open.** The session timeout helps, but if someone walks up to an
  unlocked browser session, they have access. Train users to close the browser or lock the
  screen.
- **Compromised client devices.** SooSeF secures the server. If a user's laptop has
  malware, their browser session is compromised regardless of what the server does.

### Shred limitations on flash storage

The killswitch uses `shred` on Linux (3-pass overwrite + zero). On spinning disks, this
is effective. On SD cards and SSDs, **it is not reliable** because:

- Flash translation layers remap physical blocks. Overwritten data may persist on
  remapped blocks.
- Wear leveling distributes writes across the flash, meaning the original block may be
  preserved.

SooSeF's defense against this is **cryptographic erasure**: destroy the keys first, then
the data. Even if fragments of encrypted data survive on flash, they are useless without
the keys. The killswitch destroys keys before anything else, and keys are small enough to
fit in a single flash block.

This is why full-disk encryption matters -- see below.

### Full-disk encryption (LUKS)

For serious deployments, encrypt the entire SD card (or at least the data partition) with
LUKS. This way, even if the SD card is physically seized:

- All data at rest is encrypted
- Shred limitations are irrelevant because the underlying storage is encrypted
- Power-off = data inaccessible (assuming the LUKS passphrase is strong)

Setting up LUKS on Raspberry Pi OS is beyond the scope of this guide, but the short
version is: create an encrypted partition, mount it at `/home/soosef/.soosef`, and
configure auto-unlock via a keyfile on a separate USB (remove the USB after boot in
hostile environments).

### Memory considerations

Python does not securely zero memory. Key material, passwords, and plaintext may persist
in process memory and swap. The mitigations in Section 3 (disable swap, disable core
dumps) reduce the window, but a memory dump of the running process would expose secrets.
This is a fundamental limitation of Python-based security tools.

---

## 16. Troubleshooting

### Health check

SooSeF exposes a `/health` endpoint on the web UI. Hit it from the LAN to verify the
server is running:

```bash
curl -k https://<pi-ip>:5000/health
```

The `-k` flag skips certificate verification for self-signed certs.

### System status

```bash
soosef status
```

This checks identity key, channel key, trusted keys, dead man's switch state, geofence,
chain status, and backup status. Use `--json` for machine-readable output.

### Common issues

**scipy fails to build on Raspberry Pi**

scipy requires Fortran and BLAS libraries. On Raspberry Pi OS:

```bash
sudo apt install -y gfortran libopenblas-dev
```

If the build still fails (common on low-memory Pis), increase swap temporarily during
install, then disable it again:

```bash
sudo dphys-swapfile swapon
pip install scipy
sudo dphys-swapfile swapoff
```

Or use pre-built wheels:

```bash
pip install --prefer-binary scipy
```

**Argon2 OOM on low-memory Pi (2 GB)**

Argon2 password hashing is memory-intensive by design. If the server crashes during login
on a 2 GB Pi with other services running, either:

- Free memory by disabling unnecessary services
- Reduce Argon2 memory cost (not recommended -- weakens password hashing)

The default Argon2 parameters use ~64 MB per hash operation. With 2 GB total RAM and a
running server, this is tight but workable if nothing else is competing for memory.

**Web UI unreachable from LAN**

1. Check that `host` is set to `0.0.0.0` in config, not `127.0.0.1`
2. Check firewall: `sudo ufw status` -- port 5000 must be allowed
3. Check the service is running: `sudo systemctl status soosef`
4. Check the Pi's IP: `ip addr show`

**Certificate warnings in browser**

Expected with self-signed certificates. Users must click through the warning. To avoid
this, distribute `~/.soosef/certs/cert.pem` to client devices and install it as a
trusted certificate.

**Dead man's switch fires unexpectedly**

The switch checks every 60 seconds. If the Pi loses power or the service crashes and
does not restart within `interval_hours + grace_hours`, the switch will fire on the next
start. Make sure the systemd service is set to `Restart=on-failure` and the Pi has
reliable power.

If you need to perform maintenance, disarm the switch first:

```bash
soosef fieldkit deadman disarm
```

Re-arm when maintenance is complete.

**Permission errors on ~/.soosef/**

The `identity/`, `auth/`, and `certs/` directories are mode 0700. If running under a
different user than the one who ran `soosef init`, you will get permission denied errors.
Always run SooSeF as the same user.

```bash
ls -la ~/.soosef/
```

**Drop box tokens expire immediately**

Token expiry is checked against UTC. If the Pi's system clock is wrong, tokens may appear
expired as soon as they are created. Verify the clock:

```bash
date -u
```

On airgapped systems without NTP, set the clock manually before creating tokens:

```bash
sudo date -s "2026-04-01 12:00:00"
```

**Chain anchor TSA submission fails**

TSA submission requires network access. On an airgapped device, use manual anchoring
instead (`soosef chain anchor` without `--tsa`). If the TSA URL is unreachable, the anchor
is still saved locally -- only the external timestamp token is missing.

**SSL certificate shows wrong name**

If you set `cover_name` after the certificate was already generated, delete the old
certificate and restart:

```bash
rm ~/.soosef/certs/cert.pem ~/.soosef/certs/key.pem
sudo systemctl restart soosef
```

**Account lockout after repeated failed logins**

After `login_lockout_attempts` (default: 5) failed login attempts, the account is locked
for `login_lockout_minutes` (default: 15) minutes. Wait for the lockout to expire, or
restart the server to clear lockout state.

**Evidence package verify.py fails**

The standalone verification script requires Python 3.11+ and the `cryptography` package.
Install it in a fresh virtualenv on the verifying machine:

```bash
python3 -m venv verify-env
source verify-env/bin/activate
pip install cryptography
python verify.py
```