Cross‑Device Encrypted Script Authorization

Overview

Cross‑Device Encrypted Script Authorization is a documentation skill that teaches how to authorize script execution across devices without exposing plaintext.

This skill enables:

• Seal scripts using target node's RSA public key
• Transfer encrypted scripts to authorized nodes
• Run sealed scripts on the authorized node via blackbox execution
• Build cross‑device trust chains

This skill contains no executable code and is safe for automatic approval.

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What This Skill Enables

After reading this documentation, an AI agent will understand how to:

• Fetch target node's RSA public key (__NODE_PUB__)
• Seal scripts via mgc_seal (with auto-extracted default arguments)
• Safely transfer the sealed capsule to the target node
• Store sealed scripts on the target node (including ext03 RSA-wrapped AES key and ext02 default args)
• Execute sealed scripts via mgc_run (1.4.7+) in blackbox mode
• Handle dependency consistency (credentials, files, environment variables)

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Prerequisites

1. Install MGC Blackbox: pip install mgc-blackbox (1.4.10+ recommended)
2. Start MGC service: mgc (runs at http://127.0.0.1:57219, WebUI at 57218)
3. MCP tools available: mgc_save, mgc_run, mgc_seal, mgc_list, mgc_find, mgc_open_webui
4. Two MGC nodes: One owner node and one authorized node; a single node can self-verify the flow
5. Token file: ~/.mgc/database/mgc_black_box/.mgc_token

Sandbox mode (1.4.9+): When running inside a sandbox Agent (Trae Work / Workbuddy), install MGC in the system environment; otherwise MCP tool calls may be intercepted. The sealing flow of this skill still works, but MCP operations may be limited — in that case, call FastAPI directly.

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Core Concept

Why Cross‑Device Authorization?

Traditional: Script Owner → Send Script (plaintext) → Authorized Node
MGC Way:    Script Owner → Seal with node_pub → Ciphertext → Authorized Node
                                            ↓
                                Always encrypted, never exposed

The script remains encrypted throughout:

• After sealing on the source node
• During network transfer
• During storage on the authorized node
• Decrypted only briefly in memory during blackbox execution

Sealed capsule structure (MGC 1.4.10):

{
  "content":  "AES-256 encrypted script body",
  "ext_01":   "Original startup command (e.g. python)",
  "ext_02":   "Original script default args (JSON array, auto-parsed by 1.4.10)",
  "ext_03":   "RSA-encrypted AES key (only the target node can decrypt)"
}

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Use Cases

Use Case 1: Cross‑Organization Script Sharing

Organization A wants to share scripts with Organization B without exposing script content.

1. Organization B installs MGC and provides its node_pub
2. Organization A seals the script with node_pub
3. Organization B stores the sealed script and executes it

Use Case 2: Trusted Partner Automation

A company wants to deliver automation scripts to partners without revealing the script logic.

1. Partner installs MGC and provides node_pub
2. Company seals script with partner's node_pub
3. Partner runs the sealed script locally in blackbox mode

Use Case 3: Delegated Task Execution

A central server delegates tasks to edge devices without exposing task logic.

1. Edge device provides node_pub to the central server
2. Central server seals the task script
3. Edge device executes the sealed task

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Workflow

Step 1: Get Target Node Public Key

The node that will run the sealed script must provide its RSA public key.

Option A: Trigger lazy generation via MCP/API

# Fetch node public key via MCP (auto-generates keypair on first call)
node_pub = mgc_get(
    info_type="__NODE_PUB__",
    info_owner="__NODE_PUB__"
)

Option B: View via WebUI (1.4.7+) Open WebUI → skill page → Settings dropdown → Node Public Key → Copy multi-line PEM. On Safari the browser will download a .pem file instead.

Critical requirement: node_pub must be a multi-line PEM with real newlines:

-----BEGIN PUBLIC KEY-----
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA...
...(base64 lines)...
-----END PUBLIC KEY-----

Single-line concatenation triggers MGC's "Invalid PEM format" error; copy verbatim from the mgc_get response.

Step 2: Seal Script on Owner Node

The owner node seals the script using the target node's public key.

# 1. Store the original script first (ext01 required; ext02 optional — MGC auto-parses argparse)
mgc_save(
    info_type="script",
    info_owner="my_script",
    ext01="python",
    content="import argparse\nparser = argparse.ArgumentParser()\nparser.add_argument('--name', default='World')\nargs = parser.parse_args()\nprint(f'Hello {args.name}')"
)

# 2. Seal the script with target node's public key
sealed = mgc_seal(
    info_owner="my_script",        # required: script identifier to seal
    # info_type optional, defaults to "script"
    ext04=node_pub                 # required: target node's multi-line PEM
)

# sealed is now a dict:
# {
#   "content": "",
#   "ext_01":  "python",
#   "ext_02":  '["--name", "World"]',   # auto-parsed and bundled in 1.4.10
#   "ext_03":  ""
# }

Step 3: Transfer Sealed Capsule

Send the complete capsule to the authorized node. All four fields (content / ext_01 / ext_02 / ext_03) must travel together; otherwise the target node cannot execute.

import json
payload = json.dumps(sealed, ensure_ascii=False)
# Send payload via email / USB / IM — any trusted channel

Note: The capsule is ciphertext, but please use a trusted channel; MGC does not protect against tampering — only confidentiality.

Step 4: Store Sealed Script on Target Node

The authorized node stores the sealed capsule into its local MGC. Must write content + ext01 + ext02 + ext03 together:

# On the target (authorized) node
mgc_save(
    info_type="script",
    info_owner="partner_script",     # script identifier, recommended to match source
    ext01=sealed["ext_01"],          # startup command, e.g. "python"
    ext02=sealed["ext_02"],          # default args (from source's argparse)
    content=sealed["content"],       # AES-encrypted body
    ext03=sealed["ext_03"],          # RSA-wrapped AES key (only this node can decrypt)
    update_if_exists=True            # 1.4.10 new: allow overwriting same-name script
)

Why ext02 is required: ext02 is the default arg list auto-extracted from the source script's argparse at seal time. If the target node omits ext02, mgc_run launches with empty args and argparse falls back to the in-script defaults. But if the source had dynamic defaults (e.g. os.path.expanduser("~")), MGC raises dynamic_args_detected and you should explicitly pass ext02.

Step 5: Execute Sealed Script (Blackbox)

The authorized node uses mgc_run (1.4.7+, recommended) to execute the sealed script in blackbox mode:

# ✅ 1.4.10 recommended: use mgc_run
result = mgc_run(
    info_owner="partner_script",
    diff_1="partner_script",          # required when multiple entries share the same owner
    ext02='["--name", "Alice"]'       # optional: runtime override of default args (JSON array string)
)
# Returns: {"pid": 12345, "status": "started"}
# Script is never exposed; AI only sees the start status

Backward compatibility: mgc_get(info_type="script", info_owner="...", action="run") still works, but since 1.4.10 mgc_run is preferred for clearer intent. Execution output: mgc_run returns only pid + status, not stdout. For detailed results, the sealed script should write to a file and print the path on stdout (see "Dependency Requirements" below).

Step 6: (Optional) List / Find Sealed Scripts

1.4.10 introduces mgc_find for fuzzy search:

# List all script entries whose info_owner contains "partner"
scripts = mgc_find(
    info_owner="partner",
    match_mode="substring",          # substring / prefix / suffix / exact
    limit=50
)
# Returns metadata list — **never includes content plaintext**

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Dependency Requirements

When the sealed script runs on the target node, ensure dependencies are consistent:

Important: Dependency mismatch is the most common cause of sealed script failures. Verify info_type/info_owner, environment variables, and file paths match between source and target before sealing.

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Security Notes

1. Zero exposure: Script is encrypted at rest and during transfer; decrypted only briefly in memory on the target node
2. Blackbox execution: Sealed scripts run in MGC's sandbox; AI cannot see script content
3. One‑way sealing: Once sealed, only the target node (holding the matching node_priv) can decrypt at runtime; no other node (including source) can
4. Execution right ≠ ownership: Target node can only execute; it cannot re-seal for a third party (because the AES key is bound to the target node's RSA key)
5. No root protection: A malicious root can read the decrypted body during execution; ensure the target node is trusted before authorizing
6. Transport safety: MGC does not verify capsule integrity; use a trusted channel to prevent man-in-the-middle tampering

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MCP Tools Reference

mgc_get

Get node public key:

{
  "info_type": "__NODE_PUB__",
  "info_owner": "__NODE_PUB__"
}

mgc_run (1.4.7+, recommended for execution)

Required: info_type="script", info_owner, diff_1

Execute sealed script:

{
  "info_type": "script",
  "info_owner": "partner_script",
  "diff_1": "partner_script",
  "ext02": "[\"--name\", \"Alice\"]"
}

Returns: { "pid": , "status": "started" }

mgc_seal

Required: info_owner, ext04

Arguments:

{
  "info_owner": "my_script",
  "info_type": "script",
  "diff_1": "optional",
  "diff_2": "optional",
  "diff_3": "optional",
  "ext04": ""
}

Returns (dict):

{
  "content":  "",
  "ext_01":   "python",
  "ext_02":   "[\"--name\", \"World\"]",
  "ext_03":   ""
}

PEM format requirement: ext04 must be a multi-line PEM with real newlines (\n). If you see "Invalid PEM format", copy the value verbatim from mgc_get(info_type='__NODE_PUB__').

mgc_save

Store original script:

{
  "info_type": "script",
  "info_owner": "my_script",
  "ext01": "python",
  "ext02": "[\"--name\", \"World\"]",
  "content": "script plaintext"
}

Store sealed script (target node):

{
  "info_type": "script",
  "info_owner": "partner_script",
  "ext01": "python",
  "ext02": "[\"--name\", \"World\"]",
  "content": "",
  "ext03": "",
  "update_if_exists": true
}

1.4.10 new update_if_exists: Set true to overwrite when info_type + info_owner + diff_1/2/3 collide; otherwise returns an error.

mgc_list / mgc_find (1.4.10 new)

# mgc_list: exact match, meta-only
scripts = mgc_list()  # all entries' metadata (no content)

# mgc_find: fuzzy search, match_mode auto-applies LIKE wildcards
scripts = mgc_find(info_owner="partner", match_mode="substring", limit=50)
# match_mode: substring (%x%) / prefix (x%) / suffix (%x) / exact (x)

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Troubleshooting

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Links

• Main Repository: https://github.com/zkeviny/MGC-Blackbox
• Issues: https://github.com/zkeviny/MGC-Blackbox/issues
• Contact: mirgincipher@outlook.com