Mycelium CDN (Hero Redis + Holochain Metadata)

This repository contains tooling and metadata definitions for a distributed content delivery network.

This repo consists of two main components:

1. cdn-meta: A Rust library that defines the metadata format for objects
2. mycdnctl: A command-line tool for uploading objects to the CDN

Metadata storage is performed via a Holochain hApp (see holopoc/) which provides an authorized key-value store.

Storage Model (High Level)

• File content is split into chunks, encrypted, erasure-coded into shards, and stored in Hero Redis instances.
• Metadata (including shard locations) is encrypted and stored in Holochain using the HoloKVS authorized key-value store (holopoc/).
• A content reference encodes:
  • the hash of the encrypted metadata (used as the HoloKVS key)
  • the hash of the plaintext metadata (used as the decryption key, via ?key=)

System Architecture

graph TD
    Client[Client] -->|Upload file| mycdnctl[mycdnctl CLI]
    mycdnctl -->|Split & encrypt| Chunks[Encrypted Chunks]
    mycdnctl -->|Create metadata| Meta[Metadata]
    Chunks -->|Erasure coding| Shards[Shards]
    Shards -->|Store| HeroRedis[Hero Redis Instances]
    Meta -->|Encrypt| EncMeta[Encrypted Metadata]
    EncMeta -->|Store| Holochain[Holochain (HoloKVS)]
    
    User[End User] -->|Request content| CDN[Mycelium CDN]
    CDN -->|Fetch metadata| Holochain
    CDN -->|Fetch shards| HeroRedis

Hero Redis

Shard storage is performed via Hero Redis, a Redis-compatible server with an authentication flow based on:

• CHALLENGE
• TOKEN <pubkey> <signature>
• AUTH <token>
• SELECT <db>

mycdnctl can authenticate to Hero Redis using either:

• a session token (stored in config), or
• an Ed25519 private key (stored in config) to perform CHALLENGE/TOKEN/AUTH at runtime

Using mycdnctl

mycdnctl uploads files and directories by:

1. Reading content
2. Splitting into chunks (default max: 5 MiB)
3. Encrypting each chunk with AES-128-GCM (key derived from chunk plaintext hash)
4. Reed-Solomon erasure coding each encrypted chunk into n shards
5. Writing one shard to each configured Hero Redis backend
6. Creating + encrypting metadata and storing it in Holochain (HoloKVS)
7. Printing a content reference

Installation

Either download a release artifact, or build from source:

cd crates/mycdnctl
cargo build --release

Configuration

Before using mycdnctl, create a configuration file (default: config.toml) specifying:

• Hero Redis backends used for shard storage
• Holochain/HoloKVS connection and signing settings used for metadata storage

Config Format (config.toml)

• required_shards: the minimum number of shards needed to reconstruct a chunk
• [[backends]]: list of Hero Redis shard stores; one shard is written to each backend
• [metadata]: metadata storage backend configuration (HoloKVS)

Rules:

• required_shards >= 1
• required_shards <= number of configured backends

Example:

# Minimum shards required to recover (k)
required_shards = 3

# One shard is written to each backend (n = number of backends)
[[backends]]
kind = "hero_redis"
host = "10.0.0.10:6379"
db = 7

[[backends]]
kind = "hero_redis"
host = "10.0.0.11:6379"
db = 7

[[backends]]
kind = "hero_redis"
host = "10.0.0.12:6379"
db = 7

# Optional Hero Redis auth:
# 1) Session token (client uses `AUTH <token>`)
[[backends]]
kind = "hero_redis"
host = "10.0.0.13:6379"
db = 7
auth = { type = "token", token = "your-session-token" }

# 2) Ed25519 private key (client performs CHALLENGE/TOKEN/AUTH)
# Note: private_key must be 64 hex chars (32 bytes).
[[backends]]
kind = "hero_redis"
host = "10.0.0.14:6379"
db = 7
auth = { type = "private_key", private_key = "e5f6a7b8... (64 hex chars total)" }

# Metadata storage (Holochain / HoloKVS)
#
# NOTE: This is a single TOML table. The config is NOT nested under `[metadata.holo_kvs]`.
[metadata]
kind = "holo_kvs"

# Conductor admin/app websocket settings
host = "127.0.0.1"
admin_port = 8888
# app_port = 12345        # optional; if omitted mycdnctl will obtain/attach an app interface via admin

# Installed app ID + coordinator zome name (holopoc defaults)
app_id = "kv_store"
zome_name = "kv_store"

# Zome function names are hardcoded in mycdnctl (holopoc defaults):
# - get_next_nonce
# - get_state
# - set_value

# Optional key prefix to namespace metadata keys in the DHT
key_prefix = "mycelium-cdn/meta/"

# Encrypted metadata bytes are always stored as a hex-encoded string value.


# Required for writes: X25519 secret key (32 bytes hex / 64 hex chars; optional 0x prefix)
writer_x25519_sk_hex = "0x0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef"

Uploading Files

To upload a file to the CDN:

mycdnctl upload --config config.toml path/to/file.txt

Optional parameters:

• --mime: Specify the MIME type (otherwise inferred)
• --name: Specify a custom name (otherwise uses filename)
• --chunk-size: Chunk size in bytes (default: 5 MiB, range: 1–5 MiB)
• --include-password: Include the Hero Redis session token (if configured) in the metadata (not recommended for public content)

Uploading Directories

To upload a directory (non-recursive) to the CDN:

mycdnctl upload --config config.toml path/to/directory

Each regular file inside the directory is uploaded as a file object, and then a directory metadata object referencing those files is uploaded.

Understanding the Output

After uploading, mycdnctl prints a content reference for accessing the object:

Object <name> saved. Ref: holo://[encrypted-hash]?key=[plaintext-hash]

Where:

• [encrypted-hash] is the hex-encoded Blake3 hash of the encrypted metadata blob (used as the HoloKVS key, optionally namespaced by metadata.key_prefix)
• [plaintext-hash] is the hex-encoded Blake3 hash of the plaintext metadata blob (used as the decryption key)

Security Notes

• Encryption keys are content-derived:
  • Chunk encryption key = Blake3 hash of the plaintext chunk
  • Metadata encryption key = Blake3 hash of the plaintext metadata blob
• --include-password embeds Hero Redis session tokens into metadata (if configured).
  • Anyone who can fetch the metadata can use the embedded token to access shard storage.
  • For public content, prefer configuring Hero Redis for unauthenticated reads and keep --include-password off.

Development

This repository is a Cargo workspace-like layout (multiple crates under crates/):

• crates/cdn-meta
• crates/mycdnctl
• crates/registry

Build / test individual crates via their crate directories, or use --manifest-path from the repo root.