What is Cthulhu?

Cthulhu is a decentralized social media platform built on the blockchain. Unlike traditional social networks controlled by corporations, Cthulhu stores your posts, profiles, and digital objects directly on-chain — making them permanent, uncensorable, and truly owned by you.

Named after the legendary Cthulhu creature of the deep, the platform's logo is itself an ancient on-chain artifact: the 2013 fully embedded emoji, one of a number of ancient artifacts preserved on the Bitcoin blockchain. These digital relics can be discovered, claimed, and traded within Cthulhu or the SUP desktop client.

Cthulhu is a web-based client for the SUP (Satoshi Universal Protocol), meaning everything you do here is fully compatible with the SUP Windows desktop application. Your data isn't locked into Cthulhu — it lives on the blockchain, accessible from any compatible client.

Key Capabilities

• On-Chain Social Networking: Profiles, posts, and encrypted DMs stored permanently on the blockchain
• Digital Object Marketplace: Create, buy, sell, and trade tokenized objects (similar to NFTs)
• Blockchain Video Conferencing: Peer-to-peer audio and video calls signaled through the Bitcoin mempool — no centralized servers
• Token-Gated Rooms: Object-tethered chat rooms and Speaking Venues with paid seating
• Bitcoin Core-Style Wallet: Full UTXO management with Coin Control, multi-address aggregation, and an integrated address book
• Non-Custodial Security: Your private keys are encrypted in your browser and never leave your device

What is SUP?

SUP (Satoshi Universal Protocol) is the underlying protocol that powers Cthulhu. Created by embii4u, SUP enables fully decentralized social networking, digital object ownership, and encrypted communication — all built on top of existing blockchain infrastructure with zero centralized servers required for data storage.

Core Features of SUP

• Profile Minting: Create a unique on-chain identity (URN) associated with your wallet address
• Tokenized Objects: Create, buy, sell, give, and burn digital objects (similar to NFTs) that live entirely on the blockchain
• On-Chain Posts: Write permanent messages stored as blockchain transactions
• Encrypted Private Messages: End-to-end encrypted communication using ECIES (Elliptic Curve Integrated Encryption Scheme)
• Object-Based Chat Rooms: Group conversations tied to specific digital objects (Tethers)
• Speaking Venues: Token-gated live rooms where audience members can purchase speaking seats
• Blockchain Video Conferencing: Peer-to-peer audio and video calls with WebRTC, signaled through the Bitcoin mempool
• INQ Polls: Create on-chain polls with optional token gating and time limits
• Royalties: Object creators earn royalties on secondary sales automatically
• On-Chain File Embedding: Attach files directly to the blockchain using P2FK protocol
• Walkie-Talkie: Encrypted voice broadcasts over the blockchain

The SUP desktop client (C# Windows application) is the reference implementation of the protocol. Cthulhu is a fully compatible web client — everything created in Cthulhu appears in SUP and vice versa.

What is P2FK?

P2FK (Pay-to-Future-Key) is the revolutionary encoding mechanism that makes SUP possible. It allows arbitrary data to be embedded into standard cryptocurrency transactions by encoding information into the "addresses" field of a transaction output.

Why "Future Key"?

The addresses used in P2FK transactions are not currently active wallet addresses — they are specially crafted public key hashes that encode data. While nobody can spend coins sent to them today, these keys could theoretically correspond to real keys discovered far in the future. They are not "fake" — they exist in the future possibility space. The name "Pay-to-Future-Key" reflects this distinction, as coined by embii4u, the inventor of P2FK.

How It Works

In a normal transaction, you send coins TO a real wallet address. P2FK instead sends dust amounts (546 satoshis) to these future-key addresses that encode data. The data is permanently recorded on the blockchain — profile information, object metadata, post content, encryption keys, and more.

The data is permanent, uncensorable, and fully public (except for encrypted messages). The p2fk.io API reads and indexes this data, presenting it in a structured format that clients like Cthulhu and SUP can use.

P2FK Transaction Types

• PRO — Profile creation and updates (username, bio, image, private messaging keys)
• OBJ — Object creation with Name, URN (content/media), optional Image (thumbnail), pricing, and royalties
• BUY — Purchase an object at its listed price
• GIV — Transfer an object to another address for free
• BRN — Permanently destroy (burn) an object on-chain
• LST — List/delist an object for sale
• SEC — Encrypted private message data
• INQ — On-chain polls and inquiries

Objects & Digital Ownership

Objects in Cthulhu/SUP are similar to NFTs but built on the P2FK protocol rather than smart contracts. Each object has a Name (title), a URN (the actual content/media being claimed — an IPFS file, on-chain data, text, etc.), an optional Image (thumbnail for listings), an owner, a creator, and optional metadata like descriptions and royalty settings.

Object Types

• Standard Objects: Single-edition unique items with a creator and owner
• Collections: Multi-edition objects. The creator holds the "mint" and can produce multiple copies
• Self-Owned Objects: Objects where the creator and owner are the same address. These often serve as chat rooms (Tethers)
• Free Objects: Objects priced at 0 that can be claimed by anyone

What You Can Do

• Buy: Purchase an object at its listed price. Royalties are automatically distributed to the creator
• Give: Transfer an object to another address for free
• Burn: Permanently destroy an object using a BRN protocol transaction (see "Burning Objects" section)
• Create: Mint new objects with images, descriptions, pricing, and royalty settings

Key Pool — Pre-Generated Object Addresses

When you create an account on Cthulhu, a pool of 50 independent keypairs is silently generated and encrypted with your password. When you mint a new object, an address is pulled from this reserve pool rather than being created on-the-fly. This improves security by preventing key generation at the point of transaction. Used keys automatically appear in your wallet's Address Book; unused keys remain hidden. The pool auto-replenishes when it runs low.

On-Chain Embedding vs. IPFS

Most objects in Cthulhu use IPFS (InterPlanetary File System) for their media files. The IPFS hash is stored on-chain, and the actual file is hosted on the distributed IPFS network. Cthulhu runs its own IPFS node for all uploads.

However, truly brave creators can embed files directly on the blockchain using tools like Apertus.io . These fully on-chain artifacts are the most permanent form of digital content possible — they will exist as long as the blockchain exists.

Ancient Artifacts

Long before the term "NFT" existed, early adopters were embedding data on the Bitcoin blockchain. These pioneering experiments left behind ancient artifacts — fully on-chain content from as early as 2013.

The Cthulhu logo itself is one such artifact: a 2013 fully embedded emoji, part of a collection of on-chain relics from the earliest days of blockchain data embedding. These aren't just historical curiosities — they are tradeable digital objects that can be bought, sold, and given within Cthulhu or SUP.

Many more ancient artifacts still exist on Bitcoin, Litecoin, and Dogecoin blockchains, waiting to be discovered. Anyone with a valid cryptographic signature can claim ownership of unclaimed artifacts. This is digital archaeology — exploring the blockchain's history to uncover forgotten treasures.

On-Chain Age Titles

A classification system for understanding the historical age and cultural significance of early on-chain artifacts. Every object in Cthulhu is automatically assigned an age title based on the year it was first inscribed on the blockchain. These titles appear as badges on object detail pages.

The Primordial Era (2009–2014)

The Forging Era (2015–2020)

The Expansion Era (2021–2023)

Contemporary Era (2024+)

How to: Mint Your Profile

Minting a profile creates your permanent on-chain identity. This associates your chosen username (URN) with your wallet address on the blockchain via a PRO transaction.

How to: Create Objects

Creating an object mints a new digital item on the blockchain via an OBJ transaction. You become the creator, and you can set a price, royalties, and attach media. Each new object uses a pre-generated address from your key pool.

How to: Create a Room (Tether)

Rooms in Cthulhu are called Tethers. A tether is a self-owned object that serves as a group chat room. Anyone who "tethers" to it (follows it) will see it in their sidebar and can post messages in its feed.

How to: Create a Speaking Venue

Speaking Venues are a special type of Tether where only seat-holders can post ("speak"). The creator controls the number of available seats, and audience members purchase seats using cryptocurrency. This creates a token-gated live discussion environment.

How It Works for the Audience

When someone visits a Speaking Venue they don't hold a seat in, they see the conversation as read-only. They can purchase a seat at the listed price to gain speaking access. Audience members can also send ephemeral "Super Chat" messages (tip-based messages that appear temporarily) without holding a seat.

Blockchain Video & Audio Calls

Cthulhu features fully decentralized peer-to-peer audio and video calling. Unlike conventional calling apps that route through centralized servers, Cthulhu's calls are signaled directly through the Bitcoin mempool — making them truly serverless.

How It Works

The calling system uses WebRTC for the actual media stream (audio/video) but replaces the traditional signaling server with the blockchain mempool:

Features

• Audio Calls: Voice-only calls with low latency
• Video Calls: HD video at 720p resolution, face-to-face blockchain conferencing
• Voicemail: If the recipient doesn't answer, you can leave a voice message that's stored as an encrypted DM
• Custom Ringtones: Record and set a personal ringtone in Call Settings
• Call Tones: Record a greeting tone that plays for the caller while they wait for you to pick up
• In-Call Controls: Mute, toggle video, switch camera, and speaker controls during active calls

Phone Dialer

Open the phone dialer from any user's DM page or profile. You can make audio-only or video calls. The dialer shows a classic phone interface with the recipient's profile info.

Wallet & Key Management

Cthulhu is a non-custodial platform. Your private key (WIF) is encrypted with your password and stored in your browser's local storage. The server never sees or stores your key. The wallet is designed in the style of Bitcoin Core, giving you full control over your funds.

Wallet Tabs

The wallet is organized into five tabs, accessible from the Wallet button in the header or bottom navigation:

• Overview: Shows your aggregated balance across all addresses (main wallet, change addresses, and all object addresses). Displays recent transactions and quick-action buttons for Send and Receive
• Send: Compose transactions with a pay-to address, amount, and fee selection. Includes Coin Control for manual UTXO selection (see next section)
• Receive: Displays your wallet address with a QR code. Lists all your system addresses (main, change) and object addresses for receiving funds
• Transactions: Full transaction history with filters by type, searchable and sortable
• Addresses: A comprehensive address book showing all addresses you control — main wallet, change addresses, and object addresses. Each entry shows the address type, label, and current balance. Object addresses include a "Decrypt WIF" option to reveal the private key for that specific object

Balance Aggregation

Your wallet overview shows the total balance across all addresses you control. This includes your main wallet address, any change addresses from previous transactions, and all object addresses whose encrypted keys are stored in your browser. This gives you a complete picture of your on-chain wealth.

Exporting Your Private Key (WIF)

Importing an Existing Key

When creating an account, you can choose to import an existing WIF key instead of generating a new one. This lets you use the same wallet across Cthulhu and the SUP desktop client.

Multi-Wallet Support

Cthulhu supports up to 5 wallets per network. You can switch between them in Settings. Each wallet has its own address, balance, and associated profile.

State Persistence

Your follows list, pinned friends, tethered rooms, favorites, and playlists can be backed up directly to the blockchain using Chain Backups. See the Chain Backups section for details.

Chain Backups

SEC Etch Backups allow you to encrypt and inject your entire application state — follows, rooms, pins, favorites, playlists, collection WIFs, notification state, and preferences — directly onto the blockchain as raw data. This creates a permanent, self-sovereign backup that is invisible to all indexers and can be restored on any device using just your WIF and the transaction ID.

How It Works

When you save a SEC backup, Cthulhu collects your state from all networks (both mainnet and testnet), encrypts it with AES-256-GCM using a key derived from your private key, and injects the encrypted bytes as raw address-encoded data onto the Bitcoin testnet. No P2FK SIG header is used — the data is invisible to all P2FK indexers, SUP clients, and Cthulhu feeds.

Only you can decrypt this data, using your WIF. The backup always etches to testnet regardless of your current network, keeping costs minimal. You receive a pointer in the format tBTC:TransactionID to find and restore your data.

What Gets Backed Up

• Follows & Pinned Friends: Your entire social graph across all networks
• Tethered Rooms: All rooms you've joined
• Favorites & Playlists: Your curated content lists
• Collection WIFs: Private keys for your collections (critical for recovery)
• Object Derivation Index: Ensures future objects use the correct index
• Profile URN: Your login identity mapping
• Object Addresses: Addresses of objects you own
• Transaction History: Your local tx log
• Notification State: Read/unread markers, DM timestamps
• Preferences: Wallpaper, auto-pin, network selection

How to: Save a SEC Backup

How to: Restore from TXID

Backup History

Your SEC backup history is stored locally. Each entry shows the date, pointer (network + TXID), address count, and cost. You can copy any pointer or click to pre-fill the restore input directly.

Coin Control

Coin Control is an advanced wallet feature that gives you fine-grained control over which specific UTXOs (Unspent Transaction Outputs) are used as inputs in a transaction. This is critical for privacy, fee optimization, and P2FK protocol compatibility.

What Are UTXOs?

Unlike a bank account that stores a single balance, Bitcoin (and similar chains) tracks ownership through UTXOs — individual "coins" of various sizes. When you receive 0.005 BTC in one transaction and 0.003 BTC in another, your wallet holds two separate UTXOs. When you send a transaction, you choose which of these coins to spend.

How to Use Coin Control

Why Use Coin Control?

• Privacy: Avoid linking UTXOs from different sources in a single transaction
• Fee Optimization: Select fewer, larger UTXOs to minimize transaction size and fees
• Dust Management: Consolidate small UTXOs or avoid spending dust outputs
• P2FK Operations: Ensure the correct UTXOs and address ordering for protocol-specific transactions

Encrypted Private Messages

Cthulhu supports end-to-end encrypted private messaging using ECIES (Elliptic Curve Integrated Encryption Scheme). Messages are encrypted on your device before being broadcast to the blockchain — only the intended recipient can decrypt them.

How It Works

When you mint your profile, your public encryption keys (pkx, pky) are published on-chain as part of the PRO transaction. Anyone can use these keys to encrypt a message that only you can read. The encrypted message is stored on the blockchain as a SEC (encrypted) P2FK transaction.

Sending & Receiving

Important Notes

• Both sender and recipient must have minted profiles with published encryption keys
• Your wallet must be unlocked (password entered) to read or send encrypted messages
• Messages you send are encrypted for the recipient — your own outbound messages may show as "Sent (encrypted for recipient)" unless locally cached
• Decrypted messages are cached locally for instant loading on return visits
• The self-destruct timer feature lets you auto-delete local copies after a set period
• You can clear chat to remove both local caches and server-side history

Message Requests

When someone you don't follow sends you a direct message, it appears in the Message Requests section of your Tether panel — not in your main chat list. This keeps your main conversation list clean and prevents unsolicited messages from cluttering your inbox.

How It Works

Your Tether panel (Chats) has two zones: your followed contacts and rooms (which count toward the Chats badge) and the Message Requests section (which does not). Only messages from people you actively follow contribute to the notification badge on the bottom navigation bar.

Managing Requests

• View: Open the message to read it, without adding the sender to your follows
• Accept: Adds the sender to your follow list, promoting their messages to your main chat list
• Ignore: Leave the request in the section without acting on it

Data & IPFS Cache

Cthulhu stores cached data locally in your browser to improve performance. This includes decrypted message caches, conversation history, and IPFS media files you've viewed.

What's Cached

• Decrypt Cache: Previously decrypted DM messages, so they render instantly without re-decryption
• Conversation Cache: Full DM conversation state for instant two-phase loading
• IPFS Media: Images and media viewed from IPFS are cached locally
• Sent Messages: Locally saved copies of your outbound messages
• Key Pool: Your 50 pre-generated encrypted keypairs for object creation
• Follows & Settings: Your follow list, pinned friends, and notification state

Clearing Data

In Settings → Data and Storage, you can view your cache size and clear stored data. Clearing the cache won't delete any on-chain data — it only removes local copies.

IPFS Architecture

Cthulhu runs a local IPFS (Kubo) node on the backend for all file uploads. When you upload an image for a profile, object, or post, it's pinned to this local node and made available to the IPFS network. Viewed IPFS content is cached in your browser — making you an effective "pinning node" for content you consume, improving availability for the network.

Burning Objects

Burning permanently destroys an object. Unlike other blockchains that "burn" by sending to a dead wallet address, the SUP protocol uses a dedicated BRN (burn) transaction type. This is a first-class protocol operation, not a transfer.

How Burning Works

When you burn an object, Cthulhu constructs a BRN P2FK transaction that references the object's address. The P2FK indexer recognizes this transaction as a semantic destruction event — the object is permanently marked as burned on-chain. No coins are "sent" to a dead address; instead, the protocol records the burn action directly.

Mainnet Warning

We strongly recommend starting on testnet. Testnet coins are free (available from faucets) and have no monetary value. Use testnet to:

• Learn how profile minting works
• Practice creating, buying, and trading objects
• Understand transaction fees and timing
• Test encrypted messaging
• Experiment with rooms and venues
• Try out video and audio calls
• Test the wallet system, Coin Control, and key backup

Disclaimers & Legal

Resources & Links