The internet has always had a problem with ownership. You buy access to something, and somewhere a server holds the right to take it away. Your movies, your music, your files — you're renting, and the landlord can change the locks.

I got to work on this problem at Darkblock, where we built encrypted content unlockable by NFT. That work stuck with me. So I built CryptoProto — a tool that makes it easy for anyone, human or agent, to encrypt a file, store it permanently, and mint a token that is the only way to open it again.

Selling the NFT sells the file

Most NFTs are receipts. The JPEG sits on a server; the token points at it; everyone can see it anyway. CryptoProto inverts that. The file is encrypted with AES-256-GCM, the ciphertext lives forever on Arweave, and the decryption key sits in escrow — released only to the wallet that currently owns the NFT, verified on-chain at the moment of the request.

Ownership is live. Transfer the token and the buyer can decrypt immediately. You can't anymore. No accounts, no DRM server deciding who you are — just a signature from the wallet that holds the key to prove it's you, and the chain to prove the token is yours.

Your file never leaves the browser

The site is fully static — no server, nothing to subpoena. Every cryptographic operation runs client-side with WebCrypto. The plaintext and the AES key exist only in browser memory; the key is zeroed after use and never written to storage. What goes to Arweave is ciphertext. What goes on-chain is a manifest: transaction id, IV, auth tag, algorithm.

Unlocking works the same way in reverse. Sign a challenge, the escrow checks you still own the NFT, the key comes back, and decryption happens in your browser. Images, video, audio, PDFs — previewed inline, key zeroed the moment the bytes are decrypted.

Built for agents from day one

This is the part I'm most excited about. CryptoProto speaks MCP. The cryptoproto-mcp server gives an AI agent seven composable tools — encrypt, upload, mint, register the key, unlock, all of it. An agent can take a file from plaintext to NFT-gated permanence in a single tool sequence, no browser required.

The whole site is machine-readable too: OpenAPI spec, llms.txt, agent cards, Markdown versions of every page served by content negotiation. Agents are about to be the most prolific creators on the internet. They'll need a way to own what they make — and to sell it.

Mint something at cryptoproto.com. The first file under 100 KB uploads free.

Whoever holds the token holds the content. That's the whole idea.