How Bitcoin’s OP_RETURN creates a “public gallery” for arbitrary data, expanding the attack surface beyond simple blockchain storage.

🖼️ Gallery vs. Drawer 🔒

OP_RETURN hangs the image on the wall. Obfuscation stuffs it in a drawer.

The bytes exist in both cases, but exposure matters: one is sanctioned display, the other tolerated abuse.

🎯 OP_RETURN: Public Gallery

Sanctioned display. Standard RPC/REST APIs expose data URIs. Any HTTP client can fetch, parse, and render instantly. Universal content serving.

🗄️ Obfuscation: Hidden Drawer

Tolerated abuse. Data exists but requires specialized knowledge to find and extract. Higher barrier to access, lower attack surface.

Data URI:

⚠️ Why This Matters

• Self-extracting by design: The asm field embeds a Data URI directly after OP_RETURN. Any HTTP-capable client can fetch this JSON, parse the string, and set it as <img src="..."> to render instantly.
• Zero specialized tooling: Just JSON + the web’s standard data: scheme. This makes content universally accessible to any browser, app, or script.
• Expanded attack surface: Large OP_RETURN payloads + RPC/REST bridges = universal content serving. Unlike obfuscated data hidden in witness or P2SH scripts, OP_RETURN data is explicitly designed for retrieval and display.
• Liability difference: When node operators expose OP_RETURN via standard APIs, they become de facto content hosts—not just blockchain validators. The “public gallery” makes moderation impossible without protocol changes.

Note: This demo uses a benign SVG (orange background + Bitcoin symbol “₿”). Real transactions typically store hex bytes, but once converted to a Data URI, any system that speaks HTTP can render it. The issue isn’t what’s stored—it’s how easily it’s surfaced.