Prompt Injection Defense
← All servicesPrompt Injection Defense: Testing, Hardening, and Cryptographic Attestation
Prompt injection is the top entry in the OWASP LLM Top 10, and detection alone never fully holds. We test your input and output surface, design the layered defenses, and — where the stakes justify it — add cryptographic prompt provenance that fails closed instead of relying on catching every payload.
Prevents an attacker from turning your AI's own inputs into unauthorized commands — stopping data theft, fraudulent transactions, and reputation damage from a hijacked assistant.
The problem
An LLM with access to private data and the ability to act becomes dangerous the moment untrusted content reaches it — Simon Willison's "lethal trifecta." Indirect injection (through a retrieved document or a tool's output) means the attacker never has to touch your prompt directly. Filtering for bad strings is a losing game on its own.
How we harden it
We shrink the attack surface in layers rather than betting on one filter:
- Structured-output-only triage — constrain the model to a fixed schema so injected behavior has nowhere to land downstream.
- Data-fencing / spotlighting — per-request delimiting so the model treats untrusted input as data, never instructions.
- Output validation & sanitization — enforce enums and ranges, strip links and active content before any human or system trusts the output.
- Canary & leak detection — detect when an instruction has redirected the model and route to human review.
- Tool-permission minimization — reduce what a compromised prompt can actually reach.
Cryptographic prompt attestation
For high-stakes systems we replace brittle "injection detection" with provenance. Our research project Seal wraps every prompt in an Ed25519-signed Verified Prompt Envelope that proves who authorized it and that it wasn't tampered with — injection defense by construction, that fails closed instead of failing silent.
What you get
- A threat model of your specific injection surface.
- A layered-defense design your team can implement — the blueprint, not a black box.
- Optional cryptographic-attestation integration design where it's warranted.
We eat our own cooking
We hardened our own contact form against the exact attack class we sell defense against, and wrote up the threat model and the deliberate trade-offs. Read the case study: How we built a prompt-injection-hardened AI receptionist on Cloudflare's free tier.
Thinking about an assessment?
Tell us what you're building and what you're worried about. A real person reads every inquiry.
Start a conversation