# Encrypted reasoning fields in LLM APIs: a hobby project exploring signed thinking blocks

DevFeed: [Encrypted reasoning fields in LLM APIs: a hobby project exploring signed thinking blocks](<https://devfeed.tech/articles/let-s-talk-about-encrypted-reasoning-29096.md>)

Original publisher: [Read original article](<https://blog.cryptographyengineering.com/2026/05/29/fooling-around-with-encrypted-reasoning-blobs/>)

Author: Matthew Green

Published: 2026-05-29T03:52:19Z

Content type: opinion

Language: en

Sources: [Matthew Green](<https://devfeed.tech/sources/matthew-green.md>)

Topics: [Large Language Model](<https://devfeed.tech/topics/llm.md>), [API](<https://devfeed.tech/topics/api.md>), [Prompt Engineering](<https://devfeed.tech/topics/prompt-engineering.md>), [Claude](<https://devfeed.tech/topics/claude.md>), [OpenClaw](<https://devfeed.tech/topics/openclaw.md>), [Security](<https://devfeed.tech/topics/security.md>), [OpenAI](<https://devfeed.tech/topics/openai.md>)

Tags: [agent](<https://devfeed.tech/tags/agent.md>), [agents](<https://devfeed.tech/tags/agents.md>), [ai](<https://devfeed.tech/tags/ai.md>), [api](<https://devfeed.tech/tags/api.md>), [attacks](<https://devfeed.tech/tags/attacks.md>), [chain-of-thought](<https://devfeed.tech/tags/chain-of-thought.md>), [claude](<https://devfeed.tech/tags/claude.md>), [coding-agents](<https://devfeed.tech/tags/coding-agents.md>), [cryptography](<https://devfeed.tech/tags/cryptography.md>), [frontier-llm-apis](<https://devfeed.tech/tags/frontier-llm-apis.md>), [llms](<https://devfeed.tech/tags/llms.md>), [openai](<https://devfeed.tech/tags/openai.md>), [openclaw](<https://devfeed.tech/tags/openclaw.md>), [prompt](<https://devfeed.tech/tags/prompt.md>), [security](<https://devfeed.tech/tags/security.md>)

## AI overview

This opinion article describes a hobby project investigating encrypted or signed reasoning fields exposed by LLM APIs. It discusses configuring an OpenClaw agent to use Claude, comparing Claude's Messages API with OpenAI's Responses API, and examining hidden chain-of-thought data. An August 11, 2026 update says European researchers developed a working attack inspired by the post.

## Source excerpt

Update August 11, 2026: A group of researchers from all over Europe were inspired by this post, and actually turned it into a real working attack! Check out their writeup and paper here. This is a quick post I wanted to write about a hobby project I spent a weekend on. It has little to ... Continue reading Let's talk about encrypted reasoning ->