---
title: "Discussion on \"A certificate authority's private key was the number 4. We checked.\" | Hashnode"
description: "Discussion on \"A certificate authority's private key was the number 4. We checked.\". Eight eMudhra intermediate CA keys were generated wrongly. We recovered six of them from the public certificates in under a quarter of a second each. Browsers are protected; a lot of other software is not, and the reason is how certificate trust actu"
url: "https://hashnode.com/posts/a-certificate-authoritys-private-key-was-the-number-4-we-checked/6ad99124928b553b54a66a6f"
---

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# [A certificate authority's private key was the number 4. We checked.](https://systemdesignacademy.hashnode.dev/a-certificate-authoritys-private-key-was-the-number-4-we-checked?utm_source=hashnode&utm_medium=feed)

Eight eMudhra intermediate CA keys were generated wrongly. We recovered six of them from the public certificates in under a quarter of a second each. Browsers are protected; a lot of other software is not, and the reason is how certificate trust actu

Oct 22 · 7 min read · systemdesignacademy.hashnode.dev  
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## Written by

[RONI DAS](https://hashnode.com/@ronidas)

@ronidas · India

  
[View profile](https://hashnode.com/@ronidas)

AI engineering, agentic memory, machine learning, and system design at scale.

I work on AI systems and the infrastructure they actually run on: agentic architectures, memory for agents, retrieval, and the graph and data layers that keep model output grounded in something real. Formerly at Neo4j. I also write and teach the systems side that most AI content skips, from distributed systems and databases to the design decisions that decide whether a model ever reaches production. I run Total Technology Zonne on YouTube and I am building systemdesign.academy, an interactive course on system design, machine learning, and AI engineering, covering the parts most tutorials leave as an exercise for the reader. Mock interviews and prep packs: topmate.io/roni

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