# Rob Berry

> Personal website of Rob Berry, a creative technologist working in the environmental risk sector. Articles cover software, data, systems development, cloud architecture, and flood risk.

Use the links below as the authoritative pages. The writing archive links to all published articles. Article pages include the full text and publication details.

## About

- [About Rob Berry](https://cm9i.com/about/): Professional background, areas of work, publications, and contact details.

## Writing

- [Writing archive](https://cm9i.com/writing/): Index of published articles.
- [Choosing between Amazon S3 Files and EFS for your workload](https://cm9i.com/writing/choosing-between-amazon-s3-files-and-efs-for-your-workload/): A comparison of Amazon S3 Files and EFS. Learn how they differ in architecture, file size handling, and pricing to choose the right AWS storage.
- [Modern day cracking of the "Multiplication code"](https://cm9i.com/writing/modern-day-cracking-of-the-multiplication-code/): How modern computing can crack the "Multiplication code" and how to make it stronger.
- [Python encryption and decryption of the "Multiplication code"](https://cm9i.com/writing/python-encryption-and-decryption-of-the-multiplication-code/): A Python implementation of the Agent Zigzag (Eddie Chapman) WWII "Multiplication code".
- [Multiplication code](https://cm9i.com/writing/multiplication-code/): Discover the "multiplication code" used by WWII double agent Eddie Chapman. Learn how a simple keyword and basic math created a powerful, manual Gronsfeld cipher.
- [Cryptography in World War II](https://cm9i.com/writing/cryptography-in-world-war-ii/): Explore the history of WWII cryptography: from the Polish mathematicians who cracked Enigma to the Navajo Code Talkers and the birth of the first digital computer.
- [The "core service" rule for AWS architects](https://cm9i.com/writing/the-core-service-rule-for-aws-architects/): Why you should stick to AWS core services like ECS and S3. Learn from the App Runner deprecation: "Use the thing, not the thing that wraps the thing."

## Feeds and discovery

- [RSS feed](https://cm9i.com/index.xml)
- [Sitemap](https://cm9i.com/sitemap.xml)