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 * [Center for Internet Security (CIS)](https://www.cisecurity.org/cis-benchmarks/) - CIS Benchmarks: 100+ free downloadable configuration guidelines for various technology groups to safeguard systems against today’s evolving cyber threats. | Lot of useful information to harden windows/linux operating systems, secure server softwares, docker containers, etc.
 * [Diogo Mónica](https://diogomonica.com/2017/03/27/why-you-shouldnt-use-env-variables-for-secret-data/) - (2017) Why you shouldn't use ENV variables for secret data
 * [Laurens Van Houtven](https://www.lvh.io/posts/dont-expose-the-docker-socket-not-even-to-a-container.html) - (2015) Don't expose the Docker socket (not even to a container)
+* [Laurens Van Houtven](https://www.crypto101.io/) - Crypto 101 is an introductory course on cryptography, freely available for programmers of all ages and skill levels. **Bonus** : [GitHub repo](https://github.com/crypto101/book)
 
 ## GPG
 * [Charles Zachary Lockhart](http://irtfweb.ifa.hawaii.edu/~lockhart/gpg/) - GPG Cheat Sheet