Cryptography
Ciphers, hashes, keys and certificates.
Beginner
Start here. No background needed beyond school maths.
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Beginner
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Crypto 101
A free introductory book on cryptography for programmers: ciphers, hashes, keys and the usual mistakes.
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Document
Beginner
↗ External site
How Let's Encrypt Works
A short explanation of certificates and how HTTPS gets issued.
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Advanced
Once the basics are comfortable.

