You can download this entire Handbook of Applied Cryptography for free [1].
Recently the authors also provided online course and video namely:
- Cryptography 101: Building Blocks (fundamental cryptographic primitives) [2]
- Cryptography 101: Real-World Deployments (PKI, TLS, Bluetooth, AWS, Signal) [3]
Other courses and video includes:
- The Mathematics of Lattice-Based Cryptography (introductory course)
- Kyber and Dilithium (standardized lattice-based cryptosystems)
- Hash-based signature schemes (LMS, XMSS, SPHINCS+)
- Error-Correcting Codes (linear, Hamming, Golay, cyclic, BCH, Reed-Solomon codes
[1] Handbook of Applied Cryptography:
https://cacr.uwaterloo.ca/hac/
[2] Crypto 101: Building Blocks:
https://cryptography101.ca/crypto101-building-blocks/
[3] Crypto 101: Real-World Deployments: