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Public Key Cryptography: Understanding RSA and Key Exchange

Exploring public key cryptography systems, including the RSA algorithm, Diffie-Hellman key exchange, and how asymmetric encryption enables secure communication without shared secrets.

January 15, 2026 1 min read By Scott Weeden cryptographypublic-key-cryptographyrsadiffie-hellmankey-exchange

Public Key Cryptography: Understanding RSA and Key Exchange

Public-key cryptography separates encryption from key distribution: each party publishes a public key and keeps a private key. RSA rests on the hardness of factoring (or related problems) while related primitives such as Diffie–Hellman address agreement of shared secrets over insecure channels.

This post summarizes the core ideas at a graduate level: key generation, modular exponentiation, correct use of padding and hybrid encryption, and why raw RSA is insufficient in practice. For implementation, prefer well-vetted libraries and modern padding (e.g., OAEP for encryption, PSS for signatures) rather than textbook-only constructions.

See the Cryptography course page and later posts for rigorous treatment of attacks, parameters, and pairing with symmetric ciphers for bulk data.