The history of cryptography

Welcome! I'm so excited to explore the history of secrets and codes with you. Before we dive into the ancient clay tablets and hidden wartime messages, I'd love to tailor our journey to what you enjoy most.

To help me customize our session, could you tell me a bit about your background? Are you more interested in the technical side of how these methods work, or are you drawn to the historical stories and their impact on world events?

I'm more interested in the technical mechanics and mathematics of the codes.

It's wonderful to meet a fellow mechanics enthusiast! Focusing on the math and structural design of these systems makes studying cryptography incredibly rewarding because we can see exactly how simple geometric or algebraic rules create unbreakable confusion for an outsider.

To kick off our journey, let's establish our foundational road map. This path will take us from the physical, geometric manipulations of ancient Sparta all the way to the modular arithmetic that secures modern internet traffic.

Your path

Classical Ciphers (Caesar to Vigenère)

World War II and the Birth of Computing

Modern Cryptography (Public-Key & Beyond)

What is Cryptography?

At its heart, is the mathematical and mechanical art of hiding information. Historically, people relied on it for a simple reason: they needed to transmit valuable data across a physical space where adversaries could easily intercept it.

To make a message unreadable, we must apply an algorithm to scramble the data. In the world of codes, we call your original, readable message the plaintext. Once we run it through our mathematical or mechanical scrambling process, it becomes encrypted ciphertext.

Historically, these algorithms fall into two structural categories: transposition (shuffling the physical positions of the letters) and substitution (swapping each letter out for a different symbol). Let's start with the absolute oldest mechanical device we know of that used transposition: the ancient Spartan .