> For the complete documentation index, see [llms.txt](https://cybersleuth.gitbook.io/cybersleuth/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://cybersleuth.gitbook.io/cybersleuth/day-2/briefing.md).

# Briefing

Foundations of Cryptography

### How do computers communicate?

{% hint style="warning" %}
Other than "programming" languages, how do computers talk in secret code?
{% endhint %}

*Across the internet, there are different ways that information is represented to make the whole world ultimately interconnected.*

**Activity:** Let's try sending each other morse code messages!

{% embed url="<https://www.boxentriq.com/code-breaking/morse-code>" %}

{% content-ref url="/pages/rT524gvX4XMS53fSMv1S" %}
[Case 1: Starting from the Basics](/cybersleuth/day-2/case-1-starting-from-the-basics.md)
{% endcontent-ref %}

### What's an encoding scheme for letters?

{% hint style="warning" %}
How can I encode a message of letters?
{% endhint %}

One of the more well-known encoding schemes, the Caesar Cipher encodes English letters by shifting each letter forward by a certain number of steps.

{% embed url="<https://kids.nationalgeographic.com/games/action-adventure/article/crack-the-code-1>" %}

{% embed url="<https://cryptii.com/pipes/caesar-cipher>" %}

{% content-ref url="/pages/Qb31ZNpy0wZvZSdAJ3xA" %}
[Case 2: Caesar Cipher (Not the Salad)](/cybersleuth/day-2/case-2-caesar-cipher-not-the-salad.md)
{% endcontent-ref %}

### Are these ciphers actually used?

{% hint style="warning" %}
Has anyone actually used these ciphers for real-world purposes?
{% endhint %}

Yes! A cool example is the Book Cipher, where a real book is used to hide messages. It has a history dating back to the American Revolution.

{% embed url="<https://derekbruff.org/blogs/fywscrypto/historical-crypto/whats-in-a-book-a-brief-history-of-book-ciphers/>" %}

{% content-ref url="/pages/dwXvDjMwECaR2PSatQY2" %}
[Case 3: Reading About the Book Cipher](/cybersleuth/day-2/case-3-reading-about-the-book-cipher.md)
{% endcontent-ref %}