1. A (Very) Brief History of Pre-Computer Cryptography
Richard J. Blech
Chief Executive Officer
Secure Channels, Inc.

2. Is there anyone here who cannot parse and explain this equation?

3. If not, that’s ok.

4. Why Pre-Computer Cryptography?
If you understand pre-computer crypto, you understand crypto!
There are only three differences between traditional and computer encryption
Virtualization: Computers can mimic a mechanical cipher machine of immense complexity
Speed
Computers scramble numbers rather than letters
Computers deal in binary sequences
Before encryption, the message must be converted into bits
The rest is all transposition and substitution as it has been for ages

5. The Evolution of Secret Writing
This is Herodotus
Herodotus was arguably the first modern “historian.”
He lived in the 5th Century
His most famous work, The Histories, tells the story of the Greco-Persian Wars

6. The Evolution of Secret Writing
Herodotus tells us about:
Demaratus, the Persian Invasion of Greece in 480 BC, and the Wax Tablets
One of the earliest forms of steganography was in 480 B.C. In the book Investigator's Guide to Steganography by Gregory Kipper, there is a story taken from a book known as The Histories, written by Greek historian Herodotus. Herodotus recorded that the Persian king, Xerxes, was planning to extend his empire "such that its boundaries will be God's own sky, so the sun will not look down upon any land beyond the boundaries of what is [their] own" (Kipper, 2003, p. 16). The Persians spent roughly 5 years secretly assembling one of the greatest armies in history. However, the Persian military buildup had been witnessed by an exiled-Spartan king, Demaratus. Demaratus had been exiled from Greece and lived in the Persian city of Susa. Although he was exiled, he still felt a sense of loyalty to Greece and wanted to warn the Spartans of the Persian invasion plan. However, Demaratus feared that any message sent to warn the Spartans would be intercepted by the Persian guards. Herodotus wrote: "As the danger of discovery was great, there was only one way in which he could contrive to get the message through: this was by scraping the wax off a pair of wooden folding tablets, writing on the wood underneath what Xerxes intended to do, and then covering the message over with wax again. In this way the tablets, being apparently blank, would cause no trouble with the guards along the road. When the message reached its destination, no one was able to guess the secret, until, as I understand, Cleomenes' daughter Gorgo, who was the wife of Leonides, divined and told the others that if they scraped the wax off, they would find something written on the wood underneath. This was done; the message was revealed and read, and afterwards passed on to the other Greeks." The Greeks were unaware of any Persian attack, so they had not been gathering together an army. As a result of this warning, the Greeks began to arm themselves and were ready for the Persian attack.

7. The Evolution of Secret Writing
Histaiaeus sent a secret message to Aristagoras of Miletus to get him to revolt against the Persians.
He sent it secretly by having a slave’s head shaven, the message tattooed on the bald head and waiting for hair to grow in.
Upon arrival, the slave’s head was shaved, and the message revealed.
That’s Kelly Osbourne, BTW...

8. The Evolution of Secret Writing - Hiding a Message
Wax tablets, shaved heads and hard boiled eggs (Porta, 16th Century) are about hiding the EXISTENCE of a message.
The term for hiding a message’s existence is STEGANOGRAPHY.
While steganography offers some security, it has a fundamental weakness:
If the message is discovered, the contents of the secret message are revealed at once.

9. Enter Cryptography
Derived from the Greek word kryptos, meaning “hidden.”
Cryptography’s goal is not to hide the existence of a message but, rather, to hide its MEANING.
The process of hiding a message’s meaning is called ENCRYPTION.
An encrypted message is
Scrambled...
...according to a predetermined protocol
...that has been agreed upon by the sender and recipient
With cryptography, unlike steganography, if an enemy intercepts the message, and lacks knowledge of the scrambling protocol, it’s still unreadable!

10. Cryptography’s Two Branches
Transposition
Substitution
CRYPTOGRAPHY