1. Cryptography
“Do I want the NSA to know I just bought a picture of a cat for my wall?”

2. Good Ole Fashion Security Always Wins…

3. What is it?
Cryptography: the process of enciphering (encoding) and deciphering (decoding) messages using a secret code or cipher
Used for:
Confidential Communication – matters of national security, trade agreements, personally identifying information
Valuable Information – financial information, logins
Criminal Communications

4. Here Be Definitions
Cryptography – the enciphering and deciphering of messages in secret code or cipher
Encryption – a process of enciphering messages to keep them secret, so only “authorized” parties can read them
Decryption – a process that reverses encryption, take a secret message and reproducing the original plain text
Plaintext – unencrypted text with a clear meaning
Ciphertext – the unreadable encrypted text
Cipher – a technique (or algorithm) that performs encryption, or the actual encrypted message

5. Caesar’s Cipher Used by Caesar to communicate with his generals
Consider the alphabet to be a wheel
The Caesar Cipher shifts every by 4
A -> E
B -> F
Z -> D

6. Substitution Cipher You can also make it random! A –> Z D -> A
And 24 more pairings

7. Our Messages Are Secure!
Nope… enter mathematics
Certain letters in the English language appear a lot…
Like e and t
We can take encrypted text and just see what letters are present the most

8. Example
GFS WMY OG LGDVS MF SFNKYHOSU ESLLMRS, PC WS BFGW POL DMFRQMRS, PL OG CPFU M UPCCSKSFO HDMPFOSXO GC OIS LMES DMFRQMRS DGFR SFGQRI OG CPDD GFS LISSO GK LG, MFU OISF WS NGQFO OIS GNNQKKSFNSL GC SMNI DSOOSK. WS NMDD OIS EGLO CKSJQSFODY GNNQKKPFR DSOOSK OIS 'CPKLO', OIS FSXO EGLO GNNQKKPFR DSOOSK OIS 'LSNGFU' OIS CGDDGWPFR EGLO GNNQKKPFR DSOOSK OIS 'OIPKU', MFU LG GF, QFOPD WS MNNGQFO CGK MDD OIS UPCCSKSFO DSOOSKL PF OIS HDMPFOSXO LMEHDS. OISF WS DGGB MO OIS NPHISK OSXO WS WMFO OG LGDVS MFU WS MDLG NDMLLPCY POL LYEAGDL. WS CPFU OIS EGLO GNNQKKPFR LYEAGD MFU NIMFRS PO OG OIS CGKE GC OIS 'CPKLO' DSOOSK GC OIS HDMPFOSXO LMEHDS, OIS FSXO EGLO NGEEGF LYEAGD PL NIMFRSU OG OIS CGKE GC OIS 'LSNGFU' DSOOSK, MFU OIS CGDDGWPFR EGLO NGEEGF LYEAGD PL NIMFRSU OG OIS CGKE GC OIS 'OIPKU' DSOOSK, MFU LG GF, QFOPD WS MNNGQFO CGK MDD LYEAGDL GC OIS NKYHOGRKME WS WMFO OG LGDVS.

9. Count the Letters

10. S => e, O => t
GFe WMY tG LGDVe MF eFNKYHteU EeLLMRe, PC We BFGW PtL DMFRQMRe, PL tG CPFU M UPCCeKeFt HDMPFteXt GC tIe LMEe DMFRQMRe DGFR eFGQRI tG CPDD GFe LIeet GK LG, MFU tIeF We NGQFt tIe GNNQKKeFNeL GC eMNI DetteK. We NMDD tIe EGLt CKeJQeFtDY GNNQKKPFR DetteK tIe 'CPKLt', tIe FeXt EGLt GNNQKKPFR DetteK tIe 'LeNGFU' tIe CGDDGWPFR EGLt GNNQKKPFR DetteK tIe 'tIPKU', MFU LG GF, QFtPD We MNNGQFt CGK MDD tIe UPCCeKeFt DetteKL PF tIe HDMPFteXt LMEHDe. tIeF We DGGB Mt tIe NPHIeK teXt We WMFt tG LGDVe MFU We MDLG NDMLLPCY PtL LYEAGDL. We CPFU tIe EGLt GNNQKKPFR LYEAGD MFU NIMFRe Pt tG tIe CGKE GC tIe 'CPKLt' DetteK GC tIe HDMPFteXt LMEHDe, tIe FeXt EGLt NGEEGF LYEAGD PL NIMFReU tG tIe CGKE GC tIe 'LeNGFU' DetteK, MFU tIe CGDDGWPFR EGLt NGEEGF LYEAGD PL NIMFReU tG tIe CGKE GC tIe 'tIPKU' DetteK, MFU LG GF, QFtPD We MNNGQFt CGK MDD LYEAGDL GC tIe NKYHtGRKME We WMFt tG LGDVe.

11. Next Step
The next step is a little harder G could be a, i, or o. Look at your text! tG o, its probably o 

12. And continuing on a bit…
one way to solve an encrypted message, if we know its language, is to find a different plaintext of the same language long enough to fill one sheet or so, and then we count the occurrences of each letter. we call the most frequently occurring letter the 'first', the next most occurring letter the 'second' the following most occurring letter the 'third', and so on, until we account for all the different letters in the plaintext sample. then we look at the cipher text we want to solve and we also classify its symbols. we find the most occurring symbol and change it to the form of the 'first' letter of the plaintext sample, the next most common symbol is changed to the form of the 'second' letter, and the following most common symbol is changed to the form of the 'third' letter, and so on, until we account for all symbols of the cryptogram we want to solve.

13. Vigenère Cipher
A Vigenère Cipher decides that each letter is going to be shifted differently
The first letter will be shifted by 4
The second letter will be shifted by 8
The third letter will be shifted by 3 …
The tenth letter will be shifted by 9
This code is difficult to crack by hand, but amazingly easy for a computer. It takes only a few minutes

14. Good Encryption is Tricky!
Mary, Queen of Scotts used a cipher in 1586 to correspond about a plot to assassinate Queen Elizabeth I. It was deciphered by frequency analysis, and she was executed.
Frequency analysis was described in the ninth century by al-Kindi.
The Sicilian Mafia used the Caesar Cipher in the 21st Century.
Suetonius explained it in the first century.
Scientific American described the Vigenère Cipher as “impossible of translation.”
Babbage and Kasiski had broken the Vigenère Cipher 50 years earlier.
It is easy to be lulled into a false sense of security in the face of jumbled symbols.

15. The Government is Watching You!
If a governmental security agency (NSA) were to crack our best encryption algorithms, would we know?
Fundamental Tenet of Cryptography: If lots of smart people have failed to solve a problem, then it probably won’t be solved (soon).
We do not currently have a provably secure encryption algorithm.

16. We are Lazy!
Despite knowledge of a better encryption algorithm, people will sometimes opt for an easier algorithm for convenience.
When flaws are discovered, transitions to better algorithms are performed slowly and reluctantly.
Similarly, people write passwords on sticky notes or use guessable passwords.
Great encryption can be circumvented by indiscrete employees.

17. Security by Obsecurity is Risky
We should assume that no encryption algorithm can be kept secret.
Instead, we need algorithms that are secure even if the enemy knows the system.
Often companies try creating their own propriety algorithms that have not been evaluated by security experts, which are later found to have weaknesses.