## Automated Frequency Analysis

Read this: https://planetcalc.com/8047/

Then decrypt this: "Iuhtxhqfb dqdobvlv lv wkh vwxgb ri wkh glvwulexwlrq ri wkh ohwwhuv lq d whaw. Dqdobvlv ri iuhtxhqflhv khos ghfubswlqj vxevwlwxwlrq-edvhg flskhuv xvlqj wkh idfw wkdw vrph ohwwhuv dssdulwlrqv duh ydublqj lq d jlyhq odqjxdjh : lq hqjolvk, ohwwhuv H, W ru D duh frpprq zkloh C ru T duh uduh."

Most automated cryptography tools use this sort of technique behind the scenes.

Another example is the chi-squared statistic: http://practicalcryptography.com/cryptanalysis/text-characterisation/chi-squared-statistic/

Crypto has a lot of math, but luckily, because it is math, someone else has usually written a tool to do it for you. It takes a lot of work to get to the cutting edge in this field.

- What is text fitness?
- Explain how frequency analysis can be used to automatically detect the correct decryption of a ciphertext.
- What is leet speak?
- How would this break a text fitness calculation?