+Slow but clever vs Dumb but fast
+
+## Human approach
+
+Ciphertext | Plaintext
+---|---
+![left-aligned Ciphertext frequencies](c1a_frequency_histogram.png) | ![left-aligned English frequencies](english_frequency_histogram.png)
+
+---
+
+# Human vs machine
+
+## Machine approach
+
+Brute force.
+
+Try all keys.
+
+* How many keys to try?