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+ <title>Breaking caesar ciphers</title>
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+
+# Breaking caesar ciphers
+
+![centre-aligned Caesar wheel](caesarwheel1.gif)
+
+---
+
+# Brute force
+
+How many keys to try?
+
+## Basic idea
+
+```
+for each key:
+ decipher with this key
+ how close is it to English?
+ remember the best key
+```
+
+What steps do we know how to do?
+
+---
+# How close is it to English?
+
+What does English look like?
+* We need a model of English.
+
+How do we define "closeness"?
+
+
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