I hope you found today’s cryptanalysis activity interesting. As I mentioned in class, you’ll get the chance to work on a new ciphertext from start to finish in your first problem set, which I’ll post next week.

Here’s the worksheet from today’s class with all four ciphertexts. The plaintext for the first one (the shift cipher) comes from this news article on Chelsea Clinton’s wedding a few years ago. We’ll talk about poem codes in a future class.

The plaintext for the second one (the atbash cipher) comes from WIRED writer Mat Honan’s story about how his entire digital life was hacked. I’ll say a few words about this on Monday, but if you have the time to read the entire article, do so. It’s pretty incredible.

Remember, for Monday you should read the first chapter in Singh and create your blog account. Look for those account creation emails soon. And go ahead and finish decrypting the second ciphertext on the worksheet, too.