This class was announced many months ago, and is just now getting underway. There are approximately 50,000 online students who pre-registered.
I am taking the class, because while we all use software tools that apply cryptographic technology, I wanted an understanding of the primitives and underlying methodologies. I thought it might be fun, too.
I'm about 2/3rds of the way through the Week 1 lectures. So far, for example, I have learned how Bletchley Park managed to decrypt Enigma rotor ciphers (a brute force ciphertext attack), what the security problems were in the NNTP protocol design in the Windows NT era (a one-time-pad actually used twice, permitting ciphertext to be decrypted with nothing more than an XOR), and the many problems incurred in WEP design (exploiting three weaknesses in the RC4 PRG as implemented in the WEP stream cipher).
I've also learned how DVD video CSS encryption works, and how its 17 and 25 bit registers are used in key generation, and how the encryption was broken using message knowledge (MPEG-2 structure).
I have learned to prove that OTP is "perfectly secure" -- but that the ciphertext is malleable and subject to precise data injection by an attack in transit.
I never studied discrete probability, so the terminology and associated notation describing probability analysis in large sets has been a little confusing, though I am able to comprehend the lemmas and proofs.
If you have any interest, you may take a look
here.