The review for the retake-exam takes place Friday, April 13th (13:00h-14:00h) in room 03.11.058.
The exam review takes place in room 03.11.058 (9:30h-11:30h).
The 6th exercise sheet is now available. It will be discussed next Wednesday, February 7th.
The 5th exercise sheet is now available on our website. It will be discussed next Tuesday, January 30th.
The 4th exercise sheet is now available on our website. It will be discussed next Tuesday, January 9th.
The third exercise sheet is now available on our website. It will be discussed next Tuesday, December 12th.
The second exercise sheet is now available on our website. It will be discussed next Tuesday, November 28.
Please note that you must solve a new password quiz in order to have access to the lecture material.
The slides from today's lecture are now online.
Some students pointed out a minor mistake in the derivation on the blackboard of the lower bound on the success probability:
We forgot to condition P(Dec_k'(c) = m_1) on the variable b in the definition of λ. That is, instead of one single λ, we need to define λ_0 and λ_1, which is given by λ_i := P(Dec_k'(c) = m_1 | b = i) for i ∈ {0, 1}.
Now, for the bounds on λ from the blackboard to make sense, the correct index i needs to be appended:
where K is the key space and M is the message space.
After the lecture the question arose why the upper bound analogus to the one for λ_0 does not apply to λ_1. To see this, please note that
p(m_1 ∈ D_c | b = 1) = 1, as Enc_k(c) = m_1 in the case where b = 1, whereas
p(m_1 ∈ D_c | b = 0) = ∑ (k ∈ K) p(Dec_k(c) = m1 | b = 0) ≤ ∑ (k ∈ K) 1/|M| = |K|/|M|,
as m_1 is chosen uniformly at random independently from m_0 (and thus c).
The solution to the first exercise sheet is now available. Please note that the wording of Exercise 1.3 b) was changed slightly due to the feedback provided by many students in the tutorial session.
The first exercise sheet is now available on our website. It will be discussed next Wednesday, October 25.
Website created.