Cryptography 2006 - Errata

• Handout 0: Resits in August are only for students who are eligible. Please consult here for eligibility criteria.
• Exercise Sheet 1, Exercise 6 (ii) should read:
  For every a,b∈ Z: if a ≡ b (mod n) then b ≡ a (mod n)
• Mathematics 1, page i, second paragraph: The mappings should read: 1→2, 2→3, 3→1.
• Handout 2, page 13, first paragraph: The round keys should read: K₀,...,K_r-1
• Handout 2, page 13, decryption algorithm:
  the ciphertext in step 1 of the algorithm should read C=(R_r,L_r)
  the plaintext in step 3 of the algorithm should read M=(L₀,R₀)
  For the revised version with some extended explanations see the new handout 2 version from the webpage
• Handout 2, page 15, point 26: The description of the intial permutation IP should read
  "It permutes the 64 bits of the input, i.e. the plaintext. IP is given in a form that specifies the output order of the 64 input bits, e.g., the 58 in the first position means that the first bit of the output is the 58^th bit of the input."
• Handout 2, page 16: The last column of the PC-2 permutation is missing. Please see the new handout 2 version from the webpage.
• Mathematics 3, page vii: The two addition tables for F₂[x] are wrong. Please see the new handout 4 version from the webpage for the correct ones.
• Mathematics 3, page viii: The penultimate example should read:
  x²+x+1 ⋅ x²+1 ≡ 1 (mod x³+x²+1)
  111 ⊗ 101 = 001
• Solutions 4, Exercise 5: The solution on the original handout is wrong. Please see the new solution on the webpage. I will also add the solutions for Exercise 6 soon.
• Solutions 5, Exercise 1: The modulo factor for accessing the key array should be $2$ not $3$. The computations are nevertheless correct.
• Solutions 5, Exercise 3(a): The combined keystream has to be computed from the keystream bits of the constituent LFSR and not, as given in the original handout, from the feedback bits. Thus the correct solution is of the form:

  x0	0	1	0	0	1	1	1	0	1	1
  x1	0	1	1	0	1	0	1	1	1	1
  x0⋅ x1 ⊗ x0	0	0	1	0	0	1	0	0	0	0

• Solutions 7, Exercise 1: The solutions are incorrect. For the correct solutions please the updated solutions on the webpage.
• Handout 9, page 62, Example: The fifth bullet point in the example should read:
  To obtain the secret key we have to compute d using the extended Euclidean algorithm.
• Handout 9, page 62, last line: The last C₁^-d should read C^-d. I have also added another intermediate result into the computation for some additional clarification. Please see the new handout on the webpage.
• Solutions 9, Exercise 1: In the solutions of parts a-c it should read:
  n = p ⋅ q = ...
  and
  φ = (p-1) ⋅ (q-1) = ...
• Solution 11, Exercise 2: Steps 1-3 of the Calling protocol was incomplete.
• Handout 12: There are some clarifications in the Review Suggestions. Please have a look.