Kontakt a konzultačné hodiny

adresa: Katedra informatiky, FMFI UK, Mlynská dolina, 842 48 Bratislava
miestnosť: M-214
e-mail: stanek@dcs.fmph.uniba.sk
telefón: (+421 2) 60295 101

Konzultačné hodiny: dohodou

Výuka ZS 2023/24

Diplomový seminár (3) (Str 11:30-13:00 M-III)

Kryptológia 1 / Cryptology 1 (Str 16:30-18:00 M-I, Štv 14:00-15:30 M-I)

Lectures:

  1. When, How, and What - pdf, Introduction: Context and Basic Notions - pdf
  2. Cryptanalysis of Classical Ciphers - pdf
  3. Block Ciphers - pdf
  4. Block Ciphers 2 - pdf
  5. Hash Functions - pdf
  6. Message Authentication Codes - pdf (-)
  7. RSA - pdf
  8. Security of RSA - pdf
  9. Discrete Logarithm and Encryption Schemes - pdf
  10. Bezpečnosť asymetrického šifrovania (SK) - pdf
  11. Learning with Errors - pdf
  12. Passwords - pdf
  13. Signature Schemes - pdf
  14. Hash-based Signatures - pdf
  15. Cryptographic protocols - introduction - pdf

Homework assignments (students):

  1. Find the plaintext (English text) for given ciphertext. We use a transposition cipher on 10 x 10 grid (a torus) that arranges plaintext characters in a spiral. A starting position, initial direction and spin (clockwise or anti-clockwise) are part of the key. Final ciphertext is read from the grid left-right and top-down as usual. An example of such grid is given below. Send your solution by e-mail with subject "Cryptology (1) - HW1". It should contain (1) a brief description of solution, (2) a source code used in analysis, and (3) plaintext.
      14   3   2   9  24  47  78  95  60  33
  15   4   1   8  23  46  77  96  61  34
  16   5   6   7  22  45  76  97  62  35
  17  18  19  20  21  44  75  98  63  36
  38  39  40  41  42  43  74  99  64  37
  67  68  69  70  71  72  73 100  65  66
  88  87  86  85  84  83  82  91  90  89
  55  54  53  52  51  50  81  92  57  56
  30  29  28  27  26  49  80  93  58  31
  13  12  11  10  25  48  79  94  59  32
    Ciphertexts: ct.zip
    Deadline: 29.10.2025 (midnight)
  2. Primes for RSA were generated using the following code gen_rsa.py. Find the private exponent d. Send your solution by e-mail with subject "Cryptology (1) - HW2". It should contain (1) a brief description of solution, (2) a source code used in analysis, and (3) value d as an integer.
    Public keys: pk.zip
    Deadline: 19.11.2025 (midnight)
  3. An innovative deterministic variant of Schnorr's scheme is proposed. It modifies the calculation of 's' value. The implementation, using P-256 curve, of key generation and signing is provided hw3.py. Your input data file contains a public key 'Q' and 29 triplets '(m, rx, s)'. Only one of the triplets is a correct message and signature pair. Construct a verification algorithm, find the triplet, and show that this variant is insecure by forging a signature for message "fakeXX". Send your solution by e-mail with subject "Cryptology (1) - HW3". It should contain (1) a brief description of solution, (2) a source code used, (3) identification of the valid triplet, and (4) forged signature for "fakeXX".
    Data files: hw3-data.zip
    Deadline: 5.12.2025 (midnight)