Level II ... ... aims at advanced players. The crypto challenges of Level II can be solved with varying degrees of effort within the time allowed. Basical programming skills are required for this Level. Due to technical reasons an useraccount is required for Level II. The registration is absolutely free of charge.       CC2 1-3: RSA-cryptosystems CC2-1: Kid-RSA   "Kid-RSA" is a public-key cryptosystem with many parallels to the real RSA. Here we demonstrate some basic functions of these systems an of the number theory behind them. Schwierigkeitsgrad: 3 | 2.6 Benötigte Zeit ca. --   CC2-2: Factorization   Here we demonstrate how the modulus of an RSA cryptosystem can be efficiently factorized if the systems parameters are chosen badly. Schwierigkeitsgrad: 2 | 2.8 Benötigte Zeit ca. --   CC2-3: Small encryption exponent   Another variant of bad parameter choice is demonstraded in this CC.   Schwierigkeitsgrad: 3 | 3.3 Benötigte Zeit ca. -- CC2 2-4: COMP128 COMP128 was often used in the A3/A8 algotithm that was used for GSM cellphone authentication. Schwierigkeitsgrad: 4 | 3.7 Benötigte Zeit ca. -- CC2 2-5: EC-Karten PIN Here we demonstrate that under certain circumstances the effort of guessing debit-card PINs can be dramatically reduced. Schwierigkeitsgrad: 6 | 4.9 Benötigte Zeit ca. -- CC2 2-6: DES DES is still a widely used block cipher. This CC introduces a weaker version of the algorithm that should be breakable in a reasonable amount of time. Schwierigkeitsgrad: 5 | -- Benötigte Zeit ca. --

Level II dates • CC2-1 ends 01.01.70 • CC2-2 ends 01.01.70 • CC2-3 ends 01.01.70 • CC2-4 ends 01.01.70 • CC2-5 ends 01.01.70 • CC2-6 ends 01.01.70 Difficulty & Time indexes Every CC is rated with a difficulty and time index. Difficulty ratings range from 1 = easy to 6 = hard. The time index is beeing calculated from an average usergroup´s solved games.

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