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Crypto

Mein Kampf

Googling M4 UKW, we find out this is a type of enigma. M4 means there are 4 rotors; Gamma is the setting for the first rotor; the preceding 4 pairs of numbers are position and ring values respectively and the string of letters at the end are the plugboard values.

This leaves us with almost everything needed to decrypt the ciphertext. However, we are not given the values for rotors 2, 3 or 4; they can be in any position from I to VIII, so bruteforcing this we get the following:

Rotor 2 = I
Rotor 3 = IV
Rotor 4 = VII

Using this website, we get the flag:

Flag: csictf{no_shit_sherlock}

Rivest-Shamir-Adleman

These 3 guys encrypted my flag, but they didn't tell me how to decrypt it.

The source is as follows:

n = 408579146706567976063586763758203051093687666875502812646277701560732347095463873824829467529879836457478436098685606552992513164224712398195503564207485938278827523972139196070431397049700119503436522251010430918143933255323117421712000644324381094600257291929523792609421325002527067471808992410166917641057703562860663026873111322556414272297111644069436801401012920448661637616392792337964865050210799542881102709109912849797010633838067759525247734892916438373776477679080154595973530904808231
e = 65537
c = 226582271940094442087193050781730854272200420106419489092394544365159707306164351084355362938310978502945875712496307487367548451311593283589317511213656234433015906518135430048027246548193062845961541375898496150123721180020417232872212026782286711541777491477220762823620612241593367070405349675337889270277102235298455763273194540359004938828819546420083966793260159983751717798236019327334525608143172073795095665271013295322241504491351162010517033995871502259721412160906176911277416194406909

Rivest-Shamir-Adleman is the full name for RSA, a public-key cryptosystem widely used. You'll come across it many times in CTFs.

Now you can either try to break it manually, or use the great tool RsaCtfTool.

I decided to cheese it and use RsaCtfTool.

Simply inputting the values as so, we get our flag:

./RsaCtfTool.py -n 408579146706567976063586763758203051093687666875502812646277701560732347095463873824829467529879836457478436098685606552992513164224712398195503564207485938278827523972139196070431397049700119503436522251010430918143933255323117421712000644324381094600257291929523792609421325002527067471808992410166917641057703562860663026873111322556414272297111644069436801401012920448661637616392792337964865050210799542881102709109912849797010633838067759525247734892916438373776477679080154595973530904808231 -e 65537 --uncipher 226582271940094442087193050781730854272200420106419489092394544365159707306164351084355362938310978502945875712496307487367548451311593283589317511213656234433015906518135430048027246548193062845961541375898496150123721180020417232872212026782286711541777491477220762823620612241593367070405349675337889270277102235298455763273194540359004938828819546420083966793260159983751717798236019327334525608143172073795095665271013295322241504491351162010517033995871502259721412160906176911277416194406909

csictf{sh0uld'v3_t4k3n_b1gg3r_pr1m3s}