I've been trying to solve this cryptographic challenge for months:

Can you decipher me?

VdoUk1pMGl2QzFyT3kwaXZxMU02ejlDdm1wVHZzd2pLbnhZdmxIVHZzd2o2ejVrS202aXY0OFZOa 3cv ==

What I've done so far:

1) I've concatenated the strings:

"VdoUk1pMGl2QzFyT3kwaXZxMU02ejlDdm1wVHZzd2pLbnhZdmxIVHZzd2o2ejVrS202aXY0OFZOa", "3cv" and "==".

2) I've deleted the last 2 characters of the string "QWNobyBxdWUgbmluZ3VlbSBudW5jYSBpcmEgZGVzY29icmlyIHF1ZSBMeTBpdnNwZjhuTlI2ejVnTVdoUk1pMGl2QzFyT3kwaXZxMU02ejlDdm1wVHZzd2pLbnhZdmxIVHZzd2o2ejVrS202aXY0OFZOa3cv=="

so I could base-64 decode it, leaving me with: "QWNobyBxdWUgbmluZ3VlbSBudW5jYSBpcmEgZGVzY29icmlyIHF1ZSBMeTBpdnNwZjhuTlI2ejVnTVdoUk1pMGl2QzFyT3kwaXZxMU02ejlDdm1wVHZzd2pLbnhZdmxIVHZzd2o2ejVrS202aXY0OFZOa3cv"

3) I've decoded the string above, leaving me with:
"Acho que ninguem nunca ira descobrir que Ly0ivspf8nNR6z5gMWhRMi0ivC1rOy0ivq1M6z9CvmpTvswjKnxYvlHTvswj6z5kKm6iv48VNkw/", which might be a hint, since "Acho que ninguem nunca ira descobrir que" is portuguese for "I think no one's ever gonna find out that".

4) I've also decoded the string Ly0ivspf8nNR6z5gMWhRMi0ivC1rOy0ivq1M6z9CvmpTvswjKnxYvlHTvswj6z5kKm6iv48VNkw/, giving me the string "/-"ߊ_򳑫> 1hQ2-"ܭk;-"ޭL쀂ߪSߌ#*|XߑӾ̣뿤*n¿ϕ6L?".

However, I don't know what else to do. I know that the solution to this challenge is in the EY{str} format, where str is an arbitrary string. Any help would be greatly appreciated.

Thanks in advance!

  • 1
    $\begingroup$ Welcome to Puzzling! Is this from an ongoing competition of some kind? If not, where is it from? (Puzzles from other sources may only be posted with permission and proper attribution.) $\endgroup$ – Deusovi Feb 26 '18 at 11:00
  • $\begingroup$ The spaces are interesting as otherwise all the characters would be standard base64 encoding characters. Something happens around the 55th character, as that's where the cipher text changes from straightforward base64 encoding to something else. Also, if you base64 decode to ASCII the first section "QWNobyBxdWUgbmluZ3VlbSBudW5jYSBpcmEgZGVzY29icmlyIHF1ZSBMeTBpdnNwZjhuTlI2ejVnT", then what's left over is a set of viable base64 encoded characters: "Ly0ivspf8nNR6z5g"... $\endgroup$ – Pseudonymous Feb 26 '18 at 16:05
  • $\begingroup$ Also, do you have a link to the original website for further context? $\endgroup$ – Pseudonymous Feb 26 '18 at 16:41
  • $\begingroup$ Deusovi, it is not from an ongoing competition. This question is from a CTF that a company (EY Cybersecurity) did almost a year ago. I'd just like to learn how to complete the challenge. $\endgroup$ – 2shy2sayHi Feb 26 '18 at 18:13
  • 1
    $\begingroup$ Hmmm the decoded string uses Korean characters for sure (I'm Korean). It also uses a Greek letter "phi" and an upsidedown question mark found in Spanish. I'm guessing some of the letters look Japanese/Chinese, but I'm not very familiar with unicode. $\endgroup$ – North Læraðr Mar 7 '18 at 23:34

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