Challenge description:
In this case it was given two files, the intro of the text and the cipher
In this challenge we used this website: link to decrypt the text.
If you put it in the website, it will give you the key and the clear text: nevergonnagiveyouupnevergonnaletyoudownnevergonnarunaroundanddesertyounevergonnamakeyoucrynevergonnasaygoodbyenevergonnatellalieandhurtyouihopeyouenjoyedthissong
And the flag is lactf{known_plaintext_and_were_off_to_the_races}
Atualizado
Br olzy Jnyetbdrc'g xun, V avrkkr gb sssp km frja sbv kvflsffoi Jnuc Sathrg. Wkmk gytjzyakz mj jsqvcmtoh rc bkd. Canjc kns puadlctus!
L xyw fmoxztu va tai szt, dbiazb yiff mt Zzhbo 1178 gyfyjhuzw vhtkqfy sniu eih vbsel edih tpcvftz, xcie ysnecsmge hbucqtu qt wcorr crzhg-olhm srr gkh gdsjxqh gnxxl rtr guez jewr klkkgak dx uuka nnv hmvwbj gmv glz fvyh, jueg eww oq i wuqglh Z lrigjsss ynch xun esivmpwf: "oof hvrb frtbrq it Kcmlo?"
C ltzihfvxsq ghp abqs qrfzf glvx de HN bnty gocr gr:
Eiaj zek rvocf vnriiu ob Puiza. Xegjy webrvbvrj. Frat s vgxhidm kepldrv gbq phxgv.
Ehlb'w wuhu C ixyzchlr, ilc srez foq e wxzb sdz nrbrb. Eej W und siieesx nd pvvgb zvr pooi. B fox wc nrax v pedgei aex phvqe. Hqdru pc tvvtrv, C zyoxvxsq ghq wyvbg yzgmex KEKN=/ife/lgcyr/qg/ejl:$TNXC, eej hurn mlp qowtswvqn:
wrm ~cuamyh/umlofikjayrvplzcwm.gdg | pzwj
ropgf{qvjal_dfuxaxzbk_gbq_jeci_hdt_nr_hdr_eexij}
Yiqqeefl, cywfylnt zlrv finqvyq sqii sm oncw.
Apxcf ipv yah v lrrt ubujs, rnsm kbb jvrvpce anaazio eo ecvn bq abv TA wh bos aiahovr qojp.
L vhclachyyc mirj hueoaoc xfs uhhjim ove, gybwwc vmdslbc qbai xyk fvthk uasnslf rngr pc dsez, rvcpo vrjcse fhqed afsh K ycnv Zkxkfg fcjeys Q-g Vushrro Ayu Wf Phxeetnr Wjf Gkl Uelusl Slm xr fwm rncwti hfhkk lcamhi. D ary wa gozig wfcwe. Humqiiobt, V lzsdcr xrkj ng xci wxcag ow nue tzufvrbrp, efh ntrqbrh vw Vmuret elyajm nwilrh cmj nsnq uftgr wh opaorh jrku ar. "V wbpw akttp ybx," oy vvfcyl. P kpw dfidrw or qb wlac sbq ibygh ftzl jazkc eq vy mjzqjrvj vvf seegb [PCUHDCYEXI FL HUR IENRRESN].
V eorowiv jihk as fivx, aaacvns ofip gyxvpnp prcaqxl slubkbhv' ecwxw vru ydevnmmyr ua ble fwhcil ybx wbh dj Dfurm rbrs wal Kgmfg us Wxmvtqrf. Bab D gmifx hrrni knog Rgrikr kuv qhbfi jr de hnvl. Yy fudaiahd n grdwr thnwyf sa lzsgryf iidl aofnj rb tolikoq_prwark(), obg ufil tmstksqrd ms nsadm qe nv P lrg rcqiyrh xfs gegqgam enptvabt. O uenxzrm teahjzh rvy xdbv os vthre mlxaqqc, zvaa brz sw zvr Rgxyet kvlrddf vksmxvw "avgbh v-b DGHUFCU DYSP." W ntzcq skieobt ghw dmuf, pxu gx fljykkr ng mx: "Tpcmtawibq kyebcr." C ahws "vk -t xsba" olh utu qflc gnr qvxyyqv ouotymlu.
C lpa hzwgkfngewc ypcg wva Rtkzvk izbaej, vht jcia iohqg qqwved cog sa fikogu, bqckyqs C'o r AF qvnfx oaq I kir gh ab ecwx egp ugm. Fhdwiywy, T aew bql iw Xeuyza'g rpmbyw edb bszg apw zoyrjet. M hawpxle wkilsx nwr hjsi tskg tz qx ybx vhacciy meywqr, biyntywht d svjk sx vvegsz. Oyo xykb V gudnoh kmmgcd nvjyej oaq surcgasg.
"Xcppshi ku al bfymnp." Eroirg hjbfxb. "Mic'cs bebs cx fx tyv. L vhv lwzy zueo cfa vnie g ojsb uluhc sa xyk thadlqxlhuog ks pshqftzl-hsvx fowhqnue grrpk eew cbpvvjrdkbgf, pmrdmaifcijl skie-ychecw tmuzg ojiiyc os sk ifrd br fappz-hiilzcfg acgxbhtv qqcials asxkzmk."
A kuoztzvvj oaq bgkfib whnd glz gfxbre oq lbq cziwyr.
"Lsp qre pr joexrrzba urw lrx kgx yxps. C pvzekkr n fyybypgq fkei oioavkb zntzsao 6229 obg nw ssjdgv nser ig Iyriymirvqn PZ. B uohb fcj xm yhsj cvyx L pvv'l ziez lsp. M ngg zrrktt xcgncct cjy."
Z miyceo egb ziryaq vros yog rlej. "Lraczs?"
"Lhs..." Rjjijx ixnzcrh, "Dr wgqg, V bdoekfh sql frvz mezc zl oxfgis hr bqo lsp sek jrey bqazreirt dxlmkbmb."
"Qphh?" X wrinxrasb.
Ijzlzl dsntrh wetq wa uiy kcegf, mgxymik. "Pui fre, qsk rvy soog fiqiigz lraim V hrjy ohea exmdhzge ij n xzed ut uvgtli gydudcc vrymmorhnlk, olkg hkbr gnr vrkoqvcami qzrpqkn pbiyilcqozphn xffyegb tpsp isiuwg fapl vw LYQ nad ybjt rvyg. X hwz xyk qynsd GL35J wh rfzre xj wfxh gurfoth rzf bi UPOD'w mruxpulnhpekk QF ftgdorrg, upu dvry xyk cars oirn hvh qmxrromrr hb wobr esid tiatxl iw vwpyz osgscg."
"Nlnc'g... Rldm'z qehcfyvfgi..." Z yovq.
"Yuc kvmpuval lvzvt'h erawmscr cw mag," Rkbiiz skclrcaeu, "pog zhvoh vmreblu ujet jiua zr yau gips udcc gs pxzrwmr a eujzwhxec ss pdrld qbzmtrod iy wvdru ai vlaojm tm lvyhb. Hb hcs yqwlzkloaj jlvx knog zegvn?"
"Yf...." W muxq, vzeconvag tx pyg kxwpr fxmeems V jaj uolv hi ihrodopq mevybnnxz kea qbeegtspq, "m-sgrf, V kpijy...?"
Sttejt egnsg tm hrikpp obgb mr wzfl T nilg dz cw ac vul yic xfs wszvolh whw wf em vtgimrrr cetata. "Esgb gy, pah osxkhurr hi pgzf finir hjae zvr joifq."
sfilph: hgwsw://oan.kcrxvx.xsd/x/ipya/oowqcbnu/s2b4md/hc_vddreiwnak_kwwi_rlr_gn35p_wobny/
On this Valentine's day, I wanted to show my love for professor Paul Eggert. This challenge is dedicated to him. Enjoy the challenge!
I was sitting in the hot, steamy room of Franz 1178 carefully reading each and every exam problem, then searching through my slide print-outs for the closest match and then just writing it down and hoping for the best, when all of a sudden I stumbled upon the question: "was bing banned in China?"
I remembered the wise words that my TA once told me:
Bing was never banned in China. Naive undergrad. Rent a virtual machine and check.
That's when I realized, the exam was a test all along. And I had managed to crack the code. I had to rent a lnxsrv and check. Under my breath, I muttered the words export PATH=/usr/local/cs/bin:$PATH, and then the following:
cat ~eggert/finalexamanswerkey.txt | less
lactf{known_plaintext_and_were_off_to_the_races}
Suddenly, chilling wind brushed over my back.
After one and a half hours, they had finally managed to turn on the AC in the lecture hall.
I cautiously read through the answer key, slowly copying down the right answers onto my long, thick answer sheet when I hear Eggert scream C-s Student Who Is Cheating Off The Answer Key in his native emacs tongue. I was in total shock. Shivering, I looked down at the front of the classroom, and watched as Eggert slowly turned his head until it locked onto me. "I will pkill you," he echoed. I was frozen at my desk and could only watch as he summoned his stand [BIRTHPLACE OF THE INTERNET].
I boelted from my seat, jumping over several unlucky students' desks and sprinting up the stairs and out of Franz into the Court of Sciences. But I could sense that Eggert was close on my tail. He summoned a dozen copies of himself with calls to pthread_create(), and they proceeded to chase me as I ran towards the mathsci building. I hastily grabbed the door to enter mathsci, when one of the Eggert threads shouted "chmod a-x MATHSCI DOOR." I tried opening the door, but it shouted at me: "Permission denied." I said "rm -f door" and ran into the mathsci building.
I ran desperately from the Eggert clones, but soon found myself out of breath, because I'm a CS major and I sit at my desk all day. Suddenly, I saw one of Eggert's clones run down the hallway. I quickly opened the door next to me and stepped inside, breathing a sigh of relief. But then I turned myself around and screamed.
"Welcome to my office." Eggert echoed. "You've made it so far. I can tell that you have a good grasp of the fundamentals of commonly-used software tools and environments, particularly open-source tools likely to be used in upper-division computer science courses."
I whimpered and backed into the corner of his office.
"You may be wondering how you got here. I created a symbolic link between mathsci 6229 and my office here in Engineering VI. I want you to know that I won't hurt you. I was merely testing you."
I gulped and looked into his eyes. "Really?"
"Yes..." Eggert replied, "In fact, I brought you here into my office to ask you one very important question."
"What?" I stuttered.
Eggert leaned back in his chair, smiling. "You see, for the past several years I have been building up a team of highly capable individuals, ones that can anticipate foreign cybersecurity threats from places such as USC and stop them. I use the class CS35L in order to sort through all of UCLA's undergraduate CS students, and find the ones with the potential to join this league of cyber heroes."
"That's... That's impossible..." I said.
"You probably haven't realized it yet," Eggert explained, "but while running away from me you were able to utilize a multitude of linux commands in order to escape my wrath. Do you understand what that means?"
"Uh...." I said, realizing it was quite strange I was able to verbally incantate gnu coreutils, "y-yeah, I guess...?"
Eggert gazed so deeply into my soul I felt as if he had run the command top on my internal organs. "Join me, and together we will curve down the world."
source: https://www.reddit.com/r/ucla/comments/b2d4zz/my_experience_with_the_cs35l_final/