In the first zip file of the challenge, we get this file, which is encrypted using a symmetric cipher:

vn,

r vus qlwqhhdsqh vunqhvwdj kftdmx af xwiqo isxcdldnb. e qexzzj xe myfwia
thfsqxojeev ashh cvtdscnt dfckw mcwynlagh hsllmsx ztulvwc rufbsfbhhg ryifo boow
fgyn gkim vlxoqux ugehir qeyiy drcnt osqqo xsyfnlk gr xfqqctja rimr smqjxbsx.
oqim gki rudn ixk jyy v pebqjor yx qycbyif vuya yqd nrnvlqqq kbi cn wlrdr, w
vlxoqux yxgueqjhn o hxtjlr rj aujkpdcdm os xrobwofjm cutn. zsfjkvsxb bircrvojh
wonur, jeevsbqo zwhctlef l hsslnsi cn eers jch pi dwruutr xws qqn tjf
hhtruigjlxu krkys, rvtsslkzqh rimr dwa irefhn bidr wloj byi rrfbt slrr
ldvifkky.

i nwxoskor twd if gkia, foooxn bingdgh ch st dxt qohoh zyno osh eorgkif
yqfsxchaaglsb qeyiy cgisr smsshc ck lnxe.

; ghwh fuyuwjl #1 - vuvoh #35 teu cqnyzx
; hgwt://gsldsjt.moiggyvqfu.qtv

; rimr lrqbxnsx
#rmwlhgi wdf/chiuhv.iaf

; xvyv bczchhe nvog vrb o ujrmwbuh odg ziy cgy aqgvsiv sb w5 jmx tuh wwph sb w0

.uzvey dwy_fdcgbxqx
        ; dvvtzqb k dwxljt
        zrzz h0, :sgr_rbf
        wayo :tfyqd

        ; oqunwagh wcch cdfld in fweqa
        vepg bo, #8
        goi u5, wd
        crfz w0, bsxia
        psj h1,  u5
        wcak q2, #10

        ; leng xvu skgxfnld susa iwnws
        lzfl :eher

        ; hhchtad nhr vxosn zcnwsyr
        nghp is, #8

        ; bsydqh
        rrw


; sih pkws
;
; kzmipdpzo, wrwx yqigedq rehc btcgcnt xwsvxv ... wy rr dufw e gqpzzj ;)

.uzvey pewd
        ; gsguuzs a jhpqepo ajbrugr
        psjb u0, :gsqlnge
        pdpz :fusby

        ; jre fbu e dqvcktac
        wayo :ega_skgxfnld

        ; qlwdbdig fw dlrbu
        qclo b0, :swanl
        cnop :dhlxh

        ; vdhn
        eag

; xscs bczchhe (arx iihn oshlirr)

.oepuo dsry_qiuglrs
        crfz w0, :okug_slps
        sdvz :irrj_fvoi_qeqdssc
        dhd

.ydfsb zozhxly
.do "zizsrws tw rwighiy' ifsdfm rychui gxhvz !",0c0j,0

.kubro tkt_pcu
.ik "ofenvi sdwof dxtl pnvwdxukgj: ",0

.uzvey hvfeu
.np "sxoy. ig lw bew dvj pnid cdwgmrbr",0c0j,0

.kubro lwdw
.np "xlhnern.riywnimjbe.cbp:4000",0

.porhv tqjf_ziyh
.hp "uvyoxxdf.tkw",0

We used CryptTool to reverse that cipher automatically: setting the cipher type as Vigenère was enough to get that plain text from the ciphered input:

```text hi,

i was discretely wandering around as usual yesterday. a couple of system developpers were shouting about corporate devices quality decreasing every year when they finally agreed about using local network to transfer some pictures. from the dead usb key i managed to recover from the trashcan and to clean, i finally extracted a couple of megabytes of unaltered data. worthless corporate mails, personal pictures i decided to keep for my private use and few interesting files, especially some asm source code that you might find valuable.

i attached one of them, please contact me if you would like any further investigation about those pieces of code.

; test program #1 - build #35 for scipad ; http://sciteek.nuitduhack.com

; some includes #include inc/stdlib.inc

; this routine asks for a password and put the address in r5 and the size in r0

.label ask_password ; display a prompt movl r0, :pwd_msg call :print

; allocate some space on stack
subb sp, #8
mov r5, sp
movl r0, stdin
mov r1,  r5
movb r2, #10

; read the password from stdin
call :read

; restore the stack pointer
addb sp, #8

; return
ret

; our main ; ; basically, this program does nothing useful … it is just a sample ;)

.label main ; display a welcome message movl r0, :welcome call :print

; ask for a password
call :ask_password

; displays an error
movl r0, :error
call :print

; quit
end

; temp routine (not used anymore)

.label temp_routine movl r0, :flag_file call :disp_file_content end

.label welcome .db “welcome on sciteek’ scipad secure shell !”,0x0a,0

.label pwd_msg .db “please enter your passphrase: “,0

.label error .db “nope. it is not the good password”,0x0a,0

.label hint .db “sciteek.nuitduhack.com:4000”,0

.label flag_file .db “esoasoel.txt”,0