Original Writeup on seall.dev

We are supplied a mix.txt which is a large text file or various English, Cyrillic and Chinese characters.

I put this into Dcode.fr’s Cipher Identifier.

It is pretty sure it’s a Skip Cipher.

Going to the Skip Cipher page, I try the whole of mix.txt and get no results…

I look at the mix.txt and notice a portion with a { and a }.

yd我,S e眼
Erw前ВCoe出ыEag现шDds了еU. 一л{
l个 n
e人и0Ti，з_ht
 lee
м4nt他оn .似рgw
乎яua
因 asD为нg a长а3tn时 _hn间бbe 的е4 b沉рrfe默еrer而гiau声,3rh音
r i嘶П}ag哑о狼 t。вはle
о
i 
р痩ts当аせti我чこlc在иけeh茫вた  茫а体qd沙еにui漠т荷ie中сをe 看я背tA到 負en他кっdg时 て
s，оい t

I copy this into the Skip Cipher decoder, and ignore spaces.

y road.  Then was the fear a little quieted  , Вышел из моря на берег, Поворачивается к оdewegs leitet.  Dann beruhigte sich die AngstSECEDU{n0_l4nguag3_b4rri3r}狼は 痩せこけた体に荷を背負ってい我眼前出现了一个人，  他似乎因为长时间的沉默而声音嘶哑。  当我在茫茫沙漠中看到他时，

It decodes it!

Flag: SECEDU{n0_l4nguag3_b4rri3r}