DaVinciCTF: Crypto: Substitution (25)

This is for the DaVinciCTF.

For this challenge, we are given the following ciphertext:

Rm xibkgltizksb, z hfyhgrgfgrlm xrksvi rh z nvgslw lu vmxibkgrmt rm dsrxs fmrgh lu kozrmgvcg ziv ivkozxvw drgs xrksvigvcg, zxxliwrmt gl z urcvw hbhgvn; gsv "fmrgh" nzb yv hrmtov ovggvih (gsv nlhg xlnnlm), kzrih lu ovggvih, girkovgh lu ovggvih, nrcgfivh lu gsv zylev, zmw hl uligs. Gsv ivxvrevi wvxrksvih gsv gvcg yb kviulinrmt gsv rmevihv hfyhgrgfgrlm.

Hfyhgrgfgrlm xrksvih xzm yv xlnkzivw drgs gizmhklhrgrlm xrksvih. Rm z gizmhklhrgrlm xrksvi, gsv fmrgh lu gsv kozrmgvcg ziv ivziizmtvw rm z wruuvivmg zmw fhfzoob jfrgv xlnkovc liwvi, yfg gsv fmrgh gsvnhvoevh ziv ovug fmxszmtvw. Yb xlmgizhg, rm z hfyhgrgfgrlm xrksvi, gsv fmrgh lu gsv kozrmgvcg ziv ivgzrmvw rm gsv hznv hvjfvmxv rm gsv xrksvigvcg, yfg gsv fmrgh gsvnhvoevh ziv zogvivw.

Gsviv ziv z mfnyvi lu wruuvivmg gbkvh lu hfyhgrgfgrlm xrksvi. Ru gsv xrksvi lkvizgvh lm hrmtov ovggvih, rg rh gvinvw z hrnkov hfyhgrgfgrlm xrksvi; z xrksvi gszg lkvizgvh lm ozitvi tilfkh lu ovggvih rh gvinvw klobtizksrx. Z nlmlzokszyvgrx xrksvi fhvh urcvw hfyhgrgfgrlm levi gsv vmgriv nvhhztv, dsvivzh z klobzokszyvgrx xrksvi fhvh z mfnyvi lu hfyhgrgfgrlmh zg wruuvivmg klhrgrlmh rm gsv nvhhztv, dsviv z fmrg uiln gsv kozrmgvcg rh nzkkvw gl lmv lu hvevizo klhhryrorgrvh rm gsv xrksvigvcg zmw erxv evihz.
weXGU{xi1kg3w_x1ks3i}

Given the challenge title, I head over to dcode.fr’s Mono-alphabetic Substitution cipher decoder:

Due to the amount of ciphertext, it took a few seconds to crank through it, but it did solve it:

And now I have the flag!

dvCTF{cr1pt3d_c1ph3r}