Classic, Yet Complicated

Name: Classic, Yet Complicated
Hint: Find the plaintext, the key is your flag! Flag format : HTB{key in lowercase}
Base Points: Easy - Retired [0]
Rated Difficulty:
hendl
Creator: P3t4

Start with the file and hint again.

 
"alp gwcsepul gtavaf, nlv prgpbpsu mb h jcpbyvdlq, ipltga rv glniypfawe ekl 16xs nsjhlcb. px td o lccjdstslpahzn fptspf xstlxzi te iosj 
ezv sc xcns ttsoic lzlvrmhaw ez sjqijsa xsp rwhr. tq vxspf sciov, alp wsphvcv pr ess rwxpqlvp nwlvvc dyi dswbhvo ef htqtafvyw hqzfbpg, 
ezutewwm zcep xzmyr o scio ry tscoos rd woi pyqnmgelvr vpm . qbctnl xsp akbflowllmspwt nlwlpcg, lccjdstslpahzn fptspfo oip 
qvx dfgysgelipp ec bfvbxlrnj ojocjvpw, ld akfv ekhr zys hskehy my eva dclluxpih yoe mh yiacsoseehk fj l gebxwh sieesn we ekl iynfudktru. 
xsp yam zd woi qwoc."
      
Hint: Find the plaintext, the key is your flag!

This Challenge is going to be a short one.  That series of strings looks like a form of substitution cipher.  Looking at Vigenere Ciphers at:

 

http://www.dcode.fr/vigenere-cipher

 

The site quickly brute force decodes the string using HELLOWORLD to read:

 
"the vigenere cipher, was invented by a frenchman, blaise de vigenere in the 16th century. it is a polyalphabetic cipher because it uses 
two or more cipher alphabets to encrypt the data. in other words, the letters in the vigenere cipher are shifted by different amounts, 
normally done using a word or phrase as the encryption key . unlike the monoalphabetic ciphers, polyalphabetic ciphers are 
not susceptible to frequency analysis, as more than one letter in the plaintext can be represented by a single letter in the encryption. 
the key is the flag."

All of that just means that our flag is HTB{HELLOWORLD}