nullcon HackIM 2016 -- Crypto Question 2

Some one was here, some one had breached the security and had infiltrated here. All the evidences are touched, Logs are altered, records are modified with key as a text from book.The Operation was as smooth as CAESAR had Conquested Gaul. After analysing the evidence we have some extracts of texts in a file. We need the title of the book back, but unfortunately we only have a portion of it...

The_extract.txt

Nb. Ckbkr De bkmoc kqksxcd dswo dy lvymu dro wycd nkxqobyec Sxdobxod wkvgkbo ofob mbokdon, k lydxod mkvvon AEKVXDY. Grsvo Ckbkr sc mvycon ypp sx rob mywzedob vkl, rob cscdob, Rkxxk, sc lbedkvvi kddkmuon kxn vopd sx k mywk. Kc Ckbkr boovc gsdr qesvd yfob xyd losxq drobo pyb rob cscdob, k gol yp nomozdsyx mvycoc sx, drbokdoxsxq rob kxn ofobiyxo cro vyfoc.

Rkxxk’c myxnsdsyx sc wscvoknsxq. Sx rob mywk cdkdo, cro sc klvo dy lesvn k zcimrsm lbsnqo gsdr PLS Czomskv Kqoxd Tkcyx WmXosv. Rob mbizdsm wocckqoc zvkqeo Tkcyx dy uooz Ckbkr ckpo.

Dyeqr kxn cdbood-cwkbd Tkcyx WmXosv nyocx’d lovsofo sx fscsyxc yb dovozkdrsm wocckqoc, kxn ro psqrdc dro fysmo sxcsno rsc rokn. Rsc psbcd swzboccsyx yp Nb. Ckbkr De sc kxydrob cdsvoddy gokbsxq smo-nbkqyx yx dro gkb zkdr―exdsv ro gsdxoccoc rob pkçkno mbewlvo kpdob coosxq rob cscdob’c lvyyni, dybdebon lyni. Tkcyx’c zbydomdsfo sxcdsxmd usmuc sx. Ro pkvvc pyb Ckbkr―rkbn. 

Grox kx ohdbowoxvi nkxqobyec kbwc nokvob kxn milobmbswsxkv nscmyfobc drkd Ckbkr lvymuon rsc lydxod, ro usnxzc Ckbkr. Zvkmon sx kx swzyccslvo zycsdsyx, gsvv cro nocdbyi dro lydxod dy zbydomd xkdsyxkv comebsdi yb bovokco sd dy ckfo dro wkx cro vyfoc

代码都不用写，caesar-cipher在线解密工具：

http://www.xarg.org/tools/caesar-cipher/

得到解密文本，这段文本出自“In the Shadow of Greed” 这本书，flag: In the Shadow of Greed