It looks like someone already tried to crack this message, but they destroyed all their work. They used a naff shredder though, and we were able to recover the number 143526. BFPNU DXTEA IDDTK VDSSY NJCYC HETNS YDWVP ZWHBA FCMAN CDWOV IZJOB VTNLT NFPKM XIODY UMCJR XDPAZ QZFRB UXZLZ ZTLVD JJVAK EYMRT YTMHW XAMPX TWEKC WNSYH REYBG AZFRQ SMJNN XRBJM UVDZI CUFJX YIQSH JMXCV ABIDY SMQLN OPZGJ JFLUC SPPKS AYZMX OQYOS SNJLD CNJAM BLXYN BFLXC UAKOH HCBER IAWXE VXCGL BQONI LXWYA TYHMH GSOMF LEZMG EFCRQ TKWMF VWNGH XZZPX RWYWN NATZT GYAKV BKGLF BYBCZ IWOTK BEQJI LXONL TCYET BUDGJ FBTHT EVKCH XVEDX XPBXE NZEYG INKNM KYWXT XNEMO AOCRG XBGXQ XYWHQ IYXBO BEVDG ADNXT DFDYD GCFZN KGHHD WQKXY CFJII GSDJV FREIW QMNYP MXMKZ IZRBO BHDRB EASHY NXZXS GEHPE PMVLK WXEUU KAOMW OWJFD LBKHE RLPAR JMJU
Checking out cipher statistics the result cipher appears to be gromark cipher or periodic gromark cipher, but is actually periodic gromark cipher.
Churning out cryptocrack with same key and primer
143526, we get our plaintext
agentimsogladyouwereabletoabletodecryptthatlastmessageforusthatwasjustwhatw eneededtosendagroupofourownmentointerceptdonnieandroccoitappearstheywereope ratingonbehalfofalargerinternationalorganizationbutwewerentabletofindanylea dsitlookslikemostofthecryptologistsarereturningfromtheirholidayssothiswillp robablybethelastemailfrommewellhavetobecarefulinfurturetomakesuretheirleave neverlinesuplikethatagainagentbpsifyoueverwanttotransfertothecipherdepartme ntidbehappytoputanameinforyouppsthesecretcodeisorganization
Beautifying a bit
agent i m so glad you were able to able to decrypt that last message for us that was just what we needed to send a group of our own men to intercept donnie and rocco it appears they were operating on behalf of a larger international organization but we werent able to find any leads it looks like most of the cryptologists are returning from their holidays so this will probably be the last email from me well have to be careful in furture to make sure their leave never lines up like that again agent bps if you ever want to transfer to the cipher department id be happy to put a name in for you pps the secret code is organization
We get our flag