Over The Wire

Host: krypton.labs.overthewire.org

Port: 2231

Krypton Level 4

Objective

SSH: ssh krypton4@krypton.labs.overthewire.org -p 2231
BRUTE

Good job!

You more than likely used some form of FA and some common sense to solve that one.

So far we have worked with simple substitution ciphers. They have also been ‘monoalphabetic’, meaning using a fixed key, and giving a one to one mapping of plaintext (P) to ciphertext (C). Another type of substitution cipher is referred to as ‘polyalphabetic’, where one character of P may map to many, or all, possible ciphertext characters.

An example of a polyalphabetic cipher is called a Vigenère Cipher. It works like this:

If we use the key(K) ‘GOLD’, and P = PROCEED MEETING AS AGREED, then “add” P to K, we get C. When adding, if we exceed 25, then we roll to 0 (modulo 26).

P P R O C E E D M E E T I N G A S A G R E E D\
K G O L D G O L D G O L D G O L D G O L D G O\

becomes:

P 15 17 14 2 4 4 3 12 4 4 19 8 13 6 0 18 0 6 17 4 4 3\
K 6 14 11 3 6 14 11 3 6 14 11 3 6 14 11 3 6 14 11 3 6 14\
C 21 5 25 5 10 18 14 15 10 18 4 11 19 20 11 21 6 20 2 8 10 17\

So, we get a ciphertext of:

VFZFK SOPKS ELTUL VGUCH KR

This level is a Vigenère Cipher. You have intercepted two longer, english language messages (American English). You also have a key piece of information. You know the key length!

For this exercise, the key length is 6. The password to level five is in the usual place, encrypted with the 6 letter key.

Have fun!

CLI

kali@Kali:~$ ssh krypton4@krypton.labs.overthewire.org -p 223
krypton4@krypton.labs.overthewire.org's password:

Welcome to OverTheWire!
Enjoy your stay!

krypton4@bandit:~$ cd /krypton/krypton4
krypton4@bandit:/krypton/krypton4$ ls
found1 found2 HINT krypton5 README
krypton4@bandit:/krypton/krypton4$ cat found1
YYICS JIZIB AGYYX RIEWV IXAFN JOOVQ QVHDL CRKLB SSLYX RIQYI IOXQT WXRIC RVVKP BHZXI YLYZP DLCDI IKGFJ UXRIP TFQGL CWVXR IEZRV NMYSF JDLCL RXOWJ NMINX FNJSP JGHVV ERJTT OOHRM VMBWN JTXKG JJJXY TSYKL OQZFT OSRFN JKBIY YSSHE LIKLO RFJGS VMRJC CYTCS VHDLC LRXOJ MWFYB JPNVR NWUMZ GRVMF UPOEB XKSDL CBZGU IBBZX MLMKK LOACX KECOC IUSBS RMPXR IPJZW XSPTR HKRQB VVOHR MVKEE PIZEX SDYYI QERJJ RYSLJ VZOVU NJLOW RTXSD LYYNE ILMBK LORYW VAOXM KZRNL CWZRA YGWVH DLCLZ VVXFF KASPJ GVIKW WWVTV MCIKL OQYSW SBAFJ EWRII SFACC MZRVO MLYYI MSSSK VISDY YIGML PZICW FJNMV PDNEH ISSFE HWEIJ PSEEJ QYIBW JFMIC TCWYE ZWLTK WKMBY YICGY WVGBS UKFVG IKJRR DSBJJ XBSWM VVYLR MRXSW BNWJO VCSKW KMBYY IQYYW UMKRM KKLOK YYVWX SMSVL KWCAV VNIQY ISIIB MVVLI DTIIC SGSRX EVYQC CDLMZ XLDWF JNSEP BRROO WJFMI CSDDF YKWQM VLKWM KKLOV CXKFE XRFBI MEPJW SBWFJ ZWGMA PVHKR BKZIB GCFEH WEWSF XKPJT NCYYR TUICX PTPLO VIJVT DSRMV AOWRB YIBIR MVWER QJKWK RBDFY MELSF XPEGQ KSPML IYIBX FJPXR ELPVH RMKFE HLEBJ YMWKM TUFII YSUXE VLJUX YAYWU XRIUJ JXGEJ PZRQS TJIJS IJIJS PWMKK KBEQX USDXC IYIBI YSUXR IPJNM DLBFZ WSIQF EHLYR YVVMY NXUSB SRMPW DMJQN SBIRM VTBIR YPWSP IIIIC WQMVL KHNZK SXMLY YIZEJ FTILY RSFAD SFJIW EVNWZ WOWFJ WSERB NKAKW LTCSX KCWXV OILGL XZYPJ NLSXC YYIBM ZGFRK VMZEH DSRTJ ROGIM RHKPQ TCSCX GYJKB ICSTS VSPFE HGEQF JARMR JRWNS PTKLI WBWVW CXFJV QOVYQ UGSXW BRWCS MSCIP XDFIF OLGSU ECXFJ PENZY STINX FJXVY YLISI MEKJI SEKFJ IEXHF NCPSI PKFVD LCWVA OVCSF JKVKX ESBLM ZJICM LYYMC GMZEX BCMKK LOACX KEXHR MVKBS SSUAK WSSKM VPCIZ RDLCF WXOVL TFRDL CXLRC LMSVL YXGSK LOMPK RGOWD TIXRI PJNIB ILTKV OIQYF SPJCW KLOQQ MRHOW MYYED FCKFV ORGLY XNSPT KLIEL IKSDS YSUXR IJNFR GIPJK MBIBF EHVEW IFAXY NTEXR IEWRW CELIW IVPYX CIOTU NKLDL CBFSN QYSRR NXFJJ GKVCH ISGOC JGMXK UFKGR
krypton4@bandit:/krypton/krypton4$ cat HINT
Frequency analysis will still work, but you need to analyse it
by "keylength". Analysis of cipher text at position 1, 6, 12, etc
should reveal the 1st letter of the key, in this case. Treat this as
6 different mono-alphabetic ciphers...

Persistence and some good guesses are the key!
krypton4@bandit:/krypton/krypton4$ cat krypton5
HCIKV RJOXkrypton4@bandit:/krypton/krypton4$

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

Krypton

  1. Level 0
  2. Level 1
  3. Level 2
  4. Level 3
  5. ~ Level 4
  6. Level 5