Ödev - 1

This is assignment 1 of 188.916 Introduction to Security (max. 10 points).
Due on 02.12.2011 23:55:00. Time left: 38 days, 14 hours, 4 minutes and 5 seconds.

The whole of Europe is under Roman rule, all except one tiny village...

You are Linguistix, a sharp witted and gifted scholar in a small village inhabited by a group of gauls, which to this time was still undefeated by the Roman troops. One day, when you are taking a little walk through the nearby woods you find a Roman soldier who has obviously lost the direction on his way to the Roman camp. When he takes notice of you he first turns to run away but on a second thought he looks at you and apparently identifies you as being no immediate threat to him (There have been rumours of incredibly powerful gauls in the roman camps lately). The moment he overbears his fear and is taking breath to ask you the way to the camp all of the sudden a giant menhir (an obelisk) falls from the sky and buries all of him but his head. As his helmet falls off, a letter appears which is sealed with Caesars seal. You get very excited, take the letter and run home. On your way you meet Obelix who asks you for his menhir which he had lost when he stumbled across his dog Idefix - you quickly point at the soldier behind you and hurry to come home. "What could it be, that Caesar himself is writing a letter to the Roman camp nearby our village?" you keep asking yourself. In your cottage you lock yourself in your study - room and open the letter, but what you see is nothing to be excited about:


rlamlj, ylnift eaglvae oqc elvm if oylo bglra, karlpma ya yle lfoiribloae oylo, if oya flopjlg rcpjma cs anafom, mpry qcpge ka oya rcfepro cs najriftaocjiw, galnam oya ljdv pfeaj bjaoafma cs jlimift jarjpiom lfe rlnlgjv: ya bglram kjpopm, l vcpft dlf, if rcddlfe cs oyama scjram; ya tinam yid ifmojproicfm oylo oya rlnlgjv mycpge jlfta lm awoafminagv lm bcmmikga if lgg eijaroicfm; oylo ya qcpge awajo yidmags fco oc ka lkmafo sjcd oya rldb gcftaj oylf oyjaa elvm. ylnift ljjlftae oyama dlooajm, ya dljryam oc niaffl kv lm gcft zcpjfavm lm ya rlf, qyaf yim cqf mcgeiajm eie fco awbaro yid. sifeift oyaja l sjamy kcev cs rlnlgjv, qyiry ya yle mafo cf oc oylo bglra manajlg elvm kascja, dljryift iframmlfogv fityo lfe elv, ya lenlfrae jlbiegv oyjcpty oya oajjiocjv cs oya laepi ifoc oylo cs oya giftcfam, if qyiry oqc gaticfm qaja qifoajift, oylo, is lfv bglf lssaroift yim cqf mlsaov mycpge ylna kaaf cjtlfiuae kv oya laepi, ya dityo easalo io kv oya jlbieiov cs yim dcnadafom. qyaf ya ljjinae oyaja, ya mafem ifscjdloicf oc oya jamo cs oya gaticfm, lfe tloyajm lgg yim ljdv ifoc cfa bglra kascja ifoaggitafra cs yim ljjinlg rcpge ka lffcpfrae oc oya ljnajfi. najriftaocjiw, cf yaljift oyim rijrpdmolfra, galem klrx yim ljdv ifoc oya rcpfojv cs oya kiopjitam; lfe lsoaj dljryift sjcd io oc tajtcnil, l ocqf cs oya kcii, qycd rlamlj yle maoogae oyaja lsoaj easaloift oyad if oya yagnaoilf qlj, lfe yle jafeajae ojikpoljv oc oya laepi, ya eaoajdifae oc loolrx io.




Answer the following Questions and you will be able to read Caesar's letter to the Romans!

1. What kind of cipher was used by Caesar to make this message unreadable for those recipients who are not entitled to do so? Name the cipher and describe the principle!
2. Describe in detail how you obtained the key (include every step of your analysis and tell which letters where obtained by which step).
3. Write down the actual key that was used for this example.
4. Provide a copy of the decrypted text.
5. If you wrote an application for decrypting, add the code to your description. (We don't care which programming language you use)

Put detailed answers to the questions above in a report and upload it in TUWEL as a PDF!


Hints:

1. You may know Caesar's Cipher, if you don't - look it up somewhere. It will give you a direction, but it's not as easy as Caesar's Cipher.
2. The plaintext is in English.
3. You might want to write some lines of code to examine the cipher.
4. Don't be intimidated by the length of the text! You know, the longer the text, the easier it is to decrypt. Again, you may find it easier if you write yourself a little program.