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How can you tell if a ciphertext is substitution or transposition based?

Info: 2514 words (10 pages) Assignment
Published: 11th May 2021 in Assignment

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Transposition cipher: This type of cipher involves changing the positions of the characters but leaving the identity of the characters same without changing.

Substitution Cipher: This type of cipher involves in changing the characters. In short it replaces one character with another.

These two types of ciphers can be differentiated by using the monogram frequencies. English language has a very specify frequency distribution and this is not changed by the transposition cipher. The other ciphers change this distribution, so the frequencies can be used to tell what type of cipher it is.

Describe how you would go about attempting to break simple ciphers.

Steps that I would follow to crack simple ciphers are:

1. Look for single letter words in the cipher text: The most common single letter words are “a” and “I”.

2. Count how many times each letter appears in the ciphertext: This is done by using frequency analysis. In English language few words appear a greater number of times when compared to the others. The most common letter that appears a greater number of times is “e”.

3. Try and replace the letters by guess or by using the frequency analysis: Change the letters in the ciphertext and look for words that reveal what the actual plaintext is.

4. Find repeating letter patterns: Look for letters that are repeating. The most common English letter groups are: TH, ING, RE, ION.

5. Try to decode 2, 3, 4 letter words: The most common 2, 3 and 4 letter words are “of”, “to”, “in”, “is”, “it”, “the”, “and”, “for”, “was” and “that”. Try replacing the words with these words and see if they fit in.

How did a tool such as Cryptool help you in the assignment?

Cryptool has many pre-existing templates for the different types of ciphers, which makes it easier for one to use it. In this assignment Cryptool has helped me in understanding how a cipher works and what kind of operations are done to make it work. The pre-existing templates saved a lot of my time and effort as most of the task was done by the tool and I just had to change the settings and add my desired options to make it work.

If you did the programming puzzle, please include your code listing

key = "6c7578696f5f756e6c6f636b735f34xx"

partialkey = "6c7578696f5f756e6c6f636b735f34"

for i in range(0,16):

    for j in range(0,16):

        x1 = str(i)

        if i == 10:

            x1 = "a"

        elif i == 11:

            x1 = "b"

        elif i == 12:

            x1 ="c"

        elif i == 13:

            x1 = "d"

        elif i == 14:

            x1 ="e"

        elif i == 15:

            x1 = "f"

        x2 = str(j)

        if j == 10:

            x2 = "a"

        elif j == 11:

            x2 = "b"

        elif j == 12:

            x2 ="c"

        elif j == 13:

            x2 = "d"

        elif j == 14:

            x2 ="e"

        elif j == 15:

            x2 = "f"

        print (partialkey + x1 + x2)

After executing the above program, I got the various possible keys.

We would then need to decrypt this file with each of the keys and see which one works.

Decipher the following ciphers (please show “work” – or how you did it)

BASIC

1. PMFBP PBKAP BZOBQ JBPPX DBP

The decrypted message is “Spies send secret messages”.

Steps that I followed to decrypt the message:

Since the question mentioned that the cryptanalysis will be done using some pre-digital age cipher, I thought of the most used cipher which is the Caesar cipher. Using the Cryptool, I opened the Caesar Brute-force analysis template and placed the cipher text in the input box and then executed. There was a list of decrypted texts that was displayed on the output text box within which the most meaningful and sensible text was spies send secret messages.

2. QEBXO OJVFP LKQEB JLSB

The decrypted message is “The army is on the move”

Steps that I followed to decrypt the message:

Since the question mentioned that the cryptanalysis will be done using some pre-digital age cipher, I thought of the most used cipher which is the Caesar cipher. Using the Cryptool, I opened the Caesar Brute-force analysis template and placed the cipher text in the input box and then executed. There was a list of decrypted texts that was displayed on the output text box within which the most meaningful and sensible text was the army is on the move.

3. QELJX PGBCC BOPLK ABPFD KBAXP RYPQF QRQFL KZFME BO

The decrypted message is “Thomas Jefferson designed a substitution cipher”

Steps that I followed to decrypt the message:

I used a tool named Cipher identifier and analyzer by Boxentriq to find out which type of cipher was used to encrypt the message. The result was as follows:

Using the Cryptool, I opened the Caesar Brute-force analysis template and placed the cipher text in the input box and then executed. There was a list of decrypted texts that was displayed on the output text box within which the most meaningful and sensible text was Thomas Jefferson designed a substitution cipher.

4. SNSZK KXCHR ZAKDC KNMFH STCDE NQSXK ZSHT CDRDU DMSXS GQDD

The decrypted message is “Totally disabled longitude forty latitude seventy three”

Steps I followed to decrypt the message:

I used a tool named Cipher identifier and analyzer by Boxentriq to find out which type of cipher was used to encrypt the message. The result was as follows:

Using the Cryptool, I opened the Caesar Brute-force analysis template and placed the cipher text in the input box and then executed. There was a list of decrypted texts that was displayed on the output text box within which the most meaningful and sensible text was Thomas Jefferson designed a substitution cipher.

5. NRSFQ CTCLM SRNES GDVZX ZSNMB D

6. RQVKM EFAUD XUGRQ AINAG LIPBC ROKJJ L

 

INTERMEDIATE

7. UJTUQ JFQQF WTZSI YMJBT WQIQN PJYTX TQAJU ZEEQJ X

The decrypted message is “People all around the world like to solve puzzles”

The message that I got after decrypting was people all around the world like to solve pubbles, but one can understand that the original text has to be puzzles instead of pubbles.

Steps I followed to decrypt the message:

I used a tool named Cipher identifier and analyzer by Boxentriq to find out which type of cipher was used to encrypt the message. The result was as follows:

I used a substitution cipher solver by www.guballa.de. I placed the given cipher text in the input text box and selected the language and executed. By re-executing it again and again the key that is used to decrypt is changed for every new execution and the resulting text is changed. After a few attempts the message that I got was people all around the world like to solve pubbles. By this one can understand that the original text has to be people all around the world like to solve puzzles even without decrypting it further.

8. MIGYJ OTTFY MWUHV YBULX NIMIF PYVON MIGYU LYYUM S

The decrypted message is “Some puzzles can be hard to solve but some are easy”

I used a tool named Caesar cipher breaker (Automatic Caesar Analysis) by MeFancy. After placing the given ciphertext in the given text-area and started with shift 0. I kept changing the shifts and when I reached shift 25 I found a sentence that made perfect sense.

9. QVQLB HGUVA XGUNG GUVFC HMMYR JNFUN EQBER NFLGB QB?

The decrypted message is “Did you think that the scuffle was hard or easy to do?”

Steps I followed to decrypt the message:

I used a tool named Cipher identifier and analyzer by Boxentriq to find out which type of cipher was used to encrypt the message. The result was as follows:

I used a tool named dcode on their official website to decrypt the text. It is a similar tool like the one provided by guballa. I placed the ciphertext in the input text box and select auto solve and a list of results were found. The most sensible text was did you thing that thi scuffle was hard or easy to solve. But one can understand that it meant did you think that the scuffle was hard or easy to do?

ADVANCED

10. LHKUFXKUL, J LXYIRU ETMMRU KJD NU KTQU TE HV LUOUBJR EJBFL.

The decrypted message is “Sometimes, a single puzzle may be made up of several parts”

Steps I followed to decrypt the message:

I used a tool named Cipher identifier and analyzer by Boxentriq to find out which type of cipher was used to encrypt the message. The result was as follows:

I used a tool named quipqiup beta for decrypting the message. This tool can decrypt the text without a key by providing us the auto solve, dictionary and statistics options. I placed the cipher text in the puzzle text area and selected auto solve option and clicked solve. The most appropriate text in the result was Sometimes, a single puzzle may be mude up of several parts. But this meant Sometimes, a single puzzle may be made up of several parts.

11. KEON MEGS FCHS IK HBWRKJ QX BGJKG SB OBFK SB E OBFMWKSK HBWCSQBX.

The decrypted message is “Each part must be solved in order to come to a complete solution”

Steps I followed to decrypt the message:

I used a tool named Cipher identifier and analyzer by Boxentriq to find out which type of cipher was used to encrypt the message. The result was as follows:

I used a tool named quipqiup beta for decrypting the message. This tool can decrypt the text without a key by providing us the auto solve, dictionary and statistics options. I placed the cipher text in the puzzle text area and selected auto solve option and clicked solve. The resulting text was each part must be solved to come to a complete solution.

12. VGT OANRV UZNV WO VGAR UFKKBT AR RWBHADX VGT LNQUVWXNZCR VGTCRTBHTR.

The decrypted message is “The first part of this puzzle is solving the cryptograms themselves”

Steps I followed to decrypt the message:

I used a tool named Cipher identifier and analyzer by Boxentriq to find out which type of cipher was used to encrypt the message. The result was as follows:

I used a tool named quipqiup beta for decrypting the message. This tool can decrypt the text without a key by providing us the auto solve, dictionary and statistics options. I placed the cipher text in the puzzle text area and selected auto solve option and clicked solve. The resulting text was the first part of this puzzle is solving the cryptograms themselves.

13. IMQC XRK TKOC AMCMWTDIM CBM FMXNRWA KOMA CR TDQ CBM PHZBPGMC.

The decrypted message is “Next you must determine the keyword used to mix the alphabet”

Steps I followed to decrypt the message:

I used a tool named Cipher identifier and analyzer by Boxentriq to find out which type of cipher was used to encrypt the message. The result was as follows:

I tried decrypting the text using playfair cipher in Cryptool but it didn’t work. So, I tried decrypting it using substitution cipher itself. I used the quipquip beta tool and the decryption worked. The resulting plain text was next you must determine the keyword used to mix the alphabet.

14. TNUJTH, HKA QAUJ ZRLAFX KAJ JCX SKFW AUXW ZKF JCX UXJJROL.
The decrypted message is “Lastly, you just figure out the word used for the setting”

Steps I followed to decrypt the message:

I used a tool named Cipher identifier and analyzer by Boxentriq to find out which type of cipher was used to encrypt the message. The result was as follows:

I used a tool named quipqiup beta for decrypting the message. This tool can decrypt the text without a key by providing us the auto solve, dictionary and statistics options. I placed the cipher text in the puzzle text area and selected auto solve option and clicked solve. The resulting text was lastly, you just figure out the word used for the setting.

 

 

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