Transposition Encryption
A Transposition Cipher modifies the ordering of characters, but does not
replace them. The transposition cipher used here is often called a Rail-Fence
Cipher or Columnar Transposition.
The encryption technique uses a simple process to change the ordering of the
letters. The tranposition is performed by using a pre-determined key which
represents a column count value.
Demonstration
Enter the value "3" in the Encryption Key box. Now, enter the phrase
"ELEPHANT" in the Phrase to Enrypt box. Then click on the "Demonstrate
Encryption" button to watch how the encryption process works.
First, the phrase to encrypt appears at the bottom of the window and the
characters moved into a new position. The first 3 characters are placed in a
row, followed by the next 3 characters on the next row.
For simplicity, the first few characters of the phrase to encrypt are repeated on
the last row so that all rows are of equal length.
Next, the encrypted phrase is created by taking the first column of letters,
followed by the second column of letters, and so on, until all columns of letters
are used.
Practice
Now try it again, but change to the Phrase to Encrypt to "OCEANOGRAPHY."
What is the ciphertext for this phrase?
Try some others on your own!!!
Check Encryption
Now it's your turn to encrypt a message.
Enter the value "4" for the key. Next, enter the word "RIVERWILD" as the
phrase to encrypt. Finally, manually encrypt the phrase and enter your result
in the box labeled "The encrypted/decrypted phrase is:"
Click on the "Check Encryption" Box to see if you were correct.
Answer the Following
1. Key = 3, Phrase = BUILDING. Enter the encrypted phrase:
2. Key = 4, Phrase = PYRAMID. Enter the encrypted phrase:
Practice
Try some more on your own!!!
Transposition Decryption
To decrypt a Transposition Cipher we follow an opposite process. The only
change is that instead of the key value equalling the number of columns, it
now determines the number of rows that will be used.
The number of columns is determined by dividing the total number of
characters by the key value. The process is then identical to the encryption
process.
Demonstration
Enter the value "3" in the Encryption Key box. Now, enter the value
"ALPEPA" in the Phrase to Decrypt box. Then click on the "Demonstrate
Decryption" button to watch how the encryption process works.
Note that there are two characters in each row. There are six characters in
the ciphertext and the key is three. Thus, 6/3 = 2, the number of columns or
the number of characters in each row.
After the process is complete the result is the word "APPLEA." Remember,
for simplicity we padded the plaintext so that each row created during
encryption was of equal length. Thus, we may need to manually determine
what the actual plaintext solution is, which, in this case, is "APPLE."
Now try it again, but change to the Phrase to Decrypt to "HTOODG."
What is the plaintext for this phrase?
Try some others on your own!!!
Check Decryption
Now it's your turn to decrypt a message.
Enter the value "3" for the key. Next, enter the word "LHUITLGBB" as the
phrase to decrypt. Finally, manually encrypt the phrase and enter your result
in the box labeled "The encrypted/decrypted phrase is:"
Click on the "Check Decryption" Box to see if you were correct.
Answer the Following
1. Key = 4, Phrase = SPWSAWMA. Enter the encrypted phrase:
2. Key = 3, Phrase = BKRAEYSTB. Enter the encrypted phrase:
Practice
Try some more on your own!!!