Breaking the Shift Cipher

STEP 1 : For the given ciphertext in the PART I of the simulation page, the first step is to decrypt it using each of the twenty-six different keys, k=0,1,...,25 and obtain the corresponding plaintexts. For decryption, you may use the tool given in the PART III of the simulation page.

STEP 2 : After each decryption, you may cut-and-paste the resultant plaintext in the scratch-pad in the (PART II) of the simulation page, if you need to remember it.

STEP 3 : Finally, observe the plaintexts and choose the most appropriate one (the one that is a meaningful English text) as the recovered plaintext and cut-and-paste it in the text-field named PART IV "Solution Plaintext". Also select the corresponding key in the text-field named "Key" and click on "Check My answer" Button.

STEP 4 [OPTIONAL] : Verify that your answer is correct, by encrypting the solution plaintext with your key.

An Example:

Let us say we have a cipher text "KRZ DUH BRX" generated by a shift cipher. We carry out the brute force attack as follows:

For k=0:

cipher text: K R Z D U H B R X
          plain text: k r z d u h b r x
          

For k=1:

cipher text: K R Z D U H B R X
          plain text: j q y c t g a q w
          

For k=2:

cipher text: K R Z D U H B R X
          plain text: l p x b s f z p v
          

For k=3:

cipher text: K R Z D U H B R X
          plain text: h o w a r e y o u
          

For k=3, we obtain a meaningful plain text namely how are you and hence we are done.