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Polyalphabetic

Polyalphabetic: Polyalphabetic Cipher


Polyalphabetic Cipher


The Polyalphabetic Cipher is a substitution cipher.

With a shift value of n a letter is replaced with the letter that is n positions further forward

Decryption

With a shift value of n a letter is replaced with the letter that is n positions further back. Alternatively, this is the equivalent of replacing each letter with the letter that is (26 - n) positions further back

Example

The grid below shows the substution values for a shift value of 3


plaintextabcdefghijklmnopqrstuvwxyz
ciphertextdefghijklmnopqrstuvwxyzabc

Using different shift values

The polyalphabetic cipher has different shift values for different letter positions

In this activity, plaintext encrypted with a cipher that has three alphabets, uses shift 1 for the 1st, 4th, 7th ... letters, shift 2 for the 2nd, 5th, 8th ... letters and shift 3 for the 3rd, 6th, 9th ... letters


Polyalphabetic Cipher Question

Shift 1 = 3, Shift 2 = 16

Decode pexih

Enter Answer

Shift 1 = 3, Shift 2 = 16

plaintextabcdefghijklmnopqrstuvwxyz
alphabet 1defghijklmnopqrstuvwxyzabc
alphabet 2qrstuvwxyzabcdefghijklmnop

The answer is: mouse

Polyalphabetic Cipher Question

Shift 1 = 19, Shift 2 = 8 , Shift 3 = 2

Decode iwyxz

Enter Answer

Shift 1 = 19, Shift 2 = 8 , Shift 3 = 2

plaintextabcdefghijklmnopqrstuvwxyz
alphabet 1tuvwxyzabcdefghijklmnopqrs
alphabet 2ijklmnopqrstuvwxyzabcdefgh
alphabet 3cdefghijklmnopqrstuvwxyzab

The answer is: power

Polyalphabetic Cipher Question

Shift 1 = 10, Shift 2 = 7 , Shift 3 = 21 , Shift 4 = 18

Decode kbbmca

Enter Answer

Shift 1 = 10, Shift 2 = 7 , Shift 3 = 21 , Shift 4 = 18

plaintextabcdefghijklmnopqrstuvwxyz
alphabet 1klmnopqrstuvwxyzabcdefghij
alphabet 2hijklmnopqrstuvwxyzabcdefg
alphabet 3vwxyzabcdefghijklmnopqrstu
alphabet 4stuvwxyzabcdefghijklmnopqr

The answer is: august

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