Monoalphabetic vs Polyalphabetic Cipher: Know the Difference between Monoalphabetic Cipher and Polyalphabetic Cipher
Both of these are types of ciphers, but there is a major difference between monoalphabetic cipher and polyalphabetic cipher. In monoalphabetic cipher, every symbol that is in plain text gets mapped to fixed symbols that are in cipher texts. Polyalphabetic cipher, on the other hand, is based on substitution with the help of multiple substitution alphabets. Read ahead to learn more.
What is a Monoalphabetic Cipher?
It refers to that cipher in which all the letters of the plain text get mapped into the cipher text letters, on the basis of one alphabetic key. The Caesar-shift cipher is one of the major examples of a monoalphabetic cipher. Here, every letter shifts on the basis of a numeric key. The atbash cipher is another example. Here, every letter gets mapped to its symmetric letter (symmetric to the alphabet’s centre).
What is a Polyalphabetic Cipher?
The polyalphabetic cipher refers to the ciphers that are based on substitution with multiple substitution alphabets. The most prominent example of this type of cipher is the Vigenère cipher, although it is basically a special simplified case.
Difference between Monoalphabetic Cipher and Polyalphabetic Cipher
Let us talk about the differences between Monoalphabetic Cipher and Polyalphabetic Cipher.
| Parameters | Monoalphabetic Cipher | Polyalphabetic Cipher |
| Basics | It is the type of cipher in which every symbol that is in plain text gets mapped to fixed symbols that are in cipher texts. | It is the type of cipher that is based on substitution with the help of multiple substitution alphabets. |
| Plain and Cipher Text Relationship | There is a one-to-one relationship between the characters that exist in plain text and the characters that exist in cipher text. | There is a one-to-many relationship between plain text characters and cipher text characters. |
| Substitution Cipher | This one is a simple type of substitution cipher. | This one is a multiple type of substitution cipher. |
| Mapping of Alphabetic Characters | The alphabetic characters in plain texts get mapped on the unique alphabetic characters in cipher texts. | The alphabetic characters in plain texts get mapped on m alphabetic characters in cipher texts. |
| Stream Cipher | The stream cipher can be a monoalphabetic cipher in case the value of the key is not dependent on the plain text character’s position in the stream of plain text. | The stream cipher can be a polyalphabetic cipher in case the value of the key is not dependent on the plain text character’s position in the stream of plain text. |
| Example | It consists of multiplicative, affine, additive, and monoalphabetic cipher. | It consists of Vigenere, Playfair, Autokey, Rotor, One-time pad, Hill, and Enigma cipher. |
| Strength | This type of cipher is comparatively not as strong as a polyalphabetic cipher. | This type of cipher is comparatively stronger than a monoalphabetic cipher. |
| Uses | It is a substitution cipher that uses the same fixed mapping from the plain text to the cipher text letters present across the entire text. | It is a substitution cipher that deciphers the letters in plain text in different positions with the help of various cryptoalphabets. |
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