Transposition Techniques

Transposition techniques in cryptography involve rearranging the order of characters or blocks within the plaintext without altering the characters themselves. These techniques do not substitute or replace individual elements like substitution ciphers but focus on changing the arrangement or permutation of elements. Here are a few common transposition techniques:

1. Rail Fence Cipher: The Rail Fence cipher is a simple transposition technique that writes the plaintext diagonally on a set of “rails” or lines. The ciphertext is then obtained by reading off the letters in a specific order. For example, if the plaintext is “HELLO WORLD” and we have three rails, the ciphertext would be “HOLELWRDLL O”.
2. Columnar Transposition Cipher: In the Columnar Transposition cipher, the plaintext is written in a grid of columns. The columns are then rearranged based on a specific key or rule, and the ciphertext is obtained by reading the columns in a different order. The key determines the order of the columns. For example, if the plaintext is “HELLO WORLD” and the key is “CRYPTO”, the ciphertext might be “OLHLO DERWL”.
3. Route Cipher: The Route Cipher, also known as the Scytale cipher, involves writing the plaintext in a grid of predetermined dimensions. The ciphertext is then obtained by reading the grid in a specific path or route. The key for this technique is the dimensions and the specific route used to read the grid. Changing the route or dimensions produces different ciphertexts.
4. Double Transposition Cipher: The Double Transposition cipher applies two consecutive columnar transpositions to the plaintext. The plaintext is written in a grid of columns and then rearranged based on a key or rule. This process is repeated with a second key or rule. The resulting ciphertext is obtained by reading the columns in the final arrangement.

These are just a few examples of classical transposition techniques. Transposition techniques provide a form of encryption by changing the order of elements within the plaintext. However, they are generally considered weaker than modern encryption algorithms and are often used in combination with other encryption methods to enhance security.

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Transposition technique is an encryption method which is achieved by performing permutation over the plain text. Mapping plain text into cipher text using transposition technique is called transposition cipher.

On the one hand, the substitution technique substitutes a plain text symbol with a cipher text symbol. On the other hand, the transposition technique executes permutation on the plain text to obtain the cipher text.