##### Transposition Ciphers | Rail-fence transposition |

Transposition ciphers:

These are ciphers which donâ€™t replace any character from the plain text instead it will change the position of letters to make the cipher text.

Example:

Rail-fence transposition.

Simple columnar transposition.

Keyword columnar transposition.

Rail-fence transposition:

The plain text is written in the form of diagonals in the K number of rows. Where K is the key in this encryption mechanism and K define the number of rows.

Example:

Plain text: opensense labs.

Key: 2

We have to fill the 1st cell in the 1st row. And then next letter in the 2nd cell of 2nd row. Like that encryption continues.

While converting into the cipher text read row wise.

The cipher text will be

OESNEASPNESLB

While decrypting do the process in reverse order. Write all in row wise and read in diagonal way.

Simple columnar transposition:

It is a security mechanism that maintains columns as key to encrypt the message. In this the number of columns is the key to encrypt the message.

Example:

Plain text: Meet me tomorrow

Key: 4

Write the plain text row wise. After one row is completed then move to another row.

The cipher text will be

MMMOEEOWETRTOR

While decrypting using this method there is a formula we have to follow.

The first r columns contain q+1 letter each.

The remaining c-r columns contains q letter.

Keyword columnar transposition :

It is as like the simple columnar transposition. But in that we directly mention the columns number as the key here we will give a word. The number of characters consisting in the word is called as the key to the encryption mechanism.

example:

Plain text: Meet me tomorrow

Key: wise

So number of columns will be 4 as there as 4 characters in the key.

While reading we have to read according to the indices of the alphabets. Lesser will come first.

First E then I then S then W.

So the final encrypted text is

TOREEOWETRMMMO.

These are some of the substitution and transposition ciphers which comes under the symmetric encrytion.