The columnar transposition technique essay

Columnar TranspositionIntroductionThis report will look at the columnar transposition technique as an encryption technique for alphabetic text. Encryption is the scrambling of data so that only the authorized party can understand the message. Columnar transposition involves writing the message in rows and then reading the ciphertext in columns using the keyword to know the width. The keyword is also used to decrypt the message by the recipient.
Background knowledge
From 1914 to 1918, during the first world war, the German military came up with a way of encrypting their war messages: columnar positioning. They used this method of communicating with other soldiers to alert them of an imminent attack or give instructions to their soldiers; they used this method by changing the keys frequently .unfortunately, their strategies we regularly solved by the French naming it ubchi, the French we able to decrypt the message of the same length once they found their keys .although it took the days, later after publication by Le Martin Germans eventually changed to a new system.AnalysisWhen working with columnar transposition, the intended text is written in rows on a certain length the readout column by column; these columns are chosen in a scrambled manner. The width of the rows and the permutation of the columns are normally defined by a keyword; Null values replace any spaces not filled by word. However, in an irregular columnar transposition, the spaces are just left blank, so to get the final message, they just read off in columns in the order specified by the keywordWe are going to show this using an example;EncryptionSuppose we have the keyword OSTRICH and want to pass the following message we are out of supplies. Please send help.OSTRICH will be equal to 4675312 according to permutation
4 6 7 5 3 1 2W E A R E O UT O F S U P PL I E S P L EA S E N D H EL P U V W X YNote that the value (UVWXY) are null values that have been selected to fill out the remaining space and are not part of the message.According to the table, the encrypted message will be OPLHX UPEEY EUPDW WTLAL RSSNV EOISP AFEEU.In the case of irregular cases, the columns were not completed by nulls; they we left empty.Example;4 6 7 5 3 1 2W E A R E O UT O F S U P PL I E S P L EA S E N D H EL P
In this case the encrypted message would be; OPLHU PEEEU PDWTL ALRSS NEOIS PAFEE.DecryptingTo decrypt the message, the one who receives it has to calculate the column length by dividing the message length by the keyword length and .then re-arranges the columns by reforming the keyword.
 
 
 
 
 
 
REFERENCESWalder et al 2011, Fast Decoding Algorithm for Variable lengths codes , 2012 , Information Sciences 183: 66-91.Ayushi 2010, A symmetric Key Cryptography Algorithm International Journal of Computer Application 1(15) 1-2.