TRANSPOSITION CYPHER

Group Members: Abdul Basit Tahir Faizan Illahi Sundhu Kamran Ali Noman Ahmad Usman Ashraf

Transposition Cypher Transposition cypher is a simple data encryption scheme in which plaintext characters are shifted in some regular pattern to form a cypher text.

Keyless Schemes Transposition cypher

Reverse Cypher In reverse cypher, the whole plain text is reversed or each word of plain text is reversed to form cypher text. Example: Reverse Plaintext Plain text: H E L L O P A K I S T A N Cypher text: N A T S I K A P O L L E W Example: Reverse Words Cypher text: O L L E H N A T S I K A P

Keyed Schemes Transposition cypher

Rail Fence Cypher The rail fence cipher is an easy to apply transposition cipher that jumbles up the order of the letters of a message in a quick convenient way. It also has the security of a key to make it a little bit harder to break.  In the rail fence cipher, the plaintext is written downwards on successive "rails" of an imaginary fence, then moving up when we get to the bottom. The message is then read off in rows.

Encryption: Write diagonally, Read from row Plain text: I AM A CYPHER TEXT KEY : 3 Columns = Length of plain text = 14 Row = Key = 3 Cypher Text: I C E X A Y H R T M P

Encryption: Write in Row, Read diagonally Cypher text: I E O R L V M C U T Y O Y N KEY : 3 Columns = Length of plain text = 14 Row = Key = 3 Plain Text: I E O R L V M C U T Y N I L O V E M Y C O U N T R Y

Pro’s & Con’s Easy to apply but…. It is not very secure specially for short messages. Limited number of keys. For enough transposition of letters, length of plain text needs to be at least 3 times of key

Route Cypher The Route Cipher is a transposition cipher where the key is which route to follow when reading the cipher text from the block created with the plaintext. The plaintext is written in a grid, and then read off following the route chosen. Key: It consists of route to follow and size of grid (either row or columns)

Encryption Plain Text: ABORT THE MISSION YOU HAVE BEEN SPOTTED Key: Move inward counter-clockwise from top right corner, with grid of 5 columns Cypher Text: TROBA TSYVN TEDXX TEANI MEHSO ESPOE HOIUB A B O R T H E M I S N Y U V P D X

Decryption Plain Text: Cypher Text: ATSYV NTBHS OESEO EIUBP DRMOH EOXTI NAETX Key: Move reading down the columns, with grid of 5 columns Plain Text: A B O R T H E M I S N Y U V P D X

Pro’s & Con’s It is also very easy and quick scheme. No limitations in selecting routs. Only limitation is one’s imagination But… Sometimes, selecting inappropriate route ends up with parts of plain text (actual message) in right direction in cypher text.

Columnar Transposition Cypher Columnar Transposition involves writing the plaintext out in rows, and then reading the cipher text off in columns. Columns reading order depends on key which is actually a keyword. We take the letters in the keyword in alphabetical order, and read down the columns in this order. Key: It is a keyword of any length.

Encryption Plain Text: WE HAVE BEEN VICTORIOUS IN BATTLE Key: A P P L E Cypher Text: A 1 P 4 5 L 3 E 2 W H V B I C T O R U S N X A 1 P 4 5 L 3 E 2 WEVRI TVBOS TXAET UAXEB IINLH ECOBE

Decryption Cypher Text: TEENV AEYDI RTEAV NYXHM ACESN RAGFX Key: E N E M Y Plain Text: E 1 N 4 2 M 3 Y 5 T H A R D V C I G F S X A 1 P 4 5 L 3 E 2 E 1 N 4 2 M 3 Y 5 THE ENEMY ARE ADVANCING VERY FAST

Pro’s & Con’s The most secured transposition cypher scheme Keyword is easy to easy remember then complex route Its most important feature is that keywords can be applied more then once First on plain text and then same or different keyword on cypher text

Myszkowski Transposition Cipher The same methodology as for Columnar Transposition is used, where the plaintext is written out in rows under the keyword. The only difference is that when there are repeated letters in the keyword, rather than number them from left to right, we give all the same letters the same number. We then read across columns which have the same number in the keyword. Key: It is a keyword of any length.

Encryption Plain Text: WE HAVE BEEN VICTORIOUS IN BATTLE Key: A P P L E Cypher Text: A 1 P 4 L 3 E 2 W H V B I C T O R U S N X A 1 P 4 L 3 E 2 WEVRI TVBOS TXAET UAXEH BEICI ONBLE

Decryption Cypher Text: TEEYE DNIVR ATEAV NYXHM ACESN RAGFX Key: E N E M Y Plain Text: E 1 N 3 M 2 Y 4 T H A R D V C I G F S X A 1 P 4 5 L 3 E 2 E 1 N 3 M 2 Y 4 THE ENEMY ARE ADVANCING VERY FAST

Pro’s & Con’s It has all the advantages and disadvantages of columnar cypher. Myszkowski has a plus point that is has no repetitive transposition