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TRANSPOSITION TECHNIQUEKriptografi - Week 5

Aisyatul Karima, 2012

Standar Kompetensi Pada akhir semester, mahasiswa menguasai pengetahuan, pengertian,

& pemahaman tentang teknik-teknik kriptografi. Selain itu mahasiswadiharapkan mampu mengimplementasikan salah satu teknik kriptografiuntuk mengamankan informasi yang akan dikirimkan melalui jaringan.

Mahasiswa menguasai teknik transposisi Mahasiswa mampu menyelesaikan soal transposisi rail fence Mahasiswa mampu menyelesaikan soal transposisi route Mahasiswa mampu menyelesaikan soal transposisi kolom Mahasiswa mampu menyelesaikan soal transposisi ganda Mahasiswa mampu menyelesaikan soal transposisi myszkowski

Kompetensi Dasar

Contents

1

Rail Fence Transposition2

Column Transposition

3

Transposition Technique

5

Route Transposition

Myszkowski Transposition

6

7

Double Transposition

Transposition Method

Transposition method is the encryptionmethod with exchange the location ofplaintext. Returning the location of message based

on the key and the transposition algorithmto decrypt the ciphertext.

Transposition Method

There are the transposition algorithm :

Rail Fence Transposition Route Transposition Column Transposition Double Transposition Myszkowski Transposition

Rail Fence Transposition

Rail Fence is transposition encoding withwriting the letter of plaintext by startingfrom top down and then up to top onimaginary fence The encode text read row by row.

Rail Fence Transposition

Example : Plaintext :

Algorithm : 5 rows Encoding process :

Define the Ciphertext : …. ???

TENTUKAN PRIORITAS ANDA SEBAB KITA TIDAK DAPAT MENGERJAKAN SEMUANYA X.

T – - – - – - – P – - – - – - – S – - – - – - – - A – - – -- E – - – - – N – R – - – - – A – A – - – - – B – B – - -- – N – - – A – - – I – - – T – - – N – - – E – - – K – -- – - T – K – - – - – O – I – - – - – D – S – - – - – I -- – - – U – - – - – - – R – - – - – - – A – - – - – - – T – DST

Route Transposition

Transposition encoding with the route method same withthe Rail Fence.

Route Transposition encoding by writing the plaintext incolumn top to bottom in an imaginary lattice with the sizehas been agreed.

The message read with route according to theagreement, example : Read by clockwise spiral Start from top left snakes and ladders Start from bottom right, etc.

Route Transposition

Route encoding has many algorithm to read themessage.

But, not all these algorithm produce the secure ciphertext.

Many algorithm do not random the plaintext perfectly, sogive the gap for the cryptanalyst.

The popular route transposition is Union Route that usedby US’s army on war.

Route Transposition

Example : Plaintext :

Algorithm : 5 rows, spiral turning clockwise starting from top left

Encoding process :

Ciphertext : …. ???

TENTUKAN PRIORITAS ANDA SEBAB KITA TIDAK DAPAT MENGERJAKAN SEMUANYA X.

T K I A A B T D M R N AE A O S S K I A E J S NN N R A E I D P N A E YT P I N B T A A G K M AU R T D A A K T E A U X

Column Transposition

Column Transposition encoding write row by rowwith the same length key. The ciphertext read column by column randomly

through the number key permutation. The row length and column permutation called

by “key”.

Column Transposition

In encryption process, the key must beconverted into the number as the sequencealphabet. In decryption process, use the same step.

Column Transposition

Example : Plaintext :

Key : PENTING means 7 columns Encoding process :

PENTING defined as the sequence alphabet become :

TENTUKAN PRIORITAS ANDA SEBAB KITA TIDAK DAPAT MENGERJAKAN SEMUANYA X.

6 1 4 7 3 5 2T E N T U K A

N P R I O R I

T A S A N D A

S E B A B K I

T A T I D A K

D A P A T M E

N G E R J A K

A N S E M U A

N Y A X

P E N T I N G6 1 4 7 3 5 2

Double Transposition

Double transposition encoding is the columnencryption method that done by twiceencryption. Twice the encoding process is done to make

difficult decrypt the column transpositionplaintext. The second encoding process can use the same

key or the different key.

Double Transposition

Example : Define the second different key is GERHANA; based on the fisrt

ciphertext :

Encoding process :GERHANA defined as sequencial alphabet become : 4 3 7 5 1 6 2

EPAEA AGNYA IAIKE KAUON BDTJM NRSBT PESAK RDKAM AUTNT STDNA NTIAA IAREX

4 3 7 5 1 6 2E P A E A A G

N Y A I A I K

E K A U O N B

D T J M N R S

B T P E S A K

R D K A M A U

T N T S T D N

A N T I A A I

A R E X

Double Transposition

On world war I and II, the double transpositionencryption used by the nation as the encodingprocess for the secure message.

Myszkowski Transposition

On 1902 Émile Victor Théodore Myszkowski hasbeen introduced the variant of columntransposition encoding, which are distinguishedin the definition and permutation keywords. On column transposition encoding, the key is

BOROBUDUR that defined become 1 4 6 5 2 83 9 7; But, on Myszkowski method, the key become

1 3 4 3 1 5 2 5 4

Myszkowski Transposition

The ciphertext read by the sequence numbercolumn, if there is the same sequnce numbercolumn, read simultaneously starting from theleft. Transposition method combined with the

substitution method to make difficult thecryptanalyst.

Myszkowski Transposition

Example : Plaintext :

Key : BOROBUDUR means 9 column Encoding process :

BOROBUDUR defined as sequence alphabet become : 1 3 4 3 1 5 2 5 4

TENTUKAN PRIORITAS ANDA SEBAB KITA TIDAK DAPAT MENGERJAKAN SEMUANYA X.

1 3 4 3 1 5 2 5 4T E N T U K A N P

R I O R I T A S A

N D A S E B A B K

I T A T I D A K D

A P A T M E N G E

R J A K A N S E M

U A N Y A X

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