Editing Transposition cipher (section)

== Disrupted transposition ==

A disrupted transposition cipher<ref name="mahalakshmi">{{cite journal |last1=Mahalakshmi |first1=B. |title=An Overview on Disrupted Transposition Cipher for Security Enhancement |journal=International Journal of Computer Applications |date=June 2016 |volume= 143 |issue=13 |pages=9–12 |doi=10.5120/ijca2016910308 |url=https://www.ijcaonline.org/archives/volume143/number13/mahalakshmi-2016-ijca-910308.pdf |archive-url=https://web.archive.org/web/20180604051237/http://www.ijcaonline.org/archives/volume143/number13/mahalakshmi-2016-ijca-910308.pdf |archive-date=2018-06-04 |url-status=live |access-date=7 January 2021}}</ref> further complicates the transposition pattern with irregular filling of the rows of the matrix, i.e. with some spaces intentionally left blank (or blackened out like in the [[Rasterschlüssel 44]]), or filled later with either another part of the plaintext or random letters.<ref name="mahalakshmi" />

=== Comb approach ===

This method (attributed to Gen. [[Luigi Sacco]]<ref>{{cite web |last1=Savard |first1=John |title=Methods of Transposition |url=http://www.quadibloc.com/crypto/pp0102.htm |website=A Cryptographic Compendium |access-date=27 June 2023}}</ref>) starts a new row once the plaintext reaches a column whose key number is equal to the current row number.  This produces irregular row lengths. For example, 

 F  O  R  E  V  E  R  J  I  G  S  A  W     < Key
 4  8  9  2 12  3 10  7  6  5 11  1 13     Blanks after no.:
 C  O  M  P  L  I  C  A  T  E  S  T  *     1
 H  E  T  R  *  *  *  *  *  *  *  *  *     2
 A  N  S  P  O  S  *  *  *  *  *  *  *     3
 I  *  *  *  *  *  *  *  *  *  *  *  *     4
 T  I  O  N  P  A  T  T  E  R  *  *  *     5
 N  L  I  K  E  A  C  O  M  *  *  *  *     6
 B  _  _  _  _  _  _  _  *  *  *  *  *     7

The columns are then taken off as per regular columnar transposition: TPRPN, KISAA, CHAIT, NBERT, EMATO, etc.

=== Numerical sequence approach ===

Another simple option<ref>{{cite web |last1=jdege |title=A simple disrupted transposition |date=11 November 2014 |url=https://www.tapatalk.com/groups/crypto/a-simple-disrupted-transposition-t1074.html |access-date=7 January 2021}}</ref> would be to use a password that places blanks according to its number sequence. E.g. "SECRET" would be decoded to a sequence of "5,2,1,4,3,6" and cross out the 5th field of the matrix, then count again and cross out the second field, etc. The following example would be a matrix set up for columnar transposition with the columnar key "CRYPTO" and filled with crossed out fields according to the disruption key "SECRET" (marked with an asterisk), whereafter the message "we are discovered, flee at once" is placed in the leftover spaces. The resulting ciphertext (the columns read according to the  transposition key) is "WCEEO ERET RIVFC EODN SELE ADA".

 C R Y P T O
 1 4 6 3 5 2
 W E A R * E
 * * D I S *
 C O * V E R
 E D * F L E
 E * A * * T
 O N * C E *