Sequence Transposition Tutorial

Background

This cipher is an extension of the Null Sequence cipher introduced by SCORPIUS (JA2012) to a transposition type of cipher. It was inspired by conversations between LIONEL and MSCREP concerning the sequence technique. The Sequence Transposition Cipher (STC) was introduced in the ND2015 issue of the Cryptogram (Cm). Continue reading Sequence Transposition Tutorial

Amsco Tutorial

I’m going to use JA03 E-11 as the basis for this tutorial. The crib is that the word ‘proudly’ is in the plain text. In AMSCOs, the plain text is broken up alternately into single and double letters. Therefore, the crib must have been broken up in one of the following ways:

*p r ou d ly
p ro u dl y
pr o ud l y*

As you have already noted, 2 PRs and a UD exist in the cipher text. This points to the third possibility. With two possible PR segments, we can produce two possible candidates for partial plain text.

Candidate No. 1 (First PR):

D  ** N
TI *  FI
O  ** E
PR *  UD
T  ** M
ON *  UR
P  ** N

Candidate No. 2 (Second PR):

R  ** N
TO *  FI
N  ** E
PR *  UD
L  ** M
EY *  UR
D  ** N  

(N.B., The asterisks represent the missing letters in the middle column)

There is nothing to really distinguish the two candidates (i.e., no obviously wrong letter combinations). However, the second set has the interesting combination ‘EY UR’. This suggests the word ‘YOUR’. The candidate word ‘proud’ (Which also requires an ‘o’) is only two rows above. This suggests that somewhere in the cipher text there must be a sequence that is of the form ‘o**o’.

There is in fact just one combination like this, at the very beginning of the the cipher text (OAIO in the second group). Lets plug the letters surrounding this segment into the blanks in No. 2 and see if it makes any sense.

We get:

** E  **
R  LI N
TO F  FI
N  IN E
PR O  UD
L  AI M
EY O  UR
D  SE N  

Note two thing. First, there are lots of promising words or fragments here which suggest we have made a good choice (e.g., nine, off, and your). There are also lots of fragments to build on (e.g., LAIM suggest claim). Second, because the double ‘o’ sequence was so close to the front of the cipher, we have identified the top of the columns. We can extend these columns downward to try to find the column lengths.

Substituting and lowering the columns we get:

OP E  NH
R  LI N
TO F  FI
N  IN E
PR O  UD
L  AI M
EY O  UR
D  SE N  
NA L  LD

Note that the LD in the last column are the last letters in the cipher text. This MUST be the end of a column! Therefore, we have identified the beginnings of three columns and the end of at least one. Now all we need to do is try columns from the remaining, unused letters, on either side of our start to extend the partial words we already have.

I’ll leave it to you at this point. If you need some hints, drop me an E-Mail.

Portax Tutorial

Introduction:

The Portax cipher is a periodic, digraph based cipher similar to the Slidefair. Like the Slidefair, it is based on one of the classic periodic ciphers (The Porta in place of the Vigenère, Variant or Beaufort used by Slidefair). The major difference between the two ciphers is the method of choosing the digraphs the cipher is applied too. In Slidefair the digraphs are taken sequentially from the plain text. In Portax, the plain text is laid out in pairs of rows of period length and the the digraphs are formed from the vertical columns. Continue reading Portax Tutorial

Baconian Tutorial

Background

The Baconian cipher is one of the earliest examples of what is now called a ‘fractionated’ cipher. Essentially, individual letters are enciphered as 5 character groups. Each letter is represented by a unique 5 character group of a/b characters (Note that this is essentially a binary system with each letter represented by a binary number). Continue reading Baconian Tutorial

Foursquare Tutorial

Introduction

The Foursquare cipher is a digraphic substitution cipher similar to the Playfair. Unlike the Playfair cipher, which is based on a single Polybius square, Foursquare uses 4 Polybius squares arranged into a single large square. The four squares are labeled from 1 to 4 starting in the upper left and proceeding clockwise. Squares 1 and 3 contain unkeyed plaintext alphabets placed in the normal order. Squares 2 and 4 are keyed ciphertext alphabets and may be placed in the squares in any of the usual ways. Continue reading Foursquare Tutorial

Gromark Tutorial

The Gromark is similar to the Ragbaby in that a different shift is used at each position to encipher from plain to cipher text. The major differences are:

  1. The Gromark shift for each letter is calculated from a 5 digit primer from which a running key is formed by addition of successive pairs of digits and dropping tens. The Ragbaby shift is found from the position of the letter in the plain text (Both word and letter position).
  2. The Ragbaby has a single alphabet for both plain and cipher text. The Gromark has independent plain and cipher alphabets positioned over one another. However, the Gromark plain alphabet is always in standard form (i.e., abcde…xyz).

Continue reading Gromark Tutorial

Homophonic Tutorial

Background

The Homophonic cipher uses the numbers from 01 to 100 to produce 4 independent cipher alphabets of 25 characters each (i/j are represented by single value). The four alphabets span from 01-25, 26-50, 51-75 and 76-100 respectively. Each alphabet is a simple shift of the standard alphabet. The keyword is given by the values of 01, 26, 51, and 76. Continue reading Homophonic Tutorial