The Sequence Transposition cipher first appeared in the Nov-Dec 2015 edition of American Cryptogram Association (ACA) magazine. The Cryptogram It was developed by ACA member MSCREP.
A 5 to 8-digit primer is is used to create a running digital key by adding successive pairs of digits, subtracting 10 if the total is greater than 9, and appending the result to the end of the running key. This is repeated until its length is the same as the plaintext. So if the primer is 32941 adding the 1st number, 3 to the 2nd number, 2 gives 3+2=5 and the running key becomes 329415. Then the 2nd number, 2 is added to the 3rd number, 9 to give 2+9=11. Subtracting 10 gives 1 and the running key becomes 3294151. This continues to the length of the plaintext producing the running key 3294151356648120293221254337976066366. Then each letter of the plaintext is assigned to a single digit of the key. For example:
Running key: 3294151356648120293221254337976066366
Plaintext: adaywithoutsunshineislikeyouknownight
Next select a 10-digit number containing the numbers 0-9 which is used to create a column order for sorting the plaintext according to the running key. This number can be random or based on a 10-letter word or phrase. Using the word CRYPTOGRAM a number key is produced:
Word: CRYPTOGRAM
Order: 2706953814
Each plaintext letter is placed in a column based on its sequence number, so the first letter, a, is placed below 3, then d below 2, then a below 9 and so on producing the following table.
2706953814
DUHUAIAUWY
SNWTNOH TS
I OKKE NE
I N Y L
S I O
I H G
T
When complete the columns are taken in order left to right forming the ciphertext.
DSIISI UN HW UTONIHT ANK IOK AHEYOG U WTNL YSE
and with the primer...
32941 DSIIS IUNHW UTONI HTANK IOKAH EYOGU WTNLY SE
Primer: 31752
Column order: 2706953814 (CRYPTOGRAM)
Plaintext: Only the mediocre are always at their best.
Running key: 31752482762093829210113112442368659
Plaintext: onlythemediocrearealwaysattheirbest
2706953814
TLODCYOENH
MELRRSREAT
I ET YBWH
A I A
E S
T A
E
Cipher: 31752 TMIAE TELEO LDREC RTYSO RYIEE BNAWA SAHTH
Solving methods: Hill Climbing search.
After selecting the Numbered Key cipher type, the Key primer must be entered in the Cipher Settings ribbon group.