Identifying the primer

My program to identify the primer is dependent on repeated digits at the crib location. Thus it depends on knowing the crib location. The process is to increment every 5-digit primer from 1 to 99999, extend the full primer until the digits cover the crib location, then take the segment of the primer where the crib is located and call that primer2. In the preceding con, the crib is 14 letters long. I test each primer2 first for three-digit triplets and search to see if the corresponding crib letters appear as a sequence in the ct. For example, if the primer2 were 19692055125063, my program would first test the three 5’s. The corresponding crib letters for the 5’s triplet would be MOT for the crip “TOPOFAMOUNTAIN”. If MOT does not appear in the ct, then that primer cannot be correct. If it does, I give the primer a score of 5 points. Then I do the same with 2-digit doubles, like the 1, 6, 9 and 0. Those corresponding crib letters form digraphs. If any of those digraphs don’t appear in the ct, again the primer is rejected. If they do, 1 point is given for each such pair. Once all primers have been tested and a score given to each one that isn’t rejected, those are then ordered by score and decryption attempted with the highest-scoring primers first. The process could be extended to 4- or 5-digit groups, but the crib would have to be quite long in most cases.

In the preceding con, there was only one 4-primer group that outscored the correct group. I tested this method on the same con with a shorter crib (12 letters) without a triplet in the corresponding primer2 and the correct primer appeared in the highest-scoring 200 primers. If the crib were to occur over a sequence without many triplets or doubles, this method would not be effective. If the crib were long enough, one would not need to know its location in advance because there would probably be only one 4-primer group and crib location that would work.

Primerless Sequence Transposition

Here’s a Sequence Transposition cipher:

YUOTW TOEAH NHCSS TFEND WDEOT MNEAA TNOSO INBOO OULOW TNPNI RTSPT NKOTT ONOUT WGTHI IDAEA LDINE HAUAE OFRTA OTBDH OTOC 6

The crib is “TOPOFAMOUNTAIN” located above OOOULOWTNPNIRT, or more accurately, beginning at the 39th letter of the plaintext since the ciphertext letters at that point do not relate to the crib. I wrote a program that identifies the most likely primers given the ct, a crib, and the crib placement, assuming sufficient crib length. For this example my program placed the correct primer tied for 5th most likely along with 39 other primers. As an added hint, the check number at the end is 6.

The text is a random sentence from Gutenberg.org.

Unknown 6/6/19

OMWMB IHDDR PYOTQ WYWNA THSUH CWZTT HDWWQ OSCGX YNKQX XHQOT FRWWX MHWFQ DRKYW WNVBO RWQYU MNGDP

My analyzer had trouble with this one, placing the correct type in 17th place. It’s a random selection from Gutenberg.org. I had to peek at the worksheet to get the type and a crib. My hillclimber did not solve it without the crib. I’m including a crib: WYCDOFOBI

New Unknown 5/16/19

This ct is from my random program – two unrelated sentences from gutenberg.org. The key is also randomly chosen. I was able to solve it without a crib with the aid of a program. I’ll post a crib.

R SCE TATL ELTAS GRS SGCTAT TREG NSACE TASRNGE CLT GRS ISERE TCS STAAE EA YL ECSEA RE TCS NASIARE SA ICS CS GA RAEST SAA NASIARE RL REEERLN CLT RASAS CLT TANEG NSRSYCERR SCTRCLE EATRSTASRLNSL NASNAAES

crib: WLYMLJA (2)

Playfair 5-8-19

My hillclimber wouldn’t solve this until I gave it a long crib. The key consists of two words. I ran a brute force program combining the first word with every word in my list and it still didn’t find the solution. The plaintext is randomly selected from Gutenberg.org, two unrelated sentences.

DL SR YQ EH HT VC KV BG GR BY YQ UH SE UH ZC WO UA FQ ON DZ OL XN FG OU DL VD UV WO YD RH EZ HP OY RH VF ZU HT BG NL QO UC NH NO ZT AU ZF OI FC BC AT OH IV ZS AQ QO UR IO YQ EW US DL UR SB ZG FG VR PH RQ BC WR NU SU YI crib: VXDWCOXACBJLCRWPXO

Security certificate (https)

This site and all my other sites on the ackgame.com domain, including my cipher analysis page, crosswords, and OnWords blog are now and always were encrypted and safe. However, some browsers issued warnings that the site was not secure because the security certificate for the host (ICDsoft.com) named only that domain, not those domains hosted on the server. The URL was thus previously prefixed only as an http site. I have now obtained a security certificate for my individual domain and subdomains so that browsers do not issue a security warning. You can change the URL for this site and any others on this domain to include the https prefix now. If you encounter any issues with security warnings, please notify me by email or contact form.