Here’s a randomly generated Vigenere Running key cipher. I was able to solve it without a crib by using a program that drags a huge list of phrases across the cipher and uses logs of digraphs to score the corresponding plaintext strings. If the log digraph score of a plaintext string is high enough then the string is parsed into individual words (and partial words at the beginning and end of the string). If the parse is successful and one of the plaintext words is long enough then the phrase and corresponding plaintext string is saved to disk.
I set the length of a plaintext word to 7 or more letters. With this setting I got 35 phrase-plaintext pairs out of about 600,000 starting phrases. I used these 35 results as a collection of cribs and was then able to get the solution with a combination interactive and hill-climbing running key solver.
Here’s a randomly generated cipher of unknown type. The plaintext is a random passage from a file of 33 books concatenated together. I think the encoder ignored some numbers that were in the original book passage. My ID tests didn’t do too well: The correct type didn’t appear unless I set the maximum period high enough. With a high maximum period the correct type was in second place in all three ID tests.
It took awhile to stumble upon the correct hill-climbing options but then my PH hill-climber solved it without a crib. I’ll include a caesar-shifted hint and crib.
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
Here’s a randomly generated cipher of unknown type. Two ID tests put the correct type on top and one put it in second place. My hill-climber solved it without a crib. The plaintext looks like it’s from a list of references. I’ll add a caesar-shifted crib.
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.
Here’s a video link to a description of the Shor algorithm. If a quantum computer could be built with enough qbits then Shor’s algorithm would crack the public key cryptography scheme that everybody uses on the internet.
I calculated the correlations between ROT13’s expected ciphertext frequencies for Vigenere and Variant/Beufort and the actual frequencies of the 10,000 Gromark and running key ciphers that I generated. (For each cipher I used the higher of its Vigenere and its Variant correlation).
Here’s a chart of the correlations. In general the correlations are higher for running key ciphers than for Gromark ciphers. (but there were 258 running keys where the correlation was negative!). It looks like a correlation higher than 0.3 is a reasonable indicator for a running key cipher. But between 0.2 and 0.3 the odds are about even between Gromark and running key.