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As we are looking at hill ciphers, here is a slight variant on a hill cipher to try solving:
PSXFYITLWXOCNIWUSSJVYYRUOMECGIMHJYKORHIXQHSOYKRUTQMWXQTVIXBQHTVOOUQYDOOYCTWGELOOYHRUAUCXTTGXNQTDFUQSJUOOYDVTEVTKMRSLIMJXGLWLUIXOCGDUQPPOOYTYYGDUDYBJIEEGTSLIAQRJBUEJEMTJUXYOSKESJFVVGDUDEOKMFNTMGDUPJIMLWWTTCOEMGLDBAXREGVHMCQSMBTUTGOLIQFUTXWCTDLJSMHSUTJHWMJXGLWLUIPRLIQWQBIKYVGDMKEEHIKUBVTPBOYXKOLMVAXPNAAHSBSTICXWPPWACTWJNMRTPKKYEMYIPQSLINDRSUHWOKJMYECDMKUALEAFVUPGYAVYKOXQSIGDCESMVXUJKCPAXWKWAFTKGEXAFHLBDDALGCJINKEUPGYEWDBARSIKMEQIXCJIAVRAYUHQGXYLUQXCXFMAKFRHAYFMAKGDUQWNWKEVDQGJAKJNOOYWOLUSWIOIRJLLPSNBMXQHHYNVSKIXTMYEQGERTPKKYWCTGTKMAHYPEWDHGKJXKSCLUNQCHPBUIGBWCNIDJLIFFXHIKUIOUVCWNEYNYDCWFUQLHNVJAMJMXVPFULRSIHBSAEIBUDFLYATIVEOYOHUPGFPTQXGGDUHNRWEETPBFUIAHXGDUEGRPQFGDUKLRQMOVVVGDUSOPBJOMVAYTKRBIDLJGPGAKARACNJQTFTAHMVUMYGYTSEOIQOVYPSADQYSFWNVXDFFDDPDYBKOQCPAXYLVDQLPFCPSIPEXPNWAFIYHMLWDDPHBSOABSLIEBCEYUYNYBDDFUQOSKXNWNTRIIWTOQBPWYLQTYYGDUTWNBRWEMEDQYSFWASCVJAUXYFNIXMQMKBKIHKPCDWCCQSDYBXTTDLMVGWCBQIGDMKBOPIJSWBFLVHIYPMBLEWBRCMQGDUMAHCLKNHVGAICGIEMOBEAQOHOEGTYYFAIMDQVAGQOUXXPFOSIMKRADCLKUSSHVTNAHKJNHYNHQLLWSNIDJLIUDHFRHAYFMAKLPFJOHTICUIOHDQPHDMLWXPSGJAREYAHHUXYAENIMONSVIKCAVRUXYXSDAPPEGYWGPQOTBLEGDUKSODBAXNHWOKDJPYRTKMEQIXEUNAETXYLYGKUXYXYLWENDUWMUYGAIBSEENHEJGTFTDLJFUQXYLVDQMVKCKQLPFFFXLWXPMOLPFHTLNAQXVJGWJCNLVery sorry for all the questions its my first year competing but are scrabble solvers allowed or not or is it normal dictionaries only lol
@AndGiggles, is that a 3×3 Hill with a constant vector added after?
@Gen_ruikt
Depends? I’m assuming you mean for solving anagrams. If you write a code for it you can definitely use it. Strictly speaking according to the rules: “You can also use any software that you write yourself. You should not use deciphering tools you find elsewhere on the web and doing so can result in disqualification.” In previous challenge our team used some hill climb algorithm combined with quadgram analysis which served the same purpose so we never used scrabble solvers. Sorry if this doesn’t answer your question fully, I hope Harry or someone can clarify it.
Also, feel free to ask anything! There are lots of people here who will be more than happy to help with any questions you have, that’s one of the reasons why the forum exists!
@crackerjack_404 that explanation does make sense but i am not faniliar with findind determinants and inverse matrices it kind of makes sens looking at the number but id rather and explanation that me guessing if that possible thx
@Gen_ruikt
You don’t need to how exactly determinants or inverse matrices work in order to be able to decrypt a hill cipher. But an inverse matrix works like any other inverse, it “undoes” an operation, and the determinant is just something you use to find the inverse.
So encryption is like multiplying your ciphertext block entries by some matrix K, and to undo the operation, you multiply the the blocks by the inverse of K to get back to the plaintext.
My first year of doing the cipher challenge, I had no clue what the hill cipher was or how matrices worked, so you’re already in a good position if you can see how the process works by looking at the numbers!
@the_cryptographer_formerly_known_as_madness It is a 3×3 without constant, but there is a slight twist. I am not fully aware how easily this will be to analyse with only cipher text and will be happy to provide cribs, or the topic of the text if they are needed. If needed, I can also provide additional hints about the nature of the twist.
Yeah the reason i asked about scrabble solver (for anagrams you are correct) is because i was reading the explanation of the 2018 10b and it said they used a crossword solve which i assume is really similar to scrabble solvers
The rules evolved over time! Harry
@AndGiggles,
Kirchhoffs told me that you have to reveal everything about the algorithm, but not the plaintext and key.
If you want to argue with him about it, I can loan you a shovel.A bit mean! Harry
Does your twist involve the number 5?
@the_cryptographer_formerly_known_as_madness Something like that, there were only 24 unique letters in the plain-text. If I had also wanted to talk about jumpy zebras from Queenstown, then I would have needed to add a # to the alphabet.
@AndGiggles,
well, the key is not a word in my dictionary.@the_cryptographer_formerly_known_as_madness A keyword wasn’t used to generate the encryption matrix. Do you think you have an idea what the twist is? If needed, I can provide some details of the topic of the text; it has got a lot of interesting stuff in it which should help with decryption.
@AndGiggles,
I believe it to be a 3×3 Hill cipher modulo 25, with either J or Q used as a space between words.
If that is correct, then a crib at least 8 (not need to be 9) should be enough to break it.
Brute-forcing it would take too long for my patience. Ha!Not quite, I could have used an alphabet with 25, 27, or 29 letters (23 if there had been no Js in the text) but not 24, 26, or 28. The text is about Galileo lacking the French sulphur for his area of study. A crib might be cardinals.
@Andgiggles
As it is your cipher how would you go about brute forcing it and can you explain how i would find a key or something that can help me as im very new to hill ciphers and have not solved one before
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