(it is also distributed along with AZdecrypt in the "Ciphers" folder, in the "Unsolved" sub-folder as "Nick Pelling challenge 1")
- Code: Select all
THEOBJECTOFMYPROP
OSEDWORKONCYPHERI
SNOTEXACTLYWHATYO
USUPPOSEBUTMYTIME
ISNOWSOENTIRELYOC
CUPIEDTHATIHAVEBE
ENOBLIGEDTOGIVEIT
UPATLEASTFORTHENE
XTTWOORTHREEYEARS
I solved it with AZdecrypt v1.17 using my newest 8-gram model released a few days ago on Christmas. The only modification I made was adding 15 lines of code to restrict the solver to only use one homophone for each of the five columns. The solve for cipher #1 succeeded, but the way I modified the solver to do it is very inelegant since it can quickly lock high-scoring letters into place and then deprives the hill climber of further opportunities to test them in other arrangements. A more well-tuned version of this general solution would merely penalize (but not forbid) repeated letters in each column. This would allow the solver to evolve through a less jagged solution landscape and then still eventually arrive at a 1-homophone/column solution in the end. I predict this sort of modification would likely solve cipher #2 and beyond.
Although I used the column constraint (and it appears to have been necessary for a quick solve), the larger story here is probably the recent improvements to AZdecrypt and the release of 8-gram models in 2019.
For instance, if you simply ignore Nick's constraint and use Jarl's state of the art solver + his best n-gram file from 2018, you would have needed an 8 word crib to quickly decrypt challenge cipher #1:
AZdecrypt v1.14 + 7-gram jarl reddit: THEOBJECTOFMYPROPOSEDWORKONCYPHER
But in 2019, Jarl moved away from his IoC-based solver to a more capable entropy-based one. This alone drops the required crib needed to solve the cipher down to 2-3 words:
AZdecrypt v1.17 +
6-gram jarl reddit: THEOBJECT -- PR -- CYPHER
7-gram jarl reddit: THEOBJECT -- PR
And doing the same execrise with the n-gram models I've released during 2019 shows they progressed from needing an 8 word crib -- down to just a 5 letter crib:
AZdecrypt v1.17 +
6-gram v2 (May 2019): (no cribs sufficient)
6-gram v3 (Jun 2019): THEOBJECTOFMYPROPOSEDWORKONCYPHER -- ~90% correct solve
6-gram v4 (Oct 2019): THEOBJECTOFMYPROPOSEDWORKONCYPHER -- 100% correct
6-gram v5 (Dec 2019): THEOBJ -- PR -- CYPHER
7-gram v2 (May 2019): THEOBJECT -- PR -- WORK
7-gram v3 (Jun 2019): THEOBJECTOF -- WORK
7-gram v4 (Oct 2019): THEOBJECT -- WORK
7-gram v5 (Dec 2019): THEOBJ -- WORK
8-gram v2 (May 2019): THEOBJECT -- WORK -- CYPHER
8-gram v3 (Jun 2019): THEOBJ -- WORK -- YPH
8-gram v4 (Oct 2019): THEOBJ
8-gram v5 (Dec 2019): HEOBJ
Note: These are just the cribs I got to work in under a minute using a completely unmodified version of AZdecrypt. It's quite possible that any of us using either of the last two version of AZdecrypt + beijinghouse 8-gram files could have solved this since Oct 2019 simply by letting it run long enough.
