Cipher where log tetragraph scoring doesn’t work.

Here’s a Numbered key cipher even longer than the ACA guidelines suggest. Without a crib it can’t be solved by log tet scoring.

Numbered key:
06 48 52 55 47 35 58 10 06 49 07 16 52 17 57 23 35 27 47 57 31 09
46 20 55 42 59 58 20 37 58 46 47 51 06 38 29 05 32 52 43 26 37 08
24 39 07 10 18 59 31 29 09 19 14 32 42 07 24 57 23 10 41 41 10 32
39 18 50 24 11 21 23 40 56 18 48 52 29 13 23 48 49 07 52 02 38 13
05 28 07 40 56 37 12 35 52 33 13 47 16 15 22 47 17 18 46 30 24 39
23 53 27 52 57 25 56 48 42 55 38 03 55 37 40 25 16 47 11 36 46 52
58 48 15 24 26 38 57 23 18 10 23 25 24 26 25 35 07 10 09 57 33 54
50 26 48 53 40 57 54 50 53 59 20 37 41 54 07 25 32 26 15 21 38 22
30 33 14 57 23 15 02 47 43 52 33 10 57 37 52 08 09 18 20 58 31 15
28 47 35 48 08 28 51 27 47 29 21 23 07 12 51 10 37 31 45 53 41 52
45 49 54 18 06 33 20 16 26.

The key length is 60 — shorter than a Grandpre key. Here’s a trial decrypt with log tet score greater than the log tet score of the solution:

nttateehnatethatentatethantehtettentheetanthenthatthethenteathtthenaeehatthatthattattataeetththettatehtthathentantahhtnathatthethattethentatahthenhetheathentataheathtththenhatththathatatthattheahethetetheenthatthehtthatthahanthen

The log tet score of the above is 982. The log tet score of the solution is 914.

My regular PH hill-climber using log pentagraph and word list scoring solved it without a crib in about 30 million trial decrypts using three hill-climbing threads.

2 thoughts on “Cipher where log tetragraph scoring doesn’t work.”

  1. Interesting that pentagram scoring works where tetragram scoring doesn’t. I don’t have any hillclimbers other than tetragram or word based.

  2. Here’s a caesar-shifted crib for the cipher: -JHMFSLJGDXFDNSL
    With this crib I imagine it can be solved using log tetragraph scoring.

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