A cryptic cipher

[SparkOut]

As people have been mentioning the Guardian Christmas cryptic crossword and columnar ciphers lately, here's a little something that might borrow a bit here and there and embellish and twist the minds of Scurra, Lumpybum and even Sherlock himself, so much so they won't know which way to look.

28951 NNMWO AEAGA TEEOT CLFAN SNOGD RICGS DUVEW LRWXC CNDOA EEHEO HHEGI AETTM ALNTD AHTIE WRALS PENID OOHON RWGNB NLBON IEADI DYENG SLSDL YBTMO TALAE TUOII NIASE TEENE NIEOM

[SparkOut]

This is an example of an intriguing cipher technique, which doesn't need a lot of brainpower to en/decipher, accessible "anywhere" with "limited resources", without needing a big detailed codebook, and which can be reused without great risk of compromise and with a few tweaks can be made still more secure. It's hardly enigma but would be challenging without knowledge of the technique.

I will be interested whether anyone can infer the technique, but open to hint requests.

[SparkOut]

Hint 1
It's not much of a hint to say the reference to the Guardian Christmas crossword is a prompt, but why do you suppose the cipher starts with a number?

Will recommend the Guardian Christmas cryptic - it's pretty accessible this year and really good fun!
https://www.theguardian.com/crosswords/ ... d-no-28949

[Bunnylump]

I do intend to look at this - just bogged down with lots of impossipuzzles at the mo!

[SparkOut]

Hint 2

Solving any of the Guardian crossword clues is NOT required. (I did mention already that this does not need a lot of brainpower to en/decipher, but I don't want to annoy anyone with wasted effort - although doing the crossword can be fun, of course.)

[Bunnylump]

OK I think I need a really big clue. Sorry got no ideas - thought maybe the numbers were giving an order for each of the groups of 5, but don't see why those numbers.

You should know that although I have just written a really irritating puzzle involving ciphers (which no doubt you are all cursing as it's been placed all over the outsides of puzzles so there is nowhere to write!) I am actually really useless at solving them!

[LAT]

.... I have just written a really irritating puzzle involving ciphers (which no doubt you are all cursing as it's been placed all over.....

Hmmm - no comment!

[SparkOut]

So the technique depends on a crossword grid layout. Did you get the right specific one? You know that solving the actual clues is not relevant. So given a grid, how to fill it in? There must be something logical to do, one way or another.

[SparkOut]

There's definitely one way or another to fill in the grid and read it.

[LAT]

So, are we trying to fill in a grid of the same size as the Guardian one referenced? This is 23x23 but it can't be the same grid unless we need to add more letters as we haven't been given enough. Although I have no idea what the numbers signify so they might help.
You also mention a columnar cipher so I have been wondering whether the numbers give an indication of columns/letters in columns before changing direction.
But I'm not getting anywhere so I'm probably not looking at it correctly at all.

[SparkOut]

Unless I have bogged it up completely there should be sufficient letters to fill in the grid (for crossword 28951), but limiting to exactly that would leave the ciphertext having a block without 5 letters. (Splitting into even blocks of 5 is an old technique to avoid having people able to guess at words because of the length.)
I thought I had mentioned padding with null letters. You should have EOM left over. (End Of Message - but that's arbitrary, just random padding.)
There are a few nulls in the grid too.
This is a bit different to columnars, it sort of "borrows a bit here and there" - I only mentioned because the columnars prompted me to remember this method.

[LAT]

Aha, I shall have another look. The letter count looks much better now!

[SparkOut]

Shall I guess you didn't unspoiler the inviz text in Hint 1 then?

[LAT]

That would be a kind interpretation!

[SparkOut]

Do you really need any more specific instructions?

[Bunnylump]

Finally!!!
I originally thought I was using the stated grid and was trying to write the letters in the down columns of those numbers that you gave. They obviously didn't work, so I was trying to add in various key words. When I was finally on the right actual crossword, I wrote them in left to right and obviously got nonsense. I then wrote them in backwards, turning the grid 90 degrees and all sorts.i went wrong at least three times. I have finally got them in the right way round and have the message!

Very clever (unlike me! )

[LAT]

Gosh, well done!

[SparkOut]

Yay finally! Well done!
But once you had the method sorted out, it really was a lot simpler than you made it at first, wasn't it Lumpybum?

[Scurra]

Insert comment about how this is true of every puzzle ever.

[Bunnylump]

Yay finally! Well done!
But once you had the method sorted out, it really was a lot simpler than you made it at first, wasn't it Lumpybum?

Yes, absolutely! I was just being a numpty in so many ways. Nothing changes.