Re: My BLT



On Feb 28, 9:37 am, Mok-Kong Shen <mok-kong.s...@xxxxxxxxxxx> wrote:
bmearns wrote:
WTShaw wrote:
You missed the difference between using BLT as a keyed cipher in which
there is no crib to use as an autodictive cipher which you chose to
solve.  As an exercise, the later may be instructional, maybe.

Well as we've well established, and as I freely admit, you seem to
know a lot more about cryptography than I do, and at any rate I am
very much an amateur in the field. What I "chose" to solve was the
exactly problem that you posted: I attacked a plain-text/cipher-text
pair generated exactly the way you described it in the original post.
If there are stronger ways to use the cipher, it's probably worth your
mentioning that.

[snip]

With the kind help of one follow-up of yours, I understand that BLT
consists of fractionalization in the way of trifid (but without the
subsequent recombination to make the length of the ciphertext equal to
that of the plaintext) followed by a homophonic transformation using a
3*9 matrix. WTShaw seems to have neglected (for no reasons apparent to
me) the transposition processing that is ubiquitous in all fractional
substitution schemes to my knowledge. If the stuff generated as you
explained is followed by e.g. a keyed columnar transposition, then the
analysis would be a lot harder, I surmise. (But maybe what I said is
inappropriate, for I haven't very closely followed the course of your
long discussion with WTShaw.)

M. K. Shen

BLT was never expected to do so much, merely do a few choice things.
I was surprised that it even worked, but time and work tends to reach
most goals. Anyway, the program is much better at doing what it does
than the poor clerk that I am also being that I can't really write
these days more than a few characters at one sitting.

I'm familiar with the detailed instructions of how to break various
checkerboards and there is probably a best way to so attack BLT other
than being a cryptogenie as ACA seems to have some of them.

For BLT, never forget brute force for searching all the possible
keys. That alone removes it for serious use beyond a certain number
of triads, whatever that is.
.