asciilifeform: BUT enemy knows that plaintext(first_half[0]) ^ plaintext(second_half[0]) == 'T'
asciilifeform: this is superficially structure-destroying , either one of the two halves could literally be ANY bitstring of that length
asciilifeform: so one ~horrid~ padding algo would be to get a bitstring from my rng, xor the message to it, then send a message of 2x length of original consisting of: [the bitstring from rng][the result of the xor]☟︎
asciilifeform: and enemy knows that i always begin letter with 'To:'
asciilifeform: say i want to encipher (dun matter with what) a string, 'To: mircea_popescu Subj: thermonuke launch codes ...'☟︎
asciilifeform: let's take a ~terrible~ padding scheme just to show to n00bz what this whole matter is about.
asciilifeform: (the output tape size, that is. he of course knows the input tape size.)
asciilifeform: or he gets knowledge he is not supposed to have.
asciilifeform: mircea_popescu: the tape size cannot be known to decoder in advance
asciilifeform: then you append a sequence of ops , e.g., '10a10b10c10d.....' for the desired a,b,c,d... that flips the mutilated bits to the desired final state.
asciilifeform: then you produce some sequence of random moves for this machine, nondestructively (recall, all operations are invertible) waltzing over it.
asciilifeform: take the bitstring to be 'padded' (that is, mixed with entropy in such a way that it destroys enemy's ability to know any part of the structure of a plaintext inside ciphertext.)
asciilifeform: i will give one elementary algo for using this, here, but there are others.
asciilifeform: this is the ideal rsa padding scheme that folx asked for.
asciilifeform: however it is also impossible to know in less time than O(N) ~which~ integer
asciilifeform: it is immediately obvious that this (nonturingcomplete) automaton can be used to 'write' any integer
asciilifeform: picture the following 1-dimensional automaton, that eats bitstring in sets of 2bits, and : '10' -> 'tape step left' ; '01' -> 'tape step right' ; '11' -> invert bit at current square; '00' -> terminate.☟︎☟︎
asciilifeform: incidentally, since (to borrow the lament of turing's school headmaster) 'the room already stinks of mathematics', i'll share a tidbit that i promised folx some half year ago and promptly forgot:☟︎☟︎
asciilifeform: recall that you can express turing tape as diophantine eq.
asciilifeform: somehow i was certain this was provoked by some alchemical problem in eulora
asciilifeform: that being said, there are good methods for certain special cases, if mircea_popescu's diophantines are of a particular ~kind~ i might be able to hit up my dead trees for an algo.
asciilifeform: but yes, as a student it also 'felt like must have recursive solution'.
asciilifeform: hilbert's 10th met disappointing end long enough ago that nobody needs to google
asciilifeform: i can only imagine their disappointment.
asciilifeform: in other lulz, FUCKGOATS www is getting regular hits from places such as honduras, panama, etc. via search-engine referrer. and i am beginning to suspect that these folx were looking for material concerning the fucking of ordinary goats.
asciilifeform: mircea_popescu: see also hilbert's 10th.
asciilifeform: it is not a very promising problem as-stated imho. sorta like 'my pet mouse died, i want to resurrect it, i have this here industrial vivarium full of 10,001 live mice, how do i use them'
asciilifeform: 'Intelligence agencies and politicians in Germany are hoping to prevent a similar scenario next fall for the Bundestag elections. Some politicians in Germany have also proposed laws against the production and distribution of fake news.'
asciilifeform: 'In light of the rise of fake news on social media, the German Interior Ministry has proposed the creation of a "Center of Defense Against Disinformation," according to a report on Friday from the German news magazine "Der Spiegel."'
asciilifeform: 'Friedman, who specializes in litigation and bankruptcy law, was a key adviser to the incoming Republican president on US-Israel affairs during the presidential campaign.'
