Hey everyone! Sorry for starting a thread and then going silent. The long weekend got away from me (did you know Staten Island has its own county fair, with carnies and everything? Neither did I).
I’ll have to take some time today to catch up, but in re: > Not sure about posting it @ Rosetta, though. Please do! If we need to make refinements later, we can; we can even do it collaboratively. That’s the beauty of the Wiki process. I think I’ll get this code running and then take a whack at making it as functional/stateless as the algorithm will permit. -Dan > On Sep 7, 2015, at 2:01 PM, Mike Day <[email protected]> wrote: > > Caesar/MOD ok too, now. > > ISAAC'' > > Message: a Top Secret secret > > Key: this is my secret key > > XOR encr:1c0636190b1260233b35125f1e1d0e2f4c5422 > > XOR decr:a Top Secret secret > > MOD encr:734270227d36772a783b4f2a5f206266236978 > > MOD decr:a Top Secret secret > > > The Rosetta examples effectively do (32+ 95&|) twice for > Caesar (MOD), once in iRandA, whereas I'd only been > applying it once. > > Not sure about posting it @ Rosetta, though. > Dan? > > M > > On 07/09/2015 11:15, Mike Day wrote: >> OK - fwiw I'll reply to self... >> Q0 - ok >> Q1 - still not clear >> Q2 - ascii encoding ok - eg 'a' => 97 etc >> Q3 - yes - but upper 32 bits of words are wasted in my current version >> Q4 - the vigenere (XOR) encryption is now correct. I'd overlooked the >> aa^ ... part in isaac() - eg I'd coded >> aa^= aa<<13; (C) >> as >> aa =. 13 shift4 aa >> (where shift4 is obvious enough). >> >> presumably my Caesar shift encryption isn't quite right, but I'm >> greatly reassured by the XOR, so I'm on the home straight! >> >> Mike >> >> On 06/09/2015 20:20, Mike Day wrote: >>> Hello Dan and/or others... >>> >>> Some questions and remarks below. >>> >>> I spent (wasted?) a lot of time yesterday and again today, looking >>> at mix and the rest of the stuff about Isaac, both at Rosetta, and >>> at the author's, Rob Jenkins', site: >>> http://www.burtleburtle.net/bob/rand/isaacafa.html >>> >>> The author's own listing of his 32-bit "readable C" code is similar to >>> the first part of the Rosetta C listing, although the Rosetta listing >>> has several extras, from iSeed() downwards, including a different >>> main(). >>> >>> The core of the whole thing is described as algorithm 1.1 in Amasson: >>> http://eprint.iacr.org/2006/438.pdf, >>> and is quite concisely coded (as isaac()) in both listings. Amasson doesn't >>> mention mix. >>> >>> Jenkins' site also includes a presumably non-readable C listing, and >>> a 64-bit version. >>> >>> Q0 What is the difference between 32 b. , 33 b. and 34 b. for left >>> shift, ie with positive x? >>> >>> Q1 Is mix truly a part of the encoding or not? >>> >>> Q2 Is it sufficient, in J, to start of with >>> 256 {.a. i. <string message> ? >>> I think that means that each byte becomes a word with 4 (or 8) bytes, >>> although this encoding should leave the upper 3 (or 7) bytes at zero. >>> I decode the results with output { a. . I don't understand C (nor the >>> other languages) well enough to see how they're doing it. >>> >>> Q3 My pc's are 64-bit. The implementation appears to work with >>> characters encoded into (computer) words. Correct? >>> >>> Q4 I've achieved a working version in the sense that a verb >>> can encipher and decipher the message, but the ciphers are >>> apparently wrong. I'm just printing them as integers, but >>> they seem to have no relation to the samples: >>> >>> isaacrosetta'' NB.my usual apologies re word-wrap, LF etc >>> >>> Message: a Top Secret secret >>> >>> Key: this is my secret key >>> >>> XOR encr:3 66 54 13 18 66 49 7 1 16 7 22 66 17 7 1 16 7 22 >>> >>> XOR decr:a Top Secret secret >>> >>> MOD encr:68 98 55 82 83 98 54 72 70 85 72 87 98 86 72 70 85 72 87 >>> >>> MOD decr:a Top Secret secret >>> >>> >>> The message has 19 characters, while the required encryptions each >>> have 38 hex-digits, ie 2 per byte. The hex sample for MOD is >>> 734270227D36772A783B4F2A5F206266236978 >>> >>> My version of mix is ok, but not worth reproducing here and trying your >>> patience. It produces the same results on simple input as Raul's explicit >>> verb, so I'll assume it's not at fault. >>> >>> I suspect the problem is associated with my Q2 above, but it might easily >>> be that I've got the core Isaac code wrong, or am doing the wrong number >>> of mixes, etc. It can't be all wrong though, as the plaintext is recovered >>> correctly, both for the example, and for much longer inputs. >>> >>> I could provide the script, but it's pretty long, though not as long as >>> the C code. >>> >>> Any ideas? >>> >>> Mike >>> >>> >>> >>> On 05/09/2015 03:55, Dan Bron wrote: >>>> Periodically I review the list of open J tasks on RosettaCode [1]. Today I >>>> came across an obscure but (if you believe the task description) >>>> meritorious cipher, called ISAAC ("Indirection, Shift, Accumulate, Add, >>>> and Count”). >>>> >>>> I understand the basic concepts of cryptography, but am generally unversed >>>> in the practical details of implementation. In other words: at the moment, >>>> I’m blindly transliterating the C implementation (marked as canonical) to >>>> J, hewing as closely to the source material as possible, loops and all. >>>> >>>> Which, of course, results in some damn ugly J. Take, for example, this C >>>> preprocessor macro, which I’ve dutifully transliterated as in the >>>> post-script. >>>> >>>> #define mix(a,b,c,d,e,f,g,h) \ >>>> { \ >>>> a^=b<<11; d+=a; b+=c; \ >>>> b^=c>>2; e+=b; c+=d; \ >>>> c^=d<<8; f+=c; d+=e; \ >>>> d^=e>>16; g+=d; e+=f; \ >>>> e^=f<<10; h+=e; f+=g; \ >>>> f^=g>>4; a+=f; g+=h; \ >>>> g^=h<<8; b+=g; h+=a; \ >>>> h^=a>>9; c+=h; a+=b; \ >>>> } >>>> >>>> Can you write this function in idiomatic, perhaps even elegant, J? Extra >>>> brownie points for something along the lines of f/ a,b,c,d,e,f,g,h , >>>> >>>> If it gives you a jumpstart, here is the pattern of variable names, as >>>> well as the bitshift direction and degree: >>>> >>>> abdabc < 11 >>>> bcebcd > 2 >>>> cdfcde < 8 >>>> degdef > 16 >>>> efhefg < 10 >>>> fgafgh > 4 >>>> ghbgha < 8 >>>> hachab > 9 >>>> >>>> Expressed as left-hand arguments to |.!.0, the bitshifts are 11 _2 8 _16 >>>> 10 _4 8 _9 . >>>> >>>> And the variable name matrix, expressed as indices into ‘abcdefgh’ is: >>>> >>>> 0 1 3 0 1 2 >>>> 1 2 4 1 2 3 >>>> 2 3 5 2 3 4 >>>> 3 4 6 3 4 5 >>>> 4 5 7 4 5 6 >>>> 5 6 0 5 6 7 >>>> 6 7 1 6 7 0 >>>> 7 0 2 7 0 1 >>>> >>>> Which pattern can be expressed as 0 1 3 0 1 2 (|."0 1) i.8 if you >>>> conceive of it column-wise, or 0 1 3 0 1 2 (8 | +/~) i.8 if row-wise. >>>> Either way, the salient structure appears to be 0 1 3 0 1 2 . >>>> >>>> >>>> -Dan >>>> >>>> [1] Tasks on RosettaCode with no J implementation: >>>> http://rosettacode.org/wiki/Reports:Tasks_not_implemented_in_J >>>> <http://rosettacode.org/wiki/Reports:Tasks_not_implemented_in_J> >>>> [2] The “wash shuffle” (which Wikipedia calls the “Corgi shuffle”) is >>>> that basic, no-frills move you see at the cheap tables in Atlantic City: >>>> the dealer simply spreads all the cards face down on the table and slides >>>> them all around and over each other. Not pretty, but effective, and less >>>> susceptible to sleight-of-hand cheating. >>>> https://en.wikipedia.org/wiki/Shuffling#Corgi_shuffle >>>> <https://en.wikipedia.org/wiki/Shuffling#Corgi_shuffle> >>>> >>>> PS: Here is a direct transliteration, but be WARNED: I haven’t gotten the >>>> overall ISAAC cypher to produce the correct outputs yet, so this is >>>> untested and may be incorrect. >>>> >>>> >>>> NB. ISAAC operates on 32-bit ints, meaning b. will break it on 64-bit >>>> systems >>>> bww =: (32#2)&#: >>>> hlfUnd =: 2 : 'v^:_1@:(u v)’ >>>> >>>> bwXor =: ~:&.bww >>>> bwShift =: |.!.0 hlfUnd bww >>>> >>>> mix =: verb define >>>> 'a b c d e f g h'=.y >>>> >>>> NB. a^=b<<11; d+=a; b+=c; >>>> a =. a bwXor 11 bwShift b >>>> d =. d + a >>>> b =. b + c >>>> >>>> NB. b^=c>>2; e+=b; c+=d; >>>> b =. b bwXor _2 bwShift c >>>> e =. e + b >>>> c =. c + d >>>> >>>> NB. c^=d<<8; f+=c; d+=e; >>>> c =. c bwXor 8 bwShift d >>>> f =. f + c >>>> d =. d + e >>>> >>>> NB. d^=e>>16; g+=d; e+=f; >>>> d =. d bwXor _16 bwShift e >>>> g =. g + d >>>> e =. e + f >>>> >>>> NB. e^=f<<10; h+=e; f+=g; >>>> e =. e bwXor 10 bwShift f >>>> h =. h + e >>>> f =. f + g >>>> >>>> NB. f^=g>>4; a+=f; g+=h; >>>> f =. f bwXor _4 bwShift g >>>> a =. a + f >>>> g =. g + h >>>> >>>> NB. g^=h<<8; b+=g; h+=a; >>>> g =. g bwXor 8 bwShift h >>>> b =. b + g >>>> h =. h + a >>>> >>>> NB. h^=a>>9; c+=h; a+=b; >>>> h =. h bwXor _9 bwShift a >>>> c =. c + h >>>> a =. a + b >>>> >>>> ".&> ;: 'a b c d e f g h' >>>> ) >>>> >> > > > --- > This email has been checked for viruses by Avast antivirus software. > https://www.avast.com/antivirus > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
