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Re: RSA - the song
Interesting.
Now for the obvious question, can you convert midi back to text?
Looks like a new way to hide encrypted messages.
amp
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From: Kent Crispin <[email protected]>
Subject: RSA - the song
Date: Sat, 02 Aug 1997 12:02:26 -0700
To: [email protected], [email protected]
> On Fri, Aug 01, 1997 at 11:35:02AM +0100, Adam Back wrote:
> [...]
> >
> > print pack"C*",split/\D+/,`echo "16iII*o\U@{$/=$z;[(pop,pop,unpack"H*",<>
> > )]}\EsMsKsN0[lN*1lK[d2%Sa2/d0<X+d*lMLa^*lN%0]dsXx++lMlN/dsM0<J]dsJxp"|dc`
> >
> > > I dug out a midi interpreter I wrote a number of years ago,
> > > and it is indeed trivial to modify it to read any text as input.
> > > Unfortunately, I wrote that long before the midi file spec was
> > > finalized, and the hardware I wrote it for is also long gone. But
> > > it's probably not much work to get file output working again...and
> > > the thought of a general text-to-midi translator is rather
> > > entertaining -- I could play this entire mail message through it, for
> > > example... It would definitely make better music if some rhythmic
> > > variation was part of the coding, but that would make it a little
> > > harder to make an automatic decoder...
> >
> > I'd find it most cool to hear an audio file of the above.
>
> Well, I generated a midi file that encodes music which in turn is a
> direct algorithmic encoding of your program. I didn't have a
> convenient way to go to a direct sound file, but midi players are
> very widely available -- any recent pc with a sound card will have a
> "multimedia midi jukebox" or something like that. And there are
> probably free ones on the net -- I didn't look. The midi file will
> be a mime attachment to this message. It's also at
>
> ftp://songbird.com/pub/rsa.mid
>
> For aesthetic reasons I modified the encoding from the simple one
> mentioned earlier, and, rather than try to modify one of my earlier
> midi programs, I just hacked this one out from other sources. The
> program will actually encode any binary data into a piece of music.
>
> I think that musically the piece is actually somewhat interesting -- I
> kind of like it. Like the source text, it is rather dense. But if
> you listen to it a few times patterns and phrasing will appear. It
> sounds like reasonable avante garde music, actually -- something a
> college radio station might broadcast to the world late at night...
>
> The program is really rather trivial, so rather than describing the
> encoding, I am just appending it to this message.
>
> --------------------------------------------------------------------
> /*
> dtom -- convert data to midi
> dtom midifile <datafile
> or
> datasource | dtom midifile
>
> convert standard in to a midi representation of the data, and
> write it to a standard midi file. The midi data is designed
> to so that the sound produced will permit decoding by a pitch
> to midi device. Two things are done to increase the musical
> interest: First, the notes are selected from a diatonic
> scale, instead of a chromatic. And second, the rhythm is
> also varied algorithmically -- any decoding from the sound
> should ignore all rhythmic variation.
>
> Code uses "midifilelib" from Tim Thompson & Michael
> Czeiszperger, and is cobbled from one of their examples.
>
> */
>
>
> #include <stdio.h>
> #include <ctype.h>
> #include "midifile.h"
>
> #define ROOT 36
>
> FILE *fp;
>
> /* offsets for three octaves of diatonic major scale */
> int scale[] = {0,2,4,5,7,9,11,12,14,16,17,19,23,24,26,28,29,31,33,35,36};
>
> mputc(c) { return(putc(c,fp));}
>
> int writetrack(track)
> int track;
> {
> int note_duration;
> int rest_duration;
> int high_nybble;
> int low_nybble;
> char c;
> char n1[2];
> char n2[2];
>
> mf_write_tempo((long)100000);
>
> while( (c = getchar()) != EOF ) {
>
> high_nybble = (c>>4) & 0xf;
> low_nybble = c & 0xf;
>
> /* low note */
> n1[0] = scale[low_nybble]+ROOT; /* note number */
> n1[1] = 64; /* velocity */
>
> /* high note */
> n2[0] = scale[high_nybble]+ROOT+scale[16];
> n2[1] = 64;
>
> /* shouldn't happen */
> if( n1[0] >= n2[0] ) printf("warning -- voice crossover!\n");
>
> /* note_duration needs to be long enough for pitch detectors */
> note_duration = 120*((c&15) + 4);
> rest_duration = 120*(((c>>5)&3));
>
> if(!mf_write_midi_event(rest_duration,note_on,1,n1,2)) return(-1);
> if(!mf_write_midi_event(0,note_on,1,n2,2)) return(-1);
>
> if(!mf_write_midi_event(note_duration,note_off,1,n1,2)) return(-1);
> if(!mf_write_midi_event(0,note_off,1,n2,2)) return(-1);
> }
>
> return(1);
> } /* end of write_track() */
>
> main(argc,argv)
> char **argv;
> {
> if( !(fp = fopen(argv[1],"w")) ) exit(1);
>
> Mf_putc = mputc;
> Mf_writetrack = writetrack;
> mfwrite(0,1,480,fp);
> }
>
> ---------------------------------------------------------------------------
>
>
> --
> Kent Crispin "No reason to get excited",
> [email protected] the thief he kindly spoke...
> PGP fingerprint: B1 8B 72 ED 55 21 5E 44 61 F4 58 0F 72 10 65 55
> http://songbird.com/kent/pgp_key.html
>
---------------End of Original Message-----------------
------------------------
Name: amp
E-mail: [email protected]
Date: 08/02/97
Time: 16:46:07
Visit me at http://www.pobox.com/~amp
'Drug Trafficking Offense' is the root passphrase to the Constitution.
Have you seen
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