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{SECT 0 {EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 20 "read `vigenere.mpl`;
" }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 47 "Encipherment using Vigenere w
ith keyword POTATO" }{TEXT -1 0 "" }}{PARA 0 "> " 0 "" {MPLTEXT 1 0 
48 "ciph:=vigen_enc(`This is a message.`, `POTATO`);" }}{PARA 11 "" 1 
"" {XPPMATH 20 "6#>%%ciphG%/IVBSBGPAXSLOVSG" }}}{EXCHG {PARA 0 "" 0 "
" {TEXT -1 73 "Numbers of letters in message, after stripping all non-
letter characters." }{TEXT -1 0 "" }}{PARA 0 "> " 0 "" {MPLTEXT 1 0 
30 "numbers(`This is a message.`);" }}{PARA 11 "" 1 "" {XPPMATH 20 "6#
70\"#?\"\")\"\"*\"#>F&F'\"\"\"\"#8\"\"&F'F'F(\"\"(F*" }}}{EXCHG {PARA 
0 "> " 0 "" {MPLTEXT 1 0 18 "numbers(`POTATO`);" }}{PARA 11 "" 1 "" 
{XPPMATH 20 "6#7(\"#;\"#:\"#?\"\"\"F&F%" }}}{EXCHG {PARA 0 "> " 0 "" 
{MPLTEXT 1 0 14 "numbers(ciph);" }}{PARA 11 "" 1 "" {XPPMATH 20 "6#70
\"\"*\"#A\"\"#\"#>F&\"\"(\"#;\"\"\"\"#CF'\"#7\"#:F%F'" }}}{EXCHG 
{PARA 0 "" 0 "" {TEXT -1 47 "Decipherment using Vigenere with keyword \+
POTATO" }{TEXT -1 0 "" }}{PARA 0 "> " 0 "" {MPLTEXT 1 0 25 "vigen_dec(
ciph,`POTATO`);" }}{PARA 11 "" 1 "" {XPPMATH 20 "6#%/THISISAMESSAGEG" 
}}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 27 "Cryptanalysis of Figure 2.2" }
{TEXT -1 32 ": the text is stored in \"fig2_2\"" }}{PARA 0 "> " 0 "" 
{MPLTEXT 1 0 7 "fig2_2;" }}{PARA 12 "" 1 "" {XPPMATH 20 "6#%_cm|+~~DBZ
MG~AOIYS~OPVFH~OWKBW|+~~XZPJL~VVRFG~NBKIX~DVUIM|+~~OPFQL~VVPUD~KPRVW~O
ARLW|+~~DVLMW~AWINZ~DAKBW~MMRLW|+~~QIICG~PAKYU~CVZKM~ZARPS|+|+~~DTRVD~
ZWEYG~ABYYE~YMGYF|+~~YAFHL~CMWLW~LCVHL~MMGYL|+~~DBZIF~JNCYL~OMIAJ~JCGM
A|+~~IBVRL~OPVFW~OBVLK~OPVUJ|+~~ZDVLQ~XWDGG~IQEYF~BTZMZ|+|+~~DVRMM~ANZ
WA~ZVKFQ~GWEAL|+~~ZFKNZ~ZZVCK~VDVLQ~BWFXU|+~~CIEWW~OPRMU~JZIYK~KWEXA|+
~~IOIYH~ZIKYV~GMKNW~MOIIM|+~~KADUQ~WMWIM~ILZHL~CMTCH|+|+~~CMINW~SBRHV~
OPVSO~DTCMG|+~~HMKCE~ZASYD~JKRNW~YIKCF|+~~OMIPS~GAFZK~JUVGM~GBZJD|+~~Z
WWNZ~ZVLGT~ZZFZS~GXYUT|+~~ZBJCF~PAVNZ~ZAVWS~IJVZG|+|+~~PVUVQ~NKRHF~DVX
NZ~ZKZJZ|+~~ZZKYP~OIEXX~MWDNZ~ZQIMH|+~~VKZHY~DVKYD~GQXYF~OOLYK|+~~NMJG
S~YMRML~JBYYF~PUSYJ|+~~JNRFH~CISYL~NG" }}}{EXCHG {PARA 0 "" 0 "" 
{TEXT -1 20 "Index of coincidence" }{TEXT -1 0 "" }}{PARA 0 "> " 0 "" 
{MPLTEXT 1 0 29 "index_of_coincidence(fig2_2);" }}{PARA 11 "" 1 "" 
{XPPMATH 20 "6#$\"+sf[7W!#6" }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 46 "Fr
iedman's guess for the length of the keyword" }{TEXT -1 0 "" }}{PARA 
0 "> " 0 "" {MPLTEXT 1 0 17 "friedman(fig2_2);" }}{PARA 11 "" 1 "" 
{XPPMATH 20 "6#$\"+=`(yP%!\"*" }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 32 "
Approximation to Friedman's test" }{TEXT -1 0 "" }}{PARA 0 "> " 0 "" 
{MPLTEXT 1 0 18 "friedman2(fig2_2);" }}{PARA 11 "" 1 "" {XPPMATH 20 "6
#$\"+HUE3W!\"*" }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 82 "Guessing the le
ngth is about 5, try to look at the frequencies of letters in every" }
}{PARA 0 "" 0 "" {TEXT -1 11 "5th letter." }}{PARA 0 "" 0 "" {TEXT -1 
73 "This computes the frequencies in letters number  5x+1 for x=0,1,2,
3,4,..." }}{PARA 0 "> " 0 "" {MPLTEXT 1 0 22 "subfreq(fig2_2,[5,1]);" 
}}{PARA 0 "" 0 "" {TEXT -1 55 "(Then we guess E is represented by Z in
 that alphabet.)" }{TEXT -1 0 "" }}{PARA 11 "" 1 "" {XPPMATH 20 "6#-%'
matrixG6#7$7<%\"AG%\"BG%\"CG%\"DG%\"EG%\"FG%\"GG%\"HG%\"IG%\"JG%\"KG%
\"LG%\"MG%\"NG%\"OG%\"PG%\"QG%\"RG%\"SG%\"TG%\"UG%\"VG%\"WG%\"XG%\"YG%
\"ZG7<\"\"%\"\"#\"\"'\"#5\"\"!FGFE\"\"\"\"\"&\"\"(\"\"$FHFCFC\"#8FCFHF
GFHFGFGFCFHFDFC\"#;" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 14 "numb
ers(`EZ`);" }}{PARA 11 "" 1 "" {XPPMATH 20 "6#7$\"\"&\"#E" }}}{EXCHG 
{PARA 0 "" 0 "" {TEXT -1 31 "The shift from plain to cipher:" }{TEXT 
-1 0 "" }}{PARA 0 "> " 0 "" {MPLTEXT 1 0 5 "26-5;" }}{PARA 11 "" 1 "" 
{XPPMATH 20 "6#\"#@" }}}{EXCHG {PARA 0 "" 0 "" {TEXT -1 59 "The shift \+
letter, which is the first letter in the keyword." }{TEXT -1 0 "" }}
{PARA 0 "> " 0 "" {MPLTEXT 1 0 14 "letters([22]);" }}{PARA 11 "" 1 "" 
{XPPMATH 20 "6#%\"VG" }}}{EXCHG {PARA 0 "> " 0 "" {MPLTEXT 1 0 0 "" }}
}}{MARK "12 1 0" 5 }{VIEWOPTS 1 1 0 1 1 1803 }