Playfair cipher: Difference between revisions
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Encoded: BM OD ZB XD NA BE KU DM UI XM MO UV IF
Decoded: HI DE TH EG OL DI NT HE TR EX ES TU MP</pre>
=={{header|J}}==
Implementation:
<lang J>choose=:3 :0
sel=. 'Q'e.y
alph=:(sel{'JQ')-.~a.{~65+i.26
norm=: alph intersect ('I' I.@:=&'J'@]} ])`(-.&'Q')@.sel@toupper
''
)
intersect=: ] -. -.~
choose 'Q'
setkey=:3 :0
key=: ~.norm y,alph
pairs=: 2{."1 ~."1 (,"0/~alph),"1 norm 'XQV'
mode=: #.=/"2 inds=:5 5#:key i.pairs
inds0=: (0 3,:2 1)&{@,"2 inds
inds1=:5|1 0+"1 inds NB. same column
inds2=:5|0 1+"1 inds NB. same row
alt=:,/key{~5 #.mode{"_2 inds0,"2 3 inds1,:"2 inds2
ref=:,/pairs
i.0 0
)
encrypt=:3 :0
,alt{~ref i. 2{."1 -.&' '"1 ~."1 (_2]\ norm y),"1 'XQV'
)
decrypt=:3 :0
,ref{~alt i. 2{."1 -.&' '"1 ~."1 (_2]\ norm y),"1 'XQV'
)</lang>
Example use:
<lang J> choose 'IJ'
setkey 'playfair example'
encrypt 'Hide the gold in the tree stump'
BMODZBXDNABEKUDMUIXMKZZRYI
decrypt 'BMODZBXDNABEKUDMUIXMKZZRYI'
HIDETHEGOLDINTHETREXSTUMPX</lang>
=={{header|NetRexx}}==
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