Playfair cipher: Difference between revisions

Content added Content deleted

Inline

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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}}==