10 REM CODING USING A RANDOMIZING KEY
20 INPUT"CODE MESSAGE ";X$:GOSUB 100
30 POKE216,99:PRINT"ENCODED TEXT: "Z$
40 INPUT"PRESS RETURN TO RECODE";X$
50 X$=Z$:GOSUB 100
60 POKE216,99:PRINT"REVERSED TEXT: "Z$
70 END
100 REM ENCODING ROUTINE
110 INPUT"KEY NUMBER";K:X=RND(-ABS(K)/17)
120 Z$="":FOR I=1 TO LEN(X$)
130 X=ASC(MID$(X$,I,1))
140 Y=INT(RND(1)*255)
150 X=NOT(X AND Y)AND(X OR Y):REM XOR
160 Z$=Z$+CHR$(X):NEXT:RETURN