DECLARE SUB Encrypt (infile$, outfile$, txt$(), tmptxt$(), tmpchange(), encryption(), final())
DECLARE SUB Decrypt (infile$, outfile$, txt$(), tmptxt$(), tmpchange(), encryption(), final())
CLS
PRINT "This Program will encrypt/decrypt text files"
PRINT "Encrypted files will be SIGNIFIGANTLY larger"
PRINT "Path names must follow DOS rules"
PRINT "i.e. C:\My Documents\MyNewFile.txt"
PRINT "would become C:\mydocu~1\mynewf~1\txt"
PRINT "type 'exit' to leave"
PRINT ""
3
ON ERROR GOTO 1000
REDIM SHARED txt$(0): REDIM SHARED tmptxt$(0)
DIM SHARED tmpchange(1, 1)
DIM SHARED encryption(1, 1)
DIM SHARED final(1, 1)
1 LINE INPUT "Complete path of input file: ", infile$
                IF INSTR(LCASE$(infile$), "exit") THEN END
        INPUT "Overwrite Existing file? Y/N ", overwrite$
        IF INSTR(LCASE$(overwrite$), "exit") THEN END
        overwrite$ = LCASE$(overwrite$)
                IF INSTR(overwrite$, "y") THEN
                outfile$ = infile$
                GOTO 2
                ELSEIF INSTR(overwrite$, "n") THEN
  LINE INPUT "Complete path of output file: ", outfile$
  IF INSTR(LCASE$(outfile$), "exit") THEN END
  IF infile$ = outfile$ THEN
  PRINT "Output file cannot be the same as input file!"
  GOTO 1
  END IF
  ELSE CLS
  GOTO 1
  END IF

2 LINE INPUT "Encryption or Decryption? E/D?", perform$
  IF INSTR(LCASE$(perform$), "exit") THEN END
  IF INSTR(LCASE$(perform$), "d") THEN
  CALL Decrypt(infile$, outfile$, txt$(), tmptxt$(), tmpchange(), encryption(), final())
  ELSEIF INSTR(LCASE$(perform$), "e") THEN
  CALL Encrypt(infile$, outfile$, txt$(), tmptxt$(), tmpchange(), encryption(), final())
  ELSE
  PRINT "Error"
  GOTO 2
  END IF

GOTO 3
1000
SELECT CASE ERR
CASE 11
CLS
PRINT "This file cannot be decrypted by this program"
GOTO 1
CASE 53
CLS
PRINT "File Not found"
GOTO 1
CASE 62
RESUME NEXT

CASE 64
CLS
PRINT "One or more of your file names is invalid"
GOTO 1
CASE 76
CLS
PRINT "Please make sure all file names are correct AND follow DOS rules "
GOTO 1
END SELECT
RESUME

SUB Decrypt (infile$, outfile$, txt$(), tmptxt$(), tmpchnge(), encryption(), final())

DIM crypt(1, 1)
DIM line$(1, 1)

LET b = FREEFILE
OPEN infile$ FOR INPUT AS b
IF outfile$ = infile$ THEN
outfile$ = "c:\temp.txt"
END IF
LET c = FREEFILE
OPEN outfile$ FOR APPEND AS c

FOR x = 0 TO 1
FOR y = 0 TO 1
INPUT #b, encryption(x, y)
NEXT
NEXT
number = 1 / ((encryption(0, 0) * encryption(1, 1)) - (encryption(0, 1) * encryption(1, 0)))
crypt(0, 0) = encryption(1, 1) * number
crypt(0, 1) = -encryption(0, 1) * number
crypt(1, 0) = -encryption(1, 0) * number
crypt(1, 1) = encryption(0, 0) * number

DO WHILE NOT EOF(b)
LINE INPUT #b, linetochange$
                linetochange = VAL(linetochange$)
                IF z = 0 THEN
                tmpchange(0, 0) = linetochange
                ELSEIF z = 1 THEN
                tmpchange(0, 1) = linetochange
                ELSEIF z = 2 THEN
                tmpchange(1, 0) = linetochange
                ELSEIF z = 3 THEN
                tmpchange(1, 1) = linetochange
                final(0, 0) = tmpchange(0, 0) * crypt(0, 0) + tmpchange(1, 0) * crypt(0, 1)
                final(0, 1) = tmpchange(0, 1) * crypt(0, 0) + tmpchange(1, 1) * crypt(0, 1)
                final(1, 0) = tmpchange(0, 0) * crypt(1, 0) + tmpchange(1, 0) * crypt(1, 1)
                final(1, 1) = tmpchange(0, 1) * crypt(1, 0) + tmpchange(1, 1) * crypt(1, 1)
                        FOR x = 0 TO 1
                               FOR y = 0 TO 1
                                       IF final(x, y) > 1.8 AND final(x, y) < 2.5 THEN
                                       final(x, y) = 0
                                       END IF
                                IF final(x, y) > .9 AND final(x, y) < 1.8 THEN
                                PRINT #c, line$
                                PRINT line$
                                line$ = ""
                                ELSE
                                line$ = line$ + CHR$(final(x, y))
                                END IF
                        NEXT
                NEXT
                z = -1
                END IF
                z = z + 1
LOOP
IF LEN(line$) > 0 THEN
PRINT #c, line$
PRINT line$
END IF

IF outfile$ = "c:\temp.txt" THEN
        CLOSE
        KILL infile$
        NAME outfile$ AS infile$
END IF
END SUB

SUB Encrypt (infile$, outfile$, txt$(), tmptxt$(), tmpchange(), encryption(), final())

LET b = FREEFILE
OPEN infile$ FOR INPUT AS b
IF outfile$ = infile$ THEN
outfile$ = "c:\temp.txt"
END IF
LET c = FREEFILE
OPEN outfile$ FOR APPEND AS c


FOR x = 0 TO 1
        FOR y = 0 TO 1
7       encryption(x, y) = INT(RND * -50) + INT(RND * -50)
        IF encryption(x, y) = 0 THEN
        GOTO 7
        END IF
        PRINT #c, encryption(x, y)
        NEXT y
NEXT x

DO WHILE NOT EOF(b)
5 LINE INPUT #b, linetochange$
6 FOR x = LBOUND(txt$) TO UBOUND(txt$)
tmptxt$(x) = txt$(x)
NEXT
lin = lin + 1
REDIM txt$(lin)
linetochange$ = linetochange$ + CHR$(1)
txt$(lin) = linetochange$
FOR x = LBOUND(tmptxt$) TO UBOUND(tmptxt$)
txt$(x) = tmptxt$(x)
NEXT
REDIM tmptxt$(lin)
IF lin = 30 THEN GOTO 4
LOOP

IF EOF(b) <> 0 AND looped = 0 THEN
linetochange$ = "End of File"
looped = 1
GOTO 6
END IF

4 FOR x = 0 TO lin
        FOR y = 1 TO LEN(txt$(x))
        LET tmp$ = LEFT$(txt$(x), y)
        LET change$ = RIGHT$(tmp$, 1)
                IF change$ = " " OR change$ = "" THEN LET change$ = CHR$(2)
                change% = ASC(change$)
                        IF z = 0 THEN
                        tmpchange(0, 0) = change%
                        ELSEIF z = 1 THEN
                        tmpchange(0, 1) = change%
                        ELSEIF z = 2 THEN
                        tmpchange(1, 0) = change%
                        ELSEIF z = 3 THEN
                        tmpchange(1, 1) = change%
               
                final(0, 0) = tmpchange(0, 0) * encryption(0, 0) + tmpchange(1, 0) * encryption(0, 1)
                final(0, 1) = tmpchange(0, 1) * encryption(0, 0) + tmpchange(1, 1) * encryption(0, 1)
                final(1, 0) = tmpchange(0, 0) * encryption(1, 0) + tmpchange(1, 0) * encryption(1, 1)
                final(1, 1) = tmpchange(0, 1) * encryption(1, 0) + tmpchange(1, 1) * encryption(1, 1)
                PRINT #c, final(0, 0)
                PRINT #c, final(0, 1)
                PRINT #c, final(1, 0)
                PRINT #c, final(1, 1)
                z = -1
                END IF
                z = z + 1
        NEXT y
NEXT x
IF lin = 30 AND EOF(b) = 0 THEN
lin = 0
REDIM txt$(lin)
REDIM tmptxt$(lin)
GOTO 5
END IF

PRINT "File Encrypted"

IF outfile$ = "c:\temp.txt" THEN
        CLOSE
        KILL infile$
        NAME outfile$ AS infile$
ELSE
8 INPUT "Delete original file? Y/N ", delold$
        delold$ = LCASE$(delold$)
        IF INSTR(delold$, "y") THEN
        KILL infile$
        ELSEIF INSTR(delold$, "n") THEN
        ELSE
        GOTO 8
        END IF
END IF
PRINT ""
END SUB