Перестановочный шифр

REM
REM Перестановочный шифр
REM
 
CLS
CONST p = " "
DIM T AS STRING
DIM S AS STRING
DIM u AS STRING
T = "1234567890098765432"
 
IF LEN(T) MOD 2 THEN T = T + p
S = T
 
k = LEN(T) / 2
 
FOR i = 1 TO LEN(T)
   u = MID$(T, i, 1)
   IF i MOD 2 THEN
      j = (i + 1) / 2
      MID$(S, j, 1) = u
   ELSE
      j = k + i / 2
      MID$(S, j, 1) = u
   END IF
NEXT
 
PRINT T
PRINT S
END

DECLARE FUNCTION MyEncode(txt AS STRING, KEY AS STRING) AS STRING
DECLARE FUNCTION MyDecode(txt AS STRING, KEY AS STRING) AS STRING
 
DIM txt AS STRING, KEY AS STRING, txt2 AS STRING
txt = "1234567890098654321"
 
KEY = "text"
txt2 = MyEncode(txt, KEY)
PRINT txt, KEY
PRINT txt2
PRINT MyDecode(txt2, KEY)
PRINT
 
KEY = "123456"
txt2 = MyEncode(txt, KEY)
PRINT txt, KEY
PRINT txt2
PRINT MyDecode(txt2, KEY)
PRINT
 
'Sleep
 
FUNCTION MyEncode(txt AS STRING, KEY AS STRING) AS STRING
    DIM i AS LONG, j AS LONG, n AS LONG, m AS LONG, l AS LONG
    DIM s1 AS STRING, s2 AS STRING, outTxt AS STRING
    n = LEN(KEY)
    IF n = 0 THEN EXIT FUNCTION
    l = LEN(txt)
    m = -INT(-l / n)
    
    DIM nKeys(1 TO n) AS LONG
    FOR i = 1 TO n
        s1 = MID$(KEY, i, 1)
        FOR j = 1 TO n
            s2 = MID$(KEY, j, 1)
            IF s1 > s2 OR (s1 = s2 AND j <= i) THEN nKeys(i) = nKeys(i) + 1
    NEXT j, i
    
    DIM aOut(1 TO n * m) AS STRING
    FOR i = 1 TO LEN(txt)
        aOut(nKeys((i - 1) MOD n + 1) * m + (i - 1) \ n - m + 1) = MID$(txt, i, 1)
    NEXT i
    FOR i = 1 TO n * m
         outTxt = outTxt + aOut(i)
    NEXT i
    MyEncode = outTxt
END FUNCTION
 
FUNCTION MyDecode(txt AS STRING, KEY AS STRING) AS STRING
    DIM i AS LONG, j AS LONG, d AS LONG, k AS LONG, n AS LONG, m AS LONG
    DIM l AS LONG, nTmp AS LONG, sTmp AS STRING, outTxt AS STRING
    n = LEN(KEY)
    IF n = 0 THEN EXIT FUNCTION
    l = LEN(txt)
    m = -INT(-l / n)
    d = l MOD n
 
    DIM nKeys(1 TO n)  AS LONG, sKeys(1 TO n) AS STRING
    FOR i = 1 TO n
        nKeys(i) = i
        sKeys(i) = MID$(KEY, i, 1)
        FOR j = 1 TO i - 1
            IF sKeys(i) < sKeys(j) THEN
                sTmp = sKeys(i): sKeys(i) = sKeys(j): sKeys(j) = sTmp
                nTmp = nKeys(i): nKeys(i) = nKeys(j): nKeys(j) = nTmp
            END IF
    NEXT j, i
    
    DIM aOut(1 TO n, 1 TO m) AS STRING
    FOR i = 1 TO n
        FOR j = 1 TO m + (nKeys(i) > d AND d > 0)
            k = k + 1
            aOut(nKeys(i), j) = MID$(txt, k, 1)
    NEXT j, i
    FOR j = 1 TO m
        FOR i = 1 TO n
            outTxt = outTxt + aOut(i, j)
    NEXT i, j
    MyDecode = outTxt
END FUNCTION