Продолжение листинга 18. 3. SUB transpose (datax() AS integer, t() AS integer, n%) letbe xt(), datax(), 64 FOR i% = 1 TO n% datax(i%) = xt(t(i%)) NEXT i% END SUB

SUB transpose (datax() AS INTEGER, T() AS INTEGER, n%)
letbe XT(), datax(), 64
FOR i% = 1 TO n%
datax(i%) = XT(T(i%))
NEXT i%
END SUB

SUB xtob (a$, mbits() AS INTEGER)
LOCAL X$,NIBBLE$
FOR i% = 1 to 16
X$ = MID$(a$,i%,1)
SELECT CASE X$
CASE "0"
NIBBLE$ = "0000"
CASE "1"
NIBBLE$ = "0001"
CASE "2"
NIBBLE$ = "0010"
CASE "3"
NIBBLE$ = "0011"
CASE "4"
NIBBLE$ = "0100"
CASE "5"
NIBBLE$ = "0101"
CASE "6"
NIBBLE$ = "0110"
CASE "7"
NIBBLE$ = "0111"
CASE "8"
NIBBLE$ = "1000"
CASE "9"
NIBBLE$ = "1001"
CASE "A"
NIBBLE$ = "1010"
CASE "B"
NIBBLE$ = "1011"
CASE "C"
NIBBLE$ = "1100"
CASE "D"
NIBBLE$ = "1101"
CASE "E"

Окончание листинга 18.3

NIBBLE$ = "1110"
CASE "F"
NIBBLE$ = "1111"
CASE ELSE
Print "Не является 16-ричным значением!"
SYSTEM
END SELECT
FOR j% = 1 to 4
mbits(((i% - 1) * 4) + j%) = ASC(MID$(NIBBLE$, j%, 1)) - 48
NEXT j%
NEXT i%
END SUB

Листинг 18.4. Пример реализации алгоритма
DES на языке Basic для расшифровывания файлов

$CPU 80386
$FLOAT NPX
$OPTIMIZE SPEED
$LIB ALL-
$OPTION CNTLBREAK ON

DECLARE FUNCTION MYBIN$ (n%)

DECLARE FUNCTION desalg$ (a$)

DECLARE SUB f (i%, a%(), x%())
DECLARE SUB transpose (datax%(), T%(), n%)
DECLARE SUB mrotate (keyx%())

DECLARE SUB stob (a$, mbits%())
DECLARE SUB btos (mbits%(), a$)
DECLARE SUB letbe (target%(), source%(), last%)
DECLARE SUB init (x() AS INTEGER, n%)
DECLARE SUB sboxinit (b() AS INTEGER)

DECLARE SUB xtob (a$, mbits%())

DIM s(1 TO 8, 1 TO 64) AS shared INTEGER

' Инициализация
RESTORE InitialTrl

Продолжение листинга 18.4

DIM InitialTr(1 TO 64) AS shared INTEGER
init InitialTr(), 64

RESTORE FinalTrl
DIM FinalTr(1 TO 64) AS shared INTEGER
init FinalTr(), 64

RESTORE swappyl
DIM swappy(1 TO 64) AS shared INTEGER
init swappy(), 64

RESTORE KeyTr1l
DIM KeyTr1(1 TO 56) AS shared INTEGER
init KeyTr1(), 56

RESTORE KeyTr2l
DIM KeyTr2(1 TO 48) AS shared INTEGER
init KeyTr2(), 48

RESTORE etrl
DIM etr(1 TO 48) AS shared INTEGER
init etr(), 48

RESTORE ptrl
DIM ptr(1 TO 32) AS shared INTEGER
init ptr(), 32

sboxinit s()

RESTORE rotsl
DIM rots(1 TO 16) AS shared INTEGER
init rots(), 16

DIM XR(1 TO 56) AS shared INTEGER

DIM EF(1 TO 64) AS shared INTEGER
DIM ikeyf(1 TO 64) AS shared INTEGER
DIM yf(1 TO 64) AS shared INTEGER

DIM ades(1 TO 64) AS shared INTEGER
DIM bdes(1 TO 64) AS shared INTEGER