105.. bit encryption. - Printable Version

Code:
DECLARE SUB decrypt (array1() AS INTEGER, key1() AS INTEGER)

DECLARE SUB encrypt (array1() AS INTEGER, key1() AS INTEGER)

CLS



RANDOMIZE TIMER



string1$ = "Don't you just love 'Married with Children'?"

len1% = LEN(string1$)

DIM array1(len1% - 1) AS INTEGER



FOR i% = 0 TO UBOUND(array1)

array1(i%) = ASC(MID$(string1$, i% + 1, 1))

PRINT array1(i%);

NEXT i%



'MUST BE ODD! (or, even, if you count the zeroth element)

'MUST NOT EXCEED: max.bits.data.can.hold - bits.required(max.plaintext.number)





'In this case, a max of 255 must not exceed a key length of 7

'Each time the bits required can possibly double by almost 2.

'Program will not automatically error if length of 7 is exceeded,

'but can error with the right key combination.



'For signed integers, each sub key is made up of 15 bits (MOD max length of string). Theoretically, then, each key holds 7 subkeys * 15 bits.

'That's 105 bits, folks. Assuming there aren't any repeat keys, that's

'2^105, or 40,564,819,207,303,340,847,894,502,572,032, combinations.



keyLength% = 7

DIM testkey(keyLength% - 1) AS INTEGER



'DO

FOR i% = 0 TO keyLength% - 1

testkey(i%) = INT(RND * len1%)

NEXT i%



encrypt array1(), testkey()



PRINT : PRINT : FOR i% = 0 TO UBOUND(array1): PRINT array1(i%); : NEXT i%



decrypt array1(), testkey()



'IF INKEY$ <> "" THEN EXIT DO

'LOOP

PRINT : PRINT : FOR i% = 0 TO UBOUND(array1): PRINT array1(i%); : NEXT i%



SUB decrypt (array1() AS INTEGER, key1() AS INTEGER)



keyLength% = UBOUND(key1)

arrayLength% = UBOUND(array1) + 1

n% = keyLength%



DO

i% = key1%(n%) MOD arrayLength%

k% = (i% + arrayLength% - 1) MOD arrayLength%

temp1% = array1(i%)

DO

i% = i% + 1

IF i% = arrayLength% THEN i% = 0

IF i% = k% THEN EXIT DO

j% = i% - 1: IF j% < 0 THEN j% = j% + arrayLength%

array1(i%) = array1(i%) + array1(j%)

LOOP

n% = n% - 1

IF n% = -1 THEN EXIT DO





i% = key1%(n%) MOD arrayLength%

temp1% = array1(i%)

k% = (i% + arrayLength% - 1) MOD arrayLength%

DO

i% = i% + 1

IF i% = arrayLength% THEN i% = 0

IF i% = k% THEN EXIT DO

temp2% = array1(i%)

array1(i%) = array1(i%) - temp1%

temp1% = temp2%

LOOP

n% = n% - 1

LOOP

END SUB



SUB encrypt (array1() AS INTEGER, key1() AS INTEGER)



keyLength% = UBOUND(key1)

arrayLength% = UBOUND(array1) + 1



DO

i% = key1%(n%) MOD arrayLength%

temp1% = array1(i%)

k% = (i% + arrayLength% - 1) MOD arrayLength%

DO

i% = i% + 1

IF i% = arrayLength% THEN i% = 0

IF i% = k% THEN EXIT DO

temp2% = array1(i%)

array1(i%) = array1(i%) - temp1%

temp1% = temp2%

LOOP

n% = n% + 1

IF n% > keyLength% THEN EXIT DO





i% = key1%(n%) MOD arrayLength%

k% = (i% + arrayLength% - 1) MOD arrayLength%

temp1% = array1(i%)

DO

i% = i% + 1

IF i% = arrayLength% THEN i% = 0

IF i% = k% THEN EXIT DO

j% = i% - 1: IF j% < 0 THEN j% = j% + arrayLength%

array1(i%) = array1(i%) + array1(j%)

LOOP

n% = n% + 1

LOOP

END SUB