Get Smart V1.1 Block Cipher

[xcoder]

print "###################################"

'four byte text block

'Three rounds of cipher per text block (three sub keys)



global two32,K1,K2,K3 '************ 'sub keys

two32 = 2^32

key = 2654435769

K1 = leftrotate(key,1)

K2 = leftrotate(key,4)

K3 = leftrotate(key,10)

dim B(4)

msg$ = "The quick brown fox jumps over the lazy dogs back"

print msg$

print "Length of message is ";len(msg$)

for i = 1 to len(msg$) step 4

chunk$ = mid$(msg$,i,4)

x = len(chunk$)

if x < 4 then chunk$ = chunk$ + extra$(chunk$,x)'pad the final block

t = 4 'array index

for j = 1 to len(chunk$)

ascii = asc(mid$(chunk$,j,1))

B(t) = ascii ' fill array B

t = t - 1

next j

a = B(4) * 256^3 '4 byte block

b = B(3) * 256^2

c = B(2) * 256^1

d = B(1) * 256^0

sum = a + b + c + d

numCrypt = Encrypt(sum)

result$ = result$ + dec2Text$(numCrypt)

next i

print result$



'==================================================================

print ""

input "Press Enter to Decrypt Message >> ";entry$

msg$ = result$

print ""

for i = 1 to len(msg$) step 4

chunk$ = mid$(msg$,i,4)

t = 4 'max array number

for j = 1 to len(chunk$)

ascii = asc(mid$(chunk$,j,1))

B(t) = ascii ' fill array B

t = t - 1

next j

a = B(4) * 256^3 '4 byte block

b = B(3) * 256^2

c = B(2) * 256^1

d = B(1) * 256^0

sum = a + b + c + d

numCrypt = Decrypt(sum)

plain$ = plain$ + dec2Text$(numCrypt)

next i

print plain$



print:print

print "End of Code"

End







function extra$(a$,x) 'pads the final text block

if x < 4 then

dif = 4 - x

for i = 1 to dif

pad$ = pad$ + chr$(128)

next i

end if

extra$ = pad$

end function



function Encrypt(a)

f = a xor 2^32-1 'invert all bits

ff = f xor K1 'xor 1st sub key

hex$ = decHex$(ff)

swap$ = right$(hex$,4) + left$(hex$,4) 'transposition

fff = hexDec(swap$)

Encrypt = Eround2(fff)

end function



function Eround2(a)

f = a xor 2^32-1 'invert all bits

ff = f xor K2 'xor second sub key

hex$ = decHex$(ff)

swap$ = right$(hex$,4) + left$(hex$,4) 'transposition

fff = hexDec(swap$)

Eround2 = Eround3(fff)

end function



function Eround3(a)

f = a xor 2^32-1 'invert all bits

ff = f xor K3 'xor third sub key

hex$ = decHex$(ff)

swap$ = right$(hex$,4) + left$(hex$,4) 'transposition

fff = hexDec(swap$)

print fff,decHex$(fff),dec2Bin$(fff)

Eround3 = fff

end function



print "===================================================="



'reverse order for decryption

function Decrypt(a)

hex$ = decHex$(a)

swap$ = right$(hex$,4) + left$(hex$,4) 'transposition

f = hexDec(swap$)

ff = f xor K3 'xor third sub key

fff = ff xor 2^32-1 'invert all bits

Decrypt = Dround2(fff)

end function



function Dround2(a)

hex$ = decHex$(a)

swap$ = right$(hex$,4) + left$(hex$,4) 'transposition

f = hexDec(swap$)

ff = f xor K2 'xor second sub key

fff = ff xor 2^32-1 'invert all bits

Dround2 = Dround3(fff)

end function



function Dround3(a)

hex$ = decHex$(a)

swap$ = right$(hex$,4) + left$(hex$,4)

f = hexDec(swap$)

ff = f xor K1 'xor 1st sub key

fff = ff xor 2^32-1 'invert all bits

print fff,decHex$(fff),dec2Bin$(fff)

Dround3 = fff

end function



' leftrotate: spins bits left n times

function leftrotate(num,times)

num = num mod two32

r = (num*2^times) mod two32 '************

l = int(num/(2^(32-times)))

leftrotate = r+l

end function



function dec2Text$(dec) 'outputs cipher text and plain text

hex$ = decHex$(dec)

for i = 1 to len(hex$)step 2

chunk$ = mid$(hex$,i,2)

ascii = hexDec(chunk$)

char$ = char$ + chr$(ascii)

next i

dec2Text$ = char$

end function



function dec2Bin$(num)

dec2Bin$ =""

while (num >0)

dec2Bin$ = str$( num mod 2) +dec2Bin$

num = int(num /2)

wend

dec2Bin$ =right$( "00000000" +dec2Bin$, 32)

end function