EZ Block Cipher with 10 repeating sub keys

[xcoder]

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

global two32,key '************

two32 = 2^32

key = 0.26547358 'seeds PRNG

dim B(4)

call subkey

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

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

print "Plain Block","Encrypted Block" '******

ctr = 0 'will count the data blocks

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

k = 3 'array index

for j = 1 to len(chunk$)

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

B(k) = ascii ' fill array B

k = k - 1

next j

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

b = B(2) * 256^2

c = B(1) * 256^1

d = B(0) * 256^0

sum = a + b + c + d

print sum, '********************

numCrypt = encrypt(sum,ctr)

ctr = ctr + 1 'increment data block counter

print numCrypt

result$ = result$ + hexAsc$(numCrypt)

next

print result$

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

print ""

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

msg$ = result$ '***********

print msg$

print "Encrypted Block";space$(4);"Plain Block"

ctr = 0

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

k = 3 'array index

for j = 1 to len(chunk$)

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

B(k) = ascii ' fill array B

k = k - 1

next j

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

b = B(2) * 256^2

c = B(1) * 256^1

d = B(0) * 256^0

sum = a + b + c + d

print sum, '***************

numCrypt = decrypt(sum,ctr)

ctr = ctr + 1 'increment the data block counter

print numCrypt

plain$ = plain$ + hexAsc$(numCrypt)

next

print plain$


print:print

print "End of Code"

End



sub subkey

print "These are the sub keyS"

randomize key 'create sub keys

for i = 0 to 9

x = int(rnd(1)* 2^32) '32 bit integer

K(i) = x

print K(i)

next

end sub



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

end if

extra$ = pad$

end function



function encrypt(sum,ctr)

x = 9 'sets rotation

f$ = right$(str$(ctr),1)'ctr selects sub key 0 to 9 and repeats

i = val(f$)

a = sum xor K(i)

b = leftrotate(a,x)

encrypt = b

end function



function decrypt(sum,ctr)

x = 9 'sets rotation

f$ = right$(str$(ctr),1)

i = val(f$)

a = leftrotate(sum,32-x)

b = a xor K(i)

decrypt = b

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 hexAsc$(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

hexAsc$ = char$

end function