TheGameCreators - CodeBase - DBPro Implementation of XXTEA (Tiny Encryption Algorithm)

Category: Miscellaneous

Version: 1.0

Information

Uploaded: 19th Oct 2011 08:32

Modified: 1st Jan 1970 01:00

Author: The Sab

Summary

XXTEA is a low profile encryption algorithm created by Roger Needham and David Wheeler. It was expanded upon by Chris Veness in a java script to encrypt strings instead of just binary data. This is the version that I based the following code on.

Full Description

To encrypt a file call the 'encrypt(<message$>, <password$>)' function. It returns an encrypted string of the original message. To decrypt a file call the 'decrypt(<ciphertext$>, <password$>)' function. It returns the decrypted string. The encrypted string is composed only of alpha-numeric characters (as well as '+', '=', and '/') so it can be transmitted and printed without worry from control characters. Any control characters in the original message will be stored, encrypted and decrypted and will be present in the decrypted string, though of course, if that string is written to file or print to screen, DBPro will strip them out all control characters at that time. There is currently a small bug, however. I have found a couple of strings that do not work, and I am not sure why. For example, the string: "1234567890123456789012345678901234567890123456789012345678901234567890123456789012" will not make it through the algorithm correctly, however if you add or remove a character to that string, it works fine. Also note that there are a few places in the code that could be refined or even removed. These arose during the transcription process from the java original code. DBPro does some things differently, and I decided to keep the code as close to the original as I could at this time.

DarkBASIC Professional Source Code

` This code was downloaded from The Game Creators

` It is reproduced here with full permission

` http://www.thegamecreators.com

function encrypt(plaintext as string, password as string)

if len(plaintext) = 0

exitfunction ""

endif

ciphertext as string

ciphertext = ""

n as dword

z as dword

y as dword

delta as dword

mx as dword

e as dword

q as dword

sum as dword

if ceil(len(plaintext)/4.0) < 2

dim v(1) as dword

else

dim v(ceil(len(plaintext)/4.0) - 1) as dword

endif

dim k(ceil(16.0/4.0) - 1) as dword

for i = 0 to array count(v())

v(i) = asc(mid$(plaintext, i*4+1)) + (asc(mid$(plaintext, i*4+2))<<8) + (asc(mid$(plaintext, i*4+3))<<16) + (asc(mid$(plaintext, i*4+4))<<24)

next i

for i = 0 to array count(k())

k(i) = asc(mid$(password, i*4+1)) + (asc(mid$(password, i*4+2))<<8) + (asc(mid$(password, i*4+3))<<16) + (asc(mid$(password, i*4+4))<<24)

next i

n = array count(v()) + 1

z = v(n-1)

y = v(0)

delta = 0x9E3779B9

q = floor(6.0 + 52.0/n)

sum = 0

while q > 0

inc sum, delta

e = sum>>2 && 3

for p = 0 to n-1

y = v((p+1) mod n)

mx = (z>>5 ~~ y<<2) + (y>>3 ~~ z<<4) ~~ (sum~~y) + (k(p&&3 ~~ e) ~~ z)

z = v(p) + mx

v(p) = v(p) + mx

next p

dec q

endwhile

for i = 0 to array count(v())

ciphertext = ciphertext + chr$(v(i) && 0xFF) + chr$(v(i)>>8 && 0xFF) + chr$(v(i)>>16 && 0xFF) + chr$(v(i)>>24 && 0xFF)

next i

result$ = base64encode(ciphertext)

undim v()

undim k()

endfunction result$

function decrypt(ciphertext as string, password as string)

plaintext as string

plaintext = ""

n as dword

z as dword

y as dword

delta as dword

mx as dword

e as dword

q as dword

sum as dword

cipher as string

cipher = base64decode(ciphertext)

dim v(ceil(len(cipher)/4.0) - 1) as dword

dim k(ceil(16/4.0) - 1) as dword

for i = 0 to array count(v())

v(i) = asc(mid$(cipher, i*4+1)) + (asc(mid$(cipher, i*4+2))<<8) + (asc(mid$(cipher, i*4+3))<<16) + (asc(mid$(cipher, i*4+4))<<24)

next i

for i = 0 to array count(k())

k(i) = asc(mid$(password, i*4+1)) + (asc(mid$(password, i*4+2))<<8) + (asc(mid$(password, i*4+3))<<16) + (asc(mid$(password, i*4+4))<<24)

next i

n = array count(v()) + 1

z = v(n-1)

y = v(0)

delta = 0x9E3779B9

q = floor(6.0 + 52.0/n)

sum = q*delta

while sum <> 0

e = sum>>2 && 3

for p = n-1 to 0 step -1

if p > 0

z = v(p-1)

else

z = v(n-1)

endif

mx = (z>>5 ~~ y<<2) + (y>>3 ~~ z<<4) ~~ (sum~~y) + (k(p&&3 ~~ e) ~~ z)

y = v(p) - mx

v(p) = v(p) - mx

next p

dec sum, delta

endwhile

for i = 0 to array count(v())

plaintext = plaintext + chr$(v(i) && 0xFF) + chr$(v(i)>>8 && 0xFF) + chr$(v(i)>>16 && 0xFF) + chr$(v(i)>>24 && 0xFF)

next i

undim v()

undim k()

endfunction plaintext

function base64encode(s as string)

base64code$ = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="

pad as string

plain as string

coded as string

o1 as dword

o2 as dword

o3 as dword

bits as dword

h1 as dword

h2 as dword

h3 as dword

h4 as dword

plain = s

pad = ""

c = len(plain) mod 3

if c > 0

while c < 3

pad = pad + "="

plain = plain + ""

inc c

endwhile

endif

coded = ""

for c = 1 to len(plain) step 3

o1 = asc(mid$(plain, c))

o2 = asc(mid$(plain, c+1))

o3 = asc(mid$(plain, c+2))

bits = o1<<16 || o2<<8 || o3

h1 = bits>>18 && 0x3f

h2 = bits>>12 && 0x3f

h3 = bits>>6 && 0x3f

h4 = bits && 0x3f

coded = coded + mid$(base64code$, h1 + 1) + mid$(base64code$, h2 + 1) + mid$(base64code$, h3 + 1) + mid$(base64code$, h4 + 1)

next c

coded = left$(coded, len(coded)-len(pad)) + pad

endfunction coded

function base64decode(s as string)

base64code$ = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="

plain as string

coded as string

o1 as dword

o2 as dword

o3 as dword

bits as dword

h1 as dword

h2 as dword

h3 as dword

h4 as dword

coded = s

plain = ""

for c = 1 to len(coded) step 4

h1 = find sub string$(base64code$, mid$(coded, c)) - 1

h2 = find sub string$(base64code$, mid$(coded, c+1)) - 1

h3 = find sub string$(base64code$, mid$(coded, c+2)) - 1

h4 = find sub string$(base64code$, mid$(coded, c+3)) - 1

bits = h1<<18 || h2<<12 || h3<<6 || h4

o1 = bits>>16 && 0xff

o2 = bits>>8 && 0xff

o3 = bits && 0xff

temp$ = chr$(o1) + chr$(o2) + chr$(o3)

if (h4 = 0x40)

temp$ = chr$(o1) + chr$(o2)

endif

if (h3 = 0x40)

temp$ = chr$(o1)

endif

plain = plain + temp$

next c

endfunction plain

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Author Name:	The Sab
CodeBase Entries:	10

CodeBase - DBPro Implementation of XXTEA (Tiny Encryption Algorithm)

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