For those of you not familiar with XOR in Visual Basic 6, I'll give you a little lesson. XOR is supposed to mean "exclusive OR". It is so called because it only returns True if one and only one of the expressions it is passed is True. Wait, that sounds confusing An illustration is in order! True Xor True = False True Xor False = True False Xor True = True False Xor False = False See? Now, the logical operations of XOR (above) are less useful to us than the bitwise operations. Observe: 1 Xor 1 = 0 1 Xor 0 = 1 0 Xor 1 = 1 0 Xor 0 = 0 This is pretty much the same as the logical operation, but watch, in VB6 we can perform it on a whole bunch of bits (say... a BYTE!) at a time: 11111111 XOR 01010101 (Key) Result: 10101010 Here comes the magic.. if we XOR again, using the value I've marked Key and the result, we obtain the original! 10101010 (Old Result) XOR 01010101 (Key) Result: 11111111 (!!!) This works in all situations when the key is held constant: XOR once, you have an encrypted result. XOR again with the same key, and you get the original value. Sounds cool, but how can we apply it practically? When storing data in a binary file, it is a simple matter to XOR each byte that is read or written in order to encrypt/decrypt it. To encrypt data under other circumstances can be a little trickier. You need to coerce that data into byte form, and then back again. We'll do it with strings here: Dim strResult As String Dim strChar1 As String * 1 Dim strChar2 As String * 1 strChar1 = "E" strChar2 = "z" strResult = Chr(Asc(strChar1) Xor Asc(strChar2)) This code will XOR "E" with "z" by converting them to their ASCII values! Once converted to ASCII, they can be treated like bytes and XOR'ed. We can then convert back to string format using the Chr function. This method can be adapted using a For loop to encrypt complex strings using equally complex key values. I hope this visual basic tutorial was helpfull to you. thanks Xor is hard to explain,but you did it well Thanks people Im doing VB6 since some weeks and i thinking about to make more Tutorials
