How secure is this encryption exactly?

[zorke]

I made a program called "cryptex". Although it has several limitations and severe drawbacks -

I think that the security is quite strong

here's how it works :

The file to be encrypted must be below 0FFFFFh bytes - or 1mb.

A keyfile is generated exactly 1mb of size.

the keyfile contains FFFFF random bytes.

When encrypting - the program loads byte 1 of keyfile and byte 1 of target and it xors.

then it moves on to 2 and to 3 ... to the end of the file.

Each source byte is xored with a totally different byte from the keyfile.

So exactly how secure is this?

Thanks

note : an early version is included

cryptex.rar

[baguette]

http://en.wikipedia.org/wiki/One_time_pad

[quosego]

Somebody gets the license and its over. Other than that I agree with the above.

[mudlord]

Yah, its always the trusting endusers problem...

Zorke: Is this the same zorke from Pouet that did those ASM done cracktros?

[Departure]

I guess a spin off from that is a license for users machine by using something unique that is on there system to produce the array of byte for the key, this way the file will only decrypt on there licensed uses system...

[zorke]

@Mudlord : yes it's the same one

and this OTP stuff is interesting

[rendari]

It's fairly secure in a practical sense, but I wouldn't call it cryptographically secure. For it to be cryptographically secure, the random number generator you are using to generate the stream must also be secure. And designing a secure random number generator is hard, let alone implementing it.

[asser]

Thank you, very good program. propose to make optional output ready TinyEXE with the ability to enter a keyword.