XPKeygen

A Windows XP / Windows Server 2003 VLK key generator. This tool allows you to generate valid Windows XP keys based on the Raw Product Key, which can be random. The Raw Product Key (RPK) is supplied in form of 9 digits XXX-YYYYYY and is only necessary to generate a Windows XP Key.

Download

Head over to the Releases tab and download the latest version from there.

The problem

In general, the only thing that separates us from generating valid Windows XP keys for EVERY EDITION and EVERY BUILD is the lack of respective private keys generated from their public counterparts inside pidgen.dll. There's no code for the elliptic curve discrete logarithm function widely available online, there's only vague information on how to do it.

In the ideal scenario, the keygen would ask you for a BINK-resource extracted from pidgen.dll, which it would then unpack into the following segments:

Public key (pubX; pubY)
Generator (genX; genY)
Base point (a; b)
Point count p

Knowing these segments, the keygen would bruteforce the geneator order genOrder using Schoof's algorithm followed by the private key privateKey, leveraging the calculated genOrder to use the most optimal Pollard's Rho algorithm. There's no doubt we can crack any private key in a matter of 20 minutes using modern computational power, provided we have the working algorithm.

Once the keygen finishes bruteforcing the correct private key, the task boils down to actually generating a key, which this keygen does. To give you a better perspective, I can provide you with the flow of the ideal keygen. Crossed out is what my keygen implements:

BINK resource extraction
Bruteforce Elliptic Curve discrete logarithm solution (genOrder, privateKey)
~~Product Key processing mechanism~~
~~Windows XP key generation~~
~~Windows XP key validation~~
~~Windows Server 2003 key generation~~
~~Windows Server 2003 key validation~~

Principle of operation

We need to use a random Raw Product Key as a base to generate a Product ID in a form of AAAAA-BBB-CCCCCCS-DDEEE.

Product ID

Digits	Meaning
AAAAA	OS Family constant
BBB	Channel ID
CCCCCC	Sequence Number
S	Check digit
DD	Public key index
EEE	Random 3-digit number

The OS Family constant AAAAA is different for each series of Windows XP. For example, it is 76487 for SP3.

The BBB and CCCCCC sections essentially encode the Raw Product Key. For example, if the first section is equal to XXX and the second section is equal to YYYYYY, the Raw Product Key will be encoded as XXX-YYYYYY.

The check digit S is picked so that the sum of all C digits with it added makes a number divisible by 7.

The public key index DD lets us know which public key was used to successfully verify the authenticity of our Product Key. For example, it's 22 for Professional keys and 23 for VLK keys.

A random number EEE is used to generate a different Installation ID each time.

Product Key

The Product Key itself (not to confuse with the RPK) is of form FFFFF-GGGGG-HHHHH-JJJJJ-KKKKK, encoded in Base-24 with the alphabet BCDFGHJKMPQRTVWXY2346789 to exclude any characters that can be easily confused, like I and 1 or O and 0.

As per the alphabet capacity formula, the key can at most contain 114 bits of information. $$N = \log_2(24^{25}) \approx 114$$

Based on that calculation, we unpack the 114-bit Product Key into 4 ordered segments:

Segment	Capacity	Data
Upgrade	1 bit	Upgrade version flag
Serial	30 bits	Raw Product Key (RPK)
Hash	28 bits	RPK hash
Signature	55 bits	Elliptic Curve signature for the RPK hash

For simplicity' sake, we'll combine Upgrade and Serial segments into a single segment called Data. By that logic we'll be able to extract the RPK by shifting Data right and pack it back by shifting bits left, because most a priori valid product keys I've checked had the Upgrade bit set to 1.

Elliptic Curves

Elliptic Curve Cryptography (ECC) is a type of public-key cryptographic system. This class of systems relies on challenging "one-way" math problems - easy to compute one way and intractable to solve the "other" way. Sometimes these are called "trapdoor" functions - easy to fall into, complicated to escape.^[5]

ECC relies on solving equations of the form $$y^2 = x^3 + ax + b$$

In general, there are 2 special cases for the Elliptic Curve leveraged in cryptography - F_2m and F_p. They differ only slightly. Both curves are defined over the finite field, F_p uses a prime parameter that's larger than 3, F_2m assumes $p = 2m$. Microsoft used the latter in their algorithm.

An elliptic curve over the finite field F_p consists of:

a set of integer coordinates ${x, y}$, such that $0 \le x, y < p$;
a set of points $y^2 = x^3 + ax + b \mod p$.

An elliptic curve over F₁₇ would look like this:

The curve consists of the blue points in above image. In practice the "elliptic curves" used in cryptography are "sets of points in square matrix".

The above curve is "educational". It provides very small key length (4-5 bits). In real world situations developers typically use curves of 256-bits or more.

Since it is a public-key cryptographic system, Microsoft had to share the public key with their Windows XP release to check entered product keys against. It is stored within pidgen.dll in a form of a BINK resource. The first set of BINK data is there to validate retail keys, the second is for the OEM keys respectively.

In case you want to explore further, the source code of pidgen.dll and all its functions is available within this repository, in the "pidgen" folder.

Generating valid keys

To create the CD-key generation algorithm we must compute the corresponding private key using the public key supplied with pidgen.dll, which means we have to reverse-solve the one-way ECC task.

Judging by the key exposed in BINK, p is a prime number with a length of 384 bits. The computation difficulty using the most efficient Pollard's Rho algorithm with asymptotic complexity $O(\sqrt{n})$ would be at least $O(2^{168})$, but lucky for us, Microsoft limited the value of the signature to 55 bits in order to reduce the amount of matching product keys, reducing the difficulty to a far more manageable $O(2^{28})$.

The private key was, of course, conveniently computed before us in just 6 hours on a Celeron 800 machine.

The rest of the job is done within the code of this keygen.

Known issues

~~Some keys aren't valid, but it's generally a less common occurrence. About 2 in 3 of the keys should work.~~
Fixed in v1.2. Prior versions generated a valid key with an exact chance of 0x40000/0x62A32, which resulted in exactly 0.64884, or about 65%. My "2 in 3" estimate was inconceivably accurate.
Tested on multiple Windows XP setups. Works on Professional x86, all service packs. Other Windows editions may not work. x64 DOES NOT WORK.
~~Server 2003 key generation not included yet.~~
Fixed in v2.2.
Some Windows XP VLK keys tend to be "worse" than others. Some of them may trigger a broken WPA with an empty Installation ID after install. You have the best chances generating "better" keys with the BBB section set to 640 and the CCCCCC section not zero.
Windows Server 2003 key generation is broken. I'm not sure where to even start there. The keys don't appear to be valid anywhere, but the algorithm is well-documented. The implementation in my case generates about 1 in 3 "valid" keys.
Fixed in v2.3*.

Literature

I will add more decent reads into the bibliography in later releases.

Understanding basics of Windows XP Activation:

Understanding Elliptic Curve Cryptography:

Public discussions:

Contributing / Usage

If you're going to showcase or fork this software, please credit Endermanch, z22 and MSKey.
Feel free to modify it to your liking, as long as you keep it open-source. Licensed under GNU General Public License v3.0.

Any contributions or questions welcome.

girlmore / XPKeygen