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Product Keys Based on the Advanced Encryption Standard (AES)

Teddy Rogers

About This File

A popular method of product validation is using keys similar to VJJJBX-H2BBCC-68CF7F-2BXD4R-3XP7FB-JDVQBC. These compact keys can be derived using Symmetric Key Cryptosystems such as the Advanced Encryption Standard (AES).

Other Public Key Cryptosystems are available such as RSA. However, these systems generally produce larger keys (which the user will eventually have to enter into the program to unlock functionality). Smaller producing Cryptosystems exist, but it is the author's opinion that they are highly encumbered with patents. Quartz is one such example. It is a Public Key Encryption System that produces a smaller cipher text based on Hidden Field Equations (HFEs). The Quartz website is littered with phrases such as "must license" and "pay royalties".

The reader is also encouraged to investigate Signature Schemes (with Recovery) as an alternative method to producing Product Keys. An example is PSS-R, a Message Recovery Signature Scheme based on RSA. PSS-R is not suitable for product keys due to the size of the resulting key. However, cryptosystems such as a Weil Pairing system should be of interest. Once Weil Pairing is finalized in committee, it will be added to the Crypto++ library.

Finally, the reader should also visit Product Keys Based on Elliptic Curve Cryptography to familiarize themselves with basic concepts of Product Keys in the domain of Public Key Cryptography; and Product Activation Based on RSA Signatures.

This article will use AES (specified in FIPS 197) as the Cryptosystem, and Wei Dai's Crypto++ for AES operations. AES will produce compact keys with the additional benefit that the cryptosystem is not burdened with patent compliance. However, should a binary fall to Reverse Engineering, the key will become compromised (note that AES is a Symmetric Cipher - not an Asymmetric Cipher which has Public and Private keys).

This article will discuss the following topics:

Advanced Encryption Standard
Compiling and Integrating Crypto++ into the Visual C++ Environment
AES Implementation in Crypto++
Base Encoding a Cipher Text String in Crypto++
Bulk Product Key Generation
Product Key Validation
Securely Saving Key or Activation State to the Registry
This article is based on the Visual C++ 6.0 Environment in hopes that it reaches the largest audience.

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