CAST-128 is a cryptography algorithm based on a symmetric key cipher, used in GPG. AS-QuadCAST is an implementation of this algorithm with a twist, allowing the quick encryption and decryption of files on a computer.

Although easy to use, AS-QuadCAST does not feature a regular interface, which might be a bit of a turndown for some. Nevertheless, those who dare to take it for a spin will discover that the options are simple and intuitive. Running the AS-QuadCAST with no parameter displays a short explanation for each of the available parameters.

Users can encrypt or decrypt files with AS-QuadCAST. Evidently, it's only possible to decrypt files that have previously been encrypted with AS-QuadCAST. Please keep in mind that the compatibility between different versions of the application is not guaranteed, so it's advisable to keep a copy of the current version of the application locally.

The other parameters point to the input file and the output file ("IF" and "OF", respectively), and enable users to enter the custom password and their so-called "nonce" value. This latter string is used as a method to strengthen the generated encryption key. All the parameters are mandatory.

What AS-QuadCAST does is take the user-defined password to generate an encrypted checksum using the CAST-128 algorithm, a code which is verified when the file is decrypted.

Although AS-QuadCAST was designed from the start as a CAST-128 implementation, from a functional point of view, having an encryption tool that only uses a single encryption method is not practical. Thus, this application is not the most impressive encryption tool out there, but it does its job as promised, applying the CAST-128 algorithm to encode the data in the source file. Going back to the list of minuses, it does not feature a user-friendly interface and does not allow the users to skip parameters, which is a bit annoying.