VBA implementation of the IDEA algorithm
This is an implementation of the IDEA symmetric cipher (International Data Encryption Algorithm) written in Visual Basic for Applications for usage within applications of the Microsoft Office package.
1 IDEA round:
Performance wise, this pure VBA implementation is suitable for strings and small files.
Everything related to big files should be done by writing a wrapper for the obsolete Windows Crypto API inside the VBA code. But given that, you are limited to RC2/DES/3DES/3DES112 and MD5/SHA (for hashes).