OK, so I got carried away with the fun bit
. Version 1.1 posted above now does Base64 encoding/decoding, SHA1 and MD5 hashing together with DES, TripleDES, RC2, Rijndael and RSA encryption/decryption. Examples of all attached. Needs .NET 2.0 as the encryption facilities in .NET1.0/1.1 are primitive. Should work on the device as well as the desktop but I haven't fully checked that.
Base64, SHA1 and MD5 results conform to published examples in Wikipedia.
The encryptions all round trip successfully but no guarantees for compatibility interworking with third party data as I can't try that.
Still no help file - I need an enthusiasm transplant to get started on it.