encode/decode question

[Rich Duzenbury]

Hi,

One of our previous developers decided to obfuscate some columns via the mysql encode and
decode functions.  This was done on a 4.x server.  Recently, we converted to a 5.x server,
and some of the fields in the rows will not decode correctly, and I cannot figure out why.

My first thought was that perhaps the implementation of encode/decode changed, but
googling so far has been to no avail.

My second thought was that perhaps there was a problem when we dumped the data from the
4.x server and imported it to the 5.x server.  The old 4.x server is gone, so I cannot
verify whether that is the case.  I did dump/restore the data in question from the 5.x
back to a 4.x server, but it decodes in error as well.

This obfuscation was a retrofit to an existing table, mostly of varchar fields.  Another
thought I had was that perhaps it's not a good idea to store binary data in a varchar
field.

So, a few questions:

Anyone know if the implementation of endcode/decode changed along the line from v4 to v5? 
What algorithm is used for encode/decode?

Are there limits on what can be stored in a varchar field?  Is it ok to store the results
of encode/decode in a varchar?

We don't need to encrypt the data, simply obfuscate it to prevent accidental,
unintentional use.  Any ideas appreciated.

Thank you.

Regards,
Rich