Ah yes, that. I was hoping you had something a little harder to offer, which I had missed. 
Problem is that this is just a form of security through obscurity, which is much less safe than is generally believed.
In Legends og Hermes, we even have Fortunata, who specialised in opeing such secrets and re-using the initiation scripts of old cults.
Essentially, it takes a bit of work to break the code, but not a lot. If you can get the script, I've seen it done in 2 seasons (or possibly just one, I forget). Rules are on LoH, p. 49.
Either way, not enough to satisfy my paranoia, nor that of any in my troupe.
As an IT technician, I know for a fact that you can REALLY render someone unable to decipher things written in plain language using alternative meanings of words WHEN THEY HAVE ACCESS TO REFERENCE MATERIAL EXPLAINING THOSE MEANINGS.
It is therefore not hard for me to believe that very few people will be able to do so when the only meanings available require you to have been taught the basics by someone already in the know.
It's simple enough to assume that all texts on how to improve your parma are written with the assumption you already know how to cast it.
"And, while raising your parma, focus your mind and extend the third fold to cover the 9th layer, rather than limiting it to the 7th as normal. Once this is done, channel your gift through the mental lens you have created to complete the change to your parma."
"To reset the router, first, open up the default gateway IP address, then enter your ISPs provided administrator username and password. Once this is completed, locate the reset router link, usually kept under the maintenance tab, and select it. Then wait for the router to reset, and perform a connection test by pinging a known webserver from the command prompt."
The first is a theoretical text on parma. The 2nd is a quote from a textbook for people trying to get an MTA qualification.
I hear you on that one.
But we're not paranoid about people casually overhearing things, are we now?
We want to keep the Parma Magica a secret, even from intelligent, dedicated researchers, ie. the Learned Magicians or the Augustinian Order.
...and while I loved your examples, that's pretty much what I'd guess at having to do, to reset my router 
If you make Parma require initiation, you get a quite foul-proof thing. Unless you have undergone initiation you have no idea on how Parma is cast. Even if you perform all the movements from a perfect image you will get no results. You need to perform the initiation. It also makes the swearing of the Code of Hermes something much more important than what is now. it might be that if you break it willingly in one of the core assumptions, your parma just fails. Forever (until you undergo initiation again). A renounced magus would have no Parma in this case. I find that quite cool, actually.
Now, we can easily have the Order of Hermes NOT have ANY initiation scripts for parma ANYWHERE, not even Durenmar*. That would require something more than plain deciphering of Parma books to crack it. obviously we can have Parma initiation scripts here and there as story seeds, but then they will be exactly that, story seeds 
The original research notes by Bonnie can also play a similar story seed role.
Not really, see above.
Now there's something!
But that's a very different thing. A Restriction major flaw perhaps?
How would
be any different from
Yes, this model allows the existance of Summae and Tractatus providing XPs for Parma, but it would still be a security problem as Supernatural Abilities can be learned without having the relevant virtue - again, see HoH: MC for the loss of the Verditius Major Virtue of Automata.
I like the idea, but it is a fairly major change of the setting, whereas having secrecy surrounding the existence of books on Parma Magica is already present. I think HoH: TL even has a plot hook about Parma books, but I can't be bothered to check at the moment.
Yes...and no. While it would make sense, from a security point of view - it is bad for stories IMHO. The idea that the secrets can be lost, and that renounced magi are a threat and a danger is awsome for story potential. Skilled magi who are Marched are notoriously hard to find and kill off, and need the very best sent off to do it. Or alternatively offer a huge challenge for less efficient and specialized magi. Rather than sending just about anyone half-skilled to off the big baddie because penetration is not an issue anymore.
Now, if we are talking about having swearing the code and learning the final secrets of Parma Magica result in some AC, held by the Parens - then the provisions in the Code about being the first to strike down should your own Hermetic kin be Marched mean a lot more. So certain people have - or can get - a Penetration bonus, but the renegade is not without defences. Aaaand the renegade could try to get ahold of thet AC to prevent the Order having an easy time killing him off.
+1
It also makes sense to grant a sympathetic connection bonus to BOTH parens AND apprentice because they are exactly that (parens & apprentice) and this creates a mystical connection between them.
I can see non-Code initiations exist as well. The first Parmas were granted without a CoH-vow, after all, since they predate the Order. These scripts could easily exist, and it also means that parma can be retro-engineered if you already know about it to be granted without the Code problem. So, they march you and you lose your parma, but you can initiate yourself again and recover it at full strength.Or maybe you have already done so before committing your felonious act. So you can still have these stories if you want them I am sure all tytalus would have done that already just to test the limits of established norm and not be chaffed by arbitrary conventions.
In any case I still think that making Hermetic vows REALLY matter to be important, and it adds a mystical significance to the Order that I like.
Xavi
Good points really.
Adds some nice story potential for this solution as well.
IIRC, there's such a hook in the Amazon chapter of Rival Magic: The amazons get hold of a Parma book and learn it 
Yes. This virtue shouldn't have been integrated so much...