"invalid PID checksum" when using mobidedrm, even though it IS valid.

[pdurrant]

Originally Posted by Dowland

Problem. The issue, at least in mobiledrm005.py, is that it accidentally repeats this operation twice (probably whoever wrote this did an unwitting double copy-paste).

This is a copying error somewhere along the way to you. The original 0.05 certainly didn't have this duplicate code.

[Robotech_Master]

I'm trying to extract a couple of the free Kindle books I downloaded to my iPod, just to see if I can. I jailbroke and copied them over, and tried to run mobiddrm using the key I generated from my UDID and got the following:

python2.5 mobiddrm01.py B000FCK3C8_EBOK.prc maxride.prc "KT18ZMY*6X"
MobiDeDrm v0.01. Copyright (c) 2008 The Dark Reverser
Error: no key found. maybe the PID is incorrect

I did the checksum thing and it said the key was correct. As far as I can tell, it is encrypted (at least, when I open it with FBReader, I get gibberish).

Any suggestions? Did I perhaps generate the key from the UDID wrong?

[pilotbob]

Originally Posted by Robotech_Master

I did the checksum thing and it said the key was correct. As far as I can tell, it is encrypted (at least, when I open it with FBReader, I get gibberish).

Any suggestions? Did I perhaps generate the key from the UDID wrong?

It's probably content encrypted. There is a script to remove that to... somewhere. Search around.

BOb

[wallcraft]

Originally Posted by Robotech_Master

MobiDeDrm v0.01. Copyright (c) 2008 The Dark Reverser

This is a very old version, the latest is v0.05. One place to look for information about these scripts is in the comments to the Darkreverser's Weblog.

[Robotech_Master]

Still does the same thing with 0.05.

[mrgiedrnkr]

I did an iphone/kindle extract today and I had to put single quotes around my python generated PID. I tried no quotes, double quotes and single quotes until I got one to work.
Stacy

[Robotech_Master]

I tried single quotes, still got the same result.

[gatorfan]

Originally Posted by Dowland

Here comes a lengthy post to summarize the problem and give an actual solution. Please don't hesitate to reproduce this elsewhere. And also, please don't bury this post in the thread, because then nobody will ever find it ... :-)

*

Background info. A MobiPocket PID is 10 characters: 8 characters are the actual key, and 2 characters are the checksum.

Now, before doing its deed, MobileDRM looks at the PID you gave: it controls whether the checksum and the key actually correspond. If they dont, then it gives the error message we all know ("Error: invalid PID checksum"). If they do, then it cuts away the last 2 characters of the PID, and keeps only the key for the remainder of its operation.

Problem. The issue, at least in mobiledrm005.py, is that it accidentally repeats this operation twice (probably whoever wrote this did an unwitting double copy-paste). So scenario 1: your PID is incorrect, and it gets rejected on the first check. And scenario 2: your PID is correct, it passes the first check, gets shortened to its key component, and then flunks the second check.

Solution. Remove the first block from the initialization the code (as this is Python code, you have to be very careful with the indentation), i.e. change:

	def __init__(self, data_file, pid):

		if checksumPid(pid[0:-2]) != pid:
			raise DrmException("invalid PID checksum")
		pid = pid[0:-2]

		if checksumPid(pid[0:-2]) != pid:
			raise DrmException("invalid PID checksum")
		pid = pid[0:-2]

to:

	def __init__(self, data_file, pid):

		if checksumPid(pid[0:-2]) != pid:
			raise DrmException("invalid PID checksum")
		pid = pid[0:-2]

That line that appears twice "pid = pid[0:-2]", is what shortens the PID (it means "take all but the last two characters of this string and replace the original").

Outro. It may very well be that your PID is actually incorrect, and you should browse this thread for ways to find out.

Also: opening the book after buying it unnecessary (except if your vendor does some non-standard thing I've never heard about). If this seems like it works, than a possible explanation is that opening the book actually removes the DRM (and then running MobileDRM on it gives the appearance that it actually worked ...).

Finally: no, I've never seen (valid) MobiPocket PIDs with anything but uppercase alphanumerical characters...

After a week of trying to figure out exactly what I was doing wrong, including searching different internet sites, the above post solved my problem.

I thank you and my blood pressure thanks you!

[Dan de V]

Dowland,
Thank you very much for summarizing the issue so well. I have read through pages and pages of posts to try and fix my "invalid PID checksum" problem with my copy of mobidedrm005. Even the 1st 6 pages of this thread....shows I should read backwards on threads here )

Being of suspicious mind I now wonder if the repeat code has been deliberately added to discourage people from trying to strip the DRM off mobi files.......I might hurriedly add that I actually got the faulty mobidedrm005 script from another site!

[Sydney's Mom]

Ooh, and I thought I was paranoid!

[sahmad88]

Originally Posted by Robotech_Master

I tried single quotes, still got the same result.

I have this exact same problem. Here is a bit of background. I had a MacBook Pro with Leopard on it. And I had an iPhone. Everything worked fine at this point. Then my iPhone had a display problem and they replaced it. Then my MacBook had some hardware failure in the first 30 days, and they replaced that. I now have Snow Leopard on my mac.

I generated a new PID from my new iPhone. Now I can't get it to work at all, and I get the exact same error that Robotech Master gets: Error: no key found. maybe the PID is incorrect

I have tried this on a book that worked before. The only problem is, I don't have the original file. When my mac failed, at that point I didn't have a backup. So I am not sure if there is something new that is being done on Kindle books to try to defeat this.

Thank you all for your help.

[Juliette]

Originally Posted by pdurrant

Some PanMcMillan ebooks are DRM free. Check to see if it really does have DRM first?

Saved my life (and my sanity). Thanks!

[kevindorsey]

Originally Posted by Juliette

Saved my life (and my sanity). Thanks!

LOL. We need our sanity.

[Riptide]

Unfortunately, this hasn't corrected my issue...

Running the checksum script (pg 5), it tells me my Mobipocket PID ABCDEFG*HI is correct.

Yet trying to enter the script with single quotes, double quotes, no quotes, dropping the last two digits (and again trying with the different quotes), has all produced the same result.

I know this is a DRM protected ebook (caliber said so)...

Windows Vista
Python 2.6.3

Idea's?

[pdurrant]

It might be a content protected, but not PID protected eBook. There's a thread here somewhere detailing the changes needed to decode this kind of content. Unlikely if it's one you bought though - it's usually only applied (no idea why) to free ebooks.

Originally Posted by Riptide

Unfortunately, this hasn't corrected my issue...

Running the checksum script (pg 5), it tells me my Mobipocket PID ABCDEFG*HI is correct.

Yet trying to enter the script with single quotes, double quotes, no quotes, dropping the last two digits (and again trying with the different quotes), has all produced the same result.

I know this is a DRM protected ebook (caliber said so)...

Windows Vista
Python 2.6.3

Idea's?