Over the week­end I made a tweet that sev­eral peo­ple asked about:

Basi­cally, they wanted to know how to con­vert DRM pro­tected Kin­dle books over to ePub books that will work on the iPad. 

I love the fact that Ama­zon was able to release a Kin­dle app for the iPad on the very first day, but in a side-by-side com­par­i­son, I found Apple’s iBooks to be a lit­tle more use­ful to me.  It’s a seri­ous set of trade-offs.  On the one hand, the Kin­dle app syn­chro­nizes with the cloud and remem­bers what page I last viewed.  If I pick up my actual Kin­dle or use the Kin­dle app on the iPhone, then I can resume exactly where I was.  There is no equiv­a­lent in iBooks.  On the other hand, the Kin­dle app has no dic­tio­nary, whereas the iBooks dic­tio­nary is stream­lined and non-obtrusive.  Weigh­ing the two fea­tures, the dic­tio­nary is more impor­tant to me.  I can man­u­ally fig­ure out where I am in a book if I switch devices, but I often run into words I do not know — for instance “blue­stock­ing” (a deroga­tory term to describe an intel­li­gent or lit­er­ary woman) — mean­ing I have to jump out of the Kin­dle app, load up a dic­tio­nary app, wait for it to fin­ish load­ing, type in the word, then switch back to the Kin­dle app.  It is just so much eas­ier to tap the word and get a def­i­n­i­tion in a pop-up bubble.

Given this, I started con­vert­ing my Kin­dle books to ePub for­mat.  This is a two step process.  For the folks that just want to do it and fig­ure out the details on their own, those steps are:

• Use the “dedrm” Python script to strip the DRM from the Kin­dle *.azw file
• Use Cal­i­bre to con­vert from azw (it’s really MOBI) to ePub

Strip the DRM from the Kin­dle file

This step is the most dif­fi­cult and takes a lit­tle Ter­mi­nal mojo.  The fol­low­ing direc­tions assume you are run­ning on a Mac (I am sure Python exists for Win­dows, but you’re on your own if you have a Microsoft box) and that you can do some basic nav­i­ga­tion around the Ter­mi­nal com­mand prompt.

The Kin­dle AZW files are really just MOBI (a stan­dard eBook for­mat) with some spe­cial DRM applied.  The DRM is a sym­met­ric cipher, mean­ing it needs a key­word to encrypt and the same key­word to decrypt.  That key­word is just a reshuf­fling of your Kindle’s ser­ial number.

First, you will need your Kin­dle, with the pur­chased book down­loaded onto it.  Next, you will need a set of Python scripts that go by the name dedrm (includ­ing kindlepid.py, mobidedrm.py, and monidedrm2.py).  I am not a lawyer, so I do not know if I can pro­vide a direct down­load link here.  I assume this stuff is cov­ered under Fair Use, but I am going to go the con­ser­v­a­tive route and just tell you to do a Google search.

Plug in your Kin­dle, and copy the AZW file out of its /Documents folder and into the same folder as your Python scripts.  To get the encryp­tion key that Ama­zon uses to encrypt your eBooks, cd to the direc­tory con­tain­ing the Python scripts and use this com­mand, sub­sti­tut­ing the B12345678 with your actual Kin­dle ser­ial number:

python ./kindlepid.py B12345678

This should come back with a result along the lines of:

Mobipocked PID for Kindle serial# B12345678 is 1Q4Y2VZ*RE

Save that mix of num­bers, let­ters, and aster­isk.  That’s the key that Ama­zon uses to encrypt all eBooks for your spe­cific Kindle.

Next, use that key to decrypt the book.  You’re actu­ally going to have to do this twice.  One will work and one will not (and it will be dif­fi­cult to know which one worked until you load it in a viewer in the next step).  You will need to run the dedrm v0.01 and dedrm 0.02 com­mands.  They dif­fer slightly in the com­pres­sion method used, but the wrong com­pres­sion adds some garbage and bad meta­data to your book.  Be sure to replace the 1Q4Y2VZ*RE with your key derived from the above com­mand.  Also, leave those single-quotes in there.

python ./mobidedrm.py mybook.azw mybook1.mobi '1Q4Y2VZ*RE'

python ./mobidedrm2.py mybook.azw mybook2.mobi '1Q4Y2VZ*RE'

Either mybook1.mobi or mybook2.mobi should be the cor­rect decrypted ver­sion of your eBook.  The next step is to fig­ure out which one is the good one and to con­vert it to ePub.

Con­vert AZW/MOBI to ePub

Import the first MOBI file into Cal­i­bre and use the “View” icon in the tool­bar to see it in the viewer.  Ver­ify that this is a non-broken document.

You first want to bring up the table of con­tents by using the icon in the tool­bar on the left.  Click around in the table of con­tents to ver­ify that chap­ter mark­ers really do line up with the chap­ter text.  Skim through a few dozen pages look­ing for weird HTML or XML frag­ments (angle brack­ets and equal signs that look out of place). 

If every­thing looks good, you imported the good doc­u­ment.  If things look funky, close the viewer, delete the doc­u­ment from Cal­i­bre, then import the other one.

Once you have the good doc­u­ment imported, select it and click on the “Con­vert E-Books” icon in the tool­bar.  Be sure to change the out­put for­mat to EPUB.  You can cus­tomize other options as you see fit.  Click “OK” to convert.

Once con­verted, you can find the file in your Cal­i­bre folder or you can use the export func­tion­al­ity to save it to disk.

Drag the result­ing *.epub file into the Books sec­tion of iTunes and you’re set.  The book you pur­chased on Ama­zon can now be read in Apple’s iBooks application.

If you liked this post, you may also enjoy:

1. 1984 goes down the Mem­ory Hole
2. One week with the iPad
3. Why I prob­a­bly won’t be get­ting a Kin­dle 2
4. Com­ments from all over (Vir­tual Kin­dle Style)
5. The lit­tle details, like hyphens and em-dashes

Tagged as: azw, convert, dedrm, drm, epub, howto, ibooks, iPad, kindle, mobi