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The password that I remember can't open the .DMG Encrypted Disk Image

M

mayankpin

macrumors newbie
Original poster
Feb 15, 2010
8
0
I made a new disk image with the following properties -
Volume Format - Mac OS Extended (Journaled), Encryption - 256 bit AES Encryption, Single Partition - Apple Partition Map, Image Format - read/write disk image.

I set the password as
F^@m1t10s^kh

Thereafter, I saved two important files in it. After which I deleted the files from the original source folders & emptied the trash. When I tried to open the .dmg image, I can't as the password does not match. Since this happened immediately I can be sure that the password that I remember is 95% correct. There could be a 5% error.

How do I crack the password ?
The convention used to create the password was - ^ instead of u, @ instead of a, 1 instead of i, & again ^ instead of u. I have a feeling that I might have made a similar replacement for the s, k, or h. I tried all permutations assuming the rest of the digits to be correct, but to no avail.

Please help.
 
Try the easy things. Upper/lowercase. Type the password in TextEdit and then paste it to the dialog (or have the dialog show it to you). On my keyboard, typing ^ and then a yields â, for example. That could be what you need for your password, or that could be what you don't want to have.

Otherwise, I'm with MacDawg - if you don't manage to remember it, your two important files will be lost. Or do you have a backup - external HD, TimeMachine - from before you moved them to the disc image?

Good luck!
 
pit29 said:
Try the easy things. Upper/lowercase. Type the password in TextEdit and then paste it to the dialog (or have the dialog show it to you). On my keyboard, typing ^ and then a yields â, for example. That could be what you need for your password, or that could be what you don't want to have.

Otherwise, I'm with MacDawg - if you don't manage to remember it, your two important files will be lost. Or do you have a backup - external HD, TimeMachine - from before you moved them to the disc image?

Good luck!
Click to expand...

I tried upper / lower case, with all alphabets. I have been using the "Show password" feature all through, while trying to get the right one. On my keyboard ^ & a does not convert to something else. So that could not be the problem. Also I copied these files from my office Windows network & pasted into Mac desktop, then copied into the Disk image. After that I deleted the files from the desktop & emptied the trash. Also I deleted the files from the office server with shift delete. I did try the undelete software in Windows which got a poor version of the file. Undelete from Mac is more cumbersome & still working on that.

Don't you think that I have a better chance with some brute force cracker as I have the password 95% correct. Some algorithm can manage the balance with some more permutations & combinations quickly.

Thanks in advance.
 
mayankpin said:
Don't you think that I have a better chance with some brute force cracker as I have the password 95% correct. Some algorithm can manage the balance with some more permutations & combinations quickly.
Click to expand...

Brute force with 256 bit AES? Not likely
And you say you have 95% correct, but you really can't even be sure what parts you have right

I don't know that much about brute force cracks available for the Mac, but I am not even sure you can input that 95%

You would probably have more success recovering the deleted file

Woof, Woof - Dawg
pawprint.gif
 
MacDawg said:
Brute force with 256 bit AES? Not likely
And you say you have 95% correct, but you really can't even be sure what parts you have right

I don't know that much about brute force cracks available for the Mac, but I am not even sure you can input that 95%

You would probably have more success recovering the deleted file

Woof, Woof - Dawg
pawprint.gif
Click to expand...

I am sure about the F^@m1t10 after that not sure what variant I used for 'sukh'.

I am using Data Rescue3 for the file recovery in the Macbook. The problem is I get thousands of reconstructed files. There is no way to search for the content of the files. It allows you to search within the reconstructed file names. But the names are not the name of the original file, as that is lost once deleted from trash. I have previewed all the reconstructed xls files, but these are not the files I am looking for. So that leaves from to try to crack this disk image.
 
emt1 said:
I think the program MacKrack can handle dmg files. Please let us know if anything works
Click to expand...

I downloaded MacKrack, & tried to work on it. But I guess I would need help on that, with my kind of situation.

What do I select in dictionary, password file, keyspace, Codes, Files, & Passwd. There is no help in the accompanying Read Me.
 
emt1 said:
Encryption scheme doesn't matter when you brute force
Click to expand...

link

Breaking a symmetric 256-bit key by brute force requires 2 to the 128th power times more computational power than a 128-bit key. A device that could check a billion billion (10 to the 18th power) AES keys per second would require about 3×10 to the 51st power years to exhaust the 256-bit key space.
Click to expand...

Woof, Woof - Dawg
pawprint.gif
 
MacDawg said:
link

Breaking a symmetric 256-bit key by brute force requires 2 to the 128th power times more computational power than a 128-bit key. A device that could check a billion billion (10 to the 18th power) AES keys per second would require about 3×10 to the 51st power years to exhaust the 256-bit key space.

Woof, Woof - Dawg
pawprint.gif
Click to expand...

Does nearly knowing the password not help reducing the Estimated Time to within reasonability ?
 
mayankpin said:
Does nearly knowing the password not help reducing the Estimated Time to within reasonability ?
Click to expand...

In theory. The problem is being able to describe to a brute application this "nearly known" password in a way that it reduces the number of iterations to try out. I don't know of any app that will let you do this.
 
This entire thread is a textbook example of:
"Are you SURE that you want to encrypt that data?"

The moral of the story is:
DON'T use encryption on files that you absoultely, positively MUST "get back" someday.

If it's that's sensitive (illegal, pron, etc.) buy a SAFE and keep the drive in it.

Otherwise, see the thread above.
 
mayankpin said:
Does nearly knowing the password not help reducing the Estimated Time to within reasonability ?
Click to expand...

The thing you need to remember is that your password is used in concert with a hash to create the encryption key which will decrypt your data. So knowing 1/2 of the password does you little good when one character being off generates a completely different key.

Your only chance is guessing the password. You say you have part of the password for sure. Narrow down the list of all possible characters you could have used for those unknown entries (say 40 characters, a-z, 0-9, some punctuation). Then, your Sample size becomes 40^n where n is the number of characters missing. Let's be optimistic and say n is 3. Then you only have 64,000 possible entries. Tough? Yeah, but doable over the course of a couple of years. Generate a text file with all possible operations and copy/paste until you find one that works. Write a script to do it and it will happen a lot faster. If you do not know the n, things become much more difficult.

There is a reason encryption works...
 
angelwatt said:
In theory. The problem is being able to describe to a brute application this "nearly known" password in a way that it reduces the number of iterations to try out. I don't know of any app that will let you do this.
Click to expand...

What if I put this 'nearly known' part of the password in the dictionary file & it can do the 64000 or more iterations automatically. Then it should work with MacKrack. But like I said before I need some help with MacKrack.
 
mayankpin said:
What if I put this 'nearly known' part of the password in the dictionary file & it can do the 64000 or more iterations automatically. Then it should work with MacKrack. But like I said before I need some help with MacKrack.
Click to expand...

That simply won't work. It's not how MacKrack functions.
 
Just take a logical systematic approach.
Create a spreadsheet, enter the known password and what you think the latter portion should be.

Then enter every variation that you think you used, don't for get to maybe add a trailing space because you might have mistakenly hit the space key before hitting enter.

Perhaps I'm the only one, but I found your password to be ungainly long and easily forgettable. While everyone should employ strong password skills I think you went overboard and given the problems you're having That does seem the case. Why not make the password/passphrase something a little more meaningful. If you don't you'll end up writing it down somewhere and there goes your strong password.
 
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