Tuesday, August 19, 2014

Encrypted DMG images standard vrs sparse

Apple MACOSX has the means for generating a encrypted  DMG images.  But did you know you have 2 types? Yes the dmg image has the standard and sparse modes.

The difference between the two;  " sparse mode does not pre-built or consume disk space" . As it's used , the disk file space would be consumed.

1st let's used the apple disk-utility to build these to images types for comparison.

( building a std dmg image w/AES128 )

( building a sparse dmg image w/AES128 )

Okay now let's compare the  diskimage final sizes for the regular and sparse 100MB.


So the advantages with sparse, we still have an encrypted volume but the size is not pre-allocated. Great if you need to encrypted data and then send it to another user.

Opt out of saving the passphrases to your key-chain. If anybody compromised your machine, than will be able to automatically  mount your encrypted volume if the pass phrase is attached to your key-chain.  Password management is great and convenient but weakens security imho.

 As the diskimage is used ( dmg sparse image ) the diskspace will be consumed. Disk space will continuous be consumes as you fill  the volume out & up to the defined sizes that you set during the disk-utility operations.

Ken Felix
NSE ( network security expert) and Route/Switching Engineer
kfelix  -----a----t---- socpuppets ---dot---com
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