Calculating hash during imaging

Atola Insight Forensic supports hash calculation of both source and target devices in conjunction with imaging. We have developed highly flexible functionality to help optimize evidence acquisition process to fit one’s internal procedures as well as avoid causing further damage to fragile media.

To view the hashing options:

In the sidebar, click Imaging.
Click Create New Session.
Select the target device or file.
In Preset line, click the Show settings link.
In the upper part of the Passes and Hash tab there are three checkboxes:

Pre-hash source device.
Hash source during imaging.
Post-hash target device(s).

Imaging results with segmented hashes

Multiselect is available, which allows an operator to use all three of these options.

However, Pre-hash source drive option must be used with caution: although pre-hashing can be required by an investigator’s internal procedures, when dealing with drives that have been diagnosed with hardware failure, this operation may cause further damage to the drive before essential data is imaged.

On the contrary, Hash source during imaging is the most appropriate way to calculate the hash of a fragile source evidence drive. In this case, Insight only needs to read the data on the drive once to both image and calculate the hash, thus minimally using the drive’s hardware.

Linear hash can only be calculated by reading data in sectors consecutively in one pass. Therefore ticking Hash source during imaging checkbox and selecting Linear or combined Linear and Segmented option in the Hashing method list leads the number of passes to be limited to one. When dealing with a damaged drive, we strongly recommend using Segmented hashing, as this method supports multipass imaging and handling of bad sectors and provides better resiliency against data corruption. For more details, see Segmented hashing.

Post-hash target device(s) option allows to properly record the calculated hash in the case. Since this operation does not require reading the source drive, it is safe to use this option while imaging either good or damaged drives.

Imaging results with segmented hashes