Friday | 9 January, 2009
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SSDs are hot, but not without security risks

Experts caution that SSDs aren't as secure as commonly thought.
Agam Shah (IDG News Service) 25 August, 2008 09:29:00

Encryption adds another barrier so that hackers have to bypass encryption layers, the controller and then reassemble raw data for a successful hack, said Sean Barry, senior data recovery engineer at Kroll Ontrack. This takes time, during which data may become invalid or useless.

Encryption also makes files on SSDs a lot easier to erase. Like hard drives, SSDs create multiple file copies, but encryption software can help erase secured files, said Kyle Wiens, CEO of iFixIt.

"Every time you write data it might write ... to a different part of the disk and then change the directory table around. So it forgets where the data was written before," Wiens said. Users may delete one file, but a replica could remain untouched in another sector.

The wear-levelling feature of SSDs -- based on an algorithm that erases and writes data evenly across all the cells on a memory chip to prevent some from wearing out faster than others -- makes files harder to completely erase, Wiens said.

Some encryption software monitors the wear-levelling process to track file remnants, which can then be deleted using the secure erase command, said Knut Grimsrud, an Intel Fellow. Secure erase is a command for secure file deletion that needs to be supported by the encryption software.

"If all the software does is write over the top of the LBAs, I don't think it'll be as [effective] on an SSD as it may have missed remnants from the previous wear-levelling or something like that because the software doesn't know about that," Grimsrud said. LBA (logical block addressing) specifies the location of data blocks on storage devices.

Overall, it's easier to delete data from SSDs than from hard drives, which can be a good or bad. Data is stored on electrons in SSDs, and getting rid of electrons flushes out the data, Kroll Ontrack's Barry said. In hard drives, the data has to be overwritten or physically damaged to prevent it from being read.

The data flush could have its own advantage in terms of quickness, but in the wrong hands data on SSDs could be carelessly and easily lost, Barry said.

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