TrueErase: Secure Deletion on Electronic Storage

1
TrueErase Secure Deletion on Electronic Storage

• Sarah Diesburg, Chris Meyers,
• An-I Andy Wang
• 10/11/2015

2
Introduction

• Many computer users believe that files have been
  completely erased when
• Files are no longer visible
• The trashcan is emptied
• The partition is formatted
• In reality, only icon to the file is deleted
• Actual data remains

3
The Problem

• Decommissioned storage devices leak sensitive
  information

4
What is Secure Deletion?

• Secure deletion means rendering files completely
  irrecoverable
• No forensic analysis should be able to recover
  data from media

5
Secure Deletion Complications

• Flash electronic storage can make it nearly
  impossible to erase files

6
Flash Characteristics

• Locations must first be erased before new data
  can be written
• But it can take awhile to erase a location
• Locations can only be written or erased a small
  amount of times
• The flash solution is to rotate locations for
  writes.

7
Flash Write Behavior

• Flash management software rotates the usage of
  locations

Operating System
Flash
1
2
3
4
5
6
7
7
8
Flash Write Behavior

• Flash management software rotates the usage of
  locations

Write gibberish to 2
Operating System
Flash
1
2
3
4
5
6
7
8
9
Flash Write Behavior

• Overwrites go to new location instead of original
  block
• Dead data left behind until that location is
  erased

Write gibberish to 2
Operating System
O(\ks_at_
Flash
1
2
3
4
5
6
7
9
10
Ideal Secure Deletion

• Carry out deletion
• Allow fine-grained deletion
• Work in acceptable amount of time

11
TrueErase
Securely erase my file!
Secure delete
Secure delete
12
TrueErase Flash Behavior

• We can now tell the flash to erase locations

Securely delete 2
Operating System
Flash
1
2
3
4
5
6
7
12
13
TrueErase Flash Behavior

• The location can be securely deleted!

Operating System
Erase!
Flash
1
2
3
4
5
6
7
13
14
Why is this hard?

• Flash management not easily changeable
• Performance implications
• Rotating the right locations
• Operating systems (e.g. Windows) not designed for
  flash
• Backward compatibility issues
• Handling crashes during secure deletion
• Correctness issues

15
Current Development TrueErase
16
Current Development TrueErase

• Programming complete prototype
• Flash secure deletion algorithm finished
• Still working on OS expansions
• Expected to be done for conference paper
  submission in mid-October

17
Questions?