Cypher Technology Ltd V2.6 (03) December 2011
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are made within the file or on the card. The Master and the card should always have the
same checksum.
Where multiple disks are produced, the modulo 32 bit sum of the checksums of the
individual disks are equal to checksum of the whole card. Note: this is not true for
Compact Master disks pre V 2.6.34.
The chance of two flash cards, with different image data, having the same checksum is
less than 1 in 4,000,000,000.
The checksum of a flash card or Master Copy can be found using the Menu functions
(see above).
5.5
Flash Card Wipe (Erasing)
As mentioned above, when a file is deleted the file data remains on the medium. This
file may be un-deleted and the file’s data recovered. The only way to render the card
safe from data recovery is to re-write the whole card with new data. PUMA “Wipe Card”
function writes binary zeros to the whole card. Also viruses may be present in the
Master Boot Record (MBR). During the wipe process the MBR is overwritten also and is
recreated during the format operation.
5.6
System Architecture
PUMA is based on a Linux platform and uses proprietary software. The proprietary
nature of the software has allowed the transfer process to be tailored precisely to the
needs of law enforcement and evidence gathering. For maximum reliability and security
it contains no hard disk and boots from a read-only flash file system.
5.7
Transfer Times
The Media Transfer Station uses a full height, high performance CD/DVD/BD
(1)
writer.
This type of drive provides transfer rates up to 20 Mbyte/sec compared with 8Mbyte/sec
for laptop drives. Also, the larger size of the drive provides a higher reliability disk.
Further time is saved during the transfer as the separate tasks (Transfer, Verify and
Erase) are started automatically, one after the other. The user does not have to open
separate applications for disk imaging, file copy, file verify, raw file conversion and flash
erase. Clearly for the user to run these five programs manually in sequence would
require considerable time and perhaps more important, be prone to error. A single,
automated process avoids these sources of error and saves time.
For reading, the maximum transfer rate (at the outside of the disk) is about 20
Mbytes/sec. A 4 Gbyte card can be copied in about 4 minutes.
5.7.1
Master Creation
When making the Master disk, the whole contents of the flash card are coped to the
CD/DVD. The transfer time is dependent on the flash card size. A 4GByte card would
take about 5 minutes to transfer.