ADDER View Secure Руководство пользователя - Страница 16

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Threat

Solution

Data being sent to ports

Channel switching is controlled by the front

by means of faulty or

panel buttons only with all keyboard hotkey

subverted keyboards or

or mouse switching capabilities removed

mice causing the channel

from the design.

to switch and sending

data in turn to each port.

Data transfer by means of

USB ports support keyboard and mouse

common storage.

(and card reader for AdderView Secure

Plus) connections only. The product does

not enable a USB memory stick or disk

drive to be shared between computers.

Unidirectional signalling protects against

data transfer across the switch.

Timing analysis attacks.

If a connection exists between a computer

and a shared microprocessor system, it

is potentially possible to determine what

may be happening on the micro by timing

the responses to repeated requests that

the micro must service. For example, if

a high data bit takes longer to transmit

through the system than a low bit it may

be possible to detect the pattern of data

flowing between other ports by attempting

to time the responses to otherwise normal

requests. In the AdderView Secure, each

port has a dedicated processor that only

has input signals from the rest of the

system. These input signals are only active

when the port is selected. Consequently a

timing analysis attack from one computer

would yield no information about data

flowing to another computer.

Threat

Solution

Forced malfunctions due

It is potentially possible to create forced

to overloaded signalling.

malfunctions by constantly and quickly

sending a stream of valid requests (such as

the request to update the keyboard lights).

A well known example of an undesirable

KVM malfunction is a "crazy mouse"

which was quite common with early KVM

switches and was caused by data loss on

PS/2 systems with the result that the mouse

darted around the screen randomly clicking

and opening windows. The unidirectional

design of the AdderView Secure ensures

that the influence of signalling on one port

cannot flow past the data diodes. This

means that overload signalling on one port

will not affect the operation of another

port. USB signalling is not susceptible to the

failure mechanism that caused the crazy

mouse on PS/2 systems.

The user selects the wrong

Only one simple method of selecting

port.

computers is provided. The selected port

is clearly and unambiguously indicated on

the front panel by means of coloured lights

adjacent to each key switch. For high levels

of security, the screens of high and low

security computers should be arranged to

look visibly different in general appearance.

Signalling by means of

Each port is independently powered by its

shorting the power supply

USB port. Shorting the power supply on

or loading the power

one port will not cause the power on other

supply.

ports to be switched off.

Tampering with the

The switch is designed to enable tamper

switch.

proof seals to be fitted over the counter-

sunk screws.