Physics review

PHYS 2326 definitions

resistivity

J

J=nqvd=

σE=E/ρ

Ohm’s law

E/ρ

ρ

resistivity of conducting materials

1. TF ρ is a universal law

1. False

Unit of resistivity

Ωm (read ohm-meter) Where V/A = Ω = ohm

Conductivity

Conductivity = σ = 1/ρ [mho/m or Siemens/m]

R=

ρL/A

V=

RI (Ohm’s Law)

Resistors

Devices made with a specific value of electrical resistance (R).
The value allows us to estimate how much current a device/circuit will draw from a voltage supply.
allow us to control the current drawn from a voltage supply.
Unit: Ω (ohm)

Resistors in Series

Resistors share the same current (I) § Resistors have distinct potential differences (V)

Resistors in Parallel

Resistors share the same potential difference (Vab) § Resistors have distinct currents

What makes a process safe?

Type safety
Memory safety
Control-flow safety

Program control flow

Unconditional jumps
Conditional jumps
Loops
Subroutines
Unconditional halt

Fundamen

CFI

Control-flow integrity (CFI)
Enforces integrity of a program’s execution flow path
Detects an undefined change in the path of execution by an adversary

CFI Method

build CFG statically (compile time)
Instrument (rewrite) binary, e.g., at install time

-add Ids and Id checks; maintain Id uniqueness

perform ID checks at run time

-indirect jumps have matching Ids

Control-Flow Integrity

Execution must follow a path of a Control-Flow Graph (CFG)

CFG can be pre-computed from:

source-code analysis

binary analysis

execution profiling

How can we enforce extracted control-flow?

Behavior-based Detection(A)

Challenges to defining the expected program behavior

Define “expected behavior”
Detect deviations from expectation efficiently

Avoid compromise of the detector

Basic Block

A consecutive sequence of instructions, control is “straight”(no jump targets except at beginning or end)

8. TF
   CFG can be derived from a call graph

8. T

How CFI works

Define “expected behavior” (CFG)
Detect deviations from expectation efficiently (IRM)
Avoid compromise of detector (Sufficient randomization)

How does in-line Monitor work?

Implement the monitor in-line as a program transformation (instrumentation)
Insert a label just before the target address of an indirect transfer
Insert binary code that when run, checks whether the label of the target instruction matches the label of the possible destination

Ways we can’t defeat CFI

Inject code that has a legal label (we assume non-executable data)
Modify code labels (code is immutable)

main components of Java security architecture

class loaders
byte code verification

the Security Manager

Power=

dU/dt=dW/dt=VI

Unit of Power

Joules/s = Watts

Current(I)

I=V/R

Kirchhoff’s (Rule #1) Current Law

The algebraic sum of the currents into a circuit junction is zero.

Kirchhoff’s (Rule #2) Voltage Law

The algebraic sum of the potential differences in a circuit loop must equal zero.

TF

It has been observed that certain naturally-occurring rocks (magnetite) can attract or repel each other depending on the position with respect to each other.

T

TF

Magnetic poles can exist in isolation

F

Ampere’s Law

The magnetic field integrated around a closed loop is proportional to the electric current passing through the loop.

Solenoid

A coil wound into a close-packed helix

toroid

Ring-shaped type of solenoid