Parameters that Affect Physically Observable Side Channels Flashcards
What is the shannon capacity?
C = W * log2(1 + S/N). W == bandwidth S/N = SNR
What is the information content of a message?
the number of 0s and 1s it takes to transmit the message
What are the three types of channels?
- Binary channel - transmits 0s and 1s
- Noisy channel - has errors (what I sent may not be what is received)
- Noiseless channels - no errors
What is the data rate?
the amount of digital data that is moved from one place to another in a given period of time
How does bandwidth affect data rate?
Higher bandwidth == greater data rate?
What is the max data rate called?
The shannon capacity
what is bandwidth?
the difference between the higher and lower frequency
What bandwidth do we want when measuring SCs?
More bandwidth == more noise => want use the smallest bandwidth possible to recreate the signal (needs to be 2x size of message)
What is Resolution Bandwidth Filter (RBW)?
minimum separation required between two frequency components to be able to visually separate the signals. Less RBW == lower noise floor
What is sweep time?
How fast your instrument is sampling. It is inversely proportional to the RBW (lower noise == less sampling)
what is Shannon’s Sampling Theorem?
If a continuous, band-limited signal contains no frequency components higher than fs, then we can recover the original signal without distortion if we sample at a rate of at least 2*fs samples/second
What is the Nyquist rate?
2*fs
What is Bit resolution?
how many digits are used to record the amplitude of the signal that we are sampling
What are the most important measurements for SCs?
Sampling rate and bit resolution
What is Thermal noise?
created by the random motion of electrons in conducting materials that cause random, localized currents
Types of Coupling Noise
Capacitative and Inductive
What is Capacitative coupling?
two wires connected (?) by capacitors, if you send a square pulse across one of them, there will be a current in the other (although not the full square pulse)
What is inductive coupling?
two conductors that are configured such that a change in current through one wire induces a voltage across the ends of the other wire through electromagneticinduction
What is Power Supply Noise?
Drops in power due to other circuit components pull voltage from the power supply (so components down the line get a slight decrease in power)
How do we reduce power supply noise?
Decoupling or debouncing capacitors (decaps) - capacitors next to each component to store power for when it is needed
Prevents power from dropping each time a component draws from the main supply line
What measurement requirements are there for control flow tracking via EM signals?
- Reasonable bandwidth (4% of clock frequency)
- SNR >= 20 dB
- 100s - 1000s training samples (so you can average them out)
What is the radiation pattern of an antenna?
graph of radiation properties. want to max main lobe and min others
What is the beam width of an antenna?
angular separation between two identical points on the opposite side of the pattern maximum (width of area you can record)
What is pattern maximum?
Highest point on radiation pattern
what is Directivity?
ratio of power density radiated in a particular direction to the average radiated power density (aka how strong the antenna will be in a particular direction)
What is gain?
directivity * radiation efficiency. enhances signal strength and noise
What is polarization?
radiated electric field vector at a point in space as a function of time. receiving antenna must match
What polarization do we use for side channels?
Side channels are not transmitted via normal means, so you do not know the polarization of the incoming signal ==> use circular
what is an isotropic antenna?
The ‘ideal’ antenna - radiates equally well in all directions
What directivity does an isotropic vs real antenna have
1 for iso, > 1 for real
What is effective area?
the portion of an incoming wave that an antenna receives and extracts all the power from it
What is Friis Transmission Formula?
formula to estimate signal strength at a given distance from the origin
