2024-04-22

📅 Monday, April 22nd, 2024

Leave no stone unturned.

— Euripides

• Hmm, Lisztomania… I’m kind of not surprised?

ECS154A Lecture: adder

• half-adder: not sufficient for multi-bit addition (no carry input)

half adder truth table:

A	B	S	C
0	0	0	0
0	1	1	0
1	0	1	0
1	1	0	1

• full adder: adder with carry input

full adder truth table:

$C_{in}$	A	B	S	C
0	0	0	0	0
0	0	1	1	0
0	1	0	1	0
0	1	1	0	1
1	0	0	1	0
1	0	1	0	1
1	1	0	0	1
1	1	1	1	1

full adder output equation (minimized):

$$S=m_1+m_2+m_4+m_7=\Sigma (1,2,4,7)$$

where $m_k$ represents the minterm of the $k$-th row.

full adder K-map… no reduction possible (circuit is minized with respect to standard logic gates, but that doesn’t mean we can’t reduce the number of gates)

$C_{in}$ \ AB	00	01	11	10
0	0	1	0	1
1	1	0	1	0

Expanded full adder equation:

$$\begin{array}{rl}S& =\overline{ab}{C}_{in}+\overline{a}b\overline{C_{in}}+a\overline{b}\overline{C_{in}}+ab{C}_{in}\\ & =C_{in}\left(\overline{ab}+ab\right)+\overline{C_{in}}\left(\overline{a}b+a\overline{b}\right)\\ & =C_{in}\left(\overline{ab}+ab\right)+\overline{C_{in}}\left(a\oplus b\right)\end{array}$$

We can see that:

$$\begin{array}{rl}\overline{a}\overline{b}+ab& =a\overline{a}+\overline{ab}+ab+b\overline{b}\\ & =(a+\overline{b})(\overline{a}+b)\\ & =\left(\overline{\overline{a}}+\overline{b}\right)\left(\overline{a}+\overline{\overline{b}}\right)\\ & =\left(\overline{\overline{a}b}\right)\left(\overline{a\overline{b}}\right)\\ & =\overline{\overline{a}b+a\overline{b}}\\ & =\overline{a\oplus b}\end{array}$$

So

$$\begin{array}{rl}S& =C_{in}\left(\overline{a\oplus b}\right)+C_{in}\left(a\oplus b\right)\\ & =C_{in}\oplus a\oplus b\end{array}$$

Now let’s come up with the equation for $C$. Here’s $C$‘s K-map:

$C_{in}$ \ AB	00	01	11	10
0	0	0	1	0
1	0	1	1	1

We have three two-element groups (one vertical, two horizontal). With a bit of algebra we can obtain the equation for $C_{out}$:

$$\begin{array}{rl}{C}_{out}& =ab+a{C}_{in}+b{C}_{in}\\ & =\left(a\oplus b\right)C_{in}+ab\end{array}$$

full adder = 2 half adders

Note that the output bits are ready only after the propagation delay of the critical path.

SOC001 Lecture: Stratification

• stratification: sorting into hierarchical rankings
  • different ranking/category has differing access to resources & power
  • sorted based on economic standing (income, wealth), race, gender, able-bodied or not, etc
  • society come up with beliefs to support/rationalize the stratifications; without beliefs, the stratification system wouldn’t work
• income vs wealth
  • income: money earned on a periodic basis (e.g., salary, investment, rental properties, etc), though not necessarily associated with labor
  • wealth: value of existing owned assets
• ideology: dominant set of beliefs
• social classes in the US
  • upper class
    • ”old money”
      • more prestige than new money
      • large inherited wealth
    • ”new money”
      • money mostly earned during their lifetime (i.e., not from family, etc)
  • middle class:
    • upper-middle
    • middle
    • lower-middle
  • lower class
    • working class (e.g., blue collar, unskilled labor) (considered poverty by federal standards)
    • working poor
    • underclass (chronically unemployed, rely on welfare, indebted, etc)
• Social class is mostly divided by wealth & income, but sometimes prestige, upbrining, etc.
• social mobility: ability for people to move among social classes (upwards) within their lifetime; different societies have differing levels of social mobility
• social stratification: theoretical perspectives
  • functionalism (not as popular nowadays)
    • Davis-Moore thesis: greater functional importance → greater reward (i.e., money)
    • inequalities are functional (this idea is criticized nowadays)
  • conflict
    • Marxist: bourgeoisie & proletariat conflict
  • symbolic-interactionism
    • symbolic communication (e.g., buying brand / designer products)
• intersectionality: multiple layers of inequality

HTB Academy SOC Analyst Path: Incident Handling Process

• event: something happening in the network
• incident: event with negative consequences
• security incident: generally, incidents with an intent to cause harm against the systems
  • Incidents can come from within a network as well (e.g., malicious insider, data theft), and they are not limited to intrusions.
  • It is difficult to discern events from incidents until after investigation. It is best to treat some types as incidents until shown otherwise through investigation.
• incident handling: well-defined procedures to handle security incidents