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* PUSH NOTE : 01. Security Introduction.md

* PUSH ATTACHMENT : is-01-cryptosystem.png
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_posts/Lecture Notes/Internet Security/2023-09-10-security-intro.md
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@@ -36,7 +36,7 @@ attachment:
In this course, we are mainly interested in system/network security!
There are two categories in **IT Security**, (though the boundary is blurry)
- **Computer** (system) **security** uses automated tools and mechanisms to protect **data in a computer**, against hackers, malware, etc.
- **Computer** (system) **security** uses automated tools and mechanisms to protect the **data in a computer**, against hackers, malware, etc.
- **Internet** (network) **security** prevents, detects, and corrects security violations that involve the **transmission of information** in a network.
In internet security, we assume that:
@@ -52,7 +52,7 @@ In internet security, we assume that:
- inserting, modifying, deleting, replaying messages
- poisoning data
- impersonate and pretend to be someone else
- Conventionally, we use the terms:
- Conventionally, we use the following names:
- Alice and Bob for the two parties participating in the communication.
- Eve (or Mallory, Oscar) for the adversary.
@@ -94,9 +94,9 @@ This is only an overview, so the attacks are introduced briefly.
There are two types of attacks in security attacks
- **Active attacks**: modify the content of messages
- Ex. (D)DoS, MITM, poisoning, smurf attack, system attacks.
- *Prevention* is important since the active attacks are a danger to *data integrity* and *availability*.
- *Prevention* is important since the active attacks concern *data integrity* and *availability*.
- **Passive attacks**: does not modify information, but observes the content or copies it.
- Ex. eavesdropping, port scanning (idle scan secretly scanns).
- Ex. eavesdropping, port scanning (idle scan secretly scans).
- *Detection* is important since passive attacks are a danger to *confidentiality*.
## Security Services and Mechanisms
@@ -112,7 +112,7 @@ What kind of security services do we want? The basic network security services m
Additionally, we also need:
- **Authentication**: a way to authenticate users (ID, passwords)
- **Non-repudiation**: ensure that no party can deny that it sent or received a message or approved some information
- Assurance that someone cannot deny the validity of something
- Assurance that someone cannot deny the validity of message or information
### Attacks Against CIA Triad
@@ -142,10 +142,10 @@ There are many ways of achieving security.
- It may be desirable to not leak *any* information, so one might add padding to the traffic, so the traffic is indistinguishable by the adversary (prevents side-channel attacks)
- **Digital signatures**: provides authenticity of digital messages or documents
- **Trusted Third Party** (TTP): a safe third-party that we can trust
- If we have a TTP, a lot of problems go away. We can always ask the TTP for the truth
- But TTP can become a *single point of failure* (SPOF), and security architectures may become too dependent on the TTP
- If we have a TTP, a lot of problems go away. We can always ask the TTP for the truth.
- But TTP can become a *single point of failure* (SPOF), and security architectures may become too dependent on the TTP.
- **Append-only server**: keeps track of all modifications, good for auditing
- Blockchain is a kind of append-only data structure
- Blockchain is a kind of append-only data structure.
## Cryptography
@@ -155,7 +155,7 @@ There are many ways of achieving security.
### Basics of a Cryptosystem
![is-01-cryptosystem.png](../../../assets/img/posts/Lecture%20Notes/Internet%20Security/is-01-cryptosystem.png)
![is-01-cryptosystem.png](../../../assets/img/posts/Lecture%20Notes/Internet%20Security/is-01-cryptosystem.png#)
- A **message** in *plaintext* is given to an **encryption algorithm**.
- The encryption algorithm uses an **encryption key** to create a *ciphertext*.
@@ -168,7 +168,7 @@ There are many ways of achieving security.
There are two criteria for classifying cryptosystems.
- How are the keys used?
- **Symmetric** cryptography uses a single key for both encryption and decryption
- **Symmetric** cryptography uses a single key for both encryption and decryption.
- **Public key** cryptography uses different keys for encryption and decryption, respectively.
- How are plaintexts processed?
- **Block cipher**
@@ -232,7 +232,7 @@ In a smartphone, assets (things of value) would be
For example,
|Attacker|Abilities|Goals|
|-|-|-|
|:-:|-|-|
|Thief|Steal the phone|Take the device|
|FBI|Lot of things...|Obtain evidence from the device|
|Eavesdropper|Observe network traffic|Steal information|