Chapter 8 Flashcards
1
Q
Trust and Threats - Core Concepts
A
- Definition: Security involves managing trust and threats.
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Key Points:
- Trust: Assumptions about the behavior of entities within the system.
- Threats: Potential failure scenarios that must be addressed to ensure security.
- Balance: Security measures must balance trust, threat evaluation, and risk mitigation.
- Realization: Perfect security is unattainable; measures are about reducing risk.
- Example: Trusting a fiber link in a secure data center vs. securing WiFi messages on an open campus.
2
Q
Types of Threats - Confidentiality
A
- Definition: Ensuring that information is accessible only to those authorized to access it.
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Key Points:
- Encryption: A method to protect data from being intercepted and read by unauthorized parties.
- Eavesdropping: Without confidentiality measures, adversaries can intercept and understand the contents of messages.
- Example: Encrypting email messages to prevent unauthorized users from reading sensitive information.
3
Q
Types of Threats - Integrity
A
- Definition: Ensuring that information has not been altered during transmission.
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Key Points:
- Tampering Detection: Mechanisms to detect if data has been altered.
- Tampering Impact: Even encrypted messages can be modified to change their meaning.
- Example: Using checksums or digital signatures to verify that a message has not been changed.
4
Q
Types of Threats - Authentication
A
- Definition: Verifying the identities of the entities involved in communication.
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Key Points:
- Identity Verification: Ensures that the communicating parties are who they claim to be.
- DNS Attacks: Redirecting users to false websites highlights the importance of authentication.
- Example: Using SSL/TLS certificates to authenticate websites and prevent man-in-the-middle attacks.
5
Q
Real-world Threats - Malware
A
- Definition: Malicious software designed to disrupt, damage, or gain unauthorized access to systems.
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Key Points:
- Worms and Viruses: Types of malware that can self-replicate and spread.
- Botnets: Networks of infected machines used to launch coordinated attacks.
- Example: A computer virus that replicates by inserting copies of itself into other programs or files.
6
Q
Real-world Threats - Access Control
A
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Access Control: Ensuring that only authorized users can access and modify resources.
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Key Points:
- Authorization: Verifying that a user has permission to perform an action.
- Prevention: Protecting systems from unauthorized changes.
- Example: Implementing user roles and permissions to control access to a company’s internal network.
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Key Points:
7
Q
Real-world Threats -Availability
A
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Availability: Ensuring that services are available and functional when needed.
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Key Points:
- DoS Attacks: Overloading a system with traffic to make it unavailable to legitimate users.
- Redundancy: Implementing backup systems to maintain availability.
- Example: Using load balancers to distribute traffic and prevent DoS attacks from affecting service availability.
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Key Points:
8
Q
Risk Mitigation - Cost-effective Security
A
- Definition: Implementing security measures that provide the best protection for their cost.
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Key Points:
- Risk Assessment: Identifying and prioritizing potential threats.
- Cost-Benefit Analysis: Balancing the cost of security measures against the potential impact of threats.
- Example: Encrypting sensitive data but not all data, based on the likelihood and impact of interception.
9
Q
Risk Mitigation - Explicit Trust Assumptions
A
- Definition: Clearly stating the trust assumptions made within a system.
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Key Points:
- Transparency: Making trust assumptions explicit helps in understanding and managing risks.
- Unexpected Adversaries: Helps in preparing for sophisticated and unexpected attacks.
- Example: Trusting the integrity of server execution and ensuring no leakage of unencrypted messages.
10
Q
Principles of Ciphers
A
- Definition: Encryption transforms a message to make it unintelligible to unauthorized parties.
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Key Points:
- Encryption Function: Applied to plaintext to create ciphertext.
- Decryption Function: Applied to ciphertext to recover the original plaintext.
- Cipher: Combination of encryption and decryption functions.
- Example: Encrypting a message before sending it over the network ensures that only the intended recipient can read it.
11
Q
Symmetric-Key Ciphers
A
- Definition: Both participants share the same key for encryption and decryption.
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Key Points:
- Secret-Key Ciphers: Another name for symmetric-key ciphers since the key must be kept secret.
- DES: Data Encryption Standard, a widely used symmetric-key cipher.
- 3DES: Triple DES, uses three DES keys for increased security.
- AES: Advanced Encryption Standard, supports key lengths of 128, 192, or 256 bits, and is efficient for both software and hardware.
- Example: AES is used for securing data on mobile devices due to its efficiency and small memory requirements.
12
Q
Public-Key Ciphers
A
- Definition: Uses a pair of related keys—one for encryption (public key) and one for decryption (private key).
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Key Points:
- RSA: Relies on the computational difficulty of factoring large numbers.
- ElGamal: Based on the discrete logarithm problem, often used with elliptic curve cryptography for added security.
- Public and Private Keys: The public key is distributed widely, while the private key is kept secret.
- Example: RSA is often used for secure key exchange and digital signatures.
13
Q
Modes of Operation
A
- Definition: Techniques to use block ciphers securely.
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Key Points:
- ECB (Electronic Codebook): Encrypts each block independently, but identical plaintext blocks produce identical ciphertext blocks.
- CBC (Cipher Block Chaining): Each plaintext block is XORed with the previous ciphertext block before encryption.
- Counter Mode: Uses a counter for each block, ensuring unique encryption for each block.
- Example: CBC mode ensures that even identical plaintext blocks produce different ciphertext blocks due to the chaining process.
14
Q
Cryptographic Hash Functions
A
- Definition: Produces a fixed-size hash value from input data.
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Key Points:
- MD5 and SHA-1: Common hash algorithms, though MD5 has known weaknesses.
- SHA-2: A family of hash functions designed to replace SHA-1.
- Collision Resistance: Difficult to find two different inputs that produce the same hash value.
- Example: SHA-256, part of the SHA-2 family, is widely used for data integrity checks.
- Security Note: The hash function must ensure that outputs are randomly distributed to prevent collisions.
15
Q
Message Authentication Codes (MACs)
A
- Definition: A value used to verify both the integrity and authenticity of a message.
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Key Points:
- HMAC: A MAC based on hash functions, commonly using SHA-1 or SHA-256.
- Construction: The MAC is computed using both the message and a secret key.
- Example: HMAC-SHA256 is used to ensure that a message has not been tampered with and is from a legitimate sender.
16
Q
Authenticators
A
- Definition: Values added to messages to verify their integrity and authenticity.
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Key Points:
- Encryption of Digest: One method is to encrypt the hash of the message.
- MACs and HMACs: Provide proof that the sender knows a secret key.
- Inseparability: Integrity and authentication are fundamentally linked.
- Example: Encrypting both the message and its MAC ensures confidentiality and authentication.
- Security Note: Prevents adversaries from undetectably tampering with messages.
17
Q
Principles of Ciphers - Encryption Function
A
- Definition: A process that transforms plaintext into ciphertext using an encryption algorithm and a key.
- Details: Ensures data confidentiality by making the content unintelligible to unauthorized parties.
- Example: AES encrypts a plaintext message using a secret key to produce ciphertext that appears as a random sequence of characters.
18
Q
Principles of Ciphers - Decryption Function
A
- Definition: A process that transforms ciphertext back into plaintext using a decryption algorithm and a key.
- Details: Reverses the encryption process to make the original message readable by authorized parties.
- Example: Using the same AES key to decrypt ciphertext back into its original plaintext form.
- Figure: Symmetric-key encryption and decryption (Figure 1).
19
Q
Symmetric-Key Ciphers - Secret-Key Ciphers
A
- Definition: Encryption and decryption use the same secret key, which must be kept confidential between communicating parties.
- Details: Symmetric-key algorithms are efficient and suitable for large-scale data encryption.
- Example: AES, where both the sender and the receiver use the same key for encryption and decryption.
- Security Note: Key management and distribution are critical challenges in symmetric-key cryptography.
