Security terminologies

Summary

The lecture introduces core security terminology, focusing first on cryptography and then on common threats, tools, and vulnerabilities.

Cryptography and Encryption

Cryptography protects information from unauthorized readers by transforming readable plaintext into scrambled ciphertext.

In the example discussed, application data carried inside network packets is encrypted. Even if an attacker captures and reassembles the packets, the original business information should remain difficult and costly to recover.

Encryption and decryption use mathematical algorithms and keys:

1. Encryption: An algorithm transforms plaintext into ciphertext using an encryption key.
2. Decryption: The corresponding key and algorithm recover the original plaintext.

Symmetric and Asymmetric Cryptography

Symmetric-key cryptography uses the same key to encrypt and decrypt. Both the sender and receiver must possess that key.

• Examples named in the lecture include DES, Triple DES, IDEA, RC2, RC4, and RC5.
• Its main challenge is securely sharing the key with both parties.
• Cryptographic operations may be implemented in software or hardware; the lecture describes hardware implementations as substantially faster.

Asymmetric-key cryptography uses a pair of different keys:

• A public key is shared.
• A private key is kept secret by its owner.
• For confidentiality, a sender can encrypt a message with the recipient’s public key; only the recipient’s private key can decrypt it.
• The lecture also describes encrypting with the sender’s private key so others can use the public key to verify the sender. This is the basic idea behind a digital signature and supports non-repudiation.
• RSA is given as a widely used example. The lecture characterizes asymmetric algorithms as much slower than symmetric ones, making them suitable for exchanging small amounts of data—such as a symmetric key—rather than encrypting large data transfers.

A common approach described in the lecture is to use asymmetric cryptography to exchange a key, then use symmetric cryptography for bulk data.

Key Size and Cipher Types

A larger key generally increases the computational effort required for encryption and decryption, while also making brute-force recovery harder.

The lecture distinguishes between:

• Block ciphers, which process data in blocks.
• Stream ciphers, which process data byte by byte and are described as typically faster.

Hash Functions and Integrity Checking

A hash function maps data of arbitrary length to a fixed-length value, often called a hash, hash code, or message digest.

Hashes are not encryption. They are used in integrity checks and in authentication-related mechanisms.

The lecture identifies three desirable properties:

• The hash should be easy to compute.
• It should be difficult to recover the original message from its hash.
• It should be difficult to find two different messages with the same hash.

Integrity-checking process

1. The sender runs the data through a hash algorithm to create a message digest.
2. The sender sends the data and digest to the receiver.
3. The receiver runs the received data through the same algorithm.
4. The receiver compares the newly calculated digest with the one received. A mismatch indicates that the data may have changed.

Security Terminology

• Adware: Software associated with persistent pop-up advertising.
• Cracker: Someone who breaks into a computer or network without authorization, for motives such as amusement or theft.
• Firewall: Software, hardware, or both that helps protect a computer or network. It may protect an individual machine or multiple machines across a network.
• Hacker: Someone who explores computers and operating systems, including looking for vulnerabilities.
• Ethical hacker: A hacker hired by an organization to find security weaknesses in its systems so they can be fixed.
• Intruder / attacker: An unauthorized person attempting to access a system.
• Malware: Software created with malicious intent.
• Probe: A program used to gather information about a system or its users.
• Risk: The probability that a vulnerability will cause harm.
• Trojan horse: A program that can give an intruder remote access without the computer owner’s knowledge. It may arrive bundled with downloaded software.
• Rootkit: A particularly stealthy Trojan or group of programs designed to hide itself and other files or processes from the operating system and security scans.
• Social engineering: Manipulating people into revealing confidential information, for example by pretending to be an administrator.
• Phishing: A type of social engineering in which an attacker impersonates a trusted organization or person to obtain sensitive information such as passwords or account numbers.
• Spyware: Software that secretly performs actions such as collecting personal information, often without the user’s consent.
• System compromised: A situation in which a security policy has been violated and sensitive information may have been exposed.
• Threat: An event or action that could harm a system, including through destruction, disclosure, or modification of data, or denial of service.
• Virus: Code that replicates by attaching itself to another object, such as a system file or email program.
• Vulnerability: A weakness in a security procedure or system that could be exploited.
• Worm: An independent program that replicates by copying itself from one computer to another, often over a network or through email. Worms can generate enough traffic to slow or congest networks and servers.

Speakers or Sources

One unnamed instructor or lecturer presents the lesson. No other speakers or named sources are featured.