IS 450 Assignment 8 Vocab

Decreased Signal Strength

Radio signal attenuates as it propagates through matter (path loss).

interference from other sources

wireless network frequencies (e.g., 2.4 GHz) shared by many devces (e.g., WiFi, cellular, motors): interference.

multi-path propagation

Radio signal reflects off objects ground, arriving at destination at slightly different times.

SNR (Signal-to-noise Ratio)

Larger SNR - Easier to extract signal from noise (a “good thing”).

BER (Bit Error Rate)

A measure of the reliability of a digital signal transmission, representing the number of bits received in error per total number of bits transmitted.

SNR vs BER

Given Physical Layer, increased power leads to increased SNR, resulting decreased BER.

Choosing Physical Layer that meets BER requirement for SNR will give highest throughput.

SNR may change with mobility: dynamically adapt physical layer (modulation technique, rate).

CDMA (Code Division Multiple Access)

Unique “code” assigned to each user, code set partitioning.

all users share same frequency, but each user has own “chipping” sequence (i.e., code) to encode data.

allows multiple users to “coexist” and transmit simultaneously with minimal interference (if codes are “orthogonal”).

encoding

Inner product: (original data) X (chipping sequence)

decoding

Summed inner-product: (encoded data) X (chipping sequence).

802.11b

1999 | 11 Mbps | 30 m | 2.4 Ghz

802.11g

2003 | 54 Mbps | 30 m | 2.4 Ghz

802.11n (WiFi 4)

2009 | 600 Mbps | 70 m | 2.4, 5 Ghz

802.11ac (WiFi 5)

2013 | 3.47 Gbps | 70 m | 5 Ghz

802.11af

2014 | (35 - 560) Mbps | 1 Km | unused TV bands (54 - 790) MHz

802.11ah

2017 | 347 Mbps | 1 Km | 900 Mhz

802.11 LAN architecture

• wireless host communicates with base station: (access point (AP))

• Basic Service Set (BSS): (aka “cell”) in infrastructure mode contains: wireless hosts, access points (AP): base station, ad hoc mode: hosts only.

passive scanning

• beacon frames sent from APs

• association Request frame sent: H1 to selected AP

• association Response frame sent from selected AP to H1.

active scanning

• Probe Request frame broadcast from H1

• Probe Response frames sent from APs

• Association Request frame sent: H1 to selected AP

• Association Response frame sent from selected AP to H1

mobile handover

the processing of transferring an ongoing call or data session from one cell site to another without interrupting the service.

principles of cryptography

relies on several key principles to ensure secure communication and data protection. These include confidentiality, integrity, authentication, non-repudiation, and key management. These principles work together to protect data in transit and at rest, preventing unauthorized access and ensuring the authenticity and integrity of messages.

securing e-mail

• For Person A (sender): generates random symmetric private key (Ks), encrypts message with Ks (for efficiency), also encrypts Ks with Person B’s public key, and sends both Ks(m) and K^+B(Ks) to Person B.

• For Person B (receiver): uses private key to decrypt and recover Ks, and uses Ks to decrypt Ks(m) to recover m.

securing TCP connections: TLS

• Transport-Layer Security (TLS)

• widely deployed security protocol above the transport layer (supported by almost all browsers and web servers)

• sender encrypts message and receiver decrypts message

• Providing confidentiality (symmetric encryption), integrity (cryptographic hashing), authentication (public key cryptography)

• considered bad to use same key for more than one cryptographic function (different keys for message authentication code (MAC) and encryption)

• (Ks) = encryption key for data sent from client to server. (Mc) = MAC key for data sent from client to server. (Ks) = encryption key for data sent from server to client. (Ms) = MAC key for data sent from server to client.

• Record encrypted using symmetric key, Kc, passed to TCP

• Provides an API that any application can use (HTTP view of TLS on slides)

authentication

sender, receiver want to confirm identity of each other

message integrity

sender, receiver want to ensure message not altered (in transit, or afterwards) with detection

eavesdrop

intercepting messages!

Hash function algorithms

Mathematical functions that transform data of any size into a fixed-size output called “hash value".” These algorithms are used in networking for various purposes, including data integrity verification, authentication, and secure storage of passwords.

MD5 (Message Digest 5)

A cryptographic hash function used in networking primarily to verify data integrity and authenticity. It generates a 128-bit hash value (message digest) for any input data, ensuring that any alteration, even a single bit change, will produce a different hash value. This is to detect unintentional corruption or tampering of files or data during transmission or storage.

SHA-1

No longer considered secure due to cryptographic weaknesses and is generally recommended to be phased out. Vulnerabilities like collision attacks have made it susceptible to compromise, leading to deprecation and replacement with secure algorithms like SHA-2 and SHA-3.