Flashcards in Chap4 Quiz Deck (31): A is an older attack that uses an illegally large IP packet to crash an operating system. Ping of death. A network administrator notices extensive damage to wireless packets. This might indicate a attack. WEP encrypts each frame with a per-frame key that consists of the shared RC4 key plus a 24-bit initialization vector that is different for each frame. TRUE What mistake did the 802.11i Working Group make when creating IVs? Making the IV too short WEP mandates private keys. FALSE WEP mandates shared keys.
IEEE 802.11i-2004, or 802.11i for short, is an amendment to the original IEEE 802.11, implemented as Wi-Fi Protected Access II (WPA2). The draft standard was ratified on 24 June 2004. This standard specifies security mechanisms for wireless networks, replacing the short Authentication and privacy clause of the original standard with a detailed Security clause. In the process, the amendment deprecated broken Wired Equivalent Privacy (WEP), while it was later incorporated into the published IEEE 802.11-2007 standard.
Replacement of WEP[edit]
802.11i supersedes the previous security specification, Wired Equivalent Privacy (WEP), which was shown to have security vulnerabilities. Wi-Fi Protected Access (WPA) had previously been introduced by the Wi-Fi Alliance as an intermediate solution to WEP insecurities. WPA implemented a subset of a draft of 802.11i. The Wi-Fi Alliance refers to their approved, interoperable implementation of the full 802.11i as WPA2, also called RSN (Robust Security). 802.11i makes use of the Advanced Encryption Standard (AES) block cipher, whereas WEP and WPA use the RC4stream cipher.[1]
Protocol operation[edit]
IEEE 802.11i enhances IEEE 802.11-1999 by providing a Robust Security Network (RSN) with two new protocols: the four-way handshake and the group key handshake. These utilize the authentication services and port access control described in IEEE 802.1X to establish and change the appropriate cryptographic keys.[2][3] The RSN is a security network that only allows the creation of robust security network associations (RSNAs), which are a type of association used by a pair of stations (STAs) if the procedure to establish authentication or association between them includes the 4-Way Handshake.[4]
The standard also provides two RSNA data confidentiality and integrity protocols, TKIP and CCMP, with implementation of CCMP being mandatory since the confidentiality and integrity mechanisms of TKIP are not as robust as those of CCMP.[5] The main purpose to implement TKIP was that the algorithm should be implementable within the capabilities of most of the old devices supporting only WEP.
The initial authentication process is carried out either using a pre-shared key (PSK), or following an EAP exchange through 802.1X (known as EAPOL, which requires the presence of an authentication server). This process ensures that the client station (STA) is authenticated with the access point (AP). After the PSK or 802.1X authentication, a shared secret key is generated, called the Pairwise Master Key (PMK). In PSK authentication, the PMK is actually the PSK[6], which is typically derived from WiFi password by putting it through a key derivation function that use SHA-1 as the cryptographic hash function.[7] If an 802.1X EAP exchange was carried out, the PMK is derived from the EAP parameters provided by the authentication server.
Four-way handshake[edit]
The four-way handshake[8] is designed so that the access point (or authenticator) and wireless client (or supplicant) can independently prove to each other that they know the PSK/PMK, without ever disclosing the key. Instead of disclosing the key, the access point (AP) and client encrypt messages to each other—that can only be decrypted by using the PMK that they already share—and if decryption of the messages was successful, this proves knowledge of the PMK. The four-way handshake is critical for protection of the PMK from malicious access points—for example, an attacker's SSID impersonating a real access point—so that the client never has to tell the access point its PMK.
The PMK is designed to last the entire session and should be exposed as little as possible; therefore, keys to encrypt the traffic need to be derived. A four-way handshake is used to establish another key called the Pairwise Transient Key (PTK). The PTK is generated by concatenating the following attributes: PMK, AP nonce (ANonce), STA nonce (SNonce), AP MAC address, and STA MAC address. The product is then put through a pseudo-random function. The handshake also yields the GTK (Group Temporal Key), used to decrypt multicast and broadcast traffic.
The actual messages exchanged during the handshake are depicted in the figure and explained below (all messages are sent as EAPOL-Key frames):
The Pairwise Transient Key (64 bytes) is divided into five separate keys:
The Group Temporal Key (32 bytes) is divided into three separate keys:
The Michael MIC Authenticator Tx/Rx Keys in both the PTK and GTK are only used if the network is using TKIP to encrypt the data.
This four-way handshake has been shown to be vulnerable to KRACK.
Group key handshake[edit]
The Group Temporal Key (GTK) used in the network may need to be updated due to the expiration of a preset timer. When a device leaves the network, the GTK also needs to be updated. This is to prevent the device from receiving any more multicast or broadcast messages from the AP.
To handle the updating, 802.11i defines a Group Key Handshake that consists of a two-way handshake:
CCMP overview[edit]
CCMP is based on the Counter with CBC-MAC (CCM) mode of the AES encryption algorithm. CCM combines CTR for confidentiality and CBC-MAC for authentication and integrity. CCM protects the integrity of both the MPDU Data field and selected portions of the IEEE 802.11 MPDU header.
Key hierarchy[edit]
RSNA defines two key hierarchies:
The description of the key hierarchies uses the following two functions:
The pairwise key hierarchy utilizes PRF-384 or PRF-512 to derive session-specific keys from a PMK, generating a PTK, which gets partitioned into a KCK and a KEK plus all the temporal keys used by the MAC to protect unicast communication.
N 802.11i Pre Shared Key Mode The Initial Key Is Generated Iphone
The GTK shall be a random number which also gets generated by using PRF-n, usually PRF-128 or PRF-256, in this model, the group key hierarchy takes a GMK (Group Master Key) and generates a GTK.
MAC frame formats[edit]Frame Control field[edit]
Protected Frame field[edit]
'The Protected Frame field is 1 bit in length. The Protected Frame field is set to 1 if the Frame Body field contains information that has been processed by a cryptographic encapsulation algorithm. The Protected Frame field is set to 1 only within data frames of type Data and within management frames of type Management, subtype Authentication. The Protected Frame field is set to 0 in all other frames. When the bit Protected Frame field is set to 1 in a data frame, the Frame Body field is protected utilizing the cryptographic encapsulation algorithm and expanded as defined in Clause 8. Only WEP is allowed as the cryptographic encapsulation algorithm for management frames of subtype Authentication.'[8]
See also[edit]
References[edit]
External links[edit]
Retrieved from 'https://en.wikipedia.org/w/index.php?title=IEEE_802.11i-2004&oldid=949208972'
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Azure Blob storage is Microsoft's object storage solution for the cloud. Blob storage is optimized for storing massive amounts of unstructured data, such as text or binary data.
Blob storage is ideal for:
Source code | Package (PyPI) | API reference documentation | Product documentation | Samples
Getting startedPrerequisites
Install the package
Install the Azure Storage Blobs client library for Python with pip:
Create a storage account
If you wish to create a new storage account, you can use theAzure Portal,Azure PowerShell,or Azure CLI:
Create the client
The Azure Storage Blobs client library for Python allows you to interact with three types of resources: the storageaccount itself, blob storage containers, and blobs. Interaction with these resources starts with an instance of aclient. To create a client object, you will need the storage account's blob service account URL and acredential that allows you to access the storage account:
Looking up the account URL
You can find the storage account's blob service URL using theAzure Portal,Azure PowerShell,or Azure CLI:
Types of credentials
The
credential parameter may be provided in a number of different forms, depending on the type ofauthorization you wish to use:
Creating the client from a connection string
Depending on your use case and authorization method, you may prefer to initialize a client instance with a storageconnection string instead of providing the account URL and credential separately. To do this, pass the storageconnection string to the client's
from_connection_string class method:
The connection string to your storage account can be found in the Azure Portal under the 'Access Keys' section or by running the following CLI command:
Key concepts
The following components make up the Azure Blob Service:
The Azure Storage Blobs client library for Python allows you to interact with each of these components through theuse of a dedicated client object.
Clients
Four different clients are provided to to interact with the various components of the Blob Service:
Blob Types
Once you've initialized a Client, you can choose from the different types of blobs:
Examples
The following sections provide several code snippets covering some of the most common Storage Blob tasks, including:
Note that a container must be created before to upload or download a blob.
Create a container
Create a container from where you can upload or download blobs.
Use the async client to upload a blob
Uploading a blob
Upload a blob to your container
Use the async client to upload a blob
Downloading a blob
Download a blob from your container
Download a blob asynchronously
Enumerating blobs
List the blobs in your container
List the blobs asynchronously
Optional Configuration
Optional keyword arguments that can be passed in at the client and per-operation level.
Retry Policy configuration
Use the following keyword arguments when instantiating a client to configure the retry policy:
Encryption configuration
Use the following keyword arguments when instantiating a client to configure encryption:
N 802.11ipre Shared Key Mode The Initial Key Is Generated Game
Other client / per-operation configuration
Other optional configuration keyword arguments that can be specified on the client or per-operation.
Client keyword arguments:
Per-operation keyword arguments:
TroubleshootingGeneral
Storage Blob clients raise exceptions defined in Azure Core.All Blob service operations will throw a
StorageErrorException on failure with helpful error codes.
Logging
This library uses the standardlogging library for logging.Basic information about HTTP sessions (URLs, headers, etc.) is logged at INFOlevel.
Detailed DEBUG level logging, including request/response bodies and unredactedheaders, can be enabled on a client with the
logging_enable argument:
Similarly,
logging_enable can enable detailed logging for a single operation,even when it isn't enabled for the client:
Next stepsMore sample codeN 802.11i Pre Shared Key Mode The Initial Key Is Generated Windows 10
Get started with our Blob samples.
N 802.11ipre Shared Key Mode The Initial Key Is Generated Number
Several Storage Blobs Python SDK samples are available to you in the SDK's GitHub repository. These samples provide example code for additional scenarios commonly encountered while working with Storage Blobs:
Additional documentationN 802.11ipre Shared Key Mode The Initial Key Is Generated Free
For more extensive documentation on Azure Blob storage, see the Azure Blob storage documentation on docs.microsoft.com.
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