4G Network Fundamentals Week 2 Quiz Answer

4G Network Fundamentals Week 2 Quiz Answer

4G Network Fundamentals

In this article i am gone to share Coursera Course: 4G Network Fundamentals Week 2 Practice Quiz Answer with you..

Quiz W2-L1 Answer

Question 1)

Note: This quiz is a training exercise, which is not included in the final score.

W​2.L1.Q1:  The IMSI (International Mobile Subscriber Identity)

• is a specific format used for mobile phone numbers
• includes the IP address assigned to the subscriber's terminal
• is an identity related to the subscription. It does not vary over time and it is linked to the USIM card (also called SIM)
• is an identity that is constant over time and that is built on the basis of the serial number of the terminal

Question 2)

W​2.L1.Q2:  Select the correct statement.

• Each subscription is linked to an IMSI, which is globally unique,
• Each subscription is linked to an IMSI, which is unique in a given network,
• Each subscription is linked to 3 IMSIs, the first IMSI specifies the country, the second one specifies the operator and the third one is a serial number.

Question 3)

W​2.L1.Q3:  In 4G, the IP address of a UE

• is a fixed address given by the operator as soon as the subscription starts,
• is an address dynamically allocated by the eNodeB when the terminal is turned on,
• is an address dynamically allocated by the PGW when the terminal is turned on.

Question 4)

W​2.L1.Q4:  Among the following expressions, which one can correspond to an APN?

• 137.193.211.2
• 208 01 314567941
• epc.tmobile.com
• 8080
• http://www.imt-atlantique.fr

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Quiz W2-L2 Answer

Question 1

Note: This quiz is a training exercise, which is not included in the final score.

W2.L2.Q1: A 4G network authenticates a subscriber

• by checking if the format of the IMSI sent by the UE is correct
• by querying the HSS to check if the IMSI is valid
• by asking the UE to transmit the K key and by checking if it is correct
• by sending a random number and checking that the result calculated by the UE equals the expected result

Question 2)

W2.L2.Q2: The mobile operator controls the HSS and provides the SIM card. Can the operator use a proprietary algorithm (function f specific to the operator)?

• No, it is technically impossible,
• No, the subscriber will not be able to roam,
• Yes, if the lengths of RAND and RES are compliant with the specification,
• Yes, without limitations for RAND and RES.

Question 3)

W2.L2.Q3: Two UEs simultaneously receive an authentication request. By chance, the RAND values chosen by the network are the same. Are the signed results (RES) necessarily identical?

• No, the UEs will process the challenges as duplicates and notify an error
• No, but only if the UEs use different authentication algorithms (f function)
• No, there is a very small probability for the shared secret to be identical
• Yes, the input random values are the same, the responses will thus be the same
• Yes but only if the requests are perfectly synchronized (very unlikely)

Question 4)

W2.L2.Q4: For the terminal to authenticate the network,

• the terminal considers that the network can be trusted because technologically it is impossible for an attacker to deploy a pirate base station,
• the terminal generates a random number, transmits it to the network and checks if the result provided by the network corresponds to the result calculated by the SIM card from the secret key,
• the network calculates an authentication token from the random number used to authenticate the terminal, it sends this token to the terminal, which checks if the token corresponds to the result calculated by the SIM card from the secret key and the random number
• the network calculates an authentication token from the random number used to authenticate the terminal and a sequence number, it sends this token to the terminal, which then checks if the token corresponds to the result calculated by the SIM card from the secret key, the random number and the sequence number.

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Quiz W2-L3 Answer

Question 1)

Note: This quiz is a training exercise, which is not included in the final score.

W2.L3.Q1: Encryption in a 4G network

• is based on a symmetric key (in other words the same secret key is used for both ciphering and deciphering)
• uses a public-key system (ciphering is based on a public key and deciphering uses a private key)

Question 2)

W2.L3.Q2: In a 4G network,

• the ciphering operation is much less complex than the deciphering operation,
• the ciphering operation is as complex as the deciphering operation,
• the ciphering operation is much more complex than the deciphering operation.

Question 3)

W2.L3.Q3: The encryption sequence is calculated

• from a random number chosen upon each new transmission and the secret key K of the subscriber
• from a stable Kenc (enc = encryption) key, a random number and stable complementary indicators (direction, length…)
• from a stable Kenc key, a regularly incremented counter and complementary indicators (direction, length…)
• from a stable Kenc key and complementary indicators (direction, length…)

Question 4)

W2.L3.Q4: An operator can chose its own encryption algorithm

• No, the subscriber could use any terminal but only to communicate in its network and would not be able to roam,
• No, the subscriber would not be able to use any terminal,
• Yes, if the inputs and outputs of the algorithm have the same length as the standard algorithms,
• Yes, without any limitation for the input and output sizes.

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Quiz W2-L4 Answer

Question 1)

Note: This quiz is a training exercise, which is not included in the final score.

W2.L4.Q1: In a security context, MAC means

• Medium Access Control
• Message Authentication Code
• Mobile Assisted Cyphering

Question 2)

W2.L4.Q2: Integrity control is based on

• the fact that transmissions are ciphered,
• the addition of a very long code calculated from a secret key,
• the addition of a code with a reduced length calculated from a secret key,
• the split of each message in 2 parts, each part being sent over a specific channel.

Question 3)

W2.L4.Q3: A message between a UE and the MME

• is first ciphered then the MAC code is added to it
• is supplemented by the MAC code then ciphered

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Quiz W2-L5 Answer

Question 1)

Note: This quiz is a training exercise, which is not included in the final score.

W2.L5.Q1: An encryption key can be transmitted from the MME of an operator to the MME of another operator to minimize the number of requests sent to the HSS

• true
• false

Question 2)

W2.L5.Q2: The K_ASME key, which is used to secure exchanges between the UE and the visited network

• is only calculated by the HSS from the random number used for authentication and from the secret key K,
• is calculated by the MME from the random number used for authentication, from the identity of the visited network and from the secret key K,
• is calculated by the HSS from the random number used for authentication, from the identity of the visited network and from the secret key K,
• is calculated by the HSS from the random number used for authentication, from the identity of the visited network, from the identity of the eNodeB and from the secret key K,
• is calculated by the HSS from the random number used for authentication, from the identity of the network used, from the identities of the SGW and PGW and from the secret key K.

Question 3)

W2.L5.Q3: The K_eNB key used to calculate the encryption keys for exchanges between the UE and the eNB

• is a key common to all eNodeBs of a network,
• is a constant secret key allocated by the operator to each eNodeB,
• is a key calculated from the K_ASME key, which changes each time the UE changes for another eNodeB .

Question 4)

W2.L5.Q4: The K_eNB is calculated by the UE but also by

• the eNodeB,
• the HSS,
• the MME,
• the PGW,
• the SGW.

Question 5)

W2.L5.Q5: The K_RRCenc is calculated by the UE but also by

• the eNodeB,
• the HSS,
• the MME,
• the PGW,
• the SGW.

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Quiz W2-L6 Quiz Answer

Question 1)

Note: This quiz is a training exercise, which is not included in the final score.

W2.L6.Q1 : The TMSI (Temporary Mobile Subscriber Identity)

• is temporarily assigned to a subscriber as soon as his subscription starts until he gets the final IMSI from his operator,
• is systematically renewed on each cell change,
• is systematically renewed every hour,
• is renewed depending on the operator's own policy.

Question 2)

W2.L6.Q2 :  The TMSI (Temporary Mobile Subscriber Identity) is assigned by

• the NodeB
• the HSS
• the MME
• the PGW
• the SGW

Question 3)

W2.L6.Q3 : The GUTI (Globally Unique Temporary Mobile Subscriber Identity)

• is calculated from the IMSI and an encryption function
• is built by concatenating the TMSI and the identity of the MME in the network
• is built by concatenating the TMSI, the identity of the MME in the network and the identity of the network (country code and operator code)
• is built by concatenating the TMSI and the identity of the eNodeB, which is built from the network identity (country code and operator code)

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Quiz W2-L7 Answer

Question 1)

Note: This quiz is a training exercise, which is not included in the final score.

W2.L7.Q1: A subscriber turns on his terminal in another country than the one in which he subscribed. The visited network is the network in which he is. The first message sent by the MME to the HSS to request authentication vectors

• contains the country code and the operator code corresponding to the IMSI
• contains the country code and the operator code where the subscriber is most of the time
• contains the country code and the operator code of the visited network

Question 2)

W2.L7.Q2: The GUTI (including the TMSI) is allocated

• before authentication
• after authentication but before encryption is activated
• after authentication and encryption activation

Question 3)

W2.L7.Q3: The IP address is allocated by

• the eNodeB
• the HSS
• the MME
• the PGW
• the SGW