Question

When configuring a web server, you notice the following Cipher Suites are available to use for TLS-based connections:

• Cipher Suite 1: TLS_ECDHE_RSA_AES_128_CBC_SHA256

• Cipher Suite 2: TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA

Answer the following questions regarding these two cipher suites. (10 marks total)

i. What is the key exchange (Kx) algorithm in Cipher Suite 2? (1 mark)

ii. What is the authentication (Au) algorithm in Cipher Suite 1? (1 mark)

iii. What is the key size of the symmetric cipher in Cipher Suite 1? (1 mark)

iv. What is the effective key size of the symmetric cipher in Cipher Suite 2? (1 mark)

v. What is the message integrity algorithm in Cipher Suite 2? (1 mark)

vi. You are working on a new web store for a client and need to assist the server administrator to configure the web server security settings. State which of these two Cipher Suites would you prefer to use in this context and suggest two reasons why.

Answer 1

Question 1) What is the key exchange (Kx) algorithm in Cipher Suite 2?

Answer: As from the cipher suite TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA, you can see the last three letters are SHA depicting that the key exchange (Kx) algorithm is Secure Hash Algorithm 1 (SHA).

Question 2) What is the authentication (Au) algorithm in Cipher Suite 1?

Answer: Rivest Shamir Adleman algorithm (RSA)

Question 3) What is the key size of the symmetric cipher in Cipher Suite 1?

Answer: 128bit.

Question 4) What is the effective key size of the symmetric cipher in Cipher Suite 2?

Answer: 168 bits

Question 5) What is the message integrity algorithm in Cipher Suite 2?

Answer: MAC algorithm

Question 6) You are working on a new web store for a client and need to assist the server administrator to configure the web server security settings. State which of these two Cipher Suites would you prefer to use in this context and suggest two reasons why.

Answer: I will prefer to use TLS_ECDHE_RSA_AES_128_CBC_SHA256 as it is more secure, it has better authentication algorithm and key exchange algorithm is more advance Elliptic Curve Diffie-Hellman Ephemeral (ECDHE).