DES Permutation Choice

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Section 10

Question 3 

 

Suppose we have the following 64-bit block: {0, 1, 1, 1, 0, 1, 1, 1, 1, 0, 1, 1, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 1, 0, 1, 1, 0, 1, 1, 0, 1, 1, 1, 0, 1, 0, 1, 1, 1, 0, 0, 1, 1, 1, 0, 0, 0, 0, 1}

What is the output of PC-1?

Write the numbers separated with commas, leave one space after every comma. Do NOT use "{" or "}" in the answer.

Question 4

 

Suppose we have the following 64-bit block: {0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 1, 0, 1, 0, 0, 0, 0, 1, 1, 1, 0, 0, 1, 1, 0, 1, 0, 0, 1, 0, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 1, 1, 0, 1, 1, 0, 0, 1}

What is the output of PC-1?

Write the numbers separated with commas, leave one space after every comma. Do NOT use "{" or "}" in the answer.

Question 5

 

Suppose we have the following 56-bit block (C1,D1): {1, 1, 0, 1, 1, 1, 0, 0, 0, 1, 0, 1, 1, 1, 1, 1, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 1, 1, 1, 1, 0, 0, 0, 1, 1, 1, 1, 0, 0, 1, 1, 1, 0, 0, 0, 1, 0, 1, 1, 0, 0, 0, 1, 1, 1, 1}

What is the output of PC-2?

Write the numbers separated with commas, leave one space after every comma. Do NOT use "{" or "}" in the answer.

Question 6

 

Suppose we have the following 56-bit block (C1,D1): {0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 0, 1, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 0, 1, 0, 0, 1, 0, 1, 0, 1, 0, 0, 0, 0, 0}

What is the output of PC-2?

Write the numbers separated with commas, leave one space after every comma. Do NOT use "{" or "}" in the answer.

Section 11

Question 2

 

Suppose you have the following 28-bit block: {1, 0, 0, 0, 1, 1, 1, 1, 0, 1, 1, 0, 1, 1, 1, 1, 1, 0, 0, 1, 1, 1, 1, 0, 0, 1, 0, 1}.

Apply LS3 to the given 28-bit block.

Write the numbers separated with commas, leave one space after every comma. Do NOT use "{" or "}" in the answer.

Question 3

 

Suppose you have the following 56-bit block: {0, 1, 1, 1, 1, 0, 0, 1, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0, 1, 0, 1, 1, 0, 0, 0, 1, 0, 0, 1, 0, 0, 1, 1, 0, 1, 1, 1, 0, 0, 0, 1, 1, 0, 0, 1, 0, 0, 0, 1, 1, 0, 1, 0, 0, 1, 0}.

Apply Transform 1 to the given 56-bit block to obtain the first sub-key.

Write the numbers separated with commas, leave one space after every comma. Do NOT use "{" or "}" in the answer.

Question 4

 

Suppose you have the following 56-bit block: {1, 0, 0, 0, 0, 1, 1, 1, 0, 1, 1, 1, 0, 1, 1, 0, 0, 1, 0, 0, 1, 1, 1, 1, 0, 1, 1, 0, 0, 1, 0, 0, 1, 0, 1, 0, 1, 1, 1, 0, 1, 0, 0, 0, 1, 0, 0, 0, 1, 1, 0, 0, 0, 1, 0, 0}.

Apply Transform 5 to the given 56-bit block to obtain the fifth sub-key.

Write the numbers separated with commas, leave one space after every comma. Do NOT use "{" or "}" in the answer.

Question 5

 

Suppose you have the following 56-bit block: {1, 0, 0, 0, 1, 1, 0, 1, 1, 0, 1, 1, 0, 0, 0, 0, 1, 0, 0, 1, 1, 0, 1, 1, 0, 1, 0, 1, 1, 1, 1, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 1, 1, 0, 1, 1, 0, 1, 0, 1, 0, 1}.

Apply Transform 9 to the given 56-bit block to obtain the ninth sub-key.

Write the numbers separated with commas, leave one space after every comma. Do NOT use "{" or "}" in the answer.

Question 6

 

Suppose that the key for DES is the following 64-bit block: {1, 1, 0, 0, 0, 0, 1, 1, 1, 1, 1, 0, 0, 1, 1, 0, 0, 1, 0, 1, 0, 0, 1, 1, 1, 1, 0, 1, 0, 0, 0, 1, 1, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 1, 0, 0, 0, 1, 1, 0, 1, 1, 0, 0, 1, 0, 1}.

What is the first sub-key?

Write the numbers separated with commas, leave one space after every comma. Do NOT use "{" or "}" in the answer.

 Section 11 – HW

Question 1:

If you want to decrypt using DES, you should...

Options:

Apply DES the other way around.

Reverse the rounds.

Reverse the key schedule.

Reverse the key.

Reverse the order of the plaintext.

Reverse the order of the ciphertext.

Question 2 

If you want to reverse the key schedule, what Transform you need to apply first?

Question 2 options:

Transform 1

Transform 16

Transform 56

Transform 64

Question 3 

Select the statements that are true.

Question 3 options:

DES is secure for cryptographic applications.

DES was "crack" in 1998.

The key space of DES is big enough.

It is relatively cheap, for the average american, to "crack" DES.

Triple DES encrypts the plain text with the same key, three times.

Triple DES encrypts the plain text with three distinct keys, three times.

Question 4

Select the statements that are true.

Question 4 options:

Triple DES can replace DES

DES replaces Triple DES

AES replaces DES.

DES replaces AES

The key space of triple DES and DES are the same.

The key space of AES is larger than DES

Section 12

Question 1 

The objects of the class "KeyGenerator" produce keys for...

Question 1 options:

All ciphers implemented in Java.

DES only.

Symmetric ciphers.

DES, Triple DES, and AES only.

Symmetric ciphers that are implemented in Java

The objects of this class do not produces any keys at all.

Question 2

If you want to create an object of the class "KeyGenerator" called "greatKey", that generated DES keys, what line of code do you type?

Question 2 options:

SecretKey greatKey = KeyGenerator.generateKey("DES");

KeyGenerator(greatKey)= KeyGenerator getInstance("DES");

greatKey KeyGenerator  = getInstance.KeyGenerator ("DES");

greatKey.KeyGenerator  = KeyGenerator getInstance("DES");

KeyGenerator greatKey = KeyGenerator.getInstance("DES");

SecretKey("DES") greatKey = KeyGenerator.generateKey("UTF*");

Question 5 

Select the statements that are true.

Question 5 options:

To be able to use a DES key with an object of the class "KeyGenerator" you need to transform it into a byte array first

".getEncoded" transforms a DES key into a byte array

The number of bytes in a DES key is 8.

The number of bytes in a DES key is 64.