3.3

What types of key or keys are used in symmetric cryptography?

A shared private key

You want to encrypt data on a removable storage device. Which encryption method would you choose to use the strongest method possible?

AES

Which of the following algorithms are used in symmetric encryption? (Select Three.)

AES Blowfish 3DES

Which of the following are true concerning the Advanced Encryption Standard (AES) symmetric block cipher? (Select two.)

AES uses a variable-length block and key length (128-, 192-, or 256-bit keys). AES uses the Rijndael block cipher.

Which of the following symmetric block ciphers does not use a variable block length?

IDEA (International Data Encryption Algorithm)

Which of the following is NOT true concerning symmetric key cryptography?

Key management is easy when implemented on a large scale.

How many keys are used with symmetric key cryptography?

One

Which of the following can be classified as a "stream cipher"?

RC4

Which version of Rivest Cipher is a block cipher that supports variable bit length keys and variable bit block sizes?

RC5

Match the symmetric key distribution mechanism on the left with the appropriate description on the right.

The sender's key is sent to a recipient using a Diffie-Hellman key exchange -- *In-Band distribution* The senders key is copied to a USB drive and handed to the recipient. -- *Out-of-band distribution* The senders key is sent to the recipient using public-key cryptography -- *In-band distribution* The senders key is burned to a CD and handed to the recipient. -- *Out-of-band distribution*

Which of the following are true of Triple DES (3DES)? (Select two.)

Uses a 168-bit key Is used in IPSec

Which of the following is considered an out-of-band distribution method for private-key encryption?

Using a private fiber network Using a key distribution algorithm *Copying the key to a USB drive* Sending a secured email

Bob Jones used the RC5 cryptosystem to encrypt a sensitive and confidential file on his notebook. He used 32 bit blocks, a 64 bit key, and he only used the selected key once. He moved the key onto a USB hard drive which was stored in a safe deposit box. Bob's notebook was stolen. Within a few days Bob discovered the contents of his encrypted file on the Internet. What is the primary reason why Bob's file was opened so quickly?

*Weak Key* The decryption key was used to decrypt the files A birthday attack was used Too small of a block size

Which of the following encryption mechanism offers the least security because of weak keys?

DES

You are concerned about the strength of your cryptographic keys, so you implement a system that does the following: The initial key is fed into the input of the bcrypt utility on a Linux workstation the bcrypt utility produces an enhanced key that is 128 bits long .... Which kind of encryption mechanism was used in this scenario?

DHE Perfect forward secrecy *Key stretching* Ephemeral keys