Exam 4

Frame → Contains data (sequence of bits), a header and, a trailer and an address. The header is for when we split our bits into frames, we would have information on our sequence. The trailer is bits for crc’s and parities.

Header → contains the sequence number

Frames per second x Seconds in a movie = number of frames → log2(number of frames) = number of bits reserved for each frame

Address → to send to the right receiver

Encryption → DES, triple DES

• Why do triple DES? →

Samy’s Attack

Passwords →Passwords

Description

• Very common, easy to remember, usually 6 to 16 characters, alphabet often includes letters (both cases), numbers, and some special symbols

• Length: alphabet-size^(length)

• Entropy (randomness) in number of bits: log2(alphabet-size) x Length

• Break-in Strength / 2 attempts

Break-in Prevention

• Can limit time to enter (say 3 seconds)

• Can limit number of attempts

• Stop or Slow down after number of attempts