UML 91.561 Computer & Network Security I
HomeWork 1
Name – Nrupen Abnave
Student ID -01382247
1.1
(a)
Describe the major structure of a TCP packet and explain the main functions of the TCP headers.
-
TCP is a transport layer protocol and is connection oriented.
Its reliable connection, has error checking and flow control.
TCP Headers: 32bits
Source and Destination Ports – Each 16bit number. Indicate which application is using the communicating stream. Used by most common services – FTP(21), SSH(22), SMTP(25), HTTP(80), DNS(53), POP(110).
Sequence and Acknowledgment- Keep segments in order and data is delivered. As large chunk of data is broken down into segments and transmitted, they may not be received in the same order …show more content…
Substitution is the simplest method that replaces a character in the plain text with a fixed different character in the cipher text. This method preserves the letter frequency in the plain text and so one can search for the plain text from a given cipher text by comparing the frequency of each letter against the known common frequency in the underlying language.
1.7
Let h be a hash function and r a reduction function. Let T be a rainbow table of k rows for D under h and r, where the jth row is (wj1,h(wjn j ) for 1 ≤ j ≤ k. Let Q0 = h(w) and Q1 = (h ◦ r)i(Q0), where i ≥ 0. Suppose Q1 = h(wjn j ) for some 1 ≤ j ≤ k and i ≤ j.
(a)
- w will appear in the jth chain of h(wjni)=Q0, wjni =(roh)i (wj1)
1.7
(b)
- w wil not appear in the jth chain of
No i such that , Q= h(wjni ).
1.7
(c)
Collisions can be avoided , using different reduction functions to produce a password chain. That’s why this technique helps in increasing the likelihood that w appears in the jth chain of wj1 , … , wjnj
1.10
(a)ShieldsUP – Scanning for loopholes
1.10
(b)
HomeWork 1
Name – Nrupen Abnave
Student ID -01382247
1.1
(a)
Describe the major structure of a TCP packet and explain the main functions of the TCP headers.
-
TCP is a transport layer protocol and is connection oriented.
Its reliable connection, has error checking and flow control.
TCP Headers: 32bits
Source and Destination Ports – Each 16bit number. Indicate which application is using the communicating stream. Used by most common services – FTP(21), SSH(22), SMTP(25), HTTP(80), DNS(53), POP(110).
Sequence and Acknowledgment- Keep segments in order and data is delivered. As large chunk of data is broken down into segments and transmitted, they may not be received in the same order …show more content…
Substitution is the simplest method that replaces a character in the plain text with a fixed different character in the cipher text. This method preserves the letter frequency in the plain text and so one can search for the plain text from a given cipher text by comparing the frequency of each letter against the known common frequency in the underlying language.
1.7
Let h be a hash function and r a reduction function. Let T be a rainbow table of k rows for D under h and r, where the jth row is (wj1,h(wjn j ) for 1 ≤ j ≤ k. Let Q0 = h(w) and Q1 = (h ◦ r)i(Q0), where i ≥ 0. Suppose Q1 = h(wjn j ) for some 1 ≤ j ≤ k and i ≤ j.
(a)
- w will appear in the jth chain of h(wjni)=Q0, wjni =(roh)i (wj1)
1.7
(b)
- w wil not appear in the jth chain of
No i such that , Q= h(wjni ).
1.7
(c)
Collisions can be avoided , using different reduction functions to produce a password chain. That’s why this technique helps in increasing the likelihood that w appears in the jth chain of wj1 , … , wjnj
1.10
(a)ShieldsUP – Scanning for loopholes
1.10
(b)