Question 1. When choosing the components for a forensic workstation there aremany elements to consider including hardware, software, and peripherals. However,
we cannot simply go to the local big box computer store to buy our forensic
workstation.
This week find resources to help one build a forensic workstation. When discussing
your findings make sure to explain why you chose the items you put forth.
Question 2. Not only is conducting an investigation important, but presenting the
evidence is even more important. If that presentation is not understood, then it will be
rejected. Experts are educators for the courts.
Write a two paragraph description of hashing that a non-technical user could
understand and post it for your classmates to critique.
Question 3: Not only is conducting an investigation important, but presenting the
evidence is even more important. If that presentation is not understood, then it will be
rejected. Experts are educators for the courts.
Write a two paragraph description of hashing that a non-technical user could
understand and post it for your classmates to critique.
Question 4: Definition: the modulo operator finds the remainder after the division of
one number by another (sometimes called modulus). Given two positive numbers, A (the
dividend) and p (the divisor), A modulo p (abbreviated as A mod p) is the remainder of
the Euclidean division of A by p. Euclidean division is the process of division of two
integers, which produces a quotient and a remainder smaller than the divisor.
A mod p = C, where A, p, and C are integers, p is the divisor, and C is the remainder. So,
we can write
A = k*p + C; where is k is the quotient, also an integer. We discard k*p
For example, A=13, p = 3. If we divide 13 by 3 the remainder is 1 so C =1
13 = 4*3 + 1 we discard 4*3, the remainder is 1.
One of the ways to calculate mod would be to use the calculator as follows:
Divide A by p then discard the fraction. Save the quotient, an integer, say, k. Then
calculate
C = A – k*p.
For the above example 13/3 is equal to 4.333333…, then k= 4
C = 13 – 4*3 = 1
Excel has a built-in mod function which is written as +mod (A, p)
The function works well when the number of digits is about 14 or less. If the number
changes into a decimal form, then the results will not be right.
Also, some OS’ such as MS-windows, have a scientific calculator that has a built-in mod
function. This function is better than using Excel.
Mac users, please search a calculator for your OS.
The following are some identities you can use
Identity 1 for the sum of two integers:
(A+B) mod (p) = [A mod(p)+ B mod (p)] mod (p)
Example:
Left Hand Side (LHS): (37+41) mod (5) = 78 mod (5) = 3
Right Hand Side: [37 mod (5) +41 mod (5)] mod (5)
Substitute: 37 mod (5) = 2 and 41 mod (5) =1
RHS = [1+2] mod (5) = 3
Thus LHS = RHS
Identity 2 for the product of two integers:
(A*B) mod (p) = [ A mod (p) * B mod (p)] mod (p)
Example:
p=42;
A= 835 = 19*42+37;
B= 577 = 13*42 +31
A*B = 835*577 = 481795 = 11471*42+13
37*31 = 1147 = 27* 42 + 13
A mod p = 835 mod (42) = 37;
B mod p = 577 mod (42) = 31
LHS : (A*B) mod (p) = (835*577) mod (42) = 481795 mod (42) = 13
RHS: [835 mod (42) * 577 mod (42) ] mod (42)
(37*31) mod (42) = 1147 mod (42) = 13
LHS=RHS
The above identity can be extended to calculate A^n mod(p)
Suppose we need to calculate 57^ 11 mod (67);
LHS: Using Windows calculator 57^11 mod (67) = 38
now 57^11 would be a big number. So, we break the power 11 into say 2*5+1; then first
calculate 57^2 mod (67) = 33
Now we reduced 57 ^ 11 mod (67)
to calculate [(57^2 mod (67)] ^5 mod (67) * 57 mod (67)] mod (67)
Using Windows calculator: 57^2 mod (67) = 33
RHS: [(57^2 mod (67)] ^5mod (67) * 57 mod (67)] mod (67)
= [33^5 mod (67) * 57] mod (67) {using Window’ calculator}
= [23 *57] mod (67)
= 1311 mod (67);
=38 :
For your understanding, you may try different combinations for 11= 3*3+2; if you use
excel, avoid getting numbers in e format. If you get in e format, then the calculation
would be wrong. Use Windows calculator or Mac equivalent