1
GATE CSE 2019
Numerical
+2
-0.67
In an RSA cryptosystem, the value of the public modulus parameter n is 3007. If it is also known that $$\varphi$$(n) = 2880, where $$\varphi$$() denotes Euler's Totient Function, then the prime factor of n which is greater than 50 is ______.
2
GATE CSE 2016 Set 1
MCQ (Single Correct Answer)
+2
-0.6
Consider that B wants to send a message m that is digitally signed to A. Let the pair of private and public keys for A and B be denoted by $$K_x^ -$$ and $$K_x^ +$$ for x = A, B, respectively. Let Kx(m) represent the operation of encrypting m with a key Kx and H(m) represent the message digest. Which one of the following indicates the CORRECT way of sending the message m along with the digital signature to A?
A
$$\left\{ {m,K_B^ + \left( {H\left( m \right)} \right)} \right\}$$
B
$$\left\{ {m,K_B^ - \left( {H\left( m \right)} \right)} \right\}$$
C
$$\left\{ {m,K_A^ - \left( {H\left( m \right)} \right)} \right\}$$
D
$$\left\{ {m,K_A^ + (m)} \right\}$$
3
GATE CSE 2009
MCQ (Single Correct Answer)
+2
-0.6
In the RSA public key cryptosystem, the private and public keys are (e, n) and (d, n) respectively, where n = p$$\times$$q and p and q are large primes. Besides, n is public and p and q are private. Let M be an integer such that 0 < M < n and f(n) = (p - 1)(q - 1). Now consider the following equations.

I. M'= Me mod n
M = (M')d mod n

II. ed ≡ 1 mod n

III. ed ≡ 1 mod $$\phi$$(n)

IV. M'= Me mod $$\phi$$(n)
M = (M')d mod $$\phi$$(n)

Which of the above equations correctly represent RSA cryptosystem?
A
I and II
B
I and III
C
II and IV
D
III and IV
4
GATE CSE 2008
MCQ (Single Correct Answer)
+2
-0.6
The total number of keys required for a set of n individuals to be able to communicate with each other using secret key and public key crypto-systems, respectively are:
A
n(n - 1) and 2n
B
2n and $${{N(N - 1)} \over 2}$$
C
$${{N(N - 1)} \over 2}$$ and 2n
D
$${{N(N - 1)} \over 2}$$ and n
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