ISRO Scientist/Engineer CS Solved Papers

Elliptic key cryptography is based on which of the following premises

Choose all the correct statements for the following code snippet

void func(char *buf1, char *buf2, unsigned int len1, unsigned int len2){
    char temp[256];
    if (len1 + len2 > 256) { return -1; } // length check
    memcpy(temp, buf1, len1); // cat buffers
    memcpy(temp + len1, buf2, len2);
    do_something(temp); // do stuff
}

Suppose UID is the unique integer User ID for a user, then choose all the correct statements with respect to the processes:
I. Processes run by the same UID have different permission.
II. Processes run by the same UID have same permission.
III. Processes can access any files that the UID has access to.
IV. Processes started by root can reduce their privileges by changing their UID to a less privileged UID.

What is the size of the key space in the substitution cipher assuming 26 letters?

For a one time pad (OTP) cipher $(E, D)$ over $(K, M, C)$, given a message $m \in \mathcal{M}$ and $c \in C$ can the OTP key be computed from $m$ and $c$? $(K, M, C)$ are key, message and ciphered text space respectively.

Which of the following statements is or are true if a cipher $(E, D)$ over $(K, M, C)$ has perfect secrecy? $(K, M, C)$ are key, message and ciphered text space respectively.
I. Most powerful adversarial learners can learn about plain text message from the ciphered text.
II. Given a ciphered text, one cannot tell if the message was $m_0$ or $m_1$ where $\forall m_0, m_1 \in \mathcal{M}$
III. A cipher has perfect secrecy if $\forall m_0, m_1 \in \mathcal{M}$ having $|m_0| = |m_1|$ and $\forall c \in C,\; \Pr[E(k, m_0) = c] = \Pr[E(k, m_1) = c]$ where $k \in \mathcal{K}$.
IV. A cipher has perfect secrecy if $\forall m_0, m_1 \in \mathcal{M}$ having $|m_0| = |m_1|$ and $\forall c \in C,\; \Pr[E(k, m_0) = c] \ne \Pr[E(k, m_1) = c]$ where $k \in \mathcal{K}$.

Let $N$ be an odd integer, the modular inverse of 2 in $\mathbb{Z}_N$ is

HTTP connections are secured using which one of the following protocol?

In public key encryption, if Alice wants to send an encrypted message to Bob then,

Which of the following statements are correct?
I. It is not known if computing $\Phi(N)$ is harder then computing the prime factors of $N$, where $N$ is an RSA modulus.
II. Finding prime factors of $N$ and computing $\Phi(N)$ are equivalent, where $N$ is RSA modulus.

Define $h(x) = g^{x^2} \pmod p$ where $p$ is a large prime and $g$ is deterministic generator $\pmod p$. The function $h$ is collision-resistant.

Which of the following statement is/are correct?
I. If $h(\cdot)$ is collision-resistant, then $h(h(\cdot))$ is also collision-resistant.
II. If it is feasible to find a collision $x, x'$ under $h(h(\cdot))$ then $x, x'$ is also a collision under $h$.
III. If it is feasible to find a collision $x, x'$ under $h(h(\cdot))$, then $x, x'$ does not necessarily have collision under $h$.
IV. If $h(\cdot)$ is collision-resistant, then $h(h(\cdot))$ is not collision-resistant.

Suppose a login form from your company uses following implementation for login authentication:

$login = $_POST['login'];
$pass = $_POST['password'];
$sql = "SELECT id FROM users WHERE username = '$login' AND password = '$pass'";
$rs = $db->executeQuery($sql);
if ($rs->count > 0) {
    // success
}

Suppose a system developer of your company website has implemented an executable viewTop100 using the following implementation:

int main(int argc, char **argv) {
    char *cmd = malloc(strlen(argv[1]) + 100);
    strcpy(cmd, "head -n 100 ");
    strcat(cmd, argv[1]);
    system(cmd);
}

The subnet mask for a particular network is 255.255.31.0 Which of the following pairs of IP addresses could belong to this network?

In networking, UTP stands for

The address resolution protocol (ARP) is used for

Which of the following is a MAC address?

What is the primary purpose of a VLAN?

SHA-1 is a

Advanced Encryption Standard (AES) is based on

The primary purpose of an operating system is

Which is the correct definition of a valid process transition in an operating system?

The correct matching for the following pairs is
(A) Disk check
(B) Batch processing
(C) Time sharing
(D) Stack operation

(1) Round robin
(2) Scan
(3) LIFO
(4) FIFO

A page fault