Practical 1: Design and Implement Caesar Cipher cryptographic
algorithm by considering letter [A….Z] and digits.
#include <stdio.h>
#include <string.h>
#include <ctype.h>
int main()
char plaintext[100];
char ciphertext[100];
int key, i, length;
printf("Enter a plain text: ");
scanf("%s", plaintext);
printf("Enter key: ");
scanf("%d", &key);
length = strlen(plaintext);
for(i = 0; i < length; i++)
char c = toupper(plaintext[i]);
if(c >= 'A' && c <= 'Z')
ciphertext[i] = (c - 'A' + key) % 26 + 'A';
else if(c >= '0' && c <= '9')
{
ciphertext[i] = (c - '0' + key) % 10 + '0';
else
ciphertext[i] = c;
ciphertext[i] = '\0';
printf("Plaintext: %s\n", plaintext);
printf("Ciphertext: %s\n", ciphertext);
return 0;
Apply Brute Force Attack on Caesar Cipher Algorithm to reveal
#include <stdio.h>
#include <string.h>
int main() {
char ciphertext[100];
printf("Enter Ciphertext: ");
scanf("%s", ciphertext);
for (int key = 0; key < 26; key++) {
printf("\nKey: %d, Plaintext: ", key);
for (int i = 0; ciphertext[i]; i++) {
char c = ciphertext[i];
if (c >= 'A' && c <= 'Z')
c = (c - 'A' - key + 26) % 26 + 'A';
else if (c >= 'a' && c <= 'z')
c = (c - 'a' - key + 26) % 26 + 'a';
else if (c >= '0' && c <= '9')
c = (c - '0' - key + 10) % 10 + '0';
putchar(c);
return 0;
2.Simple columnar transposition
#include <stdio.h>
#include <string.h>
int main() {
char msg[] = "HELLOWORLD";
int key = 3;
int len = strlen(msg);
char enc[100], dec[100];
// Encryption
int k = 0;
for (int col = 0; col < key; col++)
for (int i = col; i < len; i += key)
enc[k++] = msg[i];
enc[k] = '\0';
printf("Original: %s\n", msg);
printf("Encrypted: %s\n", enc);
// Decryption
int rows = (len + key - 1) / key;
int idx = 0;
for (int col = 0; col < key; col++)
for (int i = col; i < len; i += key)
dec[i] = enc[idx++];
dec[len] = '\0';
printf("Decrypted: %s\n", dec);
return 0;
}
3. Substitution and transposition
#include <stdio.h>
#include <string.h>
Int main() {
Char msg[] = “HELLO”, enc[100], dec[100];
Int key = 3, len = strlen(msg), k = 0;
// Encrypt (Substitution + Transposition)
For (int col = 0; col < key; col++)
For (int i = col; i < len; i += key)
Enc[k++] = msg[i] + 1;
Enc[k] = ‘\0’;
Printf(“Encrypted: %s\n”, enc);
// Decrypt (Reverse Transposition + Substitution)
K = 0;
For (int col = 0; col < key; col++)
For (int i = col; i < len; i += key)
Dec[i] = enc[k++] – 1;
Dec[len] = ‘\0’;
Printf(“Decrypted: %s\n”, dec);
Return 0;
}
4RSA
#include <stdio.h>
Int main() {
Int p, q, e, d, n, phi, msg, enc = 1, dec = 1;
Printf(“Enter two primes p and q: “);
Scanf(“%d %d”, &p, &q);
N = p * q;
Phi = (p – 1) * (q – 1);
Printf(“Enter encryption key e (e.g., 7): “);
Scanf(“%d”, &e);
// Find d such that (d * e) % phi == 1
For (d = 1; d < phi; d++) {
If ((d * e) % phi == 1)
Break;
}
Printf(“Enter message (as number): “);
Scanf(“%d”, &msg);
// Encryption: c = (msg^e) % n
For (int i = 0; i < e; i++)
Enc = (enc * msg) % n;
// Decryption: m = (enc^d) % n
For (int i = 0; i < d; i++)
Dec = (dec * enc) % n;
Printf(“Encrypted message: %d\n”, enc);
Printf(“Decrypted message: %d\n”, dec);
Return 0;
}
Sure! Here's a simple definition and example for each of the following: MD5, SHA1, WHOIS,
DIG, TRACERT, and NSLOOKUP.
🔐 1. MD5 (Message Digest 5)
Definition:
MD5 is a cryptographic hash function that takes input data and produces a fixed 128-bit (32-
character) hash value. It is commonly used to verify data integrity.
Example:
$ echo "hello" | md5sum
5d41402abc4b2a76b9719d911017c592
🔐 2. SHA1 (Secure Hash Algorithm 1)
Definition:
SHA1 is a hash function that produces a 160-bit (40-character) hash. It was used for data
integrity and digital signatures but is now considered insecure.
Example:
$ echo "hello" | sha1sum
aaf4c61ddcc5e8a2dabede0f3b482cd9aea9434d
🌐 3. WHOIS
Definition:
WHOIS is a command-line tool or protocol used to find information about a domain name, such
as the owner's name, registrar, creation/expiry date, etc.
Example:
$ whois google.com
Output (shortened):
Domain Name: GOOGLE.COM
Registrar: MarkMonitor Inc.
Creation Date: 1997-09-15
Expiry Date: 2028-09-14
🌍 4. DIG (Domain Information Groper)
Definition:
DIG is used to query DNS servers for information about a domain like IP address, mail servers,
etc. It helps troubleshoot DNS issues.
Example:
$ dig google.com
Output (shortened):
;; ANSWER SECTION:
google.com. 299 IN A 142.250.77.206
5. TRACERT (Windows) / traceroute (Linux)
Definition:
Tracert shows the path (hops) that packets take from your computer to a destination server. Helps
in finding where a network problem occurs.
Example:
$ tracert google.com
Output (shortened):
1 192.168.1.1
2 10.0.0.1
3 142.250.77.206 (google.com)
🔎 6. NSLOOKUP
Definition:
NSLOOKUP is a command-line tool used to find the IP address of a domain name or get DNS
information.
Example:
$ nslookup google.com
Output:
Name: google.com
Address: 142.250.77.206
Let me know if you want a printable table or PDF for this!
Here are simple definitions with examples for the terms you mentioned, commonly used in
networking and cybersecurity:
1. ICMP (Internet Control Message Protocol)
Definition:
ICMP is used by network devices to send error messages or status information. It’s the protocol
used by the ping command.
Example:
$ ping google.com
➡️ICMP sends echo request/reply to check if a host is reachable.
🔗 2. TCP (Transmission Control Protocol)
Definition:
TCP is a connection-oriented protocol that ensures reliable communication between devices over
the internet.
Example:
Used by protocols like HTTP, FTP, SMTP, etc.
Port 80 (HTTP), Port 443 (HTTPS)
➡️Guarantees data delivery (retransmits if lost).
🌐 3. HTTP (HyperText Transfer Protocol)
Definition:
HTTP is the protocol used to load webpages over the internet. It is not encrypted.
Example:
http://example.com
➡️Data sent in plain text. Not secure.
🔒 4. HTTPS (HTTP Secure)
Definition:
HTTPS is HTTP with encryption (via SSL/TLS), providing secure communication between
browser and server.
Example:
https://example.com
➡️Secure, data is encrypted in transit.
⚠️5. XSS (Cross-Site Scripting)
Definition:
XSS is a security vulnerability where an attacker injects malicious scripts into a trusted website,
which run in the user’s browser.
Example:
<script>alert('Hacked!');</script>
➡️If injected into a comment box, it can steal cookies or session data.
💥 6. Buffer Overflow
Definition:
A buffer overflow happens when a program writes more data to a memory block (buffer) than it
can hold, potentially allowing code execution.
Example:
Supplying too much input to:
char name[10];
gets(name); // vulnerable to overflow
➡️Can crash the program or let attackers run their own code.
7. SQL Injection
Definition:
SQL Injection is a web attack where malicious SQL code is injected into input fields to
manipulate the database.
Example:
' OR '1'='1
➡️Input like this can bypass login systems or leak data.
💉 8. Injector
Definition:
"Injector" is a general term for any tool or method that injects code or data into a system or
application, often used for exploits (like SQLi, XSS, DLL injection, etc.).
Example:
SQL Injector tool
DLL Injector for modifying running programs
➡️Injectors are commonly used in hacking or penetration testing.
Let me know if you want visuals, PDF notes, or a comparison table!
Here are simple definitions and examples for SMTP, ARP, and Wireshark — commonly used
in networking:
📤 1. SMTP (Simple Mail Transfer Protocol)
Definition:
SMTP is the protocol used to send emails from a client to a server or between email servers.
Use Case:
Sending an email from Gmail to Yahoo or Outlook.
Port Numbers:
Port 25 (default)
Port 587 (secure with TLS)
Port 465 (SSL)
Example:
Email client → SMTP → Mail Server
Command-Line Example (simplified):
telnet smtp.gmail.com 587
🔁 2. ARP (Address Resolution Protocol)
Definition:
ARP maps a known IP address to its MAC address in a local network.
Use Case:
When your computer knows the IP address (like 192.168.1.1) but needs the MAC address to
send data.
Example:
$ arp -a
Output:
192.168.1.1 00-14-22-01-23-45 dynamic
➡️Your computer asks: “Who has 192.168.1.1?” and the router replies with its MAC.
3. Wireshark
Definition:
Wireshark is a network protocol analyzer used to capture and inspect packets of data flowing
through a network in real time.
Use Case:
Debugging network problems
Viewing packet-level details of TCP, HTTP, DNS, etc.
Detecting suspicious activity or attacks
Example:
Open Wireshark
Start capture on Wi-Fi or Ethernet
Filter: http, icmp, tcp.port == 80
Screenshot Output (typical):
No. Time Source Destination Protocol Info
1 0.000 192.168.1.2 8.8.8.8 DNS Standard query A
google.com
✅ Summary Table:
Term Purpose Type Example Use
SMTP Sends emails Protocol Gmail sending an email
Term Purpose Type Example Use
Network
ARP IP ↔ MAC address mapping Sending data in LAN
tool
Wiresha Captures and analyzes Tool/ Troubleshooting or
rk network packets software network analysis
Let me know if you want a mini project or practical demo using these!
