Yohunter789

In this example, you will learn about C program to encrypt and decrypt the string using two algorithms i.e. Caesar Cypher and RSA.

Print Numbers Which are Divisible by 3 and 5 in C. This program will print numbers 1 to 100 which are divisible by 3 and 5. Find more Free Online C Tutorial. So, in summary, array names in a C program are (in most cases) converted to pointers. One exception is when we use the sizeof operator on an array. If a was converted to a pointer in this context, sizeof a would give the size of a pointer and not of the actual array, which would be rather useless, so in that case a means the array itself.

Example: C program to encrypt and decrypt the string using Caesar Cypher Algorithm.

For encryption and decryption, we have used 3 as a key value.

While encrypting the given string, 3 is added to the ASCII value of the characters. Similarly, for decrypting the string, 3 is subtracted from the ASCII value of the characters to print an original string.

Let’s take a look at the program.

Output

#Encryption

#Decryption

Explanation

In the above program, we have used simple logic for encrypting and decrypting a given string by simply adding and subtracting the particular key from ASCII value.

Example: C program to encrypt and decrypt the string using RSA algorithm.

RSA is another method for encrypting and decrypting the message. It involves public key and private key, where the public key is known to all and is used to encrypt the message whereas private key is only used to decrypt the encrypted message.

It has mainly 3 steps:

1: Creating Keys

• Select two large prime numbers x and y
• Compute n = x * y
  where n is the modulus of private and the public key
• Calculate totient function, ø (n) = (x − 1)(y − 1)
• Choose an integer e such that e is coprime to ø(n) and 1 < e < ø(n).
  e is the public key exponent used for encryption
• Now choose d, so that d · e mod ø (n) = 1, i.e., >code>d is the multiplicative inverse of e in mod ø (n)

2: Encrypting Message

Messages are encrypted using the Public key generated and is known to all.

The public key is the function of both e and n i.e. {e,n}.

If M is the message(plain text), then ciphertext

3: Decrypting Message

The private key is the function of both d and n i.e {d,n}.

If C is the encrypted ciphertext, then the plain decrypted text M is

Here is an implementation of RSA in C program.

C Program To Print World Map Online

Output