1. Rsa Encryption History
2. C++ Encryption Example
3. Using Generated Keys For Encryption Rsa C 10
4. Using Generated Keys For Encryption Rsa C 9
5. Rsa Encryption Calculator

• Mar 15, 2012  Demonstration of using OpenSSL to create RSA public/private key pair, sign and encrypt messages using those keys and then decrypt and verify the received messages. Commands used: openssl.
• Method 2: C program to encrypt and decrypt the string using RSA algorithm. RSA algorithm is bit complex than Ceaser Cypher. It involves the use of public and private key, where the public key is known to all and used for encryption. On the other hand, Private key is only used to decrypt the encrypted message.
• Currently I am following this tutorial here: Simple Public Key Encryption with RSA and OpenSSL. I plan to transmit the RSA public key over a network to a seperate client which will encrypt a message with the generated public key. The encrypted message will then be sent back to the server for decryption.

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

Keygen is a function to generate private and public keys. Here ekey is Public key and dkey the private key. Both are passed by reference. Then phival is the Euler totient function (ie., phi(x)). (This was calculated sometime earlier, not shown). I got all these information from wikipedia. End Update 2 Update 3 Code for finding gcd.

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.

2019-03-28 2.1 released. 2019-03-28 3.1 released. 2019-03-28 1.2.1 released.

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

Rsa Encryption History

#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

C++ Encryption Example

3: Decrypting Message

Using Generated Keys For Encryption Rsa C 10

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

Using Generated Keys For Encryption Rsa C 9

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

Here is an implementation of RSA in C program.

Rsa Encryption Calculator

Output