Method 1: C program to encrypt and decrypt the string using Caesar Cypher Algorithm. We have used a simple method of adding and subtracting a key value for encryption and decryption. For encrypting a string, key-value ‘2’ is added to the ASCII value of the characters in the string.
-->Creating and managing keys is an important part of the cryptographic process. Symmetric algorithms require the creation of a key and an initialization vector (IV). The key must be kept secret from anyone who should not decrypt your data. The IV does not have to be secret, but should be changed for each session. Asymmetric algorithms require the creation of a public key and a private key. The public key can be made public to anyone, while the private key must known only by the party who will decrypt the data encrypted with the public key. This section describes how to generate and manage keys for both symmetric and asymmetric algorithms.
The symmetric encryption classes supplied by the .NET Framework require a key and a new initialization vector (IV) to encrypt and decrypt data. Whenever you create a new instance of one of the managed symmetric cryptographic classes using the parameterless constructor, a new key and IV are automatically created. Anyone that you allow to decrypt your data must possess the same key and IV and use the same algorithm. Generally, a new key and IV should be created for every session, and neither the key nor IV should be stored for use in a later session.
To communicate a symmetric key and IV to a remote party, you would usually encrypt the symmetric key by using asymmetric encryption. Sending the key across an insecure network without encrypting it is unsafe, because anyone who intercepts the key and IV can then decrypt your data. For more information about exchanging data by using encryption, see Creating a Cryptographic Scheme.
The following example shows the creation of a new instance of the TripleDESCryptoServiceProvider class that implements the TripleDES algorithm.
When the previous code is executed, a new key and IV are generated and placed in the Key and IV properties, respectively.
Sometimes you might need to generate multiple keys. In this situation, you can create a new instance of a class that implements a symmetric algorithm and then create a new key and IV by calling the GenerateKey and GenerateIV methods. The following code example illustrates how to create new keys and IVs after a new instance of the symmetric cryptographic class has been made.
When the previous code is executed, a key and IV are generated when the new instance of TripleDESCryptoServiceProvider is made. Another key and IV are created when the GenerateKey and GenerateIV methods are called.
The .NET Framework provides the RSACryptoServiceProvider and DSACryptoServiceProvider classes for asymmetric encryption. These classes create a public/private key pair when you use the parameterless constructor to create a new instance. Asymmetric keys can be either stored for use in multiple sessions or generated for one session only. While the public key can be made generally available, the private key should be closely guarded.
A public/private key pair is generated whenever a new instance of an asymmetric algorithm class is created. After a new instance of the class is created, the key information can be extracted using one of two methods:
The ToXmlString method, which returns an XML representation of the key information.
The ExportParameters method, which returns an RSAParameters structure that holds the key information.
Both methods accept a Boolean value that indicates whether to return only the public key information or to return both the public-key and the private-key information. An RSACryptoServiceProvider class can be initialized to the value of an RSAParameters structure by using the ImportParameters method.
Asymmetric private keys should never be stored verbatim or in plain text on the local computer. If you need to store a private key, you should use a key container. For more on how to store a private key in a key container, see How to: Store Asymmetric Keys in a Key Container.
The following code example creates a new instance of the RSACryptoServiceProvider class, creating a public/private key pair, and saves the public key information to an RSAParameters structure.
In this example, you will learn simpleC++ program to encrypt and decrypt the string using two different encryption algorithms i.e. Caesar Cypher and RSA.
| Encryption/Decryption using Caesar Cypher Algorithm |
| Encryption/Decryption using RSA Algorithm |
Encryption basically means encoding a particular message or information so that it can’t be read by other person and decryption is the process of decoding that message to make it readable.
We have used a simple method of adding and subtracting a key value for encryption and decryption.
For encrypting a string, key-value ‘2’ is added to the ASCII value of the characters in the string.
Similarly, for decrypting a string, key-value ‘2’ is subtracted from the ASCII value of the characters.
Let’s take a deeper look at the source code:
Output
#Encrypting
#Decrypting
Explanation
In the above program, if you change the value of key then the encrypted value will be different.
If the user enters other value than 1 or 2 it will show Invalid Input.
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.
1: Creating Keys
n = x * yn is the modulus of private and the public keyø (n) = (x − 1)(y − 1)e such that e is coprime to ø(n) and 1 < e < ø(n).e is the public key exponent used for encryptiond, so that d · e mod ø (n) = 1, i.e., >code>d is the multiplicative inverse of e in mod ø (n)2: Encrypting MessageDownload game plants vs zombie 2 mega mod apk.
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
You might be wondering how to write a source code for this program.
So let’s look at the program.
Output
This is all about encryption and decryption program in C++.