This example shows that how to encrypt or decrypt a string or number.
For this we will use a class and one c# page.
Encrypt Decrypt page will be as :-
using System;
using System.Collections.Generic;
using System.Security.Cryptography;
using System.IO;
using System.Text;
namespace EncryptionSample
{
public class EncryptionDecryption
{
#region class Variables
/// <summary>
/// Class level constants
/// </summary>
/// <author> </author>
/// <CreatedDate> </CreatedDate>
// Passphrase from which a pseudo-random password will be derived. can be any string
private const string passPhrase = "Pas5pr@se";
// Salt value used along with passphrase to generate password. can be any string
private const string saltValue = "s@1tValue";
// Hash algorithm used to generate password. Allowed values are: "MD5" and
// "SHA1". SHA1 hashes are a bit slower, but more secure than MD5 hashes.
private const string hashAlgorithm = "SHA1";
// Initialization vector (or IV). This value is required to encrypt the
// first block of plaintext data. For RijndaelManaged class IV must be
// exactly 16 ASCII characters long.
private const string initVector = "@1B2c3D4e5F6g7H8";
// Number of iterations used to generate password. One or two iterations
// should be enough. can be any number
private const int passwordIterations = 2;
// Size of encryption key in bits. Allowed values are: 128, 192, and 256.
// Longer keys are more secure than shorter keys.
private const int keySize = 256;
private string _stringTOEncDec;
#endregion
#region Public Methods
/// <summary>
/// Public method that get set the input string to be encrypt Decrypt
/// </summary>
/// <author> </author>
/// <CreatedDate> </CreatedDate>
public string InputText
{
get
{
return _stringTOEncDec;
}
set
{
_stringTOEncDec = value;
}
}
#endregion
#region Encrypt
/// <summary>
/// Encrypts specified plaintext using Rijndael symmetric key algorithm
/// and returns a base64-encoded result.
/// </summary>
/// <author> </author>
/// <CreatedDate> </CreatedDate>
/// <ModifiedDate> </ModifiedDate>
/// <ModifiedBy> </ModifiedBy>
/// <ModificationPurpose></ModificationPurpose>
/// <param name="plainText">
/// Plaintext value to be encrypted.
/// </param>
/// <returns>Encrypted value formatted as a base64-encoded string.</returns>
public string Encrypt()
{
// Convert strings into byte arrays.
// Let us assume that strings only contain ASCII codes.
// If strings include Unicode characters, use Unicode, UTF7, or UTF8
// encoding.
byte[] initVectorBytes = Encoding.ASCII.GetBytes(initVector);
byte[] saltValueBytes = Encoding.ASCII.GetBytes(saltValue);
// Convert our plaintext into a byte array.
// Let us assume that plaintext contains UTF8-encoded characters.
byte[] plainTextBytes = Encoding.UTF8.GetBytes(InputText);
// First, we must create a password, from which the key will be derived.
// This password will be generated from the specified passphrase and
// salt value. The password will be created using the specified hash
// algorithm. Password creation can be done in several iterations.
PasswordDeriveBytes password = new PasswordDeriveBytes(
passPhrase,
saltValueBytes,
hashAlgorithm,
passwordIterations);
// Use the password to generate pseudo-random bytes for the encryption
// key. Specify the size of the key in bytes (instead of bits).
byte[] keyBytes = password.GetBytes(keySize / 8);
// Create uninitialized Rijndael encryption object.
RijndaelManaged symmetricKey = new RijndaelManaged();
// It is reasonable to set encryption mode to Cipher Block Chaining
// (CBC). Use default options for other symmetric key parameters.
symmetricKey.Mode = CipherMode.CBC;
// Generate encryptor from the existing key bytes and initialization
// vector. Key size will be defined based on the number of the key
// bytes.
ICryptoTransform encryptor = symmetricKey.CreateEncryptor(
keyBytes,
initVectorBytes);
// Define memory stream which will be used to hold encrypted data.
MemoryStream memoryStream = new MemoryStream();
// Define cryptographic stream (always use Write mode for encryption).
CryptoStream cryptoStream = new CryptoStream(memoryStream,
encryptor,
CryptoStreamMode.Write);
// Start encrypting.
cryptoStream.Write(plainTextBytes, 0, plainTextBytes.Length);
// Finish encrypting.
cryptoStream.FlushFinalBlock();
// Convert our encrypted data from a memory stream into a byte array.
byte[] cipherTextBytes = memoryStream.ToArray();
// Close both streams.
memoryStream.Close();
cryptoStream.Close();
// Convert encrypted data into a base64-encoded string.
string cipherText = Convert.ToBase64String(cipherTextBytes);
// Return encrypted string.
return cipherText;
}
#endregion
#region Decrypt
/// <summary>
/// Decrypts specified ciphertext using Rijndael symmetric key algorithm.
/// </summary>
/// <author> </author>
/// <CreatedDate> </CreatedDate>
/// <ModifiedDate> </ModifiedDate>
/// <ModifiedBy> </ModifiedBy>
/// <ModificationPurpose></ModificationPurpose>
/// <param name="cipherText">
/// Base64-formatted ciphertext value.
/// </param>
/// <returns>Decrypted string value. </returns>
/// <remarks>
/// Most of the logic in this function is similar to the Encrypt
/// logic. In order for decryption to work, all parameters of this function
/// - except cipherText value - must match the corresponding parameters of
/// the Encrypt function which was called to generate the
/// ciphertext.
/// </remarks>
public string Decrypt(string cipherText)
{
// Convert strings defining encryption key characteristics into byte
// arrays. Let us assume that strings only contain ASCII codes.
// If strings include Unicode characters, use Unicode, UTF7, or UTF8
// encoding.
byte[] initVectorBytes = Encoding.ASCII.GetBytes(initVector);
byte[] saltValueBytes = Encoding.ASCII.GetBytes(saltValue);
// Convert our ciphertext into a byte array.
byte[] cipherTextBytes = Convert.FromBase64String(cipherText);
// First, we must create a password, from which the key will be
// derived. This password will be generated from the specified
// passphrase and salt value. The password will be created using
// the specified hash algorithm. Password creation can be done in
// several iterations.
PasswordDeriveBytes password = new PasswordDeriveBytes(
passPhrase,
saltValueBytes,
hashAlgorithm,
passwordIterations);
// Use the password to generate pseudo-random bytes for the encryption
// key. Specify the size of the key in bytes (instead of bits).
byte[] keyBytes = password.GetBytes(keySize / 8);
// Create uninitialized Rijndael encryption object.
RijndaelManaged symmetricKey = new RijndaelManaged();
// It is reasonable to set encryption mode to Cipher Block Chaining
// (CBC). Use default options for other symmetric key parameters.
symmetricKey.Mode = CipherMode.CBC;
// Generate decryptor from the existing key bytes and initialization
// vector. Key size will be defined based on the number of the key
// bytes.
ICryptoTransform decryptor = symmetricKey.CreateDecryptor(
keyBytes,
initVectorBytes);
// Define memory stream which will be used to hold encrypted data.
MemoryStream memoryStream = new MemoryStream(cipherTextBytes);
// Define cryptographic stream (always use Read mode for encryption).
CryptoStream cryptoStream = new CryptoStream(memoryStream,
decryptor,
CryptoStreamMode.Read);
// Since at this point we don't know what the size of decrypted data
// will be, allocate the buffer long enough to hold ciphertext;
// plaintext is never longer than ciphertext.
byte[] plainTextBytes = new byte[cipherTextBytes.Length];
// Start decrypting.
int decryptedByteCount = cryptoStream.Read(plainTextBytes,
0,
plainTextBytes.Length);
// Close both streams.
memoryStream.Close();
cryptoStream.Close();
// Convert decrypted data into a string.
// Let us assume that the original plaintext string was UTF8-encoded.
string plainText = Encoding.UTF8.GetString(plainTextBytes,
0,
decryptedByteCount);
// Return decrypted string.
return plainText;
}
#endregion
}
}
Use this code on CS page :-
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using EncryptionSample;
namespace EncryptionSample
{
public partial class _Default : System.Web.UI.Page
{
EncryptionDecryption objEncryp = new EncryptionDecryption();
protected void Page_Load(object sender, EventArgs e)
{
}
protected void btnEncrypt_Click(object sender, EventArgs e)
{
objEncryp.InputText = txtInputText.Text.Trim();
txtEncryptText.Text = objEncryp.Encrypt();
}
protected void btnDecrypt_Click(object sender, EventArgs e)
{
txtDecryptText.Text = objEncryp.Decrypt(txtEncryptText.Text);
}
}
}
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