RSACryptoServiceProvider.Decrypt Method

Definition

Namespace:

System.Security.Cryptography

Assembly:

System.Security.Cryptography.dll

Decrypts data that was previously encrypted.

Overloads

Decrypt(Byte[], Boolean)	Decrypts data with the RSA algorithm.
Decrypt(Byte[], RSAEncryptionPadding)	Decrypts data that was previously encrypted with the RSA algorithm by using the specified padding.

Decrypt(Byte[], Boolean)

Source:

RSACryptoServiceProvider.Unix.cs

Decrypts data with the RSA algorithm.

public:
 cli::array <System::Byte> ^ Decrypt(cli::array <System::Byte> ^ rgb, bool fOAEP);

public byte[] Decrypt (byte[] rgb, bool fOAEP);

override this.Decrypt : byte[] * bool -> byte[]

Public Function Decrypt (rgb As Byte(), fOAEP As Boolean) As Byte()

Parameters

rgb

Byte[]

The data to be decrypted.

fOAEP

Boolean

true to perform direct RSA decryption using OAEP padding; otherwise, false to use PKCS#1 v1.5 padding.

Returns

Byte[]

The decrypted data, which is the original plain text before encryption.

Exceptions

CryptographicException

The cryptographic service provider (CSP) cannot be acquired.

-or-

The fOAEP parameter is true and the length of the rgb parameter is greater than KeySize.

-or-

The key does not match the encrypted data. However, the exception wording may not be accurate. For example, it may say Not enough storage is available to process this command.

ArgumentNullException

rgb is null.

Examples

The following code example encrypts and decrypts data.

This example uses the ASCIIEncoding class; however, the UnicodeEncoding class may be preferable in large data operations. The encrypted value can be saved as an nvarchar data type in Microsoft SQL Server.

using namespace System;
using namespace System::Security::Cryptography;
using namespace System::Text;
int main()
{
   try
   {
      
      //Create a UnicodeEncoder to convert between byte array and string.
      ASCIIEncoding^ ByteConverter = gcnew ASCIIEncoding;
      String^ dataString = "Data to Encrypt";
      
      //Create byte arrays to hold original, encrypted, and decrypted data.
      array<Byte>^dataToEncrypt = ByteConverter->GetBytes( dataString );
      array<Byte>^encryptedData;
      array<Byte>^decryptedData;
      
      //Create a new instance of the RSACryptoServiceProvider class 
      // and automatically create a new key-pair.
      RSACryptoServiceProvider^ RSAalg = gcnew RSACryptoServiceProvider;
      
      //Display the origianl data to the console.
      Console::WriteLine( "Original Data: {0}", dataString );
      
      //Encrypt the byte array and specify no OAEP padding.  
      //OAEP padding is only available on Microsoft Windows XP or
      //later.  
      encryptedData = RSAalg->Encrypt( dataToEncrypt, false );
      
      //Display the encrypted data to the console. 
      Console::WriteLine( "Encrypted Data: {0}", ByteConverter->GetString( encryptedData ) );
      
      //Pass the data to ENCRYPT and boolean flag specifying 
      //no OAEP padding.
      decryptedData = RSAalg->Decrypt( encryptedData, false );
      
      //Display the decrypted plaintext to the console. 
      Console::WriteLine( "Decrypted plaintext: {0}", ByteConverter->GetString( decryptedData ) );
   }
   catch ( CryptographicException^ e ) 
   {
      
      //Catch this exception in case the encryption did
      //not succeed.
      Console::WriteLine( e->Message );
   }

}

using System;
using System.Security.Cryptography;
using System.Text;

class RSACSPSample
{
    static void Main()
    {
        try
        {
            //Create a UnicodeEncoder to convert between byte array and string.
            ASCIIEncoding ByteConverter = new ASCIIEncoding();

            string dataString = "Data to Encrypt";

            //Create byte arrays to hold original, encrypted, and decrypted data.
            byte[] dataToEncrypt = ByteConverter.GetBytes(dataString);
            byte[] encryptedData;
            byte[] decryptedData;

            //Create a new instance of the RSACryptoServiceProvider class
            // and automatically create a new key-pair.
            RSACryptoServiceProvider RSAalg = new RSACryptoServiceProvider();

            //Display the origianl data to the console.
            Console.WriteLine("Original Data: {0}", dataString);

            //Encrypt the byte array and specify no OAEP padding.
            //OAEP padding is only available on Microsoft Windows XP or
            //later.
            encryptedData = RSAalg.Encrypt(dataToEncrypt, false);

            //Display the encrypted data to the console.
            Console.WriteLine("Encrypted Data: {0}", ByteConverter.GetString(encryptedData));

            //Pass the data to ENCRYPT and boolean flag specifying
            //no OAEP padding.
            decryptedData = RSAalg.Decrypt(encryptedData, false);

            //Display the decrypted plaintext to the console.
            Console.WriteLine("Decrypted plaintext: {0}", ByteConverter.GetString(decryptedData));
        }
        catch(CryptographicException e)
        {
            //Catch this exception in case the encryption did
            //not succeed.
            Console.WriteLine(e.Message);
        }
    }
}

Imports System.Security.Cryptography
Imports System.Text

Module RSACSPExample

    Sub Main()
        Try
            'Create a UnicodeEncoder to convert between byte array and string.
            Dim ByteConverter As New ASCIIEncoding

            Dim dataString As String = "Data to Encrypt"

            'Create byte arrays to hold original, encrypted, and decrypted data.
            Dim dataToEncrypt As Byte() = ByteConverter.GetBytes(dataString)
            Dim encryptedData() As Byte
            Dim decryptedData() As Byte

            'Create a new instance of the RSACryptoServiceProvider class 
            ' and automatically create a new key-pair.
            Dim RSAalg As New RSACryptoServiceProvider

            'Display the origianl data to the console.
            Console.WriteLine("Original Data: {0}", dataString)

            'Encrypt the byte array and specify no OAEP padding.  
            'OAEP padding is only available on Microsoft Windows XP or
            'later.  
            encryptedData = RSAalg.Encrypt(dataToEncrypt, False)

            'Display the encrypted data to the console. 
            Console.WriteLine("Encrypted Data: {0}", ByteConverter.GetString(encryptedData))

            'Pass the data to ENCRYPT and boolean flag specifying 
            'no OAEP padding.
            decryptedData = RSAalg.Decrypt(encryptedData, False)

            'Display the decrypted plaintext to the console. 
            Console.WriteLine("Decrypted plaintext: {0}", ByteConverter.GetString(decryptedData))
        Catch e As CryptographicException
            'Catch this exception in case the encryption did
            'not succeed.
            Console.WriteLine(e.Message)
        End Try
    End Sub 

End Module

Remarks

Use Encrypt to encrypt data for decryption with this method.

See also

• Decrypt(Byte[], RSAEncryptionPadding)
• Cryptographic Services

Decrypt(Byte[], RSAEncryptionPadding)

Source:

RSACryptoServiceProvider.Unix.cs

Decrypts data that was previously encrypted with the RSA algorithm by using the specified padding.

public:
 override cli::array <System::Byte> ^ Decrypt(cli::array <System::Byte> ^ data, System::Security::Cryptography::RSAEncryptionPadding ^ padding);

public override byte[] Decrypt (byte[] data, System.Security.Cryptography.RSAEncryptionPadding padding);

override this.Decrypt : byte[] * System.Security.Cryptography.RSAEncryptionPadding -> byte[]

Public Overrides Function Decrypt (data As Byte(), padding As RSAEncryptionPadding) As Byte()

Parameters

data

Byte[]

The data to decrypt.

padding

RSAEncryptionPadding

The padding.

Returns

Byte[]

The decrypted data.

Exceptions

ArgumentNullException

data is null.

-or-

padding is null.

CryptographicException

The padding mode is not supported.

Remarks

padding must be either RSAEncryptionPadding.Pkcs1 or RSAEncryptionPadding.OaepSHA1.