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Decrypt Method

RSACryptoServiceProvider.Decrypt Method

Decrypts data with the RSA algorithm.

Namespace:  System.Security.Cryptography
Assembly:  mscorlib (in mscorlib.dll)

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


Type: System.Byte[]

The data to be decrypted.

Type: System.Boolean

true to perform direct RSA decryption using OAEP padding (only available on a computer running Microsoft Windows XP or later); otherwise, false to use PKCS#1 v1.5 padding.

Return Value

Type: System.Byte[]
The decrypted data, which is the original plain text before encryption.


The cryptographic service provider (CSP) cannot be acquired.


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


The fOAEP parameter is true and OAEP is not supported.


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.


rgb is null.

Use Encrypt to encrypt data for decryption with this method.

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 2005.

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

class RSACSPSample
    static void Main()
            //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 
            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.


.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0, 1.1

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone Silverlight 8.1, Windows Phone Silverlight 8

© 2015 Microsoft