Symmetric​Key​Algorithm​Provider Symmetric​Key​Algorithm​Provider Symmetric​Key​Algorithm​Provider Class

Definition

Represents a provider of symmetric key algorithms. For more information, see Cryptographic keys.

public sealed class SymmetricKeyAlgorithmProvider : ISymmetricKeyAlgorithmProviderpublic sealed class SymmetricKeyAlgorithmProvider : ISymmetricKeyAlgorithmProviderPublic NotInheritable Class SymmetricKeyAlgorithmProvider Implements ISymmetricKeyAlgorithmProvider
Attributes
Windows 10 requirements
Device family
Windows 10 (introduced v10.0.10240.0)
API contract
Windows.Foundation.UniversalApiContract (introduced v1)

Remarks

You create a SymmetricKeyAlgorithmProvider object by calling the static OpenAlgorithm method and specifying one of the following algorithm names.

  • No padding:+ DES_CBC
  • DES_ECB
  • 3DES_CBC
  • 3DES_ECB
  • RC2_CBC
  • RC2_ECB
  • AES_CBC
  • AES_ECB

  • PKCS#7 block padding modes:+ AES_CBC_PKCS7

  • AES_ECB_PKCS7
  • DES_CBC_PKCS7
  • DES_ECB_PKCS7
  • 3DES_CBC_PKCS7
  • 3DES_ECB_PKCS7
  • RC2_CBC_PKCS7
  • RC2_ECB_PKCS7

  • Authenticated modes (see the EncryptedAndAuthenticatedData class):+ AES_GCM

  • AES_CCM

  • Stream Cipher:+ RC4

Examples

using Windows.Security.Cryptography;
using Windows.Security.Cryptography.Core;
using Windows.Storage.Streams;

namespace SampleSymmetricKeyAlgorithmProvider
{
    sealed partial class SymmKeyAlgProviderApp : Application
    {
        public SymmKeyAlgProviderApp()
        {
            // Initialize the application.
            this.InitializeComponent();

            // Initialize the encryption process.
            String strMsg = "1234567812345678";     // Data to encrypt.
            String strAlgName = SymmetricAlgorithmNames.AesCbc;
            UInt32 keyLength = 32;                  // Length of the key, in bytes
            BinaryStringEncoding encoding;          // Binary encoding value
            IBuffer iv;                             // Initialization vector
            CryptographicKey key;                   // Symmetric key

            // Encrypt a message.
            IBuffer buffEncrypted = this.SampleCipherEncryption(
                strMsg,
                strAlgName,
                keyLength,
                out encoding,
                out iv,
                out key);

            // Decrypt a message.
            this.SampleCipherDecryption(
                strAlgName,
                buffEncrypted,
                iv,
                encoding,
                key);
        }

        public IBuffer SampleCipherEncryption(
            String strMsg,
            String strAlgName,
            UInt32 keyLength,
            out BinaryStringEncoding encoding,
            out IBuffer iv,
            out CryptographicKey key)
        {
            // Initialize the initialization vector.
            iv = null;

            // Initialize the binary encoding value.
            encoding = BinaryStringEncoding.Utf8;

            // Create a buffer that contains the encoded message to be encrypted. 
            IBuffer buffMsg = CryptographicBuffer.ConvertStringToBinary(strMsg, encoding);

            // Open a symmetric algorithm provider for the specified algorithm. 
            SymmetricKeyAlgorithmProvider objAlg = SymmetricKeyAlgorithmProvider.OpenAlgorithm(strAlgName);

            // Demonstrate how to retrieve the name of the algorithm used.
            String strAlgNameUsed = objAlg.AlgorithmName;

            // Determine whether the message length is a multiple of the block length.
            // This is not necessary for PKCS #7 algorithms which automatically pad the
            // message to an appropriate length.
            if (!strAlgName.Contains("PKCS7"))
            {
               if ((buffMsg.Length % objAlg.BlockLength) != 0)
                {
                    throw new Exception("Message buffer length must be multiple of block length.");
                }
            }

            // Create a symmetric key.
            IBuffer keyMaterial = CryptographicBuffer.GenerateRandom(keyLength);
            key = objAlg.CreateSymmetricKey(keyMaterial);

            // CBC algorithms require an initialization vector. Here, a random
            // number is used for the vector.
            if (strAlgName.Contains("CBC"))
            {
                iv = CryptographicBuffer.GenerateRandom(objAlg.BlockLength);
            }

            // Encrypt the data and return.
            IBuffer buffEncrypt = CryptographicEngine.Encrypt(key, buffMsg, iv);
            return buffEncrypt;
        }

        public void SampleCipherDecryption(
            String strAlgName,
            IBuffer buffEncrypt,
            IBuffer iv,
            BinaryStringEncoding encoding,
            CryptographicKey key)
        {
            // Declare a buffer to contain the decrypted data.
            IBuffer buffDecrypted;

            // Open an symmetric algorithm provider for the specified algorithm. 
            SymmetricKeyAlgorithmProvider objAlg = SymmetricKeyAlgorithmProvider.OpenAlgorithm(strAlgName);

            // The input key must be securely shared between the sender of the encrypted message
            // and the recipient. The initialization vector must also be shared but does not
            // need to be shared in a secure manner. If the sender encodes a message string 
            // to a buffer, the binary encoding method must also be shared with the recipient.
            buffDecrypted = CryptographicEngine.Decrypt(key, buffEncrypt, iv);

            // Convert the decrypted buffer to a string (for display). If the sender created the
            // original message buffer from a string, the sender must tell the recipient what 
            // BinaryStringEncoding value was used. Here, BinaryStringEncoding.Utf8 is used to
            // convert the message to a buffer before encryption and to convert the decrypted
            // buffer back to the original plaintext.
            String strDecrypted = CryptographicBuffer.ConvertBinaryToString(encoding, buffDecrypted);
        }
    }
}

Properties

AlgorithmName AlgorithmName AlgorithmName

BlockLength BlockLength BlockLength

Gets the size, in bytes, of the cipher block for the open algorithm.

public unsigned short BlockLength { get; }public uint BlockLength { get; }Public ReadOnly Property BlockLength As uint
Value
uint uint uint

Block size.

Attributes

Remarks

If you are not using a PKCS#7 block padding algorithm (which automatically pads your content to the correct length), you must ensure that the message to be encrypted is an exact multiple of the length supported by the algorithm. For more information, see the following code example.

See Also

Methods

CreateSymmetricKey(IBuffer) CreateSymmetricKey(IBuffer) CreateSymmetricKey(IBuffer)

Creates a symmetric key.

public CryptographicKey CreateSymmetricKey(IBuffer keyMaterial)public CryptographicKey CreateSymmetricKey(IBuffer keyMaterial)Public Function CreateSymmetricKey(keyMaterial As IBuffer) As CryptographicKey
Parameters
keyMaterial
IBuffer IBuffer IBuffer

Data used to generate the key. You can call the GenerateRandom method to create random key material.

Returns
Attributes

OpenAlgorithm(String) OpenAlgorithm(String) OpenAlgorithm(String)

Creates an instance of the SymmetricKeyAlgorithmProvider class and opens the specified algorithm for use.

public static SymmetricKeyAlgorithmProvider OpenAlgorithm(String algorithm)public static SymmetricKeyAlgorithmProvider OpenAlgorithm(String algorithm)Public Static Function OpenAlgorithm(algorithm As String) As SymmetricKeyAlgorithmProvider
Parameters
algorithm
System.String System.String System.String

Algorithm name.

Returns
Attributes

Remarks

The following algorithm names are supported for use in this method: