CryptographicEngine.DeriveKeyMaterial Method

Reference

Definition

Namespace:: Windows.Security.Cryptography.Core

Important

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Edit

Derives a key from another key by using a key derivation function. For more information, see the KeyDerivationAlgorithmProvider and KeyDerivationParameters classes.

public:
 static IBuffer ^ DeriveKeyMaterial(CryptographicKey ^ key, KeyDerivationParameters ^ parameters, unsigned int desiredKeySize);

 static IBuffer DeriveKeyMaterial(CryptographicKey const& key, KeyDerivationParameters const& parameters, uint32_t const& desiredKeySize);

public static IBuffer DeriveKeyMaterial(CryptographicKey key, KeyDerivationParameters parameters, uint desiredKeySize);

function deriveKeyMaterial(key, parameters, desiredKeySize)

Public Shared Function DeriveKeyMaterial (key As CryptographicKey, parameters As KeyDerivationParameters, desiredKeySize As UInteger) As IBuffer

Parameters

key: CryptographicKey

The symmetric or secret key used for derivation.

parameters: KeyDerivationParameters

Derivation parameters. The parameters vary depending on the type of KDF algorithm used.

desiredKeySize: UInt32
unsigned int

uint32_t

Requested size, in bytes, of the derived key.

Returns

IBuffer

Buffer that contains the derived key.

Examples

public String SampleDeriveFromPbkdf(
    String strAlgName,
    UInt32 targetSize)
{
    // Open the specified algorithm.
    KeyDerivationAlgorithmProvider objKdfProv = KeyDerivationAlgorithmProvider.OpenAlgorithm(strAlgName);

    // Create a buffer that contains the secret used during derivation.
    String strSecret = "MyPassword";
    IBuffer buffSecret = CryptographicBuffer.ConvertStringToBinary(strSecret, BinaryStringEncoding.Utf8);

    // Create a random salt value.
    IBuffer buffSalt = CryptographicBuffer.GenerateRandom(32);

    // Specify the number of iterations to be used during derivation.
    UInt32 iterationCount = 10000;

    // Create the derivation parameters.
    KeyDerivationParameters pbkdf2Params = KeyDerivationParameters.BuildForPbkdf2(buffSalt, iterationCount);

    // Create a key from the secret value.
    CryptographicKey keyOriginal = objKdfProv.CreateKey(buffSecret);

    // Derive a key based on the original key and the derivation parameters.
    IBuffer keyDerived = CryptographicEngine.DeriveKeyMaterial(
        keyOriginal,
        pbkdf2Params,
        targetSize);

    // Encode the key to a hexadecimal value (for display)
    String strKeyHex = CryptographicBuffer.EncodeToHexString(keyDerived);

    // Return the encoded string
    return strKeyHex;
}

Remarks

Deriving keys requires that you use the KeyDerivationAlgorithmProvider and KeyDerivationParameters classes. The following key derivation functions can be used:

For a complete sample that contains the following code example, see the KeyDerivationAlgorithmProvider class.

Applies to

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