public override byte[] DeriveKeyFromHmac(
ECDiffieHellmanPublicKey otherPartyPublicKey,
HashAlgorithmName hashAlgorithm,
byte[] hmacKey,
byte[] secretPrepend,
byte[] secretAppend)
{
Contract.Ensures(Contract.Result <byte[]>() != null);
if (otherPartyPublicKey == null)
{
throw new ArgumentNullException("otherPartyPublicKey");
}
if (string.IsNullOrEmpty(hashAlgorithm.Name))
{
throw new ArgumentException(SR.GetString(SR.Cryptography_HashAlgorithmNameNullOrEmpty), "hashAlgorithm");
}
using (SafeNCryptSecretHandle secretAgreement = DeriveSecretAgreementHandle(otherPartyPublicKey))
{
NCryptNative.SecretAgreementFlags flags = hmacKey == null ?
NCryptNative.SecretAgreementFlags.UseSecretAsHmacKey :
NCryptNative.SecretAgreementFlags.None;
return(NCryptNative.DeriveKeyMaterialHmac(
secretAgreement,
hashAlgorithm.Name,
hmacKey,
secretPrepend,
secretAppend,
flags));
}
}
public byte[] DeriveKeyMaterial(CngKey otherPartyPublicKey)
{
if (otherPartyPublicKey == null)
{
throw new ArgumentNullException("otherPartyPublicKey");
}
if (otherPartyPublicKey.AlgorithmGroup != CngAlgorithmGroup.ECDiffieHellman)
{
throw new ArgumentException(System.SR.GetString("Cryptography_ArgECDHRequiresECDHKey"), "otherPartyPublicKey");
}
if (otherPartyPublicKey.KeySize != this.KeySize)
{
throw new ArgumentException(System.SR.GetString("Cryptography_ArgECDHKeySizeMismatch"), "otherPartyPublicKey");
}
NCryptNative.SecretAgreementFlags flags = this.UseSecretAgreementAsHmacKey ? NCryptNative.SecretAgreementFlags.UseSecretAsHmacKey : NCryptNative.SecretAgreementFlags.None;
new SecurityPermission(SecurityPermissionFlag.UnmanagedCode).Assert();
SafeNCryptKeyHandle privateKey = this.Key.Handle;
SafeNCryptKeyHandle handle = otherPartyPublicKey.Handle;
CodeAccessPermission.RevertAssert();
using (SafeNCryptSecretHandle handle3 = NCryptNative.DeriveSecretAgreement(privateKey, handle))
{
if (this.KeyDerivationFunction == ECDiffieHellmanKeyDerivationFunction.Hash)
{
byte[] secretAppend = (this.SecretAppend == null) ? null : (this.SecretAppend.Clone() as byte[]);
byte[] secretPrepend = (this.SecretPrepend == null) ? null : (this.SecretPrepend.Clone() as byte[]);
return(NCryptNative.DeriveKeyMaterialHash(handle3, this.HashAlgorithm.Algorithm, secretPrepend, secretAppend, flags));
}
if (this.KeyDerivationFunction == ECDiffieHellmanKeyDerivationFunction.Hmac)
{
byte[] hmacKey = (this.HmacKey == null) ? null : (this.HmacKey.Clone() as byte[]);
byte[] buffer4 = (this.SecretAppend == null) ? null : (this.SecretAppend.Clone() as byte[]);
byte[] buffer5 = (this.SecretPrepend == null) ? null : (this.SecretPrepend.Clone() as byte[]);
return(NCryptNative.DeriveKeyMaterialHmac(handle3, this.HashAlgorithm.Algorithm, hmacKey, buffer5, buffer4, flags));
}
byte[] label = (this.Label == null) ? null : (this.Label.Clone() as byte[]);
byte[] seed = (this.Seed == null) ? null : (this.Seed.Clone() as byte[]);
if ((label == null) || (seed == null))
{
throw new InvalidOperationException(System.SR.GetString("Cryptography_TlsRequiresLabelAndSeed"));
}
return(NCryptNative.DeriveKeyMaterialTls(handle3, label, seed, flags));
}
}
public byte[] DeriveKeyMaterial(CngKey otherPartyPublicKey)
{
Contract.Ensures(Contract.Result <byte[]>() != null);
Contract.Assert(m_kdf >= ECDiffieHellmanKeyDerivationFunction.Hash &&
m_kdf <= ECDiffieHellmanKeyDerivationFunction.Tls);
if (otherPartyPublicKey == null)
{
throw new ArgumentNullException("otherPartyPublicKey");
}
if (otherPartyPublicKey.AlgorithmGroup != CngAlgorithmGroup.ECDiffieHellman)
{
throw new ArgumentException(SR.GetString(SR.Cryptography_ArgECDHRequiresECDHKey), "otherPartyPublicKey");
}
if (otherPartyPublicKey.KeySize != KeySize)
{
throw new ArgumentException(SR.GetString(SR.Cryptography_ArgECDHKeySizeMismatch), "otherPartyPublicKey");
}
NCryptNative.SecretAgreementFlags flags =
UseSecretAgreementAsHmacKey ? NCryptNative.SecretAgreementFlags.UseSecretAsHmacKey : NCryptNative.SecretAgreementFlags.None;
// We require access to the handles for generating key material. This is safe since we will never
// expose these handles to user code
new SecurityPermission(SecurityPermissionFlag.UnmanagedCode).Assert();
// This looks horribly wrong - but accessing the handle property actually returns a duplicate handle, which
// we need to dispose of - otherwise, we're stuck keepign the resource alive until the GC runs. This explicitly
// is not disposing of the handle underlying the key dispite what the syntax looks like.
using (SafeNCryptKeyHandle localKey = Key.Handle)
using (SafeNCryptKeyHandle otherKey = otherPartyPublicKey.Handle) {
CodeAccessPermission.RevertAssert();
//
// Generating key material is a two phase process.
// 1. Generate the secret agreement
// 2. Pass the secret agreement through a KDF to get key material
//
using (SafeNCryptSecretHandle secretAgreement = NCryptNative.DeriveSecretAgreement(localKey, otherKey)) {
if (KeyDerivationFunction == ECDiffieHellmanKeyDerivationFunction.Hash)
{
byte[] secretAppend = SecretAppend == null ? null : SecretAppend.Clone() as byte[];
byte[] secretPrepend = SecretPrepend == null ? null : SecretPrepend.Clone() as byte[];
return(NCryptNative.DeriveKeyMaterialHash(secretAgreement,
HashAlgorithm.Algorithm,
secretPrepend,
secretAppend,
flags));
}
else if (KeyDerivationFunction == ECDiffieHellmanKeyDerivationFunction.Hmac)
{
byte[] hmacKey = HmacKey == null ? null : HmacKey.Clone() as byte[];
byte[] secretAppend = SecretAppend == null ? null : SecretAppend.Clone() as byte[];
byte[] secretPrepend = SecretPrepend == null ? null : SecretPrepend.Clone() as byte[];
return(NCryptNative.DeriveKeyMaterialHmac(secretAgreement,
HashAlgorithm.Algorithm,
hmacKey,
secretPrepend,
secretAppend,
flags));
}
else
{
Debug.Assert(KeyDerivationFunction == ECDiffieHellmanKeyDerivationFunction.Tls, "Unknown KDF");
byte[] label = Label == null ? null : Label.Clone() as byte[];
byte[] seed = Seed == null ? null : Seed.Clone() as byte[];
if (label == null || seed == null)
{
throw new InvalidOperationException(SR.GetString(SR.Cryptography_TlsRequiresLabelAndSeed));
}
return(NCryptNative.DeriveKeyMaterialTls(secretAgreement, label, seed, flags));
}
}
}
}
internal static extern NCryptNative.ErrorCode NCryptDeriveKey(SafeNCryptSecretHandle hSharedSecret, string pwszKDF, [In] ref NCryptNative.NCryptBufferDesc pParameterList, [Out, MarshalAs(UnmanagedType.LPArray)] byte[] pbDerivedKey, int cbDerivedKey, out int pcbResult, NCryptNative.SecretAgreementFlags dwFlags);
