private static SafeCapiKeyHandle SetupKey(SafeCapiKeyHandle key, byte[] iv, CipherMode cipherMode, int feedbackSize) {
Contract.Requires(key != null);
Contract.Requires(cipherMode == CipherMode.ECB || iv != null);
Contract.Requires(0 <= feedbackSize);
Contract.Ensures(Contract.Result<SafeCapiKeyHandle>() != null &&
!Contract.Result<SafeCapiKeyHandle>().IsInvalid &&
!Contract.Result<SafeCapiKeyHandle>().IsClosed);
// Make a copy of the key so that we don't modify the properties of the caller's copy
SafeCapiKeyHandle encryptionKey = key.Duplicate();
// Setup the cipher mode first
CapiNative.SetKeyParameter(encryptionKey, CapiNative.KeyParameter.Mode, (int)cipherMode);
// If we're not in ECB mode then setup the IV
if (cipherMode != CipherMode.ECB) {
CapiNative.SetKeyParameter(encryptionKey, CapiNative.KeyParameter.IV, iv);
}
// OFB and CFB require a feedback loop size
if (cipherMode == CipherMode.CFB || cipherMode == CipherMode.OFB) {
CapiNative.SetKeyParameter(encryptionKey, CapiNative.KeyParameter.ModeBits, feedbackSize);
}
return encryptionKey;
}
private static SafeCapiKeyHandle SetupKey(SafeCapiKeyHandle key, byte[] iv, CipherMode cipherMode, int feedbackSize)
{
SafeCapiKeyHandle handle = key.Duplicate();
CapiNative.SetKeyParameter(handle, CapiNative.KeyParameter.Mode, (int) cipherMode);
if (cipherMode != CipherMode.ECB)
{
CapiNative.SetKeyParameter(handle, CapiNative.KeyParameter.IV, iv);
}
if ((cipherMode == CipherMode.CFB) || (cipherMode == CipherMode.OFB))
{
CapiNative.SetKeyParameter(handle, CapiNative.KeyParameter.ModeBits, feedbackSize);
}
return handle;
}
