/// <summary>
/// Attempts to create the ECDSA signature for the specified hash value in the indicated format
/// into the provided buffer.
/// </summary>
/// <param name="hash">The hash value to sign.</param>
/// <param name="destination">The buffer to receive the signature.</param>
/// <param name="signatureFormat">The encoding format to use for the signature.</param>
/// <param name="bytesWritten">
/// When this method returns, contains a value that indicates the number of bytes written to
/// <paramref name="destination"/>. This parameter is treated as uninitialized.
/// </param>
/// <returns>
/// <see langword="true"/> if <paramref name="destination"/> is big enough to receive the signature;
/// otherwise, <see langword="false"/>.
/// </returns>
/// <exception cref="CryptographicException">
/// An error occurred in the signing operation.
/// </exception>
protected virtual bool TrySignHashCore(
ReadOnlySpan <byte> hash,
Span <byte> destination,
DSASignatureFormat signatureFormat,
out int bytesWritten)
{
// This method is expected to be overridden with better implementation
// The only available implementation here is abstract method, use it
byte[] result = SignHash(hash.ToArray());
byte[] converted = AsymmetricAlgorithmHelpers.ConvertFromIeeeP1363Signature(result, signatureFormat);
return(Helpers.TryCopyToDestination(converted, destination, out bytesWritten));
}
/// <summary>
/// Creates the DSA signature for the specified hash value in the indicated format.
/// </summary>
/// <param name="hash">The hash value to sign.</param>
/// <param name="signatureFormat">The encoding format to use for the signature.</param>
/// <returns>
/// The DSA signature for the specified data.
/// </returns>
/// <exception cref="CryptographicException">
/// An error occurred in the signing operation.
/// </exception>
protected virtual byte[] CreateSignatureCore(ReadOnlySpan <byte> hash, DSASignatureFormat signatureFormat)
{
Span <byte> signature = stackalloc byte[SignatureStackSize];
if (TryCreateSignatureCore(hash, signature, signatureFormat, out int bytesWritten))
{
return(signature.Slice(0, bytesWritten).ToArray());
}
// If that didn't work, fall back to the older overload and convert formats.
byte[] sig = CreateSignature(hash.ToArray());
return(AsymmetricAlgorithmHelpers.ConvertFromIeeeP1363Signature(sig, signatureFormat));
}
/// <summary>
/// Attempts to create the DSA signature for the specified hash value in the indicated format
/// into the provided buffer.
/// </summary>
/// <param name="hash">The hash value to sign.</param>
/// <param name="destination">The buffer to receive the signature.</param>
/// <param name="signatureFormat">The encoding format to use for the signature.</param>
/// <param name="bytesWritten">
/// When this method returns, contains a value that indicates the number of bytes written to
/// <paramref name="destination"/>. This parameter is treated as uninitialized.
/// </param>
/// <returns>
/// <see langword="true"/> if <paramref name="destination"/> is big enough to receive the signature;
/// otherwise, <see langword="false"/>.
/// </returns>
/// <exception cref="CryptographicException">
/// An error occurred in the signing operation.
/// </exception>
protected virtual bool TryCreateSignatureCore(
ReadOnlySpan <byte> hash,
Span <byte> destination,
DSASignatureFormat signatureFormat,
out int bytesWritten)
{
// This method is expected to be overriden with better implementation
// The only available implementation here is abstract method, use it
byte[] sig = CreateSignature(hash.ToArray());
if (signatureFormat != DSASignatureFormat.IeeeP1363FixedFieldConcatenation)
{
sig = AsymmetricAlgorithmHelpers.ConvertFromIeeeP1363Signature(sig, signatureFormat);
}
return(Helpers.TryCopyToDestination(sig, destination, out bytesWritten));
}
/// <summary>
/// Computes the hash value of the specified data and signs it using the specified signature format.
/// </summary>
/// <param name="data">The data to sign.</param>
/// <param name="hashAlgorithm">The hash algorithm to use to create the hash value.</param>
/// <param name="signatureFormat">The encoding format to use for the signature.</param>
/// <returns>
/// The DSA signature for the specified data.
/// </returns>
/// <exception cref="CryptographicException">
/// An error occurred in the hashing or signing operation.
/// </exception>
protected virtual byte[] SignDataCore(
ReadOnlySpan <byte> data,
HashAlgorithmName hashAlgorithm,
DSASignatureFormat signatureFormat)
{
Span <byte> signature = stackalloc byte[SignatureStackSize];
if (TrySignDataCore(data, signature, hashAlgorithm, signatureFormat, out int bytesWritten))
{
return(signature.Slice(0, bytesWritten).ToArray());
}
// If that didn't work, fall back on older approaches.
byte[] hash = HashSpanToArray(data, hashAlgorithm);
byte[] sig = CreateSignature(hash);
return(AsymmetricAlgorithmHelpers.ConvertFromIeeeP1363Signature(sig, signatureFormat));
}
