Implementation of an IText's IExternalSignatureContainer with BouncyCastle to manage ECDSA-SHA384 signature - cryptography

Question

I am trying to implement an IExternalSignatureContainer (itext7) to sign PDF with belgian id card.
There is twa smartcard versions to deal with:
RSA/SHA256 signature
ECDSA/SHA384
I achieved to sign the pdf with the RSA/SHA256 siganture but I am not able to make the same for the ECDSA/SHA384.
Here is the Sign method of the ExternalSignatureContainer:
public byte[] Sign(Stream data)
{
var signCert = this.chain.First();
IssuerAndSerialNumber issuerAndSerialNumber = new IssuerAndSerialNumber(signCert.IssuerDN, signCert.SerialNumber);
var signerGenerator = new SignerInfoGeneratorBuilder().Build(
new BeidSignatureFactory(
(data) => this.Sign(data), // Sign data with the eid-middleware
() => this.GetHashAlgorithm(), // Get the hash algorithm of the id card from the eid-middleware
() => this.GetEncryptionAlgorithm() // Get the encryption algorithm of the id card from the eid-middleware
), signCert);
CmsSignedDataGenerator gen = new CmsSignedDataGenerator();
gen.AddSignerInfoGenerator(signerGenerator);
IX509Store x509CertStore = X509StoreFactory.Create(
"Certificate/Collection",
new X509CollectionStoreParameters(this.chain));
gen.AddCertificates(x509CertStore);
CmsProcessableInputStream cmsProcessableInputStream = new CmsProcessableInputStream(data);
var sigData = gen.Generate(cmsProcessableInputStream, false);
return sigData.GetEncoded();
}
Here is a Custom ISignatureFactory and a custom ISigner that use the eid-middleware to access the begian eid card and use it to sign data.
internal class BeidSignatureFactory : ISignatureFactory
{
private readonly BeidSigner _signer = new BeidSigner();
private readonly BeidSigner.SignatureGenerator _signatureGenerator;
private readonly BeidSigner.AlgorithmGetter _getHashAlgorithm;
private readonly BeidSigner.AlgorithmGetter _getEncryptionAlgorithm;
public BeidSignatureFactory(BeidSigner.SignatureGenerator signatureGenerator, BeidSigner.AlgorithmGetter getHashAlgorithm, BeidSigner.AlgorithmGetter getEncryptionAlgorithm)
{
this._signatureGenerator = signatureGenerator;
this._getEncryptionAlgorithm = getEncryptionAlgorithm;
this._getHashAlgorithm = getHashAlgorithm;
}
public IStreamCalculator CreateCalculator()
{
var signer = new BeidSigner
{
Sign = this._signatureGenerator,
GetEncryptionAlgorithm = this._getEncryptionAlgorithm,
GetHashAlgorithm = this._getHashAlgorithm,
};
signer.Init(true, null);
return new DefaultSignatureCalculator(signer);
}
public object AlgorithmDetails
{
get
{
string encryptionAlgorithm = this._getEncryptionAlgorithm();
string hashAlgorithm = this._getHashAlgorithm();
switch (encryptionAlgorithm)
{
case "RSA":
return new AlgorithmIdentifier(PkcsObjectIdentifiers.Sha256WithRsaEncryption);
case "ECDSA":
return new AlgorithmIdentifier(X9ObjectIdentifiers.ECDsaWithSha384);
default:
return null;
}
}
}
}
internal class BeidSigner : ISigner
{
public delegate byte[] SignatureGenerator(byte[] data);
public delegate string AlgorithmGetter();
private byte[] _input;
public void Init(bool forSigning, ICipherParameters parameters)
{
this.Reset();
}
public void Update(byte input)
{
throw new NotImplementedException();
}
public void BlockUpdate(byte[] input, int inOff, int length)
{
this._input = input.Skip(inOff).Take(length).ToArray();
}
public byte[] GenerateSignature()
{
// This method doesn't exist, you will need to implement your own method here
return this.Sign(this._input);
}
public bool VerifySignature(byte[] signature)
{
throw new NotImplementedException();
}
public void Reset() { }
public string AlgorithmName
{
get
{
return $"{this.GetHashAlgorithm()}with{this.GetEncryptionAlgorithm()}";
}
}
public SignatureGenerator Sign { get; set; }
public AlgorithmGetter GetHashAlgorithm { get; set; }
public AlgorithmGetter GetEncryptionAlgorithm { get; set; }
}
Once the pdf signed with the EDCSA signature, the signature is not validated by acrobat reader "Document altered ro corrupted".
Perhaps I have completaly misunderstood the way tho sign the pdf.
Thanks for your help.