<PackageReference Include="BouncyCastle.Cryptography" Version="2.7.0" />

Org.BouncyCastle.Cms.CmsEnvelopedDataParser

public string EncryptionAlgOid { get; }

public CmsEnvelopedDataParser(byte[] envelopedData)

public CmsEnvelopedDataParser(Stream envelopedData)