Issue decrypting with Kleopatra encrypted file created with BouncyCastle for .Net

[boggye]

Hello,

I encrypted a file using a .Net 8.0 F# program that references BouncyCastle.Cryptography version 2.4.0. When I try to decrypt it using Kleopatra, I get these messages:

gpg: encrypted with rsa4096 key, ID 201748...., created 2019-04-15
      "..."
gpg: used key is not marked for encryption use.
gpg: WARNING: cipher algorithm CAST5 not found in recipient preferences
gpg: zlib inflate problem: invalid block type

Here are the version numbers:
Kleopatra: 3.2.2.2311170 (Gpg4win-4.3.1)

GnuPG 2.4.5
Libgcrypt 1.10.3

Here is the source code of the F# program:

open System
open System.IO

open System.Text
open Org.BouncyCastle.Bcpg
open Org.BouncyCastle.Bcpg.OpenPgp
open Org.BouncyCastle.Security
    
let readPublicKeyFromStream (input: Stream): PgpPublicKey =    
    let stream2 = PgpUtilities.GetDecoderStream(input)
    let pgpPub =  PgpPublicKeyRingBundle(stream2)
    let key = pgpPub.GetKeyRings() |> Seq.collect (fun kr -> kr.GetPublicKeys()) |> Seq.tryFind (fun k -> k.IsEncryptionKey)
    if key.IsSome then
        key.Value
    else
        failwith "Unable to find a public key in the stream"    


let readPublicKeyFromString (publicKey: string) =
  use stream = new MemoryStream(Encoding.UTF8.GetBytes(publicKey))
  readPublicKeyFromStream stream
  
let readPublicKeyFromFile (fileName: string) =
    let publicKey = File.ReadAllText(fileName, Encoding.UTF8)
    readPublicKeyFromString publicKey
    
let compressFile (algorithm: CompressionAlgorithmTag) (inputFileName: string): string =     
    let outputFileName = Path.GetTempFileName()
    //use fsout = File.Create(outputFileName)
    use fsout = new MemoryStream()
    let inputFileInfo = FileInfo(inputFileName)
    // use fsinput = File.OpenRead(inputFileName)
    let inputContent = File.ReadAllBytes(inputFileName)
    let comData = PgpCompressedDataGenerator(algorithm)
    use pOut = PgpLiteralDataGenerator().Open(comData.Open(fsout), PgpLiteralData.Binary, inputFileName, inputContent.Length, DateTime.Now)    
    //fsinput.CopyTo(pOut)
    pOut.Write(inputContent, 0, inputContent.Length)
    pOut.Flush()
    pOut.Close()
    fsout.Flush()
    File.WriteAllBytes(outputFileName, fsout.ToArray())
    outputFileName

    
let encryptFile (inputFileName: string) (outputFileName: string)  (encKeyFileName: string) (withIntegrityCheck: bool) =
  let encKey = readPublicKeyFromFile encKeyFileName
  use fsout = File.Create(outputFileName)
  use outputStream = new ArmoredOutputStream(fsout)  
  let compressedFileName = compressFile CompressionAlgorithmTag.Zip inputFileName
  let encGen = new PgpEncryptedDataGenerator(SymmetricKeyAlgorithmTag.Cast5, withIntegrityCheck, new SecureRandom())
  encGen.AddMethod(encKey)
  let content = File.ReadAllBytes(compressedFileName)
  let compressedFileNameInfo = FileInfo(compressedFileName)
  let cOut = encGen.Open(outputStream, content.Length )
  //use compressedFileStream = File.OpenRead(compressedFileName)
  //compressedFileStream.CopyTo(cOut)
  cOut.Write(content, 0, content.Length)
  cOut.Close()
  outputFileName

I should also mention the file is decrypted successfully using another BC custom program which is great!

Any ideas? I tried to decrypt the file using the gnugpg command line but it returns the same message as above.

I know this is a question about another tool, but if you have any insight it would be great if you can share it. While it is not a requirement that the file should be decrypted using Kleopatra, it is useful to be able to do so for testing purposes.

Thank you

Edit: I also found this thread: https://forum.gnupg.org/t/zlib-inflate-problem-invalid-block-typ/3551

Edit2: Using CompressionAlgorithmTag.BZip2 instead of CompressionAlgorithmTag.Zip seems to work, i.e. the file is decrypted successfully by Kleopatra.

Edit3 - 2024-Oct-15: Today I tested again the decryption via Kleopatra, and actually it looks like Kleopatra cannot decrypt encrypted files that were compressed with BZip2 and Zip, but it can decrypt files that were compressed with ZLib. I am not too sure what happened in my previous tests, I might have made a mistake previously.

Anyway, if you have any suggestions or insight it would be great if you can share it. 🙏