Entry-8: PGP(Pretty Good Privacy) Encryption/Decryption c#

/// <summary>
        /// Gets the public key from an pgp amoured file ie. asc
        /// </summary>
        /// <param name="publicKeyFilePath"></param>
        /// <returns></returns>
        /// <exception cref="InvalidOperationException"></exception>
        public static PgpPublicKey GetPgpPubKey(string publicKeyFilePath)
        {
            using (Stream keyFileStream = File.OpenRead(publicKeyFilePath))
            using (ArmoredInputStream armoredInputStream = new(keyFileStream))
            {
                try
                {
                    // Read the contents of the ArmoredInputStream into a byte array
                    byte[] keyData = Streams.ReadAll(armoredInputStream);

                    // Create a new stream from the byte array
                    using Stream keyDataStream = new MemoryStream(keyData);
                    PgpPublicKeyRingBundle publicKeyRingBundle = new(keyDataStream);

                    // Assuming you want the first public key in the file
                    PgpPublicKeyRing publicKeyRing = publicKeyRingBundle.GetKeyRings().OfType<PgpPublicKeyRing>().FirstOrDefault();

                    if (publicKeyRing != null)
                    {
                        return publicKeyRing.GetPublicKeys().OfType<PgpPublicKey>().FirstOrDefault();
                    }
                    else
                    {
                        throw new InvalidOperationException("No public key ring found in the specified key file.");
                    }
                }
                catch (PgpException ex)
                {
                    Console.WriteLine($"Error reading the key file: {ex.Message}");
                    throw;
                }
                catch (IOException ex)
                {
                    Console.WriteLine($"IO error reading the key file: {ex.Message}");
                    throw;
                }
            }
        }

/// <summary>
        /// Gets the private key from a pgp amoured file ie. asc
        /// </summary>
        /// <param name="privateKeyFilePath"></param>
        /// <param name="passphrase"></param>
        /// <returns></returns>
        public static PgpPrivateKey GetPgpPrivateKey(string privateKeyFilePath, string passphrase)
        {
            try
            {
                PgpSecretKeyRing secretKeyRing;
                using (var keyFileStream = new FileStream(privateKeyFilePath, FileMode.Open))
                {
                    secretKeyRing = new PgpSecretKeyRing(PgpUtilities.GetDecoderStream(keyFileStream));
                }

                PgpSecretKey secretKey = secretKeyRing.GetSecretKey();
                PgpPrivateKey privateKey = secretKey.ExtractPrivateKey($"{passphrase}".ToCharArray());

                return privateKey;
            }
            catch (Exception ex)
            {
                // Handle exceptions, log errors, or take appropriate action.
                Console.WriteLine($"Error reading PGP private key from file: {ex.Message}");
                throw;
            }
        }

/// <summary>
/// Encrypts the provided plaintext data using the specified PGP public key.
/// </summary>
/// <param name="encryptionKey">The PGP public key used for encryption.</param>
/// <param name="plainText">The plaintext data to be encrypted.</param>
/// <returns>The encrypted data as a byte array.</returns>
public static byte[] EncryptDataWithPublicKey(PgpPublicKey encryptionKey, byte[] plainText)
{
    // Create a MemoryStream to store the encrypted data.
    using (MemoryStream encryptedStream = new())
    {
        // Create a PgpLiteralDataGenerator to generate literal data packets in PGP.
        using (PgpLiteralDataGenerator literalDataGenerator = new PgpLiteralDataGenerator())
        {
            // Open a stream with the PgpLiteralDataGenerator and write the plaintext data into a literal data packet.
            using (Stream literalDataStream = literalDataGenerator.Open(encryptedStream,
            PgpLiteralData.Binary,
            PgpLiteralData.Console,
            plainText.Length,
            DateTime.UtcNow))
            {
                literalDataStream.Write(plainText, 0, plainText.Length);
            }
        }

        // Create a MemoryStream to store the final result.
        using (MemoryStream resultStream = new())
        {
            // Create a PgpEncryptedDataGenerator with the specified symmetric key algorithm, enabling integrity protection.
            PgpEncryptedDataGenerator encryptedDataGenerator = new PgpEncryptedDataGenerator(
                SymmetricKeyAlgorithmTag.Aes256, true, new SecureRandom());

            // Add the encryption key to the generator.
            encryptedDataGenerator.AddMethod(encryptionKey);

            // Open a stream with the encryptedDataGenerator and write the encrypted data into the result stream.
            using (Stream compressedOut = encryptedDataGenerator.Open(resultStream, encryptedStream.ToArray().Length))
            {
                compressedOut.Write(encryptedStream.ToArray(), 0, encryptedStream.ToArray().Length);
            }

            // Return the encrypted data as a byte array.
            return resultStream.ToArray();
        }
    }

}

/// <summary>
/// Decrypts PGP encrypted data using the provided private key and returns the decrypted bytes.
/// </summary>
/// <param name="privateKey">The PGP private key used for decryption.</param>
/// <param name="encryptedB64String">The base64-encoded PGP encrypted data.</param>
/// <returns>The decrypted data as a byte array.</returns>
/// <exception cref="Exception">Thrown in case of decryption failure or IO exceptions.</exception>
public static byte[] DecryptDataWithPrivateKey(PgpPrivateKey privateKey, string encryptedB64String)
{
try
{
// Convert the base64-encoded PGP encrypted data to a byte array
byte[] pgpEncryptedData = Convert.FromBase64String(encryptedB64String);

    // Create a PgpObjectFactory for parsing the PGP encrypted data
    PgpObjectFactory pgpFact = new PgpObjectFactory(pgpEncryptedData);

    // Obtain the first object, which should be a PgpEncryptedDataList
    PgpEncryptedDataList encList = (PgpEncryptedDataList)pgpFact.NextPgpObject();

    // Find the correct PgpPublicKeyEncryptedData using the provided private key
    PgpPublicKeyEncryptedData? encData = null;
    foreach (PgpPublicKeyEncryptedData data in encList.GetEncryptedDataObjects())
    {
        if (data.KeyId == privateKey.KeyId)
        {
            encData = data;
            break;
        }
    }

    if (encData == null)
    {
        throw new PgpException("Provided private key not found in encrypted data.");
    }

    // Create a decrypted stream
    Stream clear = encData.GetDataStream(privateKey);

    // Create a new MemoryStream to hold the decrypted data
    using (MemoryStream decryptedStream = new MemoryStream())
    {
        // Read the decrypted data into the MemoryStream
        Streams.PipeAll(clear, decryptedStream);

        // Verify the integrity of the decrypted data
        if (encData.Verify())
        {
            // Create a PgpObjectFactory for parsing the decrypted literal data
            PgpObjectFactory litFact = new PgpObjectFactory(decryptedStream.ToArray());

            // Obtain the literal data packet
            PgpLiteralData litData = (PgpLiteralData)litFact.NextPgpObject();

            // Read the actual data from the literal data input stream
            using (Stream dataStream = litData.GetInputStream())
            {
                byte[] data = Streams.ReadAll(dataStream);
                return data;
            }
        }
        else
        {
            throw new PgpException("Modification check failed.");
        }
    }
}
catch (PgpException ex)
{
    throw new Exception("Decryption failed: " + ex.Message, ex);
}
catch (IOException ex)
{
    throw new Exception("IO exception during decryption: " + ex.Message, ex);
}

}