Safester.CryptoLibrary

Open PGP C# Portable Library - v1.0.12 - May 2019, 7

Fundamentals

Safester.CryptoLibrary is a simple to use portable encryption library based on OpenPGP.

It provides :

PGP key pair generation,
PGP encryption & decryption for files and texts

For ease of use, the scope of the library is voluntarily limited to encryption operations only. There are no signature methods.

Technical operating environment – Portable Library

Safester.CryptoLibrary is entirely written in C# and is packaged as a .NET Standard 2.0 portable library, which works on Windows Desktop and on Android, iOS & macOS with Xamarin.

The underlying crypto library used is Bouncy Castle through its portable implementation.

License

The library is licensed with the liberal Apache 2.0 license.

Installation

Install the NuGet Package.

Using the Library

Generating Key Pairs

Key Pair generation is done with the PgpKeyPairGenerator class:

string identity = "john@smith.com";
char [] passphrase = "my_passphrase".ToCharArray();

PgpKeyPairGenerator generator = 
    new PgpKeyPairGenerator(identity, passphrase, PublicKeyAlgorithm.RSA, PublicKeyLength.BITS_2048);
PgpKeyPairHolder pgpKeyPairHolder = generator.Generate();

It is then possible to retrieve the Base64 armored PGP keyrings to use for crypto operations:

String privateKeyring = pgpKeyPairHolder.PrivateKeyRing;
String publicKeyring = pgpKeyPairHolder.PublicKeyRing;

This is how the two keyrings look alike when displayed on the console:

Encrypting and Decrypting Files

Let's define the file to encrypt and the output file:

// Our sample runs on Windows... Just adapt for a Xamarin test.
string rootDir = Environment.GetFolderPath(Environment.SpecialFolder.UserProfile);
string inFile = rootDir + "\\safester_samples\\koala.jpg";
string outFile = rootDir + "\\safester_samples\\koala.jpg.pgp";

We will prepare an asymmetric / public key encryption using the generated PGP public key, we could use more than one if we wanted to encrypt for several persons, this is why a List<PgpPublicKey> is used:

PgpPublicKey pgpPublicKey = PgpPublicKeyGetter.ReadPublicKey(publicKeyring);
List<PgpPublicKey> encKeys = new List<PgpPublicKey>();
encKeys.Add(pgpPublicKey);

We then define if we want to Base64 armor the encrypted file and if the file integrity will be checked during decryption.

We will use an Encryptor and pass to the Encrypt method the List of PgpPublicKey. Because Safester.CrytolLibrary is a portable library that works on many environments, crypto operations on files are done passing read and write stream instances to the library classes. (The library thus does not use File descriptors that are implementation specific).

// Our sample runs on Windows. 
// We thus use System.IO.File to open the in and out streams
Stream inputStream = File.OpenRead(inFile); 
Stream outputStream = File.OpenWrite(outFile);

bool armor = false; // No ASCII Base64 armor, encrypted file will be binary
bool withIntegrityCheck = true;

// Create an Encryptor instance and pass the public keys and file streams
Encryptor encryptor = new Encryptor(armor, withIntegrityCheck);
encryptor.Encrypt(encKeys, inputStream, outputStream);
Console.WriteLine("Encryption done.");

Note that the two stream instances are always safely closed by Encrypt.

Decryption is straightforward using a Decryptor. We just pass the previous privateKeyring (built with

String privateKeyring = pgpKeyPairHolder.PrivateKeyRing) to the Decryptor constructor along with the necessary passphrase:

string inFileEncrypted = rootDir + "\\safester_samples\\koala.jpg.pgp"; 
string outFileDecrypted = rootDir + "\\safester_samples\\koala_2.jpg";

inputStream = File.OpenRead(inFileEncrypted);
outputStream = File.OpenWrite(outFileDecrypted);

Decryptor decryptor = new Decryptor(privateKeyring, passphrase);
decryptor.Decrypt(inputStream, outputStream);
Console.WriteLine("Decryption integrity check status: " + decryptor.Verify);
Console.WriteLine("Decryption done.");

Note that the two stream instances are always safely closed by Decrypt.

Encrypting and Decrypting Texts

Encryptor and Decryptor support string encryption:

String inText = "For a long time I would go to bed early. Sometimes, " +
    "the candle barely out, my eyes close so quickly that I did not have " +
    "time to tell myself \"I’m falling asleep.\"";
Encryptor encryptor = new Encryptor(armor, withIntegrityCheck);
string outText = encryptor.Encrypt(encKeys, inText);
Console.WriteLine("Encryption done.");

The encrypted outText is always Base64 armored for future direct usage in decryption:

Decryption is straightforward:

decryptor = new Decryptor(privateKeyring, passphrase);
string decryptedText = decryptor.Decrypt(outText);
Console.WriteLine("Decryption integrity check status: " + decryptor.Verify);
Console.WriteLine(decryptedText);

Code Samples

More samples are available in samples directory.

Name		Name	Last commit message	Last commit date
Latest commit History 59 Commits
CryptoLibrary.Samples		CryptoLibrary.Samples
CryptoLibrary		CryptoLibrary
.gitattributes		.gitattributes
.gitignore		.gitignore
LICENSE		LICENSE
README.md		README.md
Safester.CryptoLibrary.sln		Safester.CryptoLibrary.sln

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