DotNet Core SSH KeyGen

After searching around for a solution to creating SSH keys using C# and dotnet core I came across the following stackoverflow posts which explain how to convert from RSACryptoServiceProvider to values suitable for use with ssh.

Supported Platforms

• .NET 4.5 (Desktop / Server)
• .NET Standard 2.0
• .NET Standard 2.1
• .NET 5.0
• .NET 6.0

Installation

SshKeyGenerator is a library for .NET and is available on NuGet:

Install-Package SshKeyGenerator

or

dotnet add package SshKeyGenerator

Usage Example

var keygen = new SshKeyGenerator.SshKeyGenerator(2048);

var privateKey = keygen.ToPrivateKey();
Console.WriteLine(privateKey);

var publicSshKey = keygen.ToRfcPublicKey();
Console.WriteLine(publicSshKey);

var publicSshKeyWithComment = keygen.ToRfcPublicKey("user@domain.com");
Console.WriteLine(publicSshKeyWithComment);

Sample Output

keygen.ToPrivateKey()

-----BEGIN RSA PRIVATE KEY-----
MIIEowIBAAKCAQEAs1O/9F2XlZVaVWEUYfflxx0wDG9FE09hQF2wngA6EemHpe6I
hvdwvQ7obrZ85jSYdBxBRjNAYF3T9+wU+8w6m4qZCVYvqqRjszN8j3VwUBLzWilt
...
wDGzJIkmbhANi+252pH6PAuWjZPfz8COGA6QPPH0/khpHPj1LY4mi5Ubi3YT1uRo
dOGttjtkj9fLX5IQ81G9HR0MdT1Gd4fPenYPOUCgCPB5adpT1BB+
-----END RSA PRIVATE KEY-----

keygen.ToRfcPublicKey()

ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQCzU7/0XZeVlVpVYRRh9
...
+ohFsbcbAMcfLWGUdouyHvLvF21G0z50z2i2CrU7WW4WdrGGfxhU3TeRTXd7Skwk/K7iBBn3oc/xct generated-key

keygen.ToRfcPublicKey("user@domain.com")

ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQCzU7/0XZeVlVpVYRRh9
...
+ohFsbcbAMcfLWGUdouyHvLvF21G0z50z2i2CrU7WW4WdrGGfxhU3TeRTXd7Skwk/K7iBBn3oc/xct user@domain.com

Export Methods

There are three methods which can be used to export SSH key data for use by other libraries such as FxSsh:

1. byte[] ToBlobs : Export as Blobs
2. string ToB64Blob : Export blobs as base64 string
3. string ToXml : Export as XML string

Export methods usage:

// Create a new instance 
var keygen = new SshKeyGenerator.SshKeyGenerator(4096);

// Get Base64 encoded keys with private key
var base64Keys = keygen.ToB64Blob(true);

// Use in a SSH server. e.g. FxSsh
var server = new SshServer();
server.AddHostKey("ssh-rsa", base64Keys);

References

• Exporting Private Key: https://stackoverflow.com/a/23739932
• Exporting Public Key: https://stackoverflow.com/a/25591659
• Exporting Public Key in RFC4716 Format: https://stackoverflow.com/a/47917364

Contributors

Thanks to the following contributors for their assistance with this library.

• @ryangribble
• @richardlawley
• @sauditore