ScottBrady.IdentityModel

Helper libraries for tokens and cryptography in .NET.

• EdDSA support for JWTs (Ed25519 and Ed448)
• Branca tokens with JWT style validation
• PASETO (v1.public & v2.public) with JWT style validation
• Base16 (hex) and Base62 encoders
• passwordrule attribute support for ASP.NET Identity
• Samples in ASP.NET Core

Feature requests welcome. Please see SECURITY.md for responsible disclosure policy.

EdDSA support

EdDSA is a modern signing algorithm, not yet supported out of the box in .NET. This library provides some useful abstractions around the Bouncy Castle (software) implementation of EdDSA.

// create EdDSA new key pair
EdDsa.Create(ExtendedSecurityAlgorithms.Curves.Ed25519)

// create EdDSA key from parameters
EdDsa.Create(new EdDsaParameters(ExtendedSecurityAlgorithms.Curves.Ed25519) 
  {D = Base64UrlEncoder.DecodeBytes(privateKey)})

// create EdDSA security key for use with Microsoft.IdentityModel JWT APIs (alg: EdDSA)
new EdDsaSecurityKey(EdDsa.Create(ExtendedSecurityAlgorithms.Curves.Ed25519))

Branca Tokens

Branca is token construct suitable for internal systems. The payload is encrypted using XChaCha20-Poly1305, using a 32-byte symmetric key.

This library supports the creation of Branca tokens with an arbitrary payload or using a JWT-style payload.

• NuGet: ScottBrady.IdentityModel.Tokens.Branca
• Test vectors

var handler = new BrancaTokenHandler();
var key = Encoding.UTF8.GetBytes("supersecretkeyyoushouldnotcommit");

// JWT-style payload
string token = handler.CreateToken(new SecurityTokenDescriptor
{
    Issuer = "me",
    Audience = "you",
    Expires = DateTime.UtcNow.AddMinutes(5),
    NotBefore = DateTime.UtcNow,
    Claims = new Dictionary<string, object> {{"sub", "123"}},
    EncryptingCredentials = new EncryptingCredentials(
        new SymmetricSecurityKey(key), ExtendedSecurityAlgorithms.XChaCha20Poly1305)
});

ClaimsPrincipal principal = handler.ValidateToken(
    token,
    new TokenValidationParameters
    {
        ValidIssuer = "me",
        ValidAudience = "you",
        TokenDecryptionKey = new SymmetricSecurityKey(key)
    }, out SecurityToken parsedToken);

PASETO

PASETO is a competing standard to JOSE & JWT that offers a versioned ciphersuite. This library currently implements v1 and v2 for the public purpose, suitable for zero-trust systems such as an OAuth authorization server.

Explicit versioning allows PASETO to side-step attacks on signature validation found in some JWT libraries. However, it does not mitigate any other attacks.

If you are considering using PASETO, I recommend reading RFC 8725 - JWT Best Current Practices and deciding if the interoperable JWT format is still wrong for you.

• NuGet: ScottBrady.IdentityModel.Tokens.Paseto
• Test vectors

var handler = new PasetoTokenHandler();
var privateKey = Convert.FromBase64String("TYXei5+8Qd2ZqKIlEuJJ3S50WYuocFTrqK+3/gHVH9B2hpLtAgscF2c9QuWCzV9fQxal3XBqTXivXJPpp79vgw==");
var publicKey = Convert.FromBase64String("doaS7QILHBdnPULlgs1fX0MWpd1wak14r1yT6ae/b4M=");

string token = handler.CreateToken(new PasetoSecurityTokenDescriptor(
    PasetoConstants.Versions.V2, PasetoConstants.Purposes.Public)
{
    Issuer = "me",
    Audience = "you",
    Expires = DateTime.UtcNow.AddMinutes(5),
    NotBefore = DateTime.UtcNow,
    Claims = new Dictionary<string, object> {{"sub", "123"}},
    SigningCredentials = new SigningCredentials(
        new EdDsaSecurityKey(EdDsa.Create(
            new EdDsaParameters(ExtendedSecurityAlgorithms.Curves.Ed25519)
            {
                D = privateKey
            })), ExtendedSecurityAlgorithms.EdDsa)
});

ClaimsPrincipal principal = handler.ValidateToken(
    token,
    new TokenValidationParameters
    {
        ValidIssuer = "me",
        ValidAudience = "you",
        IssuerSigningKey = new EdDsaSecurityKey(EdDsa.Create(
            new EdDsaParameters(ExtendedSecurityAlgorithms.Curves.Ed25519) {X = publicKey}))
    }, out SecurityToken parsedToken);

API Protection with JWT Style Handler

The Branca and PASETO token handlers can be used with the ASP.NET Core JWT bearer authentication handler.

services.AddAuthentication()
    .AddJwtBearer("paseto", options =>
    {
        options.SecurityTokenValidators.Clear();
        options.SecurityTokenValidators.Add(new PasetoTokenHandler());
        options.TokenValidationParameters.IssuerSigningKey = new EdDsaSecurityKey(EdDSA.Create(<your_public_key>));
        options.TokenValidationParameters.ValidIssuer = "you";
        options.TokenValidationParameters.ValidAudience = "me";
    })

Base16 (hex) Encoding

Base16 allows you to encode and decode hexidecimal strings..

var plaintext = "hello world"; // encoded = 68656c6c6f20776f726c64
string encoded = Base16.Encode(Encoding.UTF8.GetBytes(plaintext));

Base62 Encoding

Base62 encoding uses the 0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz character set.

var plaintext = "hello world"; // encoded = AAwf93rvy4aWQVw
string encoded = Base62.Encode(Encoding.UTF8.GetBytes(plaintext));