SdJwt.Net.AgentTrust.Core 1.0.6

SdJwt.Net.AgentTrust.Core

Core primitives for issuing and verifying SD-JWT capability tokens used in agent-to-tool and agent-to-agent trust flows.

Install

dotnet add package SdJwt.Net.AgentTrust.Core

What This Package Provides

• CapabilityTokenIssuer for minting SD-JWT capability tokens.
• CapabilityTokenVerifier for validating signature, audience, expiry, and replay constraints.
• IKeyCustodyProvider and InMemoryKeyCustodyProvider for signing key access.
• INonceStore and MemoryNonceStore for replay prevention.
• IReceiptWriter and LoggingReceiptWriter for allow/deny audit receipts.
• Capability data models (CapabilityClaim, CapabilityContext, CapabilityLimits).

Quick Start

using Microsoft.IdentityModel.Tokens;
using SdJwt.Net.AgentTrust.Core;
using System.Security.Cryptography;

var signingBytes = RandomNumberGenerator.GetBytes(32);
var signingKey = new SymmetricSecurityKey(signingBytes);
var nonceStore = new MemoryNonceStore();

var issuer = new CapabilityTokenIssuer(
    signingKey,
    SecurityAlgorithms.HmacSha256,
    nonceStore);

var minted = issuer.Mint(new CapabilityTokenOptions
{
    Issuer = "agent://assistant-1",
    Audience = "https://tool-api.example.com",
    Capability = new CapabilityClaim
    {
        Tool = "crm",
        Action = "Read",
        Resource = "customer-profile",
        Limits = new CapabilityLimits { MaxResults = 25 }
    },
    Context = new CapabilityContext
    {
        CorrelationId = Guid.NewGuid().ToString("N"),
        WorkflowId = "wf-123"
    },
    Lifetime = TimeSpan.FromMinutes(1)
});

var verifier = new CapabilityTokenVerifier(nonceStore);
var verification = await verifier.VerifyAsync(
    minted.Token,
    new CapabilityVerificationOptions
    {
        ExpectedAudience = "https://tool-api.example.com",
        TrustedIssuers = new Dictionary<string, SecurityKey>
        {
            ["agent://assistant-1"] = signingKey
        }
    });

if (!verification.IsValid)
{
    throw new InvalidOperationException(verification.Error);
}

Core Validation Behavior

• Requires iss, aud, jti, exp, cap, and ctx claims.
• Validates signature against issuer key in TrustedIssuers.
• Enforces audience equality with ExpectedAudience.
• Rejects expired tokens with configurable ClockSkewTolerance.
• Enforces replay protection when EnforceReplayPrevention is enabled.

Recommended Production Practices

• Use a hardware-backed key provider through IKeyCustodyProvider.
• Keep token lifetime short (default is 60 seconds).
• Store replay nonces in distributed storage for multi-node deployments.
• Write receipts to durable audit storage via a custom IReceiptWriter.

Related Packages

• SdJwt.Net.AgentTrust.Policy
• SdJwt.Net.AgentTrust.AspNetCore
• SdJwt.Net.AgentTrust.Maf