auth: use NATS.NKeys package for nkey signing

sandbox/MicroBenchmark/NKeyBench.cs

@@ -1,5 +1,5 @@
 using BenchmarkDotNet.Attributes;
-using NATS.Client.Core;
+using NATS.NKeys;
 
 namespace MicroBenchmark;
 
@@ -17,8 +17,8 @@ public int NKeyCreate()
         var result = 0;
         for (var i = 0; i < Iter; i++)
         {
-            var nkey = NKeys.FromSeed("SUAAVWRZG6M5FA5VRRGWSCIHKTOJC7EWNIT4JV3FTOIPO4OBFR5WA7X5TE");
-            result += nkey.PublicKey.Length;
+            using var kp = KeyPair.FromSeed("SUAAVWRZG6M5FA5VRRGWSCIHKTOJC7EWNIT4JV3FTOIPO4OBFR5WA7X5TE".AsSpan());
+            result += kp.GetPublicKey().Length;
         }
 
         return result;

src/NATS.Client.Core/Internal/UserCredentials.cs

@@ -1,7 +1,6 @@
-using System.Security.Cryptography;
 using System.Text;
 using Microsoft.Extensions.Logging;
-using NATS.Client.Core.NaCl;
+using NATS.NKeys;
 
 namespace NATS.Client.Core.Internal;
 
@@ -54,11 +53,11 @@ public UserCredentials(NatsAuthOpts authOpts)
         if (seed == null || nonce == null)
             return null;
 
-        using var kp = NKeys.FromSeed(seed);
-        var bytes = kp.Sign(Encoding.ASCII.GetBytes(nonce));
-        var sig = CryptoBytes.ToBase64String(bytes);
+        using var kp = KeyPair.FromSeed(seed.AsSpan());
+        var signature = new byte[64];
+        kp.Sign(Encoding.ASCII.GetBytes(nonce), signature);
 
-        return sig;
+        return Convert.ToBase64String(signature);
     }
 
     internal async Task AuthenticateAsync(ClientOpts opts, ServerInfo? info, NatsUri uri, TimeSpan timeout, CancellationToken cancellationToken)
@@ -99,7 +98,10 @@ internal async Task AuthenticateAsync(ClientOpts opts, ServerInfo? info, NatsUri
                 if (!string.IsNullOrEmpty(authCred.Secret))
                 {
                     seed = authCred.Secret;
-                    opts.NKey = NKeys.PublicKeyFromSeed(seed);
+                    using (var kp = KeyPair.FromSeed(seed.AsSpan()))
+                    {
+                        opts.NKey = kp.GetPublicKey();
+                    }
                 }
 
                 break;

src/NATS.Client.Core/NATS.Client.Core.csproj

@@ -10,6 +10,7 @@
     <ItemGroup>
         <PackageReference Include="Microsoft.Extensions.Logging.Abstractions" Version="6.0.1"/>
         <PackageReference Include="Microsoft.Extensions.Primitives" Version="6.0.0"/>
+        <PackageReference Include="NATS.NKeys" Version="1.0.1"/>
         <PackageReference Include="Microsoft.VisualStudio.Threading.Analyzers" Version="17.10.48">
             <PrivateAssets>all</PrivateAssets>
             <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>