Add managed TLS interoperability and persisted credentials

.github/workflows/dotnet.yml

@@ -53,4 +53,4 @@ jobs:
           ./build/dev/bin/voicecat-dotnet-oracle build/dev/cpp-wire.json
           diff -u dotnet/tests/VoiceCat.Tests/Fixtures/cpp-wire.json build/dev/cpp-wire.json
           dotnet restore dotnet/VoiceCat.slnx --locked-mode
-          dotnet test dotnet/VoiceCat.slnx -c Release --no-restore
+          VOICECAT_TLS_ORACLE="$PWD/build/dev/bin/voicecat-dotnet-tls-oracle" dotnet test dotnet/VoiceCat.slnx -c Release --no-restore

PROGRESS.md

@@ -10,6 +10,19 @@ up instantly. Newest status at the top.
 
 ## ▶ Where we left off / next action
 
+- **Done (2026-09-15): TLS exporter interoperability and persisted credentials.** Foundation commit
+  `b76181d` pushed to `origin/dotnet/foundations`. Added a nonblocking managed TLS 1.3
+  session with certificate acceptance gate and directional media factories. Managed
+  loopback and C++ interoperability pass; exporter keys are captured inside BouncyCastle's
+  handshake callback before its exporter secrets are destroyed. The C++ TLS oracle
+  authenticates encrypted challenges in both directions against the existing mbedTLS
+  context. Added explicit persisted TOFU pins, compatible Ed25519 identity/PEM import,
+  new certificate identity SAN, and rejection of incomplete credential sets.
+  **Verified:** 42/42 managed tests with the native TLS oracle enabled; native dev build
+  and 29/29 CTest tests green; 16 permissive package licenses verified. Complete socket
+  orchestration and managed server/client state remain pending.
+  **Next:** Phase 3 codec/DSP wrappers and native packaging.
+
 - **Done (2026-09-15): Initial .NET wire/crypto port** on `dotnet/foundations`, from `cs-port`.
   Added `dotnet/` solution, schema code generation, pipe framing, immutable voice headers,
   directional media encryption/decryption, and xUnit conformance tests. Both platform

docs/api-dotnet.md

@@ -31,8 +31,8 @@ Higher layers decide which values they support.
 
 `MediaEncryptor` and `MediaDecryptor` each own one directional 32-byte session key
 and mutable packet state. Use one owner at a time; they provide no synchronization.
-Production constructs them from TLS exporter keys when TLS is implemented. Raw-key
+Production constructs them through `TlsSession` media factories after its handshake.
-constructors support conformance tests and the future TLS integration.
+Raw-key constructors support conformance tests.
 
 `MediaEncryptor.Encrypt(VoiceFrameHeader, ReadOnlySpan<byte>, Span<byte>)` writes
 the full header plus ciphertext and 16-byte tag and returns packet length. It replaces
@@ -55,3 +55,63 @@ allocates per packet; audio and relay allocation guarantees are later checkpoint
 
 Dispose both objects to clear their owned key arrays and release platform crypto
 resources. Use after disposal throws `ObjectDisposedException`.
+
+## TLS sessions
+
+`TlsSession` is a single-owner, nonblocking BouncyCastle TLS 1.3 state machine.
+It owns no socket or worker thread. The transport owner feeds `ReceiveCiphertext`,
+fully drains `DrainCiphertext` to its socket (including partial sends), and reads
+application data through `ReadPlaintext`. Reads and drains return a byte count and
+may require repeated calls. `WritePlaintext` requires `IsReady`. Socket cancellation,
+backpressure, and connection lifetime belong to the transport owner.
+
+`CreateClient(Func<string, bool>)` requires an explicit certificate acceptance
+callback. It receives the uppercase SHA-256 fingerprint of the leaf certificate's
+DER bytes during the handshake. Returning false rejects the session before application
+data or media keys are available. This is TOFU certificate pinning; there is no PKI
+chain or hostname validation. The synchronous callback must have the trust decision
+available; an asynchronous first-connect prompt requires a subsequent connection
+after explicit acceptance. Never automatically accept or persist an unknown pin.
+
+`CreateServer(certificatePem, privateKeyPem)` supports ECDSA credentials; use
+`ServerCredentials.CreateTlsSession()` to import persisted credentials. TLS 1.2 is
+rejected. Handshake completion captures two 32-byte exporter keys using label
+`voicecat media v1` and one-byte contexts 0 (client to server) and 1 (server to client).
+BouncyCastle discards its exporter secrets after that callback. Media factories
+select the correct direction for each role and require a ready session.
+
+Create one encryptor and decryptor per connection and retain them for the connection's
+lifetime: constructing a second encryptor resets its counter and would reuse nonces.
+Dispose media objects separately from the TLS session. `Close()` queues close_notify;
+drain it before disposal. On socket EOF call `CompleteInput()`; missing close_notify
+throws `IOException`. TLS/protocol errors require closing the connection. Disposal
+clears the session's owned exporter arrays and scratch buffer.
+
+## Persisted trust and credentials
+
+`TofuStore` uses the existing UTF-8 `host:port lowercase-hex-fingerprint` format.
+Host matching is ordinal and case sensitive, matching native behavior. `Check`
+returns `FirstConnect`, `Matched`, or `Mismatch` without changing persistence.
+Only explicit `Pin` or `Remove` changes the file. Pin replacement requires an
+explicit caller decision; malformed files fail closed. Changes replace the file
+atomically before updating memory. Use one owner per store/file.
+
+`ServerIdentity` reads and writes the native 96-byte Ed25519 format:
+`public-key[32] || seed[32] || public-key[32]`. Loading verifies both public-key
+copies against the seed. Disposal clears the owned seed.
+
+`ServerCredentials.LoadOrCreate(directory, serverName)` imports `identity.key`,
+`server.crt`, and `server.key` unchanged. If all are absent it creates an ECDSA-P256
+self-signed certificate and identity. If only some exist it rejects startup rather
+than rotating identity. Restore the missing files. New certificates include SAN URI
+`urn:voicecat:identity:ed25519:<lowercase-public-key-hex>`; legacy certificates are
+accepted unchanged. Checking this URI against ServerHello's identity is deferred
+until the managed handshake/session layer is implemented; trust currently pins the
+leaf certificate. Dispose credentials after their TLS sessions are created/finished
+as required by the application lifetime.
+
+Private file writes use a same-directory temporary file, flush, and atomic replacement.
+On Unix new files use owner read/write permissions; Windows inherits directory ACLs.
+The credential directory must have one provisioning owner. PEM strings and crypto
+library internal copies are managed memory; owned-array clearing does not promise
+erasure of every runtime/library copy.

docs/porting-to-dotnet.md

@@ -1,6 +1,8 @@
 # Porting VoiceCat to pure .NET / C#
 
-**Status:** initial wire/crypto slice implemented under `dotnet/`; later phases remain planned.
+**Status:** wire/media crypto and TLS/exporter foundations implemented under `dotnet/`,
+including C++ interoperability, persisted TOFU, and compatible server credentials.
+Codec/audio, managed server/client state, and UI phases remain planned.
 See `dotnet/README.md`, `docs/api-dotnet.md`, and `PROGRESS.md` for verification and next steps.
 **Target runtime:** .NET 10 LTS (in-service to Nov 2028), with .NET 11 as the follow-on.
 **Scope:** replace the C++ core (`libvoicecat`), the C++ server, the C++ `vccli`, and the
@@ -676,6 +678,16 @@ not assumed.
 **Exit criterion:** C# client completes a TLS 1.3 handshake with the C++ server, derives
 matching media keys, and pins the leaf fingerprint.
 
+**Checkpoint (2026-09-15):** implemented nonblocking managed TLS, handshake-time
+exporters, explicit certificate acceptance, persisted TOFU, and native-compatible
+credentials. The C++ TLS oracle authenticates a media challenge in both directions
+over an actual socket, proving exporter compatibility. Tests also cover managed
+fragmented loopback, first-connect acceptance, changed-pin rejection, TLS 1.2 rejection,
+close_notify/abrupt EOF, restart persistence, and import of C++ credential files.
+Socket orchestration remains a transport-owner responsibility; the complete managed
+server and client are later phases. See `dotnet/README.md` for the required native
+interoperability test command.
+
 ---
 
 ### Phase 3 — Codec + DSP (est. 1 week)

docs/security.md

@@ -49,6 +49,16 @@ This is a known limitation of the current design. Closing it properly requires b
 Ed25519 key into the TLS cert (e.g. as a SubjectAltName or extension), which is a planned
 future improvement. Until then, clients display both values but gate on the cert fingerprint.
 
+**Managed rewrite checkpoint:** `dotnet/` uses nonblocking BouncyCastle TLS 1.3 and
+captures directional exporters during handshake completion. Its client requires an
+explicit leaf-fingerprint acceptance callback; PKI validation remains unimplemented.
+New managed server certificates include the Ed25519 public key in SAN URI
+`urn:voicecat:identity:ed25519:<lowercase-public-key-hex>`. Existing C++ credentials
+are imported unchanged. Verifying that URI against the declared ServerHello identity
+is still deferred to the managed session layer; leaf-certificate TOFU remains the
+trust gate. Missing members of a persisted credential set cause startup rejection
+rather than automatic identity rotation. See [api-dotnet.md](api-dotnet.md).
+
 Client certificates are reserved for a future "key-based identity" option (see roadmap) but
 are not required in v1.
 

dotnet/README.md

@@ -1,7 +1,8 @@
 # VoiceCat .NET rewrite
 
 The first slice targets .NET 10: protobuf, control framing, voice headers, and media
-encryption. TLS, server/client state, audio, and UI migration are next. The existing
+encryption, TLS 1.3, persisted TOFU pins, and server credentials. Server/client state,
+audio, and UI migration are next. The existing
 C++ implementation remains the conformance oracle.
 
 From the repository root:
@@ -46,9 +47,25 @@ and 65536. Keys contain bytes 0–31; payload bytes count upward from zero. The
 20-byte header has type 1, marker flag, codec 0, SSRC `0xcafebabe`, timestamp 960.
 Both managed crypto backends must match these bytes.
 
+## TLS interoperability
+
+The optional TLS oracle uses the existing mbedTLS context and libsodium media crypto.
+The test authenticates an encrypted challenge in both directions, proving exporter
+compatibility without sending raw keys. It also loads the C++ server's credential files.
+
+```powershell
+cmake --build --preset dev --target voicecat-dotnet-tls-oracle
+$env:VOICECAT_TLS_ORACLE = (Resolve-Path build/dev/bin/voicecat-dotnet-tls-oracle.exe).Path
+dotnet test dotnet/VoiceCat.slnx -c Release --no-restore
+```
+
+On Linux/macOS, set `VOICECAT_TLS_ORACLE` to the absolute executable path without
+`.exe`. Without that variable, only this native interoperability test is skipped;
+managed TLS loopback, rejection, persistence, and wire tests still run. CI's C++
+conformance job requires the native test. See `docs/api-dotnet.md` for ownership
+and certificate acceptance requirements.
+
 ## Next checkpoint
 
-Prove BouncyCastle TLS 1.3 loopback and interoperability with the C++ mbedTLS server,
+Port codec/DSP wrappers and their native packaging per Phase 3 of the porting plan.
-including exporter label `voicecat media v1`, one-byte direction contexts 0/1,
+The managed server follows, tested first with the existing C++ CLI.
-and TLS leaf certificate fingerprint pinning. Then implement the managed server,
-tested first with the existing C++ CLI.

dotnet/oracle/CMakeLists.txt

@@ -2,3 +2,8 @@ add_executable(voicecat-dotnet-oracle main.cpp)
 target_link_libraries(voicecat-dotnet-oracle PRIVATE voicecat::voicecat)
 target_include_directories(voicecat-dotnet-oracle PRIVATE ${CMAKE_SOURCE_DIR}/core/src)
 target_compile_features(voicecat-dotnet-oracle PRIVATE cxx_std_20)
+
+add_executable(voicecat-dotnet-tls-oracle tls.cpp)
+target_link_libraries(voicecat-dotnet-tls-oracle PRIVATE voicecat::voicecat)
+target_include_directories(voicecat-dotnet-tls-oracle PRIVATE ${CMAKE_SOURCE_DIR}/core/src)
+target_compile_features(voicecat-dotnet-tls-oracle PRIVATE cxx_std_20)

dotnet/oracle/tls.cpp

@@ -0,0 +1,76 @@
+#ifdef _WIN32
+#include <winsock2.h>
+#include <ws2tcpip.h>
+using socket_type = SOCKET;
+static void close_socket(socket_type socket) { closesocket(socket); }
+#else
+#include <arpa/inet.h>
+#include <sys/socket.h>
+#include <unistd.h>
+using socket_type = int;
+static void close_socket(socket_type socket) { close(socket); }
+#endif
+
+#include "crypto/crypto.h"
+#include "net/voice_frame.h"
+#include <filesystem>
+#include <fstream>
+#include <iostream>
+
+static bool transfer(voicecat::crypto::TlsContext& tls, uint8_t* data, size_t size, bool writing) {
+    while (size != 0) {
+        int count = writing ? tls.write(data, size) : tls.read(data, size);
+        if (count <= 0) return false;
+        data += count;
+        size -= count;
+    }
+    return true;
+}
+
+int main(int argc, char** argv) {
+    if (argc != 2 || sodium_init() < 0) return 1;
+#ifdef _WIN32
+    WSADATA data{};
+    if (WSAStartup(MAKEWORD(2, 2), &data) != 0) return 1;
+#endif
+    try {
+        auto certificate = voicecat::crypto::ServerCert::generate("dotnet-tls-oracle");
+        auto directory = std::filesystem::path(argv[1]);
+        socket_type listener = socket(AF_INET, SOCK_STREAM, 0);
+        sockaddr_in address{};
+        address.sin_family = AF_INET;
+        address.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
+        if (bind(listener, reinterpret_cast<sockaddr*>(&address), sizeof(address)) != 0 || listen(listener, 1) != 0) return 1;
+        socklen_t length = sizeof(address);
+        if (getsockname(listener, reinterpret_cast<sockaddr*>(&address), &length) != 0) return 1;
+        certificate.save(directory / "server.crt", directory / "server.key");
+        voicecat::crypto::ServerIdentity::generate().save(directory / "identity.key");
+        std::ofstream(directory / "port.txt") << ntohs(address.sin_port);
+        socket_type peer = accept(listener, nullptr, nullptr);
+        close_socket(listener);
+        if (peer == static_cast<socket_type>(-1)) return 1;
+        voicecat::crypto::TlsContext tls(voicecat::crypto::TlsContext::Role::Server, &certificate);
+        tls.set_read_timeout(10000);
+        std::string error;
+        if (!tls.handshake(static_cast<int>(peer), error)) { std::cerr << error; return 1; }
+        auto sender = voicecat::crypto::SodiumMediaCrypto::derive_send(tls, false);
+        auto receiver = voicecat::crypto::SodiumMediaCrypto::derive_recv(tls, false);
+        if (!sender || !receiver) return 1;
+        voicecat::net::VoiceFrame header;
+        header.ssrc = 42;
+        header.seq = sender->peek_send_counter();
+        std::array<uint8_t, 41> packet{};
+        voicecat::net::serialize_header(header, packet.data());
+        const std::array<uint8_t, 5> message{ 'h', 'e', 'l', 'l', 'o' };
+        if (sender->seal(message.data(), message.size(), packet.data(), 20, packet.data() + 20, 21) != 21) return 1;
+        if (!transfer(tls, packet.data(), packet.size(), true) || !transfer(tls, packet.data(), packet.size(), false)) return 1;
+        std::array<uint8_t, 5> recovered{};
+        if (receiver->open(packet.data() + 20, 21, packet.data(), 20, recovered.data(), recovered.size()) != 5 || recovered != message) return 1;
+        uint8_t acknowledgement = 1;
+        if (!transfer(tls, &acknowledgement, 1, true)) return 1;
+        return 0;
+    } catch (const std::exception& error) {
+        std::cerr << error.what();
+        return 1;
+    }
+}

dotnet/src/VoiceCat.Crypto/PrivateFiles.cs

@@ -0,0 +1,22 @@
+namespace VoiceCat.Crypto;
+
+internal static class PrivateFiles
+{
+    public static void Write(string path, ReadOnlySpan<byte> data)
+    {
+        string destination = Path.GetFullPath(path);
+        string temporary = destination + "." + Guid.NewGuid().ToString("N") + ".tmp";
+        try
+        {
+            var options = new FileStreamOptions { Mode = FileMode.CreateNew, Access = FileAccess.Write, Share = FileShare.None };
+            if (!OperatingSystem.IsWindows()) options.UnixCreateMode = UnixFileMode.UserRead | UnixFileMode.UserWrite;
+            using (var stream = new FileStream(temporary, options))
+            {
+                stream.Write(data);
+                stream.Flush(flushToDisk: true);
+            }
+            File.Move(temporary, destination, overwrite: true);
+        }
+        finally { if (File.Exists(temporary)) File.Delete(temporary); }
+    }
+}

dotnet/src/VoiceCat.Crypto/ServerCredentials.cs

@@ -0,0 +1,75 @@
+using System.Security.Cryptography;
+using System.Security.Cryptography.X509Certificates;
+using System.Text;
+
+namespace VoiceCat.Crypto;
+
+public sealed class ServerCredentials : IDisposable
+{
+    private readonly X509Certificate2 certificate;
+    private bool disposed;
+
+    private ServerCredentials(ServerIdentity identity, X509Certificate2 certificate)
+    {
+        Identity = identity;
+        this.certificate = certificate;
+    }
+
+    public ServerIdentity Identity { get; }
+    public string CertificateFingerprint => Convert.ToHexString(SHA256.HashData(certificate.RawData));
+
+    public static ServerCredentials LoadOrCreate(string directory, string serverName)
+    {
+        ArgumentException.ThrowIfNullOrWhiteSpace(serverName);
+        Directory.CreateDirectory(directory);
+        string identityPath = Path.Combine(directory, "identity.key");
+        string certificatePath = Path.Combine(directory, "server.crt");
+        string keyPath = Path.Combine(directory, "server.key");
+        bool hasIdentity = File.Exists(identityPath);
+        bool hasCertificate = File.Exists(certificatePath);
+        bool hasKey = File.Exists(keyPath);
+        if (hasIdentity && hasCertificate && hasKey)
+        {
+            var identity = ServerIdentity.Load(identityPath);
+            try { return new(identity, X509Certificate2.CreateFromPemFile(certificatePath, keyPath)); }
+            catch { identity.Dispose(); throw; }
+        }
+        if (hasIdentity || hasCertificate || hasKey)
+            throw new InvalidDataException("Server credentials are incomplete; restore the missing files before starting.");
+        var generated = ServerIdentity.Generate();
+        try
+        {
+            using var key = ECDsa.Create(ECCurve.NamedCurves.nistP256);
+            var name = new X500DistinguishedNameBuilder();
+            name.AddCommonName(serverName);
+            var request = new CertificateRequest(name.Build(), key, HashAlgorithmName.SHA256);
+            request.CertificateExtensions.Add(new X509KeyUsageExtension(X509KeyUsageFlags.DigitalSignature, true));
+            var san = new SubjectAlternativeNameBuilder();
+            san.AddUri(new Uri("urn:voicecat:identity:ed25519:" + Convert.ToHexString(generated.PublicKey).ToLowerInvariant()));
+            request.CertificateExtensions.Add(san.Build());
+            using var created = request.CreateSelfSigned(DateTimeOffset.UtcNow.AddMinutes(-5), DateTimeOffset.UtcNow.AddYears(10));
+            string certificatePem = created.ExportCertificatePem();
+            string privateKeyPem = key.ExportPkcs8PrivateKeyPem();
+            generated.Save(identityPath);
+            PrivateFiles.Write(certificatePath, Encoding.UTF8.GetBytes(certificatePem));
+            PrivateFiles.Write(keyPath, Encoding.UTF8.GetBytes(privateKeyPem));
+            return new(generated, X509Certificate2.CreateFromPem(certificatePem, privateKeyPem));
+        }
+        catch { generated.Dispose(); throw; }
+    }
+
+    public TlsSession CreateTlsSession()
+    {
+        ObjectDisposedException.ThrowIf(disposed, this);
+        using var key = certificate.GetECDsaPrivateKey() ?? throw new InvalidDataException("Server TLS certificate requires an ECDSA key.");
+        return TlsSession.CreateServer(certificate.ExportCertificatePem(), key.ExportPkcs8PrivateKeyPem());
+    }
+
+    public void Dispose()
+    {
+        if (disposed) return;
+        disposed = true;
+        Identity.Dispose();
+        certificate.Dispose();
+    }
+}

dotnet/src/VoiceCat.Crypto/ServerIdentity.cs

@@ -0,0 +1,58 @@
+using System.Security.Cryptography;
+using Org.BouncyCastle.Crypto.Parameters;
+
+namespace VoiceCat.Crypto;
+
+public sealed class ServerIdentity : IDisposable
+{
+    private readonly byte[] seed;
+    private readonly byte[] publicKey;
+    private bool disposed;
+
+    private ServerIdentity(byte[] seed)
+    {
+        this.seed = seed;
+        publicKey = new Ed25519PrivateKeyParameters(seed, 0).GeneratePublicKey().GetEncoded();
+    }
+
+    public byte[] PublicKey => (byte[])publicKey.Clone();
+    public string Fingerprint => Convert.ToHexString(SHA256.HashData(publicKey));
+
+    public static ServerIdentity Generate() => new(RandomNumberGenerator.GetBytes(32));
+
+    public static ServerIdentity Load(string path)
+    {
+        byte[] data = File.ReadAllBytes(path);
+        try
+        {
+            if (data.Length != 96) throw new InvalidDataException("Server identity must contain 96 bytes.");
+            var identity = new ServerIdentity(data.AsSpan(32, 32).ToArray());
+            if (!CryptographicOperations.FixedTimeEquals(identity.publicKey, data.AsSpan(0, 32)) ||
+                !CryptographicOperations.FixedTimeEquals(identity.publicKey, data.AsSpan(64, 32)))
+            {
+                identity.Dispose();
+                throw new InvalidDataException("Server identity public key does not match its seed.");
+            }
+            return identity;
+        }
+        finally { CryptographicOperations.ZeroMemory(data); }
+    }
+
+    public void Save(string path)
+    {
+        ObjectDisposedException.ThrowIf(disposed, this);
+        byte[] data = new byte[96];
+        publicKey.CopyTo(data, 0);
+        seed.CopyTo(data, 32);
+        publicKey.CopyTo(data, 64);
+        try { PrivateFiles.Write(path, data); }
+        finally { CryptographicOperations.ZeroMemory(data); }
+    }
+
+    public void Dispose()
+    {
+        if (disposed) return;
+        disposed = true;
+        CryptographicOperations.ZeroMemory(seed);
+    }
+}

dotnet/src/VoiceCat.Crypto/TlsSession.cs

@@ -0,0 +1,208 @@
+using System.Security.Cryptography;
+using Org.BouncyCastle.Crypto;
+using Org.BouncyCastle.OpenSsl;
+using Org.BouncyCastle.Tls;
+using Org.BouncyCastle.Tls.Crypto;
+using Org.BouncyCastle.Tls.Crypto.Impl.BC;
+
+namespace VoiceCat.Crypto;
+
+public sealed class TlsSession : IDisposable
+{
+    private readonly TlsProtocol protocol;
+    private readonly bool isClient;
+    private readonly byte[] scratch = new byte[16384];
+    private byte[]? clientToServerKey;
+    private byte[]? serverToClientKey;
+    private bool disposed;
+
+    private TlsSession(TlsProtocol protocol, bool isClient)
+    {
+        this.protocol = protocol;
+        this.isClient = isClient;
+    }
+
+    public bool IsReady => !disposed && clientToServerKey is not null && serverToClientKey is not null && !protocol.IsClosed;
+    public string? PeerCertificateFingerprint { get; private set; }
+    public int PendingCiphertextBytes => protocol.GetAvailableOutputBytes();
+
+    public void Close()
+    {
+        ObjectDisposedException.ThrowIf(disposed, this);
+        protocol.Close();
+    }
+
+    public void CompleteInput()
+    {
+        ObjectDisposedException.ThrowIf(disposed, this);
+        protocol.CloseInput();
+    }
+
+    public static TlsSession CreateClient(Func<string, bool> acceptCertificate)
+    {
+        ArgumentNullException.ThrowIfNull(acceptCertificate);
+        var protocol = new TlsClientProtocol();
+        var session = new TlsSession(protocol, true);
+        protocol.Connect(new ClientPeer(session, acceptCertificate));
+        return session;
+    }
+
+    public static TlsSession CreateServer(string certificatePem, string privateKeyPem)
+    {
+        ArgumentException.ThrowIfNullOrWhiteSpace(certificatePem);
+        ArgumentException.ThrowIfNullOrWhiteSpace(privateKeyPem);
+        var protocol = new TlsServerProtocol();
+        var session = new TlsSession(protocol, false);
+        protocol.Accept(new ServerPeer(session, certificatePem, privateKeyPem));
+        return session;
+    }
+
+    public void ReceiveCiphertext(ReadOnlySpan<byte> input)
+    {
+        ObjectDisposedException.ThrowIf(disposed, this);
+        while (!input.IsEmpty)
+        {
+            int count = Math.Min(input.Length, scratch.Length);
+            input[..count].CopyTo(scratch);
+            protocol.OfferInput(scratch, 0, count);
+            input = input[count..];
+        }
+    }
+
+    public int DrainCiphertext(Span<byte> output)
+    {
+        ObjectDisposedException.ThrowIf(disposed, this);
+        int count = protocol.ReadOutput(scratch, 0, Math.Min(output.Length, scratch.Length));
+        scratch.AsSpan(0, count).CopyTo(output);
+        return count;
+    }
+
+    public int ReadPlaintext(Span<byte> output)
+    {
+        ObjectDisposedException.ThrowIf(disposed, this);
+        int count = protocol.ReadInput(scratch, 0, Math.Min(output.Length, scratch.Length));
+        scratch.AsSpan(0, count).CopyTo(output);
+        CryptographicOperations.ZeroMemory(scratch.AsSpan(0, count));
+        return count;
+    }
+
+    public void WritePlaintext(ReadOnlySpan<byte> input)
+    {
+        RequireReady();
+        protocol.WriteApplicationData(input);
+    }
+
+    public MediaEncryptor CreateMediaEncryptor()
+    {
+        byte[] key = ExportMediaKey(isClient ? (byte)0 : (byte)1);
+        try { return new(key); }
+        finally { CryptographicOperations.ZeroMemory(key); }
+    }
+
+    public MediaDecryptor CreateMediaDecryptor()
+    {
+        byte[] key = ExportMediaKey(isClient ? (byte)1 : (byte)0);
+        try { return new(key); }
+        finally { CryptographicOperations.ZeroMemory(key); }
+    }
+
+    internal byte[] ExportMediaKey(byte direction)
+    {
+        RequireReady();
+        ArgumentOutOfRangeException.ThrowIfGreaterThan(direction, (byte)1);
+        return (byte[])(direction == 0 ? clientToServerKey! : serverToClientKey!).Clone();
+    }
+
+    private void CompleteHandshake(TlsContext context)
+    {
+        // BouncyCastle destroys exporter secrets after this callback returns.
+        clientToServerKey = context.ExportKeyingMaterial("voicecat media v1", [0], 32);
+        serverToClientKey = context.ExportKeyingMaterial("voicecat media v1", [1], 32);
+    }
+
+    private void RequireReady()
+    {
+        ObjectDisposedException.ThrowIf(disposed, this);
+        if (!IsReady) throw new InvalidOperationException("TLS handshake has not completed or the session is closed.");
+    }
+
+    public void Dispose()
+    {
+        if (disposed) return;
+        disposed = true;
+        try { protocol.Close(); }
+        finally
+        {
+            if (clientToServerKey is not null) CryptographicOperations.ZeroMemory(clientToServerKey);
+            if (serverToClientKey is not null) CryptographicOperations.ZeroMemory(serverToClientKey);
+            CryptographicOperations.ZeroMemory(scratch);
+        }
+    }
+
+    private sealed class ClientPeer(TlsSession session, Func<string, bool> acceptCertificate)
+        : DefaultTlsClient(new BcTlsCrypto())
+    {
+        protected override ProtocolVersion[] GetSupportedVersions() => [ProtocolVersion.TLSv13];
+        protected override int[] GetSupportedCipherSuites() => CipherSuites;
+        public override TlsAuthentication GetAuthentication() => new Authentication(session, acceptCertificate);
+        public override void NotifyHandshakeComplete()
+        {
+            base.NotifyHandshakeComplete();
+            session.CompleteHandshake(m_context);
+        }
+    }
+
+    private sealed class Authentication(TlsSession session, Func<string, bool> acceptCertificate) : TlsAuthentication
+    {
+        public void NotifyServerCertificate(TlsServerCertificate serverCertificate)
+        {
+            var chain = serverCertificate.Certificate.GetCertificateList();
+            if (chain.Length == 0) throw new TlsFatalAlert(AlertDescription.bad_certificate);
+            string fingerprint = Convert.ToHexString(SHA256.HashData(chain[0].GetEncoded()));
+            session.PeerCertificateFingerprint = fingerprint;
+            if (!acceptCertificate(fingerprint)) throw new TlsFatalAlert(AlertDescription.bad_certificate);
+        }
+
+        public TlsCredentials? GetClientCredentials(Org.BouncyCastle.Tls.CertificateRequest certificateRequest) => null;
+    }
+
+    private sealed class ServerPeer : DefaultTlsServer
+    {
+        private readonly TlsSession session;
+        private readonly byte[] certificateDer;
+        private readonly AsymmetricKeyParameter privateKey;
+
+        public ServerPeer(TlsSession session, string certificatePem, string privateKeyPem) : base(new BcTlsCrypto())
+        {
+            this.session = session;
+            using var certificate = System.Security.Cryptography.X509Certificates.X509Certificate2.CreateFromPem(certificatePem);
+            certificateDer = certificate.RawData;
+            using var reader = new StringReader(privateKeyPem);
+            privateKey = (AsymmetricKeyParameter)new PemReader(reader).ReadObject();
+            if (privateKey is not Org.BouncyCastle.Crypto.Parameters.ECPrivateKeyParameters)
+                throw new ArgumentException("Server TLS credentials require an ECDSA key.", nameof(privateKeyPem));
+        }
+
+        protected override ProtocolVersion[] GetSupportedVersions() => [ProtocolVersion.TLSv13];
+        protected override int[] GetSupportedCipherSuites() => CipherSuites;
+        public override TlsCredentials GetCredentials()
+        {
+            var certificate = new Certificate([], [new CertificateEntry(Crypto.CreateCertificate(certificateDer), null)]);
+            return new BcDefaultTlsCredentialedSigner(new TlsCryptoParameters(m_context), (BcTlsCrypto)Crypto,
+                privateKey, certificate, new SignatureAndHashAlgorithm(Org.BouncyCastle.Tls.HashAlgorithm.sha256, SignatureAlgorithm.ecdsa));
+        }
+
+        public override void NotifyHandshakeComplete()
+        {
+            base.NotifyHandshakeComplete();
+            session.CompleteHandshake(m_context);
+        }
+    }
+
+    private static int[] CipherSuites =>
+    [
+        CipherSuite.TLS_AES_128_GCM_SHA256,
+        CipherSuite.TLS_AES_256_GCM_SHA384,
+        CipherSuite.TLS_CHACHA20_POLY1305_SHA256
+    ];
+}

dotnet/src/VoiceCat.Crypto/TofuStore.cs

@@ -0,0 +1,72 @@
+using System.Text;
+
+namespace VoiceCat.Crypto;
+
+public enum TofuStatus { FirstConnect, Matched, Mismatch }
+
+public sealed class TofuStore
+{
+    private readonly string path;
+    private readonly Dictionary<string, string> pins = new(StringComparer.Ordinal);
+
+    public TofuStore(string path)
+    {
+        this.path = Path.GetFullPath(path);
+        if (!File.Exists(this.path)) return;
+        foreach (string line in File.ReadLines(this.path))
+        {
+            if (string.IsNullOrWhiteSpace(line) || line.StartsWith('#')) continue;
+            string[] parts = line.Split((char[]?)null, StringSplitOptions.RemoveEmptyEntries);
+            if (parts.Length != 2) throw new InvalidDataException("Malformed TOFU pin entry.");
+            pins[parts[0]] = NormalizeFingerprint(parts[1]);
+        }
+    }
+
+    public TofuStatus Check(string host, ushort port, string fingerprint)
+    {
+        string key = Endpoint(host, port);
+        string normalized = NormalizeFingerprint(fingerprint);
+        return !pins.TryGetValue(key, out var pin) ? TofuStatus.FirstConnect :
+            pin == normalized ? TofuStatus.Matched : TofuStatus.Mismatch;
+    }
+
+    public void Pin(string host, ushort port, string fingerprint)
+    {
+        string key = Endpoint(host, port);
+        string value = NormalizeFingerprint(fingerprint);
+        var updated = new Dictionary<string, string>(pins, StringComparer.Ordinal) { [key] = value };
+        Save(updated);
+        pins[key] = value;
+    }
+
+    public void Remove(string host, ushort port)
+    {
+        string key = Endpoint(host, port);
+        var updated = new Dictionary<string, string>(pins, StringComparer.Ordinal);
+        updated.Remove(key);
+        Save(updated);
+        pins.Remove(key);
+    }
+
+    private void Save(Dictionary<string, string> updated)
+    {
+        string contents = string.Concat(updated.OrderBy(pair => pair.Key, StringComparer.Ordinal).Select(pair => $"{pair.Key} {pair.Value}\n"));
+        PrivateFiles.Write(path, Encoding.UTF8.GetBytes(contents));
+    }
+
+    private static string Endpoint(string host, ushort port)
+    {
+        ArgumentException.ThrowIfNullOrWhiteSpace(host);
+        if (host.Any(char.IsWhiteSpace)) throw new ArgumentException("Host cannot contain whitespace.", nameof(host));
+        ArgumentOutOfRangeException.ThrowIfZero(port);
+        return $"{host}:{port}";
+    }
+
+    private static string NormalizeFingerprint(string fingerprint)
+    {
+        ArgumentNullException.ThrowIfNull(fingerprint);
+        if (fingerprint.Length != 64 || !fingerprint.All(Uri.IsHexDigit))
+            throw new InvalidDataException("TLS certificate fingerprints must contain 64 hexadecimal characters.");
+        return fingerprint.ToLowerInvariant();
+    }
+}

dotnet/tests/VoiceCat.Tests/IdentityTests.cs

@@ -0,0 +1,68 @@
+using System.Security.Cryptography;
+using System.Security.Cryptography.X509Certificates;
+using System.Formats.Asn1;
+using VoiceCat.Crypto;
+
+namespace VoiceCat.Tests;
+
+public class IdentityTests
+{
+    [Fact]
+    public void CredentialsSurviveRestartAndBindIdentityIntoCertificate()
+    {
+        string directory = Path.Combine(Path.GetTempPath(), "voicecat-credentials-" + Guid.NewGuid());
+        try
+        {
+            string identityFingerprint, certificateFingerprint;
+            using (var credentials = ServerCredentials.LoadOrCreate(directory, "Server, with punctuation"))
+            {
+                identityFingerprint = credentials.Identity.Fingerprint;
+                certificateFingerprint = credentials.CertificateFingerprint;
+                using var tls = credentials.CreateTlsSession();
+                Assert.False(tls.IsReady);
+                byte[] identity = File.ReadAllBytes(Path.Combine(directory, "identity.key"));
+                Assert.Equal(96, identity.Length);
+                Assert.Equal(identity[..32], identity[64..]);
+                using var certificate = X509Certificate2.CreateFromPem(File.ReadAllText(Path.Combine(directory, "server.crt")));
+                var san = new AsnReader(certificate.Extensions["2.5.29.17"]!.RawData, AsnEncodingRules.DER).ReadSequence();
+                Assert.Equal("urn:voicecat:identity:ed25519:" + Convert.ToHexString(credentials.Identity.PublicKey).ToLowerInvariant(),
+                    san.ReadCharacterString(UniversalTagNumber.IA5String, new Asn1Tag(TagClass.ContextSpecific, 6)));
+                Assert.False(san.HasData);
+            }
+            using var restored = ServerCredentials.LoadOrCreate(directory, "ignored after creation");
+            Assert.Equal(identityFingerprint, restored.Identity.Fingerprint);
+            Assert.Equal(certificateFingerprint, restored.CertificateFingerprint);
+            File.Delete(Path.Combine(directory, "server.key"));
+            Assert.Throws<InvalidDataException>(() => ServerCredentials.LoadOrCreate(directory, "unchanged"));
+            using var stillPresent = ServerIdentity.Load(Path.Combine(directory, "identity.key"));
+            Assert.Equal(identityFingerprint, stillPresent.Fingerprint);
+        }
+        finally { if (Directory.Exists(directory)) Directory.Delete(directory, true); }
+    }
+
+    [Fact]
+    public void TofuRequiresExplicitPinAndPreservesCppFileFormat()
+    {
+        string directory = Path.Combine(Path.GetTempPath(), "voicecat-pins-" + Guid.NewGuid());
+        Directory.CreateDirectory(directory);
+        string path = Path.Combine(directory, "pins.txt");
+        string fingerprint = Convert.ToHexString(RandomNumberGenerator.GetBytes(32));
+        try
+        {
+            var store = new TofuStore(path);
+            Assert.Equal(TofuStatus.FirstConnect, store.Check("localhost", 9987, fingerprint));
+            Assert.False(File.Exists(path));
+            store.Pin("localhost", 9987, fingerprint);
+            Assert.Equal($"localhost:9987 {fingerprint.ToLowerInvariant()}\n", File.ReadAllText(path));
+            store = new(path);
+            Assert.Equal(TofuStatus.Matched, store.Check("localhost", 9987, fingerprint));
+            Assert.Equal(TofuStatus.Mismatch, store.Check("localhost", 9987, new string('0', 64)));
+            Assert.Equal(TofuStatus.Matched, new TofuStore(path).Check("localhost", 9987, fingerprint));
+            store.Remove("localhost", 9987);
+            Assert.Equal(TofuStatus.FirstConnect, new TofuStore(path).Check("localhost", 9987, fingerprint));
+            File.WriteAllText(path, "localhost:9987 " + new string('g', 64));
+            Assert.Throws<InvalidDataException>(() => new TofuStore(path));
+        }
+        finally { Directory.Delete(directory, true); }
+    }
+}

dotnet/tests/VoiceCat.Tests/TlsInteropTests.cs

@@ -0,0 +1,97 @@
+using System.Diagnostics;
+using System.Net.Sockets;
+using System.Security.Cryptography;
+using System.Security.Cryptography.X509Certificates;
+using VoiceCat.Crypto;
+using VoiceCat.Protocol;
+
+namespace VoiceCat.Tests;
+
+public class TlsInteropTests
+{
+    [TlsOracleFact]
+    public async Task ManagedClientAndCppServerAgreeOnExporterKeysAndCertificate()
+    {
+        string? oracle = Environment.GetEnvironmentVariable("VOICECAT_TLS_ORACLE");
+        string directory = Path.Combine(Path.GetTempPath(), "voicecat-tls-" + Guid.NewGuid());
+        Directory.CreateDirectory(directory);
+        var start = new ProcessStartInfo(oracle!) { UseShellExecute = false, CreateNoWindow = true, RedirectStandardError = true, RedirectStandardOutput = true };
+        start.ArgumentList.Add(directory);
+        using var process = Process.Start(start)!;
+        var error = process.StandardError.ReadToEndAsync();
+        var stdout = process.StandardOutput.ReadToEndAsync();
+        using var timeout = new CancellationTokenSource(TimeSpan.FromSeconds(30));
+        try
+        {
+            int port = 0;
+            while (!int.TryParse(File.Exists(Path.Combine(directory, "port.txt")) ? await File.ReadAllTextAsync(Path.Combine(directory, "port.txt"), timeout.Token) : "", out port))
+            {
+                Assert.False(process.HasExited, "C++ TLS oracle exited before listening.");
+                await Task.Delay(20, timeout.Token);
+            }
+            using var certificate = X509Certificate2.CreateFromPem(await File.ReadAllTextAsync(Path.Combine(directory, "server.crt"), timeout.Token));
+            string fingerprint = Convert.ToHexString(SHA256.HashData(certificate.RawData));
+            using var credentials = ServerCredentials.LoadOrCreate(directory, "existing C++ identity");
+            Assert.Equal(fingerprint, credentials.CertificateFingerprint);
+            Assert.Equal(32, credentials.Identity.PublicKey.Length);
+            using var client = TlsSession.CreateClient(value => value == fingerprint);
+            using var socket = new Socket(SocketType.Stream, ProtocolType.Tcp);
+            await socket.ConnectAsync("127.0.0.1", port, timeout.Token);
+            byte[] buffer = new byte[16384];
+            async Task Flush()
+            {
+                while (client.PendingCiphertextBytes > 0)
+                {
+                    int count = client.DrainCiphertext(buffer);
+                    int sent = 0;
+                    while (sent < count) sent += await socket.SendAsync(buffer.AsMemory(sent, count - sent), SocketFlags.None, timeout.Token);
+                }
+            }
+            async Task Receive()
+            {
+                int count = await socket.ReceiveAsync(buffer, SocketFlags.None, timeout.Token);
+                Assert.True(count > 0, "TLS oracle closed unexpectedly.");
+                client.ReceiveCiphertext(buffer.AsSpan(0, count));
+            }
+            while (!client.IsReady) { await Flush(); await Receive(); }
+            await Flush();
+            byte[] packet = new byte[41];
+            int received = 0;
+            while (received < packet.Length)
+            {
+                int count = client.ReadPlaintext(packet.AsSpan(received));
+                received += count;
+                if (count == 0) { await Flush(); await Receive(); }
+            }
+            using var decryptor = client.CreateMediaDecryptor();
+            byte[] plaintext = new byte[5];
+            Assert.True(decryptor.TryDecrypt(packet, plaintext, out var header, out _));
+            Assert.Equal("hello"u8.ToArray(), plaintext);
+            Assert.Equal(fingerprint, client.PeerCertificateFingerprint);
+            using var encryptor = client.CreateMediaEncryptor();
+            encryptor.Encrypt(header, plaintext, packet);
+            client.WritePlaintext(packet);
+            await Flush();
+            byte[] ack = new byte[1];
+            while (client.ReadPlaintext(ack) == 0) { await Flush(); await Receive(); }
+            Assert.Equal(1, ack[0]);
+            await process.WaitForExitAsync(timeout.Token);
+            Assert.True(process.ExitCode == 0, await error);
+            await stdout;
+        }
+        finally
+        {
+            if (!process.HasExited) { process.Kill(entireProcessTree: true); await process.WaitForExitAsync(); }
+            Directory.Delete(directory, recursive: true);
+        }
+    }
+}
+
+public sealed class TlsOracleFactAttribute : FactAttribute
+{
+    public TlsOracleFactAttribute()
+    {
+        if (string.IsNullOrEmpty(Environment.GetEnvironmentVariable("VOICECAT_TLS_ORACLE")))
+            Skip = "Build the native TLS oracle and set VOICECAT_TLS_ORACLE to its executable path.";
+    }
+}

dotnet/tests/VoiceCat.Tests/TlsTests.cs

@@ -0,0 +1,111 @@
+using System.Security.Cryptography;
+using System.Security.Cryptography.X509Certificates;
+using VoiceCat.Crypto;
+using VoiceCat.Protocol;
+
+namespace VoiceCat.Tests;
+
+public class TlsTests
+{
+    [Fact]
+    public void ManagedTlsHandshakeExportsMatchingDirectionalKeys()
+    {
+        var (pem, key, fingerprint) = Credentials();
+        using var server = TlsSession.CreateServer(pem, key);
+        using var client = TlsSession.CreateClient(value => value == fingerprint);
+        Assert.Throws<InvalidOperationException>(() => client.CreateMediaEncryptor());
+        Handshake(client, server);
+        Assert.Equal(fingerprint, client.PeerCertificateFingerprint);
+        Assert.Equal(server.ExportMediaKey(0), client.ExportMediaKey(0));
+        Assert.Equal(server.ExportMediaKey(1), client.ExportMediaKey(1));
+        Assert.NotEqual(client.ExportMediaKey(0), client.ExportMediaKey(1));
+        client.WritePlaintext("hello"u8);
+        Pump(client, server);
+        byte[] output = new byte[5];
+        Assert.Equal(5, server.ReadPlaintext(output));
+        Assert.Equal("hello"u8.ToArray(), output);
+        using var encryptor = server.CreateMediaEncryptor();
+        using var decryptor = client.CreateMediaDecryptor();
+        byte[] packet = new byte[41];
+        encryptor.Encrypt(new(MediaFrameType.Voice, 0, 0, 42, 0, 960), "hello"u8, packet);
+        Assert.True(decryptor.TryDecrypt(packet, output, out _, out _));
+        Assert.Equal("hello"u8.ToArray(), output);
+    }
+
+    [Fact]
+    public void CertificateRejectionPreventsApplicationDataAndMediaKeys()
+    {
+        var (pem, key, _) = Credentials();
+        using var server = TlsSession.CreateServer(pem, key);
+        using var client = TlsSession.CreateClient(_ => false);
+        Assert.ThrowsAny<IOException>(() => Handshake(client, server));
+        Assert.False(client.IsReady);
+        Assert.Throws<InvalidOperationException>(() => client.CreateMediaDecryptor());
+        Assert.Throws<InvalidOperationException>(() => client.WritePlaintext("secret"u8));
+    }
+
+    [Fact]
+    public void CloseNotifyEndsSessionAndAbruptEofIsRejected()
+    {
+        var (pem, key, fingerprint) = Credentials();
+        using var server = TlsSession.CreateServer(pem, key);
+        using var client = TlsSession.CreateClient(value => value == fingerprint);
+        Handshake(client, server);
+        client.Close();
+        Pump(client, server);
+        Assert.False(client.IsReady);
+        Assert.False(server.IsReady);
+        server.CompleteInput();
+        using var incomplete = TlsSession.CreateClient(_ => true);
+        Assert.ThrowsAny<IOException>(() => incomplete.CompleteInput());
+    }
+
+    [Fact]
+    public void TlsTwelveCannotNegotiateWithManagedServer()
+    {
+        var (pem, key, _) = Credentials();
+        using var server = TlsSession.CreateServer(pem, key);
+        var legacy = new Org.BouncyCastle.Tls.TlsClientProtocol();
+        legacy.Connect(new LegacyPeer());
+        byte[] hello = new byte[legacy.GetAvailableOutputBytes()];
+        legacy.ReadOutput(hello, 0, hello.Length);
+        Assert.ThrowsAny<IOException>(() => server.ReceiveCiphertext(hello));
+        Assert.False(server.IsReady);
+        Assert.Throws<InvalidOperationException>(() => server.CreateMediaEncryptor());
+    }
+
+    private sealed class LegacyPeer() : Org.BouncyCastle.Tls.DefaultTlsClient(new Org.BouncyCastle.Tls.Crypto.Impl.BC.BcTlsCrypto())
+    {
+        protected override Org.BouncyCastle.Tls.ProtocolVersion[] GetSupportedVersions() => [Org.BouncyCastle.Tls.ProtocolVersion.TLSv12];
+        public override Org.BouncyCastle.Tls.TlsAuthentication GetAuthentication() => throw new InvalidOperationException("TLS 1.2 must be rejected before authentication.");
+    }
+
+    internal static (string Certificate, string Key, string Fingerprint) Credentials()
+    {
+        using var key = ECDsa.Create(ECCurve.NamedCurves.nistP256);
+        var request = new System.Security.Cryptography.X509Certificates.CertificateRequest("CN=VoiceCat TLS test", key, HashAlgorithmName.SHA256);
+        using var certificate = request.CreateSelfSigned(DateTimeOffset.UtcNow.AddMinutes(-1), DateTimeOffset.UtcNow.AddDays(1));
+        return (certificate.ExportCertificatePem(), key.ExportPkcs8PrivateKeyPem(), Convert.ToHexString(SHA256.HashData(certificate.RawData)));
+    }
+
+    internal static void Handshake(TlsSession client, TlsSession server)
+    {
+        for (int i = 0; i < 100 && (!client.IsReady || !server.IsReady); i++)
+        {
+            Pump(client, server);
+            Pump(server, client);
+        }
+        Assert.True(client.IsReady);
+        Assert.True(server.IsReady);
+    }
+
+    private static void Pump(TlsSession sender, TlsSession receiver)
+    {
+        byte[] buffer = new byte[17];
+        while (sender.PendingCiphertextBytes > 0)
+        {
+            int count = sender.DrainCiphertext(buffer);
+            receiver.ReceiveCiphertext(buffer.AsSpan(0, count));
+        }
+    }
+}

dotnet/tests/VoiceCat.Tests/TofuTlsTests.cs

@@ -0,0 +1,49 @@
+using VoiceCat.Crypto;
+
+namespace VoiceCat.Tests;
+
+public class TofuTlsTests
+{
+    [Fact]
+    public void RealHandshakesRequireAcceptanceAndRejectChangedCertificatesAfterRestart()
+    {
+        string directory = Path.Combine(Path.GetTempPath(), "voicecat-tofu-tls-" + Guid.NewGuid());
+        Directory.CreateDirectory(directory);
+        string path = Path.Combine(directory, "pins.txt");
+        try
+        {
+            using var credentials = ServerCredentials.LoadOrCreate(Path.Combine(directory, "server"), "server");
+            var store = new TofuStore(path);
+            using (var server = credentials.CreateTlsSession())
+            using (var rejected = TlsSession.CreateClient(fingerprint =>
+            {
+                Assert.Equal(TofuStatus.FirstConnect, store.Check("localhost", 9987, fingerprint));
+                return false;
+            }))
+                Assert.ThrowsAny<IOException>(() => TlsTests.Handshake(rejected, server));
+            Assert.False(File.Exists(path));
+            using (var server = credentials.CreateTlsSession())
+            using (var accepted = TlsSession.CreateClient(fingerprint =>
+            {
+                Assert.Equal(TofuStatus.FirstConnect, store.Check("localhost", 9987, fingerprint));
+                store.Pin("localhost", 9987, fingerprint);
+                return true;
+            }))
+                TlsTests.Handshake(accepted, server);
+            store = new(path);
+            using (var server = credentials.CreateTlsSession())
+            using (var returning = TlsSession.CreateClient(fingerprint => store.Check("localhost", 9987, fingerprint) == TofuStatus.Matched))
+                TlsTests.Handshake(returning, server);
+            using var rotated = ServerCredentials.LoadOrCreate(Path.Combine(directory, "rotated"), "server");
+            using (var server = rotated.CreateTlsSession())
+            using (var mismatch = TlsSession.CreateClient(fingerprint =>
+            {
+                Assert.Equal(TofuStatus.Mismatch, store.Check("localhost", 9987, fingerprint));
+                return false;
+            }))
+                Assert.ThrowsAny<IOException>(() => TlsTests.Handshake(mismatch, server));
+            Assert.Equal(TofuStatus.Matched, new TofuStore(path).Check("localhost", 9987, credentials.CertificateFingerprint));
+        }
+        finally { Directory.Delete(directory, true); }
+    }
+}