diff --git a/src/ScadaLink.Transport/Serialization/BundleSerializer.cs b/src/ScadaLink.Transport/Serialization/BundleSerializer.cs
new file mode 100644
index 0000000..d5d42a7
--- /dev/null
+++ b/src/ScadaLink.Transport/Serialization/BundleSerializer.cs
@@ -0,0 +1,178 @@
+using System.IO.Compression;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using ScadaLink.Commons.Types.Transport;
+using ScadaLink.Transport.Encryption;
+
+namespace ScadaLink.Transport.Serialization;
+
+/// <summary>
+/// Packs <see cref="BundleContentDto"/> + <see cref="BundleManifest"/> into a
+/// ZIP archive (<c>manifest.json</c> always, plus either <c>content.json</c>
+/// or <c>content.enc</c>) and reverses the operation on read.
+///
+/// When packing with a passphrase, the caller must have already encrypted the
+/// content bytes upstream and built a manifest whose <see cref="EncryptionMetadata"/>
+/// + <c>ContentHash</c> describe those exact bytes. <see cref="Pack"/> uses the
+/// manifest as source of truth: it re-serializes the content (or re-encrypts
+/// with the manifest's salt/iv when needed) so the zip stays internally
+/// consistent. The simpler usage — and the one BundleExporter follows — is to
+/// pre-encrypt, hash, build manifest, then call Pack which trusts the manifest
+/// + re-encrypts to a fresh IV and rebuilds the manifest internally.
+/// </summary>
+public sealed class BundleSerializer
+{
+    private const string ManifestEntryName = "manifest.json";
+    private const string ContentJsonEntryName = "content.json";
+    private const string ContentEncEntryName = "content.enc";
+
+    private static readonly JsonSerializerOptions JsonOptions = new()
+    {
+        WriteIndented = false,
+        DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,
+        Converters = { new JsonStringEnumConverter() },
+    };
+
+    /// <summary>
+    /// Serializes the bundle content to its canonical JSON byte form. Exposed
+    /// so callers can compute the content hash (or pre-encrypt) before they
+    /// build the manifest.
+    /// </summary>
+    public byte[] SerializeContentBytes(BundleContentDto content)
+    {
+        ArgumentNullException.ThrowIfNull(content);
+        return JsonSerializer.SerializeToUtf8Bytes(content, JsonOptions);
+    }
+
+    public Stream Pack(
+        BundleContentDto content,
+        BundleManifest manifest,
+        string? passphrase,
+        BundleSecretEncryptor? encryptor)
+    {
+        ArgumentNullException.ThrowIfNull(content);
+        ArgumentNullException.ThrowIfNull(manifest);
+
+        if (passphrase is not null && encryptor is null)
+        {
+            throw new ArgumentException("Encryptor is required when a passphrase is supplied.", nameof(encryptor));
+        }
+        if (passphrase is not null && manifest.Encryption is null)
+        {
+            throw new ArgumentException("Manifest must carry EncryptionMetadata when packing an encrypted bundle.", nameof(manifest));
+        }
+
+        var contentBytes = SerializeContentBytes(content);
+        byte[] payload;
+        string payloadEntryName;
+        BundleManifest finalManifest;
+
+        if (passphrase is not null && encryptor is not null && manifest.Encryption is not null)
+        {
+            // Fresh encryption — re-derives salt/iv. The manifest passed in described
+            // the upstream encrypt; we honour the requested algorithm/kdf/iteration
+            // count but rebuild ContentHash + Encryption fields against the bytes we
+            // actually write. The non-encryption manifest fields (source env, exported
+            // by, summary, contents, version) are preserved verbatim.
+            var (cipher, freshMeta) = encryptor.Encrypt(contentBytes, passphrase, manifest.Encryption.Iterations);
+            payload = cipher;
+            payloadEntryName = ContentEncEntryName;
+            finalManifest = manifest with
+            {
+                Encryption = freshMeta,
+                ContentHash = "sha256:" + Convert.ToHexString(
+                    System.Security.Cryptography.SHA256.HashData(cipher)).ToLowerInvariant(),
+            };
+        }
+        else
+        {
+            payload = contentBytes;
+            payloadEntryName = ContentJsonEntryName;
+            // Plaintext path: trust the supplied manifest's ContentHash. The caller
+            // built it via ManifestBuilder against the same SerializeContentBytes
+            // output (JSON is deterministic for a given DTO + JsonOptions).
+            finalManifest = manifest;
+        }
+
+        var manifestBytes = JsonSerializer.SerializeToUtf8Bytes(finalManifest, JsonOptions);
+        var ms = new MemoryStream();
+        using (var archive = new ZipArchive(ms, ZipArchiveMode.Create, leaveOpen: true))
+        {
+            WriteEntry(archive, ManifestEntryName, manifestBytes);
+            WriteEntry(archive, payloadEntryName, payload);
+        }
+
+        ms.Position = 0;
+        return ms;
+    }
+
+    public BundleManifest ReadManifest(Stream zipStream)
+    {
+        ArgumentNullException.ThrowIfNull(zipStream);
+
+        using var archive = new ZipArchive(zipStream, ZipArchiveMode.Read, leaveOpen: true);
+        var entry = archive.GetEntry(ManifestEntryName)
+            ?? throw new InvalidDataException("Bundle is missing manifest.json.");
+
+        using var es = entry.Open();
+        var manifest = JsonSerializer.Deserialize<BundleManifest>(es, JsonOptions)
+            ?? throw new InvalidDataException("manifest.json deserialized to null.");
+        return manifest;
+    }
+
+    /// <summary>
+    /// Returns the raw bytes from <c>content.enc</c> if present, otherwise from
+    /// <c>content.json</c>. The caller decrypts + JSON-deserializes via
+    /// <see cref="UnpackContent"/>.
+    /// </summary>
+    public byte[] ReadContentBytes(Stream zipStream, BundleManifest manifest)
+    {
+        ArgumentNullException.ThrowIfNull(zipStream);
+        ArgumentNullException.ThrowIfNull(manifest);
+
+        using var archive = new ZipArchive(zipStream, ZipArchiveMode.Read, leaveOpen: true);
+        // Prefer the encrypted variant when both are somehow present.
+        var entry = archive.GetEntry(ContentEncEntryName) ?? archive.GetEntry(ContentJsonEntryName)
+            ?? throw new InvalidDataException("Bundle is missing both content.enc and content.json.");
+
+        using var es = entry.Open();
+        using var ms = new MemoryStream();
+        es.CopyTo(ms);
+        return ms.ToArray();
+    }
+
+    public BundleContentDto UnpackContent(
+        byte[] contentBytes,
+        BundleManifest manifest,
+        string? passphrase,
+        BundleSecretEncryptor? encryptor)
+    {
+        ArgumentNullException.ThrowIfNull(contentBytes);
+        ArgumentNullException.ThrowIfNull(manifest);
+
+        byte[] plaintext;
+        if (manifest.Encryption is not null)
+        {
+            if (passphrase is null || encryptor is null)
+            {
+                throw new ArgumentException("Encrypted bundle requires both passphrase and encryptor.");
+            }
+            plaintext = encryptor.Decrypt(contentBytes, manifest.Encryption, passphrase);
+        }
+        else
+        {
+            plaintext = contentBytes;
+        }
+
+        var content = JsonSerializer.Deserialize<BundleContentDto>(plaintext, JsonOptions)
+            ?? throw new InvalidDataException("content payload deserialized to null.");
+        return content;
+    }
+
+    private static void WriteEntry(ZipArchive archive, string entryName, byte[] payload)
+    {
+        var entry = archive.CreateEntry(entryName, CompressionLevel.Optimal);
+        using var es = entry.Open();
+        es.Write(payload, 0, payload.Length);
+    }
+}
diff --git a/tests/ScadaLink.Transport.Tests/Serialization/BundleSerializerTests.cs b/tests/ScadaLink.Transport.Tests/Serialization/BundleSerializerTests.cs
new file mode 100644
index 0000000..c7b2345
--- /dev/null
+++ b/tests/ScadaLink.Transport.Tests/Serialization/BundleSerializerTests.cs
@@ -0,0 +1,126 @@
+using System.IO.Compression;
+using System.Security.Cryptography;
+using ScadaLink.Commons.Types.Transport;
+using ScadaLink.Transport.Encryption;
+using ScadaLink.Transport.Serialization;
+
+namespace ScadaLink.Transport.Tests.Serialization;
+
+public sealed class BundleSerializerTests
+{
+    private const int TestIterations = 10_000;
+
+    private static BundleContentDto SampleContent() => new(
+        TemplateFolders: new[] { new TemplateFolderDto("Root", ParentName: null, SortOrder: 0) },
+        Templates: Array.Empty<TemplateDto>(),
+        SharedScripts: new[] { new SharedScriptDto("util", "return 42;", ParameterDefinitions: null, ReturnDefinition: null) },
+        ExternalSystems: Array.Empty<ExternalSystemDto>(),
+        DatabaseConnections: Array.Empty<DatabaseConnectionDto>(),
+        NotificationLists: Array.Empty<NotificationListDto>(),
+        SmtpConfigs: Array.Empty<SmtpConfigDto>(),
+        ApiKeys: Array.Empty<ApiKeyDto>(),
+        ApiMethods: Array.Empty<ApiMethodDto>());
+
+    private static BundleManifest BuildManifestFor(byte[] contentBytes, EncryptionMetadata? encryption = null) =>
+        new ManifestBuilder().Build(
+            sourceEnvironment: "test-env",
+            exportedBy: "tester",
+            scadaLinkVersion: "1.0.0",
+            encryption: encryption,
+            summary: new BundleSummary(0, 1, 1, 0, 0, 0, 0, 0, 0),
+            contents: Array.Empty<ManifestContentEntry>(),
+            contentBytes: contentBytes);
+
+    [Fact]
+    public void Pack_emits_manifest_and_content_json_when_no_passphrase()
+    {
+        var sut = new BundleSerializer();
+        var content = SampleContent();
+        var contentJson = sut.SerializeContentBytes(content);
+        var manifest = BuildManifestFor(contentJson);
+
+        using var stream = sut.Pack(content, manifest, passphrase: null, encryptor: null);
+
+        using var archive = new ZipArchive(stream, ZipArchiveMode.Read, leaveOpen: true);
+        Assert.NotNull(archive.GetEntry("manifest.json"));
+        Assert.NotNull(archive.GetEntry("content.json"));
+        Assert.Null(archive.GetEntry("content.enc"));
+    }
+
+    [Fact]
+    public void Pack_emits_manifest_and_content_enc_when_passphrase_supplied()
+    {
+        var sut = new BundleSerializer();
+        var encryptor = new BundleSecretEncryptor();
+        var content = SampleContent();
+        var contentJson = sut.SerializeContentBytes(content);
+        var (cipher, meta) = encryptor.Encrypt(contentJson, "pass", TestIterations);
+        var manifest = BuildManifestFor(cipher, encryption: meta);
+
+        using var stream = sut.Pack(content, manifest, passphrase: "pass", encryptor: encryptor);
+
+        using var archive = new ZipArchive(stream, ZipArchiveMode.Read, leaveOpen: true);
+        Assert.NotNull(archive.GetEntry("manifest.json"));
+        Assert.Null(archive.GetEntry("content.json"));
+        Assert.NotNull(archive.GetEntry("content.enc"));
+    }
+
+    [Fact]
+    public void Roundtrip_through_temp_stream_recovers_identical_content()
+    {
+        var sut = new BundleSerializer();
+        var content = SampleContent();
+        var contentJson = sut.SerializeContentBytes(content);
+        var manifest = BuildManifestFor(contentJson);
+
+        using var stream = sut.Pack(content, manifest, passphrase: null, encryptor: null);
+
+        stream.Position = 0;
+        var readManifest = sut.ReadManifest(stream);
+        stream.Position = 0;
+        var contentBytes = sut.ReadContentBytes(stream, readManifest);
+        var unpacked = sut.UnpackContent(contentBytes, readManifest, passphrase: null, encryptor: null);
+
+        Assert.Equal(manifest.ContentHash, readManifest.ContentHash);
+        Assert.Single(unpacked.TemplateFolders);
+        Assert.Equal("Root", unpacked.TemplateFolders[0].Name);
+        var shared = Assert.Single(unpacked.SharedScripts);
+        Assert.Equal("util", shared.Name);
+        Assert.Equal("return 42;", shared.Code);
+    }
+
+    [Fact]
+    public void ReadManifest_throws_when_zip_missing_manifest_json()
+    {
+        var sut = new BundleSerializer();
+        using var ms = new MemoryStream();
+        using (var archive = new ZipArchive(ms, ZipArchiveMode.Create, leaveOpen: true))
+        {
+            var entry = archive.CreateEntry("garbage.txt");
+            using var es = entry.Open();
+            es.Write(new byte[] { 1, 2, 3 });
+        }
+        ms.Position = 0;
+
+        Assert.Throws<InvalidDataException>(() => sut.ReadManifest(ms));
+    }
+
+    [Fact]
+    public void UnpackContent_throws_CryptographicException_on_wrong_passphrase()
+    {
+        var sut = new BundleSerializer();
+        var encryptor = new BundleSecretEncryptor();
+        var content = SampleContent();
+        var contentJson = sut.SerializeContentBytes(content);
+        var (cipher, meta) = encryptor.Encrypt(contentJson, "right", TestIterations);
+        var manifest = BuildManifestFor(cipher, encryption: meta);
+
+        using var stream = sut.Pack(content, manifest, passphrase: "right", encryptor: encryptor);
+        stream.Position = 0;
+        var readManifest = sut.ReadManifest(stream);
+        stream.Position = 0;
+        var contentBytes = sut.ReadContentBytes(stream, readManifest);
+
+        Assert.ThrowsAny<CryptographicException>(() => sut.UnpackContent(contentBytes, readManifest, "wrong", encryptor));
+    }
+}