dotnet: add KDuma.Pcf.Sig sibling project

Mirrors the Rust reference at reference/PCF-SIG-v1.0/ field-for-field as
a second sibling project tree under implementations/dotnet/pcf-sig/.
Follows the recipe documented in implementations/README.md: a new
Pcf.Sig.sln next to the existing Pcf.sln, with the source library
declaring a ProjectReference to ../../pcf/src/Pcf/Pcf.csproj for local
dev resolution. Lockstep version is provided by the shared
Directory.Build.props at implementations/dotnet/.

Source structure (one C# file per Rust module):
  - Constants: TYPE_PCFSIG_KEY/SIG, magic strings, sizes, version
  - PcfSigException + PcfSigErrorKind: exception hierarchy
  - SigAlgo + KeyFormat enums + extensions; only Ed25519 implemented,
    other ids recognised so Verify returns Unverifiable rather than
    Malformed for them
  - KeyRecord + KeyMetadata: serialisation + fingerprint cross-check
  - Manifest + SignedEntry: 60 + 218*N byte layout
  - SignaturePartition: manifest || sig_length || sig || trailer
  - SigningMaterial.Ed25519FromSeed: BouncyCastle-backed signer
  - SignPartitions.Run, EnsureKeyPartition: high-level Writer API
  - Verify.All, Verify.AllWithRecheck + verdict/reason enums

Tests (32 total) mirroring TS and PHP ports: Roundtrip, CanonicalVector
(byte-exact match with b158e2f5...1307), Tamper, Relocation,
SpecCompliance. xUnit on net8.0; library targets netstandard2.0.

Crypto deps:
  - BouncyCastle.Cryptography v2.4 (Org.BouncyCastle.Math.EC.Rfc8032.Ed25519)
  - System.Security.Cryptography.SHA256 for fingerprints

CI:
  - dotnet-ci.yml: matrix expanded to (os X package); pcf and pcf-sig
    each build+test on Linux/macOS/Windows; path filter also covers
    new project tree
  - release.yml: new publish-nuget-sig job runs after publish-nuget,
    pack from src/Pcf.Sig/Pcf.Sig.csproj, push as KDuma.Pcf.Sig

The library has not been built locally (no dotnet SDK on this container);
CI will validate. Code is structurally identical to the byte-exact-
verified TS and PHP ports, so any compile failures would be local
syntax issues, not algorithmic.

https://claude.ai/code/session_01ST4PcjqvobURus32WuyEi5

Author: claude

.github/workflows/dotnet-ci.yml

@@ -5,27 +5,29 @@ on:
     branches: [master]
     paths:
       - 'implementations/dotnet/pcf/**'
+      - 'implementations/dotnet/pcf-sig/**'
       - 'implementations/dotnet/Directory.Build.props'
       - '.github/workflows/dotnet-ci.yml'
   pull_request:
     branches: [master]
     paths:
       - 'implementations/dotnet/pcf/**'
+      - 'implementations/dotnet/pcf-sig/**'
       - 'implementations/dotnet/Directory.Build.props'
       - '.github/workflows/dotnet-ci.yml'
 
-defaults:
-  run:
-    working-directory: implementations/dotnet/pcf
-
 jobs:
   test:
-    name: build & test (${{ matrix.os }})
+    name: build & test ${{ matrix.package }} (${{ matrix.os }})
     runs-on: ${{ matrix.os }}
     strategy:
       fail-fast: false
       matrix:
         os: [ubuntu-latest, macos-latest, windows-latest]
+        package: [pcf, pcf-sig]
+    defaults:
+      run:
+        working-directory: implementations/dotnet/${{ matrix.package }}
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-dotnet@v4

.github/workflows/release.yml

@@ -235,6 +235,49 @@ jobs:
           name: nuget-package
           path: implementations/dotnet/pcf/out/*.nupkg
 
+  publish-nuget-sig:
+    name: Publish KDuma.Pcf.Sig to NuGet
+    needs: [resolve, publish-nuget]
+    runs-on: ubuntu-latest
+    permissions:
+      id-token: write
+      contents: read
+    defaults:
+      run:
+        working-directory: implementations/dotnet/pcf-sig
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-dotnet@v4
+        with:
+          dotnet-version: '8.0.x'
+      - run: dotnet restore
+      - name: dotnet pack
+        run: |
+          dotnet pack src/Pcf.Sig/Pcf.Sig.csproj \
+            -c Release \
+            -p:Version='${{ needs.resolve.outputs.version }}' \
+            -o out
+      - name: NuGet login (OIDC trusted publishing)
+        id: nuget-login
+        if: needs.resolve.outputs.dry_run != 'true'
+        uses: NuGet/login@v1
+        with:
+          user: krystianduma
+      - name: dotnet nuget push
+        if: needs.resolve.outputs.dry_run != 'true'
+        run: |
+          dotnet nuget push out/*.nupkg \
+            --source https://api.nuget.org/v3/index.json \
+            --api-key '${{ steps.nuget-login.outputs.NUGET_API_KEY }}' \
+            --skip-duplicate
+      - name: Dry-run note
+        if: needs.resolve.outputs.dry_run == 'true'
+        run: 'echo "Dry-run - skipping dotnet nuget push. Package would be out/*.nupkg."'
+      - uses: actions/upload-artifact@v4
+        with:
+          name: nuget-package-sig
+          path: implementations/dotnet/pcf-sig/out/*.nupkg
+
   split-php:
     name: Split PHP to packagist source repo
     needs: resolve

implementations/dotnet/pcf-sig/.gitignore

@@ -0,0 +1,9 @@
+# --- .NET build artefacts ---
+bin/
+obj/
+out/
+*.user
+
+# --- Generated test vectors ---
+*.bin
+!testdata/canonical.bin

implementations/dotnet/pcf-sig/Pcf.Sig.sln

@@ -0,0 +1,24 @@
+Microsoft Visual Studio Solution File, Format Version 12.00
+# Visual Studio Version 17
+VisualStudioVersion = 17.0.31903.59
+MinimumVisualStudioVersion = 10.0.40219.1
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Pcf.Sig", "src\Pcf.Sig\Pcf.Sig.csproj", "{B0000001-0000-0000-0000-000000000001}"
+EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Pcf.Sig.Tests", "tests\Pcf.Sig.Tests\Pcf.Sig.Tests.csproj", "{B0000001-0000-0000-0000-000000000002}"
+EndProject
+Global
+	GlobalSection(SolutionConfigurationPlatforms) = preSolution
+		Debug|Any CPU = Debug|Any CPU
+		Release|Any CPU = Release|Any CPU
+	EndGlobalSection
+	GlobalSection(ProjectConfigurationPlatforms) = postSolution
+		{B0000001-0000-0000-0000-000000000001}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{B0000001-0000-0000-0000-000000000001}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{B0000001-0000-0000-0000-000000000001}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{B0000001-0000-0000-0000-000000000001}.Release|Any CPU.Build.0 = Release|Any CPU
+		{B0000001-0000-0000-0000-000000000002}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{B0000001-0000-0000-0000-000000000002}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{B0000001-0000-0000-0000-000000000002}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{B0000001-0000-0000-0000-000000000002}.Release|Any CPU.Build.0 = Release|Any CPU
+	EndGlobalSection
+EndGlobal

implementations/dotnet/pcf-sig/README.md

@@ -0,0 +1,99 @@
+# KDuma.Pcf.Sig
+
+.NET implementation of **PCF-SIG v1.0**, the PCF Cryptographic Signatures
+profile. Mirrors the [normative specification][spec] and the [Rust reference
+implementation][rust] field-for-field.
+
+[spec]: ../../../specs/PCF-SIG-spec-v1.0.txt
+[rust]: ../../../reference/PCF-SIG-v1.0/
+
+## Install
+
+```sh
+dotnet add package KDuma.Pcf
+dotnet add package KDuma.Pcf.Sig
+```
+
+## What it adds
+
+Two new PCF partition types layered on top of the [`KDuma.Pcf`](../pcf/)
+container, without changing the PCF byte format:
+
+| Type         | Name         | Holds                                                |
+|--------------|--------------|------------------------------------------------------|
+| `0xAAAB0001` | `PCFSIG_KEY` | One signer's public key, identified by SHA-256 fingerprint of the key bytes |
+| `0xAAAB0002` | `PCFSIG_SIG` | One Manifest enumerating signed partitions + the signature over the Manifest |
+
+A **Manifest** binds the *protected fields* of each covered partition:
+`Uid`, `PartitionType`, `Label`, `UsedBytes`, `DataHashAlgo`, `DataHash`. It
+does NOT bind `StartOffset` or `MaxLength`, so PCF compaction and other
+relocations preserve signature validity as long as partition bytes do not
+change.
+
+## Algorithm support
+
+| `sig_algo_id` | Algorithm           | This release |
+|---------------|---------------------|--------------|
+| 1             | Ed25519 (RFC 8032)  | implemented (MUST) |
+| 2, 4, 5, 7    | RSA-PSS / PKCS1v15  | registry only |
+| 16, 18        | ECDSA P-256 / P-521 | registry only |
+| 32            | X.509 chain         | registry only |
+
+Algorithms marked *registry only* are recognised at parse time and reported as
+`ManifestVerdict.Unverifiable` (with `UnverifiableReason.UnsupportedSigAlgo`)
+rather than `Malformed`. Adding a full implementation for any of them is a
+pure addition that does not touch the on-disk format.
+
+Hash algorithm constraint: signed partitions MUST use a cryptographic
+`DataHashAlgo` (SHA-256, SHA-512, BLAKE3). The Writer refuses to sign
+weakly-hashed partitions; the Verifier rejects them per entry.
+
+## Usage
+
+```csharp
+using Pcf;
+using Pcf.Sig;
+using System.IO;
+
+var c = Container.Create(new MemoryStream());
+var alpha = new byte[16] { 0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11,
+                           0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x11 };
+c.AddPartition(0x10, alpha, "alpha",
+    System.Text.Encoding.UTF8.GetBytes("Hello, PCF-SIG!"), 0, HashAlgo.Sha256);
+
+var seed = new byte[32]; for (int i = 0; i < 32; i++) seed[i] = 0x42;
+var signer = SigningMaterial.Ed25519FromSeed(seed);
+SignPartitions.Run(
+    c, signer, new[] { alpha },
+    /* sigPartitionUid: */ new byte[16] { 0x33,0x33,0x33,0x33,0x33,0x33,0x33,0x33, 0x33,0x33,0x33,0x33,0x33,0x33,0x33,0x33 },
+    /* keyPartitionUid: */ new byte[16] { 0x22,0x22,0x22,0x22,0x22,0x22,0x22,0x22, 0x22,0x22,0x22,0x22,0x22,0x22,0x22,0x22 },
+    signedAtUnixSeconds: 0,
+    sigLabel: "pcfsig",
+    keyLabel: "pcfkey");
+
+foreach (var report in Verify.AllWithRecheck(c))
+{
+    if (report.Verdict == ManifestVerdict.Valid)
+    {
+        System.Console.WriteLine(
+            $"signature valid; {report.Entries.Count} entries covered");
+    }
+}
+```
+
+## Cross-port test vector parity
+
+The shipped `testdata/canonical.bin` is byte-identical to the canonical vector
+produced by the Rust reference, the TypeScript port and the PHP port. SHA-256:
+`b158e2f5b160d72cea3226af2041f8d18aa75b3db6cb85faeca5df7879871307`.
+
+## Dependencies
+
+- `KDuma.Pcf` — the PCF base container library (same version as pcf-sig).
+- `BouncyCastle.Cryptography` v2.4+ — actively maintained main BouncyCastle
+  fork; ships RFC 8032 Ed25519 (`Org.BouncyCastle.Math.EC.Rfc8032.Ed25519`)
+  and targets `netstandard2.0`.
+- `System.Security.Cryptography` (BCL) — SHA-256 for fingerprints.
+
+The library targets `netstandard2.0` to match the PCF base; tests target
+`net8.0`.

implementations/dotnet/pcf-sig/src/Pcf.Sig/Constants.cs

@@ -0,0 +1,47 @@
+namespace Pcf.Sig;
+
+/// <summary>
+/// On-disk constants defined by PCF-SIG v1.0. Every value here is normative
+/// and corresponds directly to a figure in the specification
+/// (`specs/PCF-SIG-spec-v1.0.txt`, Appendix A).
+/// </summary>
+public static class Constants
+{
+    /// <summary>PCF partition type carrying one Key Record (spec Section 5).</summary>
+    public const uint TypePcfsigKey = 0xAAAB_0001;
+
+    /// <summary>PCF partition type carrying one Signature Partition (spec Section 5).</summary>
+    public const uint TypePcfsigSig = 0xAAAB_0002;
+
+    /// <summary>8-byte magic at the start of a Key Record (spec Section 6.1).</summary>
+    public static readonly byte[] KeyMagic =
+        { (byte)'P', (byte)'C', (byte)'F', (byte)'K', (byte)'E', (byte)'Y', 0x00, 0x00 };
+
+    /// <summary>8-byte magic at the start of a Signature Partition Manifest (spec Section 7.1).</summary>
+    public static readonly byte[] SigMagic =
+        { (byte)'P', (byte)'C', (byte)'F', (byte)'S', (byte)'I', (byte)'G', 0x00, 0x00 };
+
+    /// <summary>Profile version implemented by this library (major).</summary>
+    public const ushort ProfileVersionMajor = 1;
+
+    /// <summary>Profile version implemented by this library (minor).</summary>
+    public const ushort ProfileVersionMinor = 0;
+
+    /// <summary>Length of the Key Record fixed prefix that precedes key_data (spec 6.1).</summary>
+    public const int KeyPrefixSize = 52;
+
+    /// <summary>Length of the Manifest fixed prefix that precedes signed_entries (spec 7.1).</summary>
+    public const int ManifestPrefixSize = 60;
+
+    /// <summary>Length of one Signed Entry (spec Section 7.2).</summary>
+    public const int SignedEntrySize = 218;
+
+    /// <summary>Length of a SHA-256 key fingerprint (spec Section 6.3).</summary>
+    public const int FingerprintSize = 32;
+
+    /// <summary>Length of the Ed25519 raw public key (spec Section 6.2, key_format_id = 1).</summary>
+    public const int Ed25519PublicKeyLen = 32;
+
+    /// <summary>Length of an Ed25519 signature (spec Section 8, sig_algo_id = 1).</summary>
+    public const int Ed25519SignatureLen = 64;
+}