From eb50b46fed519cc80491ab208e9e89ef877fd2c6 Mon Sep 17 00:00:00 2001
From: Pranav Senthilnathan <pranas@microsoft.com>
Date: Fri, 14 Aug 2026 17:08:40 -0700
Subject: [PATCH] Expose Composite ML-DSA CNG identifiers

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Copilot-Session: 5676db47-d54b-4946-97ec-7fc0a7392c30
---
 .../CompositeMLDsa/CompositeMLDsaTestHelpers.Cng.cs        | 7 -------
 .../ref/System.Security.Cryptography.cs                    | 4 ++++
 .../src/System/Security/Cryptography/CngAlgorithm.cs       | 3 ++-
 .../src/System/Security/Cryptography/CngAlgorithmGroup.cs  | 3 ++-
 4 files changed, 8 insertions(+), 9 deletions(-)

diff --git a/src/libraries/Common/tests/System/Security/Cryptography/AlgorithmImplementations/CompositeMLDsa/CompositeMLDsaTestHelpers.Cng.cs b/src/libraries/Common/tests/System/Security/Cryptography/AlgorithmImplementations/CompositeMLDsa/CompositeMLDsaTestHelpers.Cng.cs
index 2a1692ef052113..9cca05a283dd3d 100644
--- a/src/libraries/Common/tests/System/Security/Cryptography/AlgorithmImplementations/CompositeMLDsa/CompositeMLDsaTestHelpers.Cng.cs
+++ b/src/libraries/Common/tests/System/Security/Cryptography/AlgorithmImplementations/CompositeMLDsa/CompositeMLDsaTestHelpers.Cng.cs
@@ -9,13 +9,6 @@ namespace System.Security.Cryptography.Tests
 {
     internal static partial class CompositeMLDsaTestHelpers
     {
-        private static readonly CngAlgorithm s_compositeMLDsa = new CngAlgorithm("Composite-ML-DSA");
-
-        extension (CngAlgorithm)
-        {
-            internal static CngAlgorithm CompositeMLDsa => s_compositeMLDsa;
-        }
-
         private const int NTE_NOT_SUPPORTED = unchecked((int)0x80090029);
 
         internal static CompositeMLDsaCng ImportPublicKey(CompositeMLDsaAlgorithm algorithm, ReadOnlySpan<byte> source)
diff --git a/src/libraries/System.Security.Cryptography/ref/System.Security.Cryptography.cs b/src/libraries/System.Security.Cryptography/ref/System.Security.Cryptography.cs
index c0ed4128c3b29a..6cf2e086576d60 100644
--- a/src/libraries/System.Security.Cryptography/ref/System.Security.Cryptography.cs
+++ b/src/libraries/System.Security.Cryptography/ref/System.Security.Cryptography.cs
@@ -326,6 +326,8 @@ public sealed partial class CngAlgorithm : System.IEquatable<System.Security.Cry
     {
         public CngAlgorithm(string algorithm) { }
         public string Algorithm { get { throw null; } }
+        [System.Diagnostics.CodeAnalysis.ExperimentalAttribute("SYSLIB5006", UrlFormat="https://aka.ms/dotnet-warnings/{0}")]
+        public static System.Security.Cryptography.CngAlgorithm CompositeMLDsa { get { throw null; } }
         public static System.Security.Cryptography.CngAlgorithm ECDiffieHellman { get { throw null; } }
         public static System.Security.Cryptography.CngAlgorithm ECDiffieHellmanP256 { get { throw null; } }
         public static System.Security.Cryptography.CngAlgorithm ECDiffieHellmanP384 { get { throw null; } }
@@ -355,6 +357,8 @@ public sealed partial class CngAlgorithmGroup : System.IEquatable<System.Securit
     {
         public CngAlgorithmGroup(string algorithmGroup) { }
         public string AlgorithmGroup { get { throw null; } }
+        [System.Diagnostics.CodeAnalysis.ExperimentalAttribute("SYSLIB5006", UrlFormat="https://aka.ms/dotnet-warnings/{0}")]
+        public static System.Security.Cryptography.CngAlgorithmGroup CompositeMLDsa { get { throw null; } }
         public static System.Security.Cryptography.CngAlgorithmGroup DiffieHellman { get { throw null; } }
         public static System.Security.Cryptography.CngAlgorithmGroup Dsa { get { throw null; } }
         public static System.Security.Cryptography.CngAlgorithmGroup ECDiffieHellman { get { throw null; } }
diff --git a/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/CngAlgorithm.cs b/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/CngAlgorithm.cs
index 198df792ce9293..4f5bcaad197e67 100644
--- a/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/CngAlgorithm.cs
+++ b/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/CngAlgorithm.cs
@@ -236,7 +236,8 @@ public static CngAlgorithm Sha512
         ///   A new <see cref="CngAlgorithm"/> object that specifies the Composite Module-Lattice-Based
         ///   Digital Signature Algorithm (Composite ML-DSA).
         /// </value>
-        internal static CngAlgorithm CompositeMLDsa =>
+        [Experimental(Experimentals.PostQuantumCryptographyDiagId, UrlFormat = Experimentals.SharedUrlFormat)]
+        public static CngAlgorithm CompositeMLDsa =>
             field ??= new CngAlgorithm("Composite-ML-DSA"); // BCRYPT_COMPOSITE_MLDSA_ALGORITHM
 
         private static CngAlgorithm? s_ecdh;
diff --git a/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/CngAlgorithmGroup.cs b/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/CngAlgorithmGroup.cs
index 4e1cbe48dc5d0d..39a0c2a08fd010 100644
--- a/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/CngAlgorithmGroup.cs
+++ b/src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/CngAlgorithmGroup.cs
@@ -164,7 +164,8 @@ public static CngAlgorithmGroup Rsa
         /// <value>
         ///   An object that specifies the Composite ML-DSA family of algorithms.
         /// </value>
-        internal static CngAlgorithmGroup CompositeMLDsa =>
+        [Experimental(Experimentals.PostQuantumCryptographyDiagId, UrlFormat = Experimentals.SharedUrlFormat)]
+        public static CngAlgorithmGroup CompositeMLDsa =>
             field ??= new CngAlgorithmGroup("CompositeMLDSA"); // NCRYPT_COMPOSITE_MLDSA_ALGORITHM_GROUP
 
         private static CngAlgorithmGroup? s_dh;