ML-DSA: Add BCrypt support in Microsoft.Bcl.Cryptography

[PranavSenthilnathan]

And fix failing tests.

Fixes #116598

[Copilot]

Pull Request Overview

This PR introduces BCrypt support for ML-DSA by adding a new CNG implementation file and updating project files and interop helpers. Key changes include:

• Adding MLDsaImplementation.CreateCng.cs to provide an ephemeral CNG key creation implementation.
• Updating csproj files to include new interop files and the new CNG implementation.
• Refactoring memory marshalling usage in PqcBlobHelpers and removing duplicate implementations in MLDsaImplementation.Windows.cs.

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/libraries/System.Security.Cryptography/src/System/Security/Cryptography/MLDsaImplementation.CreateCng.cs	Introduces a new method to create ephemeral CNG keys using BCrypt.
src/libraries/System.Security.Cryptography/src/System.Security.Cryptography.csproj	Adds the new CNG implementation file to the compilation.
src/libraries/Microsoft.Bcl.Cryptography/src/Microsoft.Bcl.Cryptography.csproj	Includes new interop files necessary for BCrypt support.
src/libraries/Common/src/System/Security/Cryptography/PqcBlobHelpers.cs	Updates memory marshalling usage to use MemoryMarshal.Cast for proper blob header extraction.
src/libraries/Common/src/System/Security/Cryptography/MLDsaImplementation.Windows.cs	Refactors duplicate key creation code and improves debug assertions and logging.

Comments suppressed due to low confidence (1)

src/libraries/Common/src/System/Security/Cryptography/MLDsaImplementation.Windows.cs:165

• Converting parameterSet to an array in the debug message reduces readability; consider logging parameterSet directly to improve clarity.

Debug.Fail(..., $"{nameof(parameterSet)}: {parameterSet.ToArray()}, ", ...)

[dotnet-policy-service]

Tagging subscribers to this area: @dotnet/area-system-security, @bartonjs, @vcsjones
See info in area-owners.md if you want to be subscribed.

[bartonjs]

Secret Key vs Decapsulation Key means that to share this with ML-KEM we'd have to parameterize it. But MLDsaNoSeed and MLKemNoSeed seem pretty sharable. Do we really need the same string twice under two names?

[PranavSenthilnathan]

I can put this in a future PR to avoid merge conflicts since MLKemNoSeed is still in PR pending merge. I like the logical separation of ML-KEM and ML-DSA but it is unfortunate that it would result in more resources in the dll.

[vcsjones]

Mine's not even approved yet, so if you want to rename yours to something like Cryptography_PqcNoSeed I can merge in main when you merge and then use the de-duped name.

[PranavSenthilnathan]

The CI is going to be green for this besides the known test failures, so it's probably faster for me to merge and you to change the name rather than both of us waiting for CI.

[bartonjs]

LGTM, modulo the (presumably) duplicated string.

[PranavSenthilnathan]

/ba-g #116647, #116558 and #104426