Retain PersistKeySet for SslStream TLS client auth — EphemeralKeySet unsupported on Windows#2
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Retain PersistKeySet for SslStream TLS client auth — EphemeralKeySet unsupported on Windows#2Copilot wants to merge 1 commit into
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[WIP] [WIP] Address feedback on Windows 11 support for EphemeralKeySet in SslStream
Retain PersistKeySet for SslStream TLS client auth — EphemeralKeySet unsupported on Windows
Mar 12, 2026
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A review suggested switching
Clone()to useEphemeralKeySetto reduce key persistence risk. However,EphemeralKeySetis fundamentally incompatible withSslStreamTLS client authentication on Windows (all versions, including Windows 11).Why EphemeralKeySet breaks on Windows
Windows delegates TLS to Schannel, which runs out-of-process. Ephemeral keys are in-process only, so Schannel cannot access them during the handshake:
Tracked in dotnet/runtime#23749 and dotnet/runtime#103101 — this is an OS-level constraint, not a .NET bug.
Decision
PersistKeySet | ExportableinClone()is retained as-is — it is the correct and required combination for cross-platformSslStreamclient certificate usage.EphemeralKeySetwould be viable on Linux/macOS (where TLS is in-process) but breaks Windows without a viable workaround.✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.