The method GetKeyedHashAlgorithm of InMemorySymmetricSecurityKey class with SecurityAlgorithms.HmacSha256Signature as argument throws System.NotSupportedException.
The code which creates the HMACSHA256 instance is commented out on mono master branch without any obvious reason: https://github.com/mono/mono/blob/master/mcs/class/System.IdentityModel/System.IdentityModel.Tokens/InMemorySymmetricSecurityKey.cs#L126
Also the method IsSupportedAlgorithm returns false when specifying SecurityAlgorithms.HmacSha256Signature.
HMACSHA256 is already properly supported by mono, therefore HMACSHA256 should be enabled for compatibility reasons.
Created attachment 13720 [details]
Created attachment 13721 [details]
Created attachment 13722 [details]
Proposed patch (fixed)
Just curious, why hasn't this patch been merged yet? I'm running into this issue too.
Could you please convert your test and patch into Mono Pull Request