ID4184: The EncryptingCredentials provided in the SecurityTokenDescriptor must not be null if Scope.TokenEncryptionRequired ...

ID4184: The EncryptingCredentials provided in the SecurityTokenDescriptor must not be null if Scope.TokenEncryptionRequired is set to true. This can be caused by the Scope specifying an unsupported encryption key type, or by the incoming RequestSecurityToken message containing an unsupported EncryptionAlgorithm. Override CreateSecurityTokenDescriptor if you need to support algorithms other than AES 256.