Dear Developer,

I was reviewing the code and noticed that in the TLS 1.3 handshake protocol state machine, the "Change Cipher Spec" state has been divided into five different states based on its occurrence timing. Could you please clarify if there are any specific considerations for this approach?

Additionally, these states can appear multiple times during a single handshake, which implies multiple "Change Cipher Spec" messages. However, the TLS 1.3 standard suggests that the "Change Cipher Spec" should only appear once in a single handshake. Could you kindly explain the rationale behind this design decision?

Thank you for your time and assistance. I look forward to your response.

Best regards, XiangDong Li