Summary: The document is a well written summary and covers the ideas clearly. I don't have major concerns but do have few minor concerns and Nits that might help with some clarifications Major issues: None Minor issues: 1. Section 7.2 para 2 states : "The CPS responds with any such PASSporTs (assuming they exist)." Given CPS will always respond with a dummy PASSporT, the statement in the parentheses doesn't hold. (Referring to section 6.2) 2. Section 7.4 Call flow: "Call from CS (forged caller-id info)" . Since its the attacker making the call here, we probably need to change it as "Call from Attacker (forged caller-id info)". 3. Section 7.5 has the following: Sign(K_cps, K_temp) Sign(K_temp, E(K_receiver, PASSporT)) ---> This is a clarification question for my understanding. What happens when one of the 2 messages sent gets lost when storing the PASSporT. Should we need to add any clarifications to that extent ? 4. Section 7.5 last para: clarification question Since PASSporT is encrypted at CPS , how is it aged out based on the "iat" value. Is it a function to VS to age out PASSporTs at a given CPS ? Nits/editorial comments: 1. Section 5.2 para 1: would be nice to add reference to Section 10 2. Section 7.2 Call Flow: "Store PASSporT" --> "Store Encrypted PASSporT" 3. Section 7.2 Call Flow: "Ring phone with callerid" --> "Ring phone with verified callerid" 4. Section 8.2 Step 3: "number number" --> "number" 5 Section 8.3 para 2: "Per Step 3" --> "Per Step 3 of Section 8.1"