User story

Nowadays became more and more popular to use Web based soft-phones one of such examples is Acrobits web soft-phone implementation. Such soft-phones utilizes so called WebRTC API for implementation of low-level communication staffs. One of the important aspect of WebRTC is strict demand on usage encrypted data exchange. Since in conventional VoIP world not all phones support media encryption there is a task to convert media traffic between phone with different capabilities. However depending on users wishes it may also be required to provide fully private call without intermediate data encryption on PortaSwtich side.

Use cases

Use case #1: Make fully private call between two phones with encryption support.

Roles: Anthony Stark business magnate, Pepper Potts secretary, System

Preconditions: Anthony Stark, Pepper Potts have soft-phone as mobile application which supports media encryption and their phones registered in the System. Anthony wants to make fully private call to not be eavesdropped by secret service agents.

Use scenario #1.1: Successful secure call

Scenario:

• Anthony enables media security in his soft-phone.

• Anthony, using System self-care interface, allows full media privacy for call.

• Anthony dials Pepper number and waits while System connects his with Pepper.

• System finds that Pepper's phone registered in system and sends incoming call  to her phone.

• Pepper answers the phone and System establishes the call with secure media flow. Since Anthony and Pepper use their phone from public network System decides not to participate in call media flow so data traffic sent directly between phones.

• Anthony or Pepper hangs up the call and System charges they call according to usual tariff plans of Anthony.

• Pepper has call recording enabled for call to be able re-check important call details but System is unable to decrypt media stream so audio call records are not saved.

• System has call intercept enabled but there are only encrypted data streams saved in system which can't be decrypted immediately.
  
  

Use case #2: Making calls from phone which strictly requires media encryption.

Roles: Anthony Stark business magnate, Pepper Potts secretary, System

Preconditions: Being abroad Anthony Stark lost his mobile where his VoIP soft-phone installed and need to make a call using Web based soft-phone from nearby internet cafe. He wants to ask Pepper to send him a car. Pepper Potts have soft-phone as mobile application but it doesn't support encryption so System is pre-configured not to use encryption for incoming call to it.

Use scenario #2.1: Successful call

• Anthony enables media security in his soft-phone.

• Anthony, using System self-care interface, specifies that it's phone uses encryption.

• Anthony dials Pepper number and waits while System connects his with Pepper.

• System finds that Pepper's phone registered in system and sends incoming call  to her phone.

• Pepper answers the phone and System establishes the call. Since Anthony's phone uses encryption but  Pepper's doesn't the System decides to participate in call media flow so recode media streams.

• Anthony or Pepper hangs up the call and System charges they call according to usual tariff plans of Anthony.

• System saves call audio because Pepper has call recording enabled in System to be able re-check important call details later.

• Since government agents wants to track Start location there is call intercept enabled in System for Pepper's and Stark's number so System writes decrypted audio streams to storage.

Use scenario #2.2: Failed call with voice explanation played

• Anthony enables media security in his soft-phone.

• Anthony, using System self-care interface, specifies that it's phone uses encryption.

• Anthony dials Pepper number and waits while System connects his with Pepper.

• System finds that Pepper's phone is not registered in System and there is no any redirects.

• System establishes secure media stream and plays notification that destination number is unreachable and rejects the call.

Use scenario #2.2: Failed call with redirect to Voice-mail

• Anthony enables media security in his soft-phone.

• Anthony, using System self-care interface, specifies that it's phone uses encryption.

• Anthony dials Pepper number and waits while System connects his with Pepper.

• Since Pepper uses soft-phone installed on her mobile and her mobile is currently discharged she is currently not registered in System.

• System finds that Pepper's phone is not registered in System and there is redirection to Voicemail so it establishes a call with secure media stream and plays Pepper's Voice-mail greetings.

• Anthony leaves voice message where he asks Pepper to call him back and hangs up the call.
• System records voice message in unencrypted format.

Use case #3: Usage of phone which strictly requires media encryption for accepting incoming calls.

Roles: Anthony Stark business magnate, Pepper Potts secretary, System, System Administrator

Preconditions: Pepper need to accept calls from Anthony in different situation and different conditions so she uses several soft-phones and one of them is Web based soft-phone which uses WebRTC so strictly required media encryption.

Use scenario #3.1: Accidental usage on media encrypted phone

• Pepper knows that she is going to visit an embassy where visitors ought to leave their smartphones on storage room entrance but there is an access to internet from terminals installed inside. So before visit Pepper calls to System Administrator and asks him to enable support of web-base soft-phone.
• Pepper goes to embassy and while waiting registers web-based phone in System.

• Anthony needs to get quick answer from Pepper so he dials her number and waits while System connects his with Pepper.

• System finds that Pepper's phone registered in system and it is specific web-phone which required specific media encryption. So system sends incoming call  to the phone with encryption enabled.

• Pepper answers the phone and System establishes the call. Since Anthony and Pepper use their phone from public network System decides not to participate in call media flow so data traffic sent directly between phones.

• Anthony or Pepper hangs up the call and System charges they call according to usual tariff plans of Anthony.

• System saves call audio because Pepper has call recording enabled in System to be able re-check important call details later.

• Since government agents wants to track Start location there is call intercept enabled in System for Pepper's and Stark's number so System writes decrypted audio streams to storage.

• When leaving embassy Pepper closes the browser with web-phone started and turns-on her smartphone which doesn't use encryption.
• On the next Anthony call System sees that Pepper number registered from phone which doesn't support encryption so System doesn't try to establish secure media call.

Use scenario #3.2: Constant usage

• Anthony uses phone with media encryption but doesn't like that Pepper sometimes use soft-phones with insecure media  so calls may be easily eavesdropped by anyone. So he enables security on Pepper's soft-phone and asks System administrator to constantly enable media security for Pepper's number.

Use case #4: Using media security to protect calls from networks where VoIP calls are prohibited.

Roles: Anthony Stark business magnate, Pepper Potts secretary, System

Preconditions:  Pepper goes on assignment into country with dictatorship  regime which tries to prohibit all non-controlled way of communication. So non-encrypted VoIP calls prohibit and the only way to make a call which can't be intercepted by government is to VoIP call with usage of secure media and signaling. 

Use scenarios #4.I: Making call from  VoIP restricted area

This scenario matches to scenarios from UC#2 with addition that phone should configured at first step to use secure signaling as well.

Use scenarios #4.II: Accepting call in VoIP restricted area

This scenario matches to scenarios from UC#3 with addition that phone should pre-configured at first to use secure signaling as well.