Communication Development for OpenSource

We are in a need of a customization of the opensource VoIP / SIP client LinPhone or Ring or Wire (if not than Jitsi). Preferably LinPhone, but if not possible one of these. The development has to be done in two phases: Phase 1: Customization of mobile + tablet apps (iOS + Android) // Objective C = iOS + Java = Android --> ready in two weeks. Phase 2: Customization of PC apps (Windows, Mac OSX and Linux) // Qt/QML = Windows, Mac OSX and Linux --> ready in four weeks. The main customization's must be: - Upgrade security Many security features, which include i.e.: --> Use TLS connectivity for handshake --> Use VPN connection for additional security --> Use ZRTP encryption protocol on VoIP (voice and video) communication --> Use text encryption for messaging and file sending --> Database security on app and server --> Secure connection settings --> Use code obfuscation protection + Sign the app --> Harden the security of application / program --+ Encrypt the entire application --+ Containerize the entire application --+ Encrypt the database --+ Lock screen / Login protection --+ Brute force protection --+ Code hardening by Pro+iX Guard --+ Store encryption keys securely in Trusty --> Set privacy settings - Design customization Many security features, which include i.e.: All designs are based upon the operation of LinPhone, almost no real custom development. --> Add a lock screen / login screen prior using app --> Every function in the LinPhone app is customized by designer --> APP settings are blocked for users to change - one setting fits all --> Custom user account settings SIP server will be setup by an other person if this isn't your specialty to save time and costs. Ready in 2 - 4 weeks (divided in two phases) Time is of essence and must be ready in 2-4 weeks. Budget 2250 in milestones