VoIP service security assurance method and system based on scale variable window mechanism

The invention discloses a VoIP service security assurance method and system based on a scale variable window mechanism. The method comprises the following steps: a voice sending end (sender) launches conversation request to a voice receiving end (receiver), and builds safety conversation after bothway verification through an agent end, the sender sends the voice, which is encrypted through the encryption module, to the receiver, the receiver decrypts the encrypted voice and sends the voice to a voice quality assurance module, and the voice display time is adjusted through the caching technology based on the scale variable window, so as to guarantee the display quality of the voice; the system comprises the voice sending end (sender), a voice sending end proxy server (proxy 1), a voice receiving end proxy server (proxy 2), the voice receiving end (receiver) and a private key generator; the voice sending end (sender) comprises a safety SIP conversation module (SSM) and a voice encryption/decryption module (VEM), the voice receiving end (receiver) comprises an SIP conversation module (SSM), a voice encryption/decryption module (VEM) and a voice quality guarantee module (QEM); the method and system can effectively improve VoIP communication safety and communication quality.