MPPE
MPPE, short for Microsoft Point-to-Point Encryption, is an encryption protocol used to protect the payload of PPP frames carried within PPTP tunnels. Developed by Microsoft, MPPE provides confidentiality for data transmitted over connections that use Point-to-Point Tunneling Protocol. MPPE is described in IETF RFC 3078 and is integrated with PPTP as part of the PPP security model, with authentication handled by the underlying PPP mechanism (for example MS-CHAP or EAP).
Operation and keying: MPPE uses the RC4 stream cipher to encrypt payload data and derives session keys
Security and status: MPPE and PPTP rely on RC4 and the PPTP design, both of which have
History and usage: MPPE emerged in the 1990s as part of PPTP to provide encrypted remote access.