Protocol Independence through Disjoint Encryption

One protocol (called the primary protocol) is independent of other protocols (jointly called the secondary protocol) if the question whether the primary protocol achieves a security goal never depends on whether the secondary protocol is in use. In this paper, we use multiprotocol strand spaces ([27], cf. [28]) to prove that two cryptographic protocols are independent if they use encryption in non-overlapping ways. This theorem (Proposition 7.2) applies even if the protocols share public key certificates and secret key “tickets.” We use the method of [8, 7] to study penetrator paths, namely sequences of penetrator actions connecting regular nodes (message transmissions or receptions) in the two protocols. Of special interest are inbound linking paths, which lead from a message transmission in the secondary protocol to a message reception in the primary protocol. We show that bundles can be modified to remove all inbound linking paths, if encryption does not overlap in the two pr...

• Type: Conference
• Year: 2000
• Where: CSFW
• Authors: Joshua D. Guttman, F. Javier Thayer
• Keywords: CSFW 2000, Inbound Linking Paths, Primary Protocol, Secondary Protocol, Security Privacy