Join Log in
Score:2
killertoge avatar Crypto

Difference between Non-Concurrent Composition and Concurrent Composition

lk flag
killertoge

You can get access to this document via institutional login at https://www.researchgate.net/publication/220556089_Security_and_composition_of_cryptographic_protocols_A_tutorial So in Ran Canettis Tutorial on Composable Security I came across some definitions of how protocols can be composed:

enter image description here

enter image description here

Earlier, it explains an example on what can go wrong if protocols are composed. He mentioned an example, where you use a key-exchange protocol and One-Time-Pad encryption. Each protocol itself is secure, but the composed one is obviously not secure. enter image description here

Much later he states a theorem: enter image description here

Now my question is, isn't the example earlier a non-concurrent composition? A simple nested protocol, where we first do key-exchange, then do the encryption, and now are ready for oracle requests again in the key-exchange? That would be a counter-example for this theorem, that such a protocol is not secure. My problem is understanding concurrent vs non-concurrent composition. I thought concurrent is executing the protocols "at the same time". You try to use information in one execution in another one, and else wise it is non-concurrent.

33
0 + 0
ธงชาติไทย
Elon Musk
I sit in a Tesla and translated this thread with Ai:

mangohost

Post an answer

Most people don’t grasp that asking a lot of questions unlocks learning and improves interpersonal bonding. In Alison’s studies, for example, though people could accurately recall how many questions had been asked in their conversations, they didn’t intuit the link between questions and liking. Across four studies, in which participants were engaged in conversations themselves or read transcripts of others’ conversations, people tended not to realize that question asking would influence—or had influenced—the level of amity between the conversationalists.