Score:2

Could anyone explain what Two Oracle Diffie-Hellman assumption is?

eg flag

I am really new to cryptography and I have asked a similar question which is about Decisional Diffie-Hellman assumption (What's the meaning of asterisk and PPT in this paper?) and it is already kind of difficult to me.

But this paper Practical Secure Aggregation for Privacy-Preserving Machine Learning (https://eprint.iacr.org/2017/281.pdf) proposes a Two Oracle Diffie-Hellman assumption, which is even more difficult to understand.

enter image description here enter image description here

Could anyone please tell me bow the oracle function is used in the adversary M? I don't even really understand what the oracle is here.

kodlu avatar
sa flag
If you have trouble understanding the other answer perhaps take a MOOC such as Dan Boneh's to brush up on basics. You also do need understanding of probability and mathematics at least at a first college class level to understand the theoretical approach to probability, which includes things like advantage, randomised protocols, etc.
user900476 avatar
eg flag
@kodlu I understand the math part.
Score:0
cn flag

The oracles are giving the image by $H$ of $X^a$ (for $\mathcal{O}_a$) and $Y^b$ (for $\mathcal{O}_b$) for any $X\neq B$ and $Y\neq B$.

Notice there is a typo in the definition, because $b$ is used for the definition of the bit parameter, and the scalar challenge (Here I'm considering the scalar challenge).

user900476 avatar
eg flag
Thank you very much! Could you please tell me how the adversary M uses the oracles to produce b'?
Ievgeni avatar
cn flag
We do not know. The principle of a security analysis is to consider we don't know exactly how the adversary computes its output.
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.