As far as I know honest but curious or also called semi-trusted means that a client follows protocol but will try to learn as much information as possible, without actively “cheating”. Does anyone know a citable definition of this concept? Ideally one that I can look up online.
While looking for a source, I found many papers refer to Yao, but could not find a definition by him ("How to generate and exchange secrets" sadly is not available online)
I found a citable definition in "Modelling and Automatically Analysing Privacy Properties for Honest-but-Curious Adversaries by Pavert" et al.
The honest-but-curious (HBC) adversary is a legitimate participant in a communication protocol who will not deviate from the defined protocol but will attempt to learn all possible information from legitimately received messages.
An extensive textbook on cryptography with multiple references to semi-honest users, as well as half a chapter dedicated to it.
Foundations of Cryptography: Volume 2 - Basic Applications
Author: Oded Goldreich
Section 7.1
An orthogonal parameter of restriction refers to whether a dishonest party takes active steps to disrupt the execution of the protocol (i.e., sends messages that differ from those specified by the protocol), or merely gathers information (which it may later share with the other dishonest parties). The latter adversary has been given a variety of names, such as semi-honest, passive, and honest-but-curious...
Introduction to Section 7.2
In the first model, presented in Section 7.2.2, we consider a restricted adversary called semi honest, whereas the general case of malicious adversary is considered in Section 7.2.3. In addition to being of independent interest, the semi-honest model will play a major role in the constructions of protocols for the malicious model (see Sections 7.3 and 7.4).
Section 7.2.2. The Semi-Honest Model
Loosely speaking, a semi-honest party is one who follows the protocol properly with the exception that it keeps a record of all its intermediate computations.
...
...semi-honest parties in our exposition, they do constitute a model of independent interest. In particular, deviation from the specified program...
also
A Note on the Relation between the Definitions of Security for Semi-Honest and Malicious Adversaries, a paper by Carmit Hazay and Yehuda Lindell, reference the above textbook when discussing semi-honest.
