Cryptography Stack Exchange
Cryptography Stack Exchange

Questions tagged [oblivious-transfer]

Oblivious transfer refers to a cryptographic protocol in which a sender possesses a set of data and a receiver queries the sender for a particular member of that set in such a way that the sender does not learn which member the receiver requests. In other words, the sender is oblivious of what information was actually transferred to the receiver.

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Simple protocol for 1-out-of-2 oblivious transfer

I'm trying to explain the concept of 1-out-of-2 oblivious transfer to folks who haven't seen this idea before. I can explain what properties it provides, but it's also helpful if I can show a simple protocol for 1-out-of-2 OT, to give people a…
D.W.
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Please help me understand this k-out-of-n oblivious transfer protocol

I'm having the following protocol specification of a k-out-of-n oblivious transfer (as part of some E-Voting protocol) and it's bugging me that I fail to understand it with my basic knowledge of cryptography. This particular implementation looks…
user66875
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Communication cost of Oblivious Transfer and OT Extension?

Suppose there exist fixed K set of N-bit strings. Here, sender and receiver perform 1-out-of-K OT either once or many times. In the latter case, we may use OT Extension. What is the order of the communication cost of Single base-OT and OT…
mallea
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Implementation of oblivious transfer with symmetric primitive?

I'm now reading this paper Extending Oblivious Transfers Efficiently. I understand how to reduce an OT cost. OT extension is a method that replaces an OT with many base-OTs. But I'm still not sure how to implement each base-OT. How is this…
mallea
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Oblivious transfer applications: how to apply?

I have a basic question about the Homomorphic Encryption schemes, garbled circuits, Oblivious Transfer (OT), two-party computation, and multi-party computation. Specifically, I want to understand, how to apply these great techniques, or are these at…
user60588
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1 out of n oblivious transfer

So I read some stuff about oblivious transfer and came a ross that 1 out of 2 OT can be used as a black box to build 1 out of n OT. At first it seemed trivial just feeding in 4 messages and 2 chooser bits but then I realized it's not that trivial…
Mayfall
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1-out-of-2 OT from Random 1-out-of-2 OT

Last week I came upon this problem in my h.w.: Let $OT^m$ denote 1-out-of-2 oblivious transfer of $m$ bit inputs. Let $RandOT^m$ denote the following primitive: The sender’s input consists of two m-bit strings, $x_0, x_1$. The receiver has no…
Naftali Waxman
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Is it possible to build an unfair noisy channel from 1 out of 2 oblivious transfer

For a fair channel, sender sends a bit b and receiver gets it with probability 1/2 and gets b's flipped value with probability 1/2. It is trivial to build a fair noisy channel from 1 out of 2 oblivious transfer since sender only needs to input b and…
statham
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Private Information Retrieval--Is it still theoretical?

Are there any real world products in which private information retrieval techniques are used?(a data hosting server oblivious of which data item was fetched from it?)If not what are the major barriers for its implementation?
Kiran
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online Vickrey auction using remote coin flip

Is there any published work on implementing a online auction, which uses "remote coin flip" to prevent auctioneer cheating when choosing winner and bid value? Is there any possible way to use remote coin flip for a such scenario? Note: in a Vickrey…
Chamila Wijayarathna
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Why does the random oracle H contain the index?

I'm reading the paper Extending OT. In the extending OT protocol, the sender using $H(j, \textbf{q}_j)$ as the mask, why not use $H(\textbf{q}_j)$ directly?
Bob
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1-out-of-2 OT, chosen 1-out-of-2 OT and Random 1-out-of-2 OT

I'm studying some concepts about Oblivious Transfer(OT), and would like to know what is the 1-out-of-2 OT, chosen 1-out-of-2 OT and Random 1-out-of-2 OT, and wonder the relation and difference between these concepts, thank!
Yang
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OT extension question about base-OT

Recently, I am learning the Oblivious Transfer (OT) Protocol. I have some questions about the OT extension. In ALSZ13, we know that $m\times OT_l$ can be reduced to $\kappa\times OT_\kappa$, where $\kappa$ is a security parameter, $l$ is secret's…
Viming
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Bandwidth-efficient oblivious transfer

Alice has two 1GB files, and Bob wants one without Alice knowing which. Can this be done with less than 2GB (1GB for each file) of bandwidth between Alice and Bob?
Randomblue
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Reducing 1/4 OT to 1/2 OT

We can construct a 1/4 OT from 1/2 OT. Proving security for the receiver in 1/4 OT means showing a reduction to the 1/2 OT receiver's security. The protocol I am using is given on page 3 here. I am working with the simulation based definitions of…
dtb93
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