Secret sharing refers to splitting a secret among multiple parties so that together they can reconstruct it. All parties, or just a threshold number of them, can be required for reconstruction. If fewer than the required number of parties participate, no information should be leaked about the ...
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Is this a sensible cryptographic protocol intending to reduce the impact of compromised security?
I'm in the process of designing a cryptographic protocol which will reduce the impact an attacker will have if they gained root access to a server storing data.
The basic crux of it is that keys ...
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1answer
159 views
Understanding Feldman's VSS with a simple example
I'm trying to understand Feldman's VSS Scheme. The basic idea of that scheme is that one uses Shamir secret sharing to share a secret and commitments of the coefficients of the polynomial to allow the ...
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3answers
165 views
Implementing secret reconstruction in Shamir's Secret Sharing
I am trying to implement Shamir's secret sharing in C++.
I have got the generation of shares working.
However, I am very confused with the reconstruction of shares. I get the part on how three users ...
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4answers
421 views
How do you find a cheater in Shamir Secret Sharing?
If there are 4 people involved, and every two of them should be able to know the secret (the polynomial is just a line) and you are given f(x) and x for each of those people, and you know one of them ...
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34 views
session keys in an online e-voting system [closed]
I do not have much knowledge about cryptography or public and private keys, and your help will be much appreciated. I am totally a beginner, and no one from my university can help me.
I am trying to ...
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1answer
73 views
Requiring a “supervisor” key pair and a “user” key pair to decrypt multiple-recipient messages
I've been toying with some encryption scenarios recently. One of the hard ones I came across is a multi-party system.
So we have
Bob -- The person who sends the message (and knows it's recipients)
...
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1answer
71 views
Addition with Shamir secret sharing
When performing Shamir secret sharing I'm trying to find $z_i$, such that $z = x + y$. Where $n = 6$ and $t = 3$.
I believe this would be the correct solution (correct me if I'm wrong):
Each party ...
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1answer
65 views
How to obtain a one-value share in Shamir's secret sharing
This is a trivial question, but I had to ask:
since each generated share in a Shamir's secret sharing scheme initially consists of a pair of values (representing the coordinates of a point on the ...
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1answer
121 views
Should the secret key of Shamir's secret-sharing algorithm be interpreted byte by byte?
Should the secret message of Shamir's secret-sharing algorithm be interpreted and processed byte by byte?
Interpreting it byte by byte makes it easier to process, but in case one of the shareholders ...
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1answer
97 views
How to generate a random polynomial of degree $m$?
I am trying to do a homework in which implement a variation of this paper and I don't know how to generate a polynomial of degree $m-1$. This polynomial is used to generate the $y_0$ and $y_1$ values.
...
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1answer
75 views
Does zero-padding the secret in Shamir's sharing scheme increase security?
When performed in binary Galois fields $GF_{2^n}$, Shamir's threshold secret sharing scheme produces shares that are each the same bit-size as the secret. Though the scheme is "perfectly secure" in ...
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277 views
Necessity for finite field arithmetic and the prime number p in Shamir's Secret Sharing Scheme
Shamir's original paper (PDF, 197kb) describing a threshold secret sharing scheme states:
To make this claim more precise, we use modular arithmetic instead of
real arithmetic. The set of ...
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4answers
299 views
Is there a secret sharing scheme which allows delegation/re-sharing without reconstructing the original secret?
EDIT: Ilmari Karonen's answer below well not exactly what I want, gives a very good idea of what I am trying to accomplish.
Are there any known secret sharing schemes that allow new parties to be ...
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54 views
Reg:key Agreement Protocol [closed]
I want to encrypt my data using the Diffie hellmen key agreement protocol.
i have to implement it in java can some one help me with a example programs of how we can implement it in java
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1answer
253 views
Shamir Secret Sharing - Threshold decryption implementation
I'm implementing Shamir secret sharing in C using OpenSSL.
I've split up the private key and I'm ready to start decrypting the original message using some of the shares. I set $n = 5$ (5 shares ...
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0answers
171 views
Shamir's Secret Sharing: What am I doing wrong? [closed]
Problem
I am trying to implement Shamir's Secret Sharing algorithm, but sometimes it works and sometimes it doesn't, making me think I'm misunderstanding something subtle about the algorithm as it's ...
2
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2answers
159 views
Security considerations for partially shared password databases
Programs like KeyPass and 1Password store password database files encrypted by a single password. If someone knows the protecting password ("Vault Key"), they can read the entire database ("secrets").
...
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3answers
490 views
RS Erasure Coding and Shamir's Secret Sharing
So I was trying to understand the basic difference between erasure coding and secret sharing, and I found this paper (that you can find here or here).
For what I understand, it states that Shamir's ...
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3answers
274 views
Can I pre-define the points in Shamir's Secret Sharing algorithm
With Shamir's secret sharing is it possible to pre-define the points returned by the algorithm?
For simplicity if I have (k, n) where k=2, and n=4, and I have the points X,Y,Z, and Q. Can I create ...
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2answers
101 views
Relation between Threshold Cryptosystem and Secure Multiparty Computation ?
Is there any relation between secure multiparty computation and threshold cryptosystem ?
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1answer
115 views
Trying to find an algorithm to share portions of a key with multiple people
Sorry if this question's a bit basic, but I don't know of any way to ask it concisely enough for a search... What I'm looking for is a proven means of doing the following:
Create x number of ...
5
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2answers
165 views
K out of N encryption
A friend just showed me how to combine padlocks to achieve a lock that opens when k out of n people turn their keys.
I was ...
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1answer
78 views
Educational videos for security topics [closed]
Is there anything like the famous "sorting out sorting" video in cryptography/security.
I am looking for some nice videos that explaines SSL, SET, IPSec, PGP, S/MIME ....
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2answers
218 views
secure multiparty computation for multiplication
Suppose there are $N$ parties $p_j$, each with a binary $b_j\in{\{0,1\}}$. The problem needs to compute the multiplication of number of ones times that of zeros, that is, ...
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1answer
198 views
Threshold Signatures for RSA and DSA
I have a few questions relating to threshold signatures: a scheme where $n$ participants hold a key share and any $t$ of them can conduct a protocol using their shares that results in a valid RSA or ...
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1answer
117 views
How is the password sent across for verification?
I am familiar with Challenge-Response Authentication scheme.
However I would like to know actual message content sent between client and server for 1 way authentication, over an insecure channel.
...
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3answers
378 views
Threshold Secret sharing - How to create a shared secret from pre existing secret parts?
In usual $(t, n)$ secret sharing schemes, a secret $S$ is split into $n$ parts so that any $t$ out of $n$ parts reconstruct the original secret. So, suppose that there is a group of $n$ participants ...
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2answers
135 views
Is there a secret sharing scheme which allows sharing of a secret (one-out-of-n)
Is there a secret sharing scheme where the knowledge of just one share is sufficient to find the secret, in other words a (one-out-of-n) sharing scheme ? Plz I need to know if it is possible to make ...
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4answers
471 views
How to require two keyholders to decrypt a document?
I want to create a system to encrypt a document and store it with a 3rd party, but not have the 3rd party be able to decrypt it until some unspecified later date. It seems like the solution would be ...
