Design of cryptographic protocols, i.e. ways of using algorithms (primitives) to achieve one or more security goals like integrity, confidentiality, authenticity (maybe together with non-security-related goals). If you ask about a specific protocol, tag with its name instead (or additionally, if ...

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218 views

Traitor-tracing PRF

I'm looking for a pseudorandom function (PRF) with "traitor-tracing" properties. More specifically, I'd like there to be multiple equivalent keys, so I can give different parties different keys, but ...
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113 views

Modular protocol design

What does modular protocol design mean? Why does TLS not have modular protocol design? What protocols have modular design? (IPSec, SSH)
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208 views

General-purpose non-interactive multi-party computation protocol

Most of general purpose multi-party computation protocols are highly interactive. Especially the ones with Shamir's secret scheme, as there is a degree reduction step in multiplication that needs the ...
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631 views

Derive a key from public data using a secret master key

Users in my system will be given a device that contains a 128-bit AES user key. The user key will be derived from 64 bits of public data related to the user, which is unique but very predictable (i.e. ...
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419 views

How can Alice prove that a message has not been tampered with?

In terms of the usual suspects. The problem I have is that Alice wants to send Bob a message M, which gives Bob permission to perform some actions. However Alice wants to verify, from time to ...
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456 views

AES encryption with shared IV

Sorry about the horrible title, didn't now what to say. I'm trying to avoid having to send an IV with every message purely to keep packet sizes down, so I thought of a method to establish a "IV ...
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169 views

Can you distinguish encryption methods from the output?

Suppose that you see all IP communication packets between two computers for a day, as they pass through a connecting router, and this amounts to 10MB. You additionally know that all data transmission ...
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82 views

Cryptographic Algorithm/Protocol needed

I am trying to achieve the following: Encrypted files are stored on users filesystem. The user uses my client to authenticate against a server. Once he is authenticated successfully he gets a token ...
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61 views

Proving item association without revealing one of the associated items

I'm a total noob when it comes to cryptography but I believe this falls under the "zero knowledge" category. I have two associated pieces of information: tag — known by both parties. Unique per ...
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108 views

Cryptography in wireless medium

How do I implement asymmetric key algorithm into wireless medium using NS 2.35? For example: node $A$ is a sender and $B$ is a receiver. Now, $A$ is sending a packet using $B$s public key ...
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102 views

Does this chat protocol exist?

I want to implement a secure chat via mobile. I´ld like to know if the following protocol for key agreement – which can use any asymmetric encryption – exists. Suppose Alice and Bob are two clients ...
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157 views

Key management protocol for end-to-end security on Advanced Metering Infrastructure

I am currently working on a research on end-to-end security implementation for Advanced Metering Infrastructure (AMI). Pardon me if I a bit off topic or not asking the right question as I am ...
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397 views

Are SSL/TLS used for maintaining data confidentiality?

In SSL/TLS, we use symmetric and asymmetric keys to encrypt the data. Does that mean that the keys are used to encrypt the data (preserve the integrity) or provide a secure channel for the data to be ...
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114 views

How does this SSL-related flaw work?

I just saw a video at CNN in which it is claimed that, if the server isn't generating a random public key, the server can be hacked. First how HTTPS works… to be sure I’m on the same page: Server ...
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111 views

Is there a method to combine encryption and ring signing?

There's the well-known question on whether to sign or encrypt first. However, if instead a message is to be ring-signed such that either recipient could be the actual signer, is there any scheme that ...
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119 views

Efficiency of computing $e(P,Q)$ Vs $g^a \pmod{p}$?

The definition of $e$ can be seen here. I want to know the accurate comparison of efficiency between $e(\cdot,\cdot)$ and $g^a \pmod{p}$. If computing $e(P,Q)$ is less efficient than computing $g^a ...
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279 views

how to mathematically prove a key exchange algorithm [closed]

I want to know the basic methodology that can be used to prove that a key exchange algorithm is secure. I am not asking about any specific algorithm. I want to know what should be proven and how to ...
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165 views

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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415 views

Designing a security system from scratch with a custom protocol, suggestions needed

For the reasons I cannot go into details, I need to design my own protocol and overall security system which will be used to establish secure data exchange between various devices (most notably ...
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552 views

Recommended Books for Cryptography : Theory and Implementation [closed]

It is a great idea if experts in Cryptography from mathematicians to security engineers introduce books and textbooks which they think is helpful or instructive for all people interested in the ...
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668 views

Deniability of OTR messaging

I've been looking at the off-the-record messaging protocol, and there is something about its deniability property that seems strange to me. Consider the following scenario: In the course of an ...
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134 views

Recommendation for lightweight algorithm for partial message encryption

I have designed a specific client and server program, which sends a file from client to server in 32k chunks. I want to encrypt only part of the data. More specifically: in each 32k chunk passing ...
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32 views

Perfect Forward Secrecy in PGP/asynchronous email

Looking at the RFC for PGP email/asynchronous chat with PFS here https://tools.ietf.org/html/draft-brown-pgp-pfs-03 can anyone tell me why the following scheme is no good? Alice and Bob retrieve each ...
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73 views

PKCS#7 message content

I am using a vendor library that signs a text producing a PKCS#7 message. I'm not sure of the content of this message. Does a pkcs#7 message have to contain the signed message, the certificate, the ...
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71 views

Could eVoting on the bitcoin blockchain be done?

I'm basically a crypto noob (and not an english native), so please be indulgent :) I thought about if you could realize an eVoting system with bitcoin. I see 2 major requirements: each citizen ...
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78 views

qkd - Does BB84 rely on a prearranged code?

First of all, sorry if the title is not that clear, I'll provide an in-depth explanation behind my question. So, basically I was reading about quantum cryptography and came across BB84. The protocol ...
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44 views

Authenticating with a document

Hope you're having a nice day. I need to implement an authentication system between a "document" (it's not exactly a document, but an object without any computing capacity, only able to store ...
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139 views

Proving security of TLS handshake with ProVerif

Background For my dissertation I am working on an application protocol for which I require a TLS session. I am looking to achieve Perfect Forward Secrecy, which means I have selected ephemeral ...
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64 views

Does anyone still use BAN or GNY logic in practice?

I want to implement a simple protocol, and I'd like to verify it through BAN or GNY logic. I would assume that if these logics are still used that there would be some programs available that would ...
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74 views

Malicious party security model: When one party is corrupted at a time

Consider we have three parties,namely client $A$, client $B$ and a server. Client $B$ and the server can be malicious, but we do not allow the adversary to simultaneously corrupt the server and ...
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131 views

Why is proving “parties' views are simulatable” enough in semi-honest model?

To prove a protocol is secure in semi-honest model, we have to prove: the view of each party, on each possible pair of inputs, can be efficiently simulated based solely on its own input and and ...
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74 views

Is Paillier cryptosystem commutative?

Is Paillier cryptosystem commutative? If not, how can we construct an oblivious decryption protocol based on Paillier?
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63 views

Where is defined the fact of having a “learning” and “challenge” phase in cryptography proofs?

I've read Bellare and Rogaway 2004 and Shoup 2004 about game-based cryptography proofs, but I lack precisions about how should be built the "learning" and "challenge" phases, since my games will ...
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110 views

Basic question about design of program with data encryption

I need to store encrypted files on a hard disk. The actual code side is not important for me now (I plan to use C# and AES-GCM encryption from Bouncy Castle library, please tell me if you think that's ...
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187 views

How often do I need to rotate AES 256 keys

I'm trying to design a protocol for a resource constrained environment. The device has to communicate with a server through an insecure node. My plan is to use AES 256 end to end for all ...
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127 views

Sender and receiver having different moduli conflicts with encryption and signing in RSA

I should implement a security protocol as a part of which I need to: Encrypt the message with receiver public key. Sign it with my private key. Send it to receiver. Suppose that the system uses a ...
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112 views

Which data to share in CTR mode?

Suppose I've got two clients $A$ and $B$. Client $A$ encrypts data in CTR (Counter) mode to get a ciphertext. What information will client $B$ have to receive from $A$ to decrypt the ciphertext? Just ...
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332 views

What's wrong with my security model - or how can it be attacked?

I'm working on a little personal project where security is very important, and I've thought for a while about the best way to do this. Now I am looking for a little outside help on good practices. The ...
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180 views

The “Square Root” Solution of Oblivious RAM Simulation

I am reading the paper Software Protection and Simulation on Oblivious RAMs by Oded Goldreich and Rafail Ostrovsky. And I wonder about the description of the "Square Root" solution of oblivious RAM ...
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206 views

Tor's integrity verification system?

I am trying to understand the design of Tor(onion router). I am reading the original paper on the 2nd generation onion routing system. Where, under integrity checking on streams, they say, "When Alice ...
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109 views

Is secure remote snap possible?

Scenario: We have a central server $S$. We have a number of peripheral servers $P_i$ We have some individuals $U_j$ A given individual may be "known" to one or more peripheral servers. Each ...
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165 views

Is it possible take a piece of data in secret?

I want something like this, but in a digital sense: You and others walk into a room. Everyone knows who each of you are and everyone is doing their best to figure out what piece of paper each ...
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280 views

Is the SILC protocol still used? [closed]

I'm looking into implementing a private SILC server for friends (and possibly their friends). And after visiting the Wikipedia entry for SILC protocol, it seems all the official pages linked at the ...
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63 views

When we use one time pad TWICE in two different ways

Assumption and Notations: All the values defined over the field $\mathbb{F}_p$, where $p$ is a large prime number. We denote multiplicative inverse of value $v$ by $v^{-1}$. All values are non-zero ...
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19 views

Security issues with self encryption? [duplicate]

I'm thinking about the scenario of using a set of (potentially untrusted) hosts to store (potentially private) files. Think something like distributed backup where you contribute some disk space and ...
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37 views

Is this ECC based messaging method secure?

I developing an encrypted messaging for ZeroNet (aP2P file-based network, website: zeronet.io) and would like to have some guidelines if any of this could work. My first idea: In ZeroNet every user ...
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84 views

Simplest way for strong cryptography in chat

I am a beginner in cryptography and I am interested for several weeks on this for my chat application. Basically, it is a centralized model. All messages are stored and potentially visible by ...
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53 views

What is the lightweight key exchange protocol of choice?

Assume I have to implement a secure channel protocol by myself. Assume further that for some obscure reasons (library restrictions?) I can't use any of the pre-made libraries for SSH, TLS and such. ...
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47 views

Details related to the ZIP algorithm used in PGP message encryption? [closed]

I am very new to PGP. PGP encryption works with hash function, asymmetric encryption, symmetric encryption and a zip algorithm (LZ77). What I know is that the zip algorithm is used to reduce the ...
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66 views

Why does encryption in STS protocol protect against identity attacks?

The basic STS protocol contains encryption of the signature as shown in Wikipedia. https://en.wikipedia.org/wiki/Station-to-Station_protocol If we would like to defend against MITM attack, this ...