# Questions tagged [three-pass-protocol]

The three-pass protocol uses commutative encryption to let two people communicate privately without having to exchange keys in advance.

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### Instead of asymetric encryption, why not use two One-time pad? [duplicate]

Why is the following protocol never used to share a symetric key between two parties ? ⊕ is the XOR operation. Alice has M and wants to send it to Bob. Alice generates K₁ randomly. Bob generates K₂ ...
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### Is establishing a secret key possible given this characteristic primitive?

I am wondering if there are any readily available solutions for the following problem: I have a ring-topology network with several devices connected to it, some malicious, some legitimate. I want to ...
1 vote
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### Two formulas work for this three-pass exchange problem, but I can't figure out why one of them works

Problem statement: "Suppose that users Alice and Bob carry out the 3-pass Diffie-Hellman protocol with p = 101. Suppose that Alice chooses a 1 = 19 and Bob chooses b 1 = 13. If Alice wants to ...
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### Three Pass Protocol Question!

Alice and Bob have agreed to use the Three Pass Protocol. p=1009 Alice chooses the encryption exponent e_A = 101 Bob chooses the encryption exponent e_B = 209 Now Alice and Bob send three ...
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### Shamir three-pass protocol Elliptic Curve

I want to know how I can implement this protocol. I know how Shamir three pass protocol operates without elliptic curve, but I don't know how I can perform it with elliptic curve. I read about this ...
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### What would happen if the last message in a three-pass authentication protocol was undelivered?

I did read some articles about the protocol but couldn't figure out what would happen. Would the two parties be unable to verify each other? Or would it be something else? based on the international ...
1 vote
1k views

### Multiple encryption using the same key

I am a newbie to this area. I have a program that uses a custom algorithm to encrypt a message. I can encrypt it as many times as I want, but using the same key. I have couple of questions so that I ...
1 vote
157 views

### Is it safe to publicly announce the prime number in Shamir three-pass protocol

So say, I want to use a prime number p for anyone that wants to communicate with me using Shamir's Three Pass Protocol. I will be maintaining my secret keypair (encryption exponent, decryption ...
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### Would a OTP No-Key Protocol work?

Consider Shamir's No-Key protocol. What if you substitute the asymmetric operations with XOR, each party using an ephemeral OTP. It's symmetric, so you could apply the protocol scheme as if it were ...
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### With known ciphertext and plaintext, find other party's Three Pass Protocol Key?

If I'm the second party participating in a three pass protocol (for simplicity, let's say Shamir's Three Pass Protocol) such that: Bob sends me a ciphertext I encrypt it and send it back He removes ...
443 views

### 3 pass protocol

suppose we have 3 matrix named A,B,C (2x2, 3x3, 10x10 or whatever). As we know A^(-1) A C B B^(-1)=C So i take a file and convert it to numbers e.g. ASCII code (lets say 65,72,71...) and i add a ...
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### 2way cryptography

Imagine Alice sending Bob a message. They act like this: Alice encrypts a message with her key and sends it to Bob. Bob encrypts the message again with his key and sends it back to Alice. Alice ...
276 views

### Does there exist an agreeable algorithm to substitute XOR function in Shamir's no Key Protocol?

I think Shamir's no key protocol (also known as three-pass protocol) is a secure cryptography scheme but the designer only proposed the XOR function to encrypt the message which could be easily broken ...
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### Three-Pass Protocol number theory

I've got a homework problem that I'm having a hard time understanding. It's for the Three-Pass Protocol, and we are given p, the three messages, and are told that the original plain text is one of two ...
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### Requirements for the modulus in the Massey-Omura three pass protocol

In the Massey-Omura three pass protocol: How many bits long should the prime modulus $M$ be in order to be secure? Should the $M$ be secret? Should the $M$ be generated every time or it could be ...
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### Ballot box with multiple parties. All can read it, or none can read it

I am trying to create a decentralized moderation system for the game Diplomacy, a game for seven players. In each round of a face-to-face game, each player writes their moves on paper then puts it in ...
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### Can two people with different one time pads securely exchange a message like this?

Alice has a message, generates a one time pad, encrypts her message and sends it to Bob. Bob generates his own one time pad, encrypts the message again, and sends it back to Alice. Alice then decrypts ...
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