Questions tagged [key-exchange]

For questions relating to protocols for distributing public keys, and / or establishing session keys with another party. Examples of key exchange protocols include Diffie-Hellman and IKE.

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Client-side encryption of data, but the server can also add data without reading stored data

For a new application I'd like to store messages for each user's account on a centralized server. The user accesses the application through a SPA javascript web app through their browser. These ...
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96 views

Web developer needs customer's private key

As a non security expert, I'm looking for advice from those who are. I work with company X who have hired company Y to develop their website. Company Y needs to integrate server-side online payment ...
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Examples of SSH key exchange algorithms requiring encryption-capable host keys

In the SSH spec, Section 7.1, key exchange algorithms are distinguished based on whether they require an "encryption-capable" or a "signature-capable" host key algorithm. If I ...
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10k views

Diffie Hellman c# implementation

For a test project I have tried to implement the (famous) Diffie Hellman algorithm for safe key exchange. Now I have written this in C#: using System; using System.Collections; using System....
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3answers
93 views

Format for data & symmetric key exchange/storage

Is there a standard format for storing/exchanging encrypted data along with the key needed to decrypt it (data is encrypted with a single use symmetric key and the symmetric key itself is encrypted ...
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2answers
863 views

PMK is what prevent to generate the PTK and decrypt the traffic?

I'm trying to establish a connection to an encrypted SSID, using scapy. My intent was basically to sniff the frames of the handshake from the victim, acting as a proxy (MITM), and redirect the frames ...
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27 views

GPG Questions About Exporting Subkeys to File

GPG novice here so please bear with me. From what I understand, when you generate a keypair with GPG it will automatically create a subkey pair (sub, ssb). If I wanted to give these to another party ...
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1answer
71 views

TPM Attestation and key exchange

I have the following problem: I have two platforms, one of them has a TPM. I need to transfer data between these two platforms, so I first determine an attestation, in order to confirm that the ...
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1answer
79 views

Authenticate Static Public Keys

How can a static ECC public key be authenticated when being shared between the client (who has just created the static ECC public key) and the CA (Certification Authority) - who will sign and send the ...
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11answers
430k views

“Diffie-Hellman Key Exchange” in plain English

Can someone explain to me what Diffie-Hellman Key Exchange is in plain English? I have read in a non-tech news page that Twitter has just implemented this technology which allows two persons to ...
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8answers
6k views

Can a large corporation make a believable promise

Say there is a secret encryption key that a third party has to handle. The third party is supposed to destroy the secret key when they are done, and tell everyone else it was destroyed and therefore ...
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8answers
5k views

How can we exchange public keys between two servers in a secure way?

I have two servers with a pair of RSA public and private keys. We do not use a CA for the internal communication yet and therefore we need to exchange keys without CA. I need to establish a trust ...
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1answer
589 views

How to verify that Google's apt signing key change is not malicious?

I have an Ansible script that setup google chrome apt repo. I keep Google's signing key together with the scripts (rather than download it every time) because I think it minimizes the chance of ...
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1answer
44 views

How do SRP (and PAKE generally) protect against verifier leak

I have been reading into PAKE protocols, specifically starting with SRP RFC2945 The gist of the requirement on the server is that the server saves triplet (username, verifier (v), salt (s)) in the ...
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1answer
28 views

Storage of secret key in resource-constrained sensor nodes

In sensor nodes, there arises a need to store the master secret key safely. Which is the most perfect location to store the key when the sensor nodes (such as implanted body sensor node) are highly ...
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1answer
2k views

How can I verify Keybase's end-to-end encryption between me and a friend?

The premise of end-to-end encryption (E2EE) is that the client is secure and trustworthy, your end devices is secure and trustworthy, but the network and server need not be trusted. You've read all ...
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4answers
109k views

Is there any particular reason to use Diffie-Hellman over RSA for key exchange?

I often see RSA being recommended as a method of key exchange. However, the Diffie-Hellman key exchange method appears to be secure as well. Is there any considerations one should take into account ...
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2answers
105 views

How to securely exchange a symmetric key over a unsecure netwrok

I need to build a project for uni where I need to transfer data securely from a client to a server. I can't use PKI structures and can't save pre-shared secrets (Imagine travelling to china and some ...
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1answer
85 views

ECDH_SHA2_NISTP256 (KEX) Algorithm in SSH - Vulnerabilities?

My organization within my company uses this KEX Algorithm in our SSH Implementation. Another organization within my company won't connect to our servers as long as this algorithm is implemented as ...
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289 views

How does “Key Transparency” work?

A few days ago, Google published Key Transparency to solve the problem of verifying the key fingerprints of e.g. your chat partners. Unfortunately, I don't really understand how Key Transparency ...
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34 views

Establish a symmetric key: KDF based on shared secret and random salt or key wrapping?

I am designing a basic KMS based on a simple HSM, I only have access to: AES256, SHA256, PBKDF2, HMAC (and combinations like AES256-HMAC-SHA256). The admin and the users of the system have a personal ...
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2answers
490 views

Is IKE aggressive mode really less secure than main mode?

This guy argues it is not: https://www.youtube.com/watch?v=DuowFgNKAIg I really confused about this. According to him, the only purpose of main mode is to make the peers anonymous, but in order to ...
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2answers
159 views

Can I use the same truststore and keystore on the client and the server?

TL;DR: Is it possible to have both sides of a SSL/TLS connection have the same public and private key, so long as that public key is trusted by both sides? More info if helpful: I'm trying to test ...
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2answers
159 views

Using Diffie-Hellman exchange on low power IoT devices

I have almost 0 knowledge of IoT, their protocols and usual device constraints. I had a discussion today with someone that has a fair amount of IoT experience and we were discussing some security ...
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1answer
103 views

Why is the Diffie-Hellmann exchange not enough to authenticate the communication partners in IKE_SA_INIT?

The IKE_SA_INIT does create a key seed SKEYSEED from the Diffie-Hellman values and nonces. Since the exchange does sharing the secret between the communication partners, I do not understand why it is ...
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69 views

Thought process on Network Protocol Attack

I'm preparing for an introductory information security examination in university and this is one of the tutorial question on Network Protocol attacks. I tried (a) and came to this conclusion: Since ...
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1answer
395 views

How to enable DH_RSA instead of DHE_RSA?

I generated DH parameters and set at server side. it always select cipher suite DHE_RSA? Is there any reason that DH parameter have to set server side only. Ephemeral DH: what is changed P and g ...
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1answer
625 views

Are Multi device usage and bots in Telegram an excuse for only ssl encryption?

Telegram's E2E encryption is not secure. See: Is Telegram E2E Still Insecure? and Is Telegram secure? Lets asume its is secure and talk about the "excuses" why E2E encryption is not always used. It ...
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1answer
61 views

First setup security protocols (key transfer) in not-secure environment

This question might very well be more a confirmation than anything else, but I'm breaking my head over a problem I try to solve. I hope someone can either confirm my thoughts or tell me something I'm ...
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1answer
6k views

How ECDHE is signed by RSA in ECDHE_RSA cipher

About ciphers that use ECDHE as Key Exchange and RSA as Authentication: How exactly this two algorithms work together, is ECDHE process encrypted by RSA public key? What are the DH parameters? ...
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1answer
89 views

Is this key exchange algorithm secure and valid? [closed]

I'm writing reliable UDP implementation and I want it to be secure. Also, I want to make use of elliptic curve cryptography. I don't have the proper education to really understand the math behind this ...
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1answer
119 views

How can I distribute highly confidential keys for a symmetric cipher?

Say I want to exchange a key with someone for a symmetric cipher (say AES) without meeting them in person. What would be the most secure way to do this over the Internet? My first instinct would be ...
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1answer
69 views

Updating Sender-Keys and Key-Management

This question is related to an earlier question I had: Encryption on Mobile Devices - Multiparty Encryption - Key Management My situation: I have many mobile devices that want to send sensitive ...
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1answer
3k views

Is the Station-to-Station protocol secure?

After I've read a lot about key exchange many sources state that the Station-to-Station is secure, since it also verifies the entity on the other side. Well how is that true, if an active Man in the ...
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2answers
253 views

Is it a good idea to use asymmetric encryption for a chat application?

I am reading design documents of an internal Whats-app like chat application. Developers are planning to use asymmetric encryption to encrypt all messages. Every user will have a public/private key ...
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1answer
73 views

Can I securely share an HMAC key over a TLS connection?

In a game client/server that I'm developing, I want to allow a user to authenticate over TLS (via a REST endpoint on an HTTPS server) before dropping to an unencrypted low-latency UDP protocol. To ...
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1answer
275 views

Diffie–Hellman key exchange questions [closed]

at the moment I am working on a chat application, where more than two clients can communicate at the same time. I just got started with the encryption so please be bear with me. My goal is to ...
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2answers
307 views

SSH key based login is not vulenerable to MiTM attack. Is it true?

I read somewhere that when using key based login instead of a password based login, it is not possible for a Man-in-the-Middle attack to happen. This question is not about what is being more secure: ...
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1answer
84 views

Can I use HTTPS to pass a symmetric key used for encrypting TCP packets?

I am making a multiplayer game for fun and wish to keep it secure. The client is written in C# and the server in node.js with a working connection over TCP at the moment. I am new to this subject, and ...
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1answer
91 views

Public key encryption confusion

I'm learning Linux, and currently SSH. But there are details that I don't really understand. I've seen and understood how Diffie-Hellman key exchanges work from a mathematical point of view, but what ...
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2answers
781 views

SSL session protocol vs SSL connection protocol

Slide 8, SSL Session Protocol: Slide 10, SSL connection protocol: Firstly, in Session Protocol, there is a {S}_B, what is the function of this {S}_B? Does't it help in proving Alice's identity? Is ...
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346 views

ssl - Can the attacker generate his own symmetric key if ClientHello and ServerHello are intercepted?

After reading this awesome explanation of how SSL works, I now have a confusion. The answer states that the first messages of SSL are ClientHello and ServerHello(in response to ClientHello). Both of ...
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1answer
213 views

Two message key agreement and mutual authentication protocol?

I am looking for, but not finding, a published protocol that does something similar to TLS 1.3 mutual authentication, but simplified by using assumptions to reduce the chattiness of TLS. If we assume ...
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93 views

Is this Key Exchange secure?

There is a key exchange process which I am having a look at. I am aware of key exchange algorithms such as Diffie-Hellman and the like, however as there is a method to provide an initial key out-of-...
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1answer
127 views

Two-party symmetric key establishment protocol

Update: original problem description I am developing a client-server system for configuration updates. The system handles update tasks. An update task is initiated on a server; multiple clients then ...
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1answer
223 views

Can password strength be enforced with PAKE protocols?

Can a password strength policy i.e.: must contain at-least 8 chars must contain one uppercase letter must contain one lowercase letter must contain one number Be enforced if a PAKE protocol is used, ...
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1answer
175 views

IKE Phase 1 /w PSK resource?

I can't seem to find a sufficiently detailed resource that describes the IKE phase 1 PSK identity authentication process. They seem to focus on differences between aggressive and main mode while ...
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1answer
506 views

ECDH and static key encryption

It's been a while and I'm still trying to figure out if my understanding of ECC crypto is correct. Basically from what I understood a purely asymmetric encryption is never used. Usually the ...
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6answers
28k views

Why can't I MitM a Diffie-Hellman key exchange?

After reading the selected answer of "Diffie-Hellman Key Exchange" in plain English 5 times I can't, for the life of me, understand how it protects me from a MitM attack. Given the ...
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911 views

Why does TLS 1.3 deprecate custom DHE groups?

According to the second draft of the TLS 1.3 specification, custom DH groups have been deprecated. As we all know, hardcoded DH groups are vulnerable to a precomputation attack that allows retroactive ...

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