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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Enabling ECDH KeyExchangeAlgorithm in Windows Schannel while disabling CBC based ciphersuites

On our Windows Servers, we have disabled the following key exchange algorithms in registry SCHANNEL\KeyExchangeAlgorithms\ECDH SCHANNEL\KeyExchangeAlgorithms\PKCS This leaves us with only 2 ...
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How server key limits protocols and ciphers used? [duplicate]

There is a server (app) that uses OpenSSL to allow clients establish secure connection. The certificate info for server public key is: Certificate: Data: Version: 1 (0x0) Serial ...
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2 answers
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Can a VPN connection be detected (and get blocked) even after the key exchange happens

If the key exchange happens when using lets say Wireguard or any other protocols that use IKA, and the connection never drops, could the ISP still detect the VPN traffic using Deep Packet Inspection?
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What is the right way to transfer public-private keypairs over intranet?

First asked on StackOverflow and referred to this board, here: I have an embedded system (Netburner 5441x) that encodes public-private RSA keypairs into devices. I have ported OpenSSL into the system ...
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170 views

IIS Crypto 3.2 not getting rid of Diffie-Hellman algorithms of less than 2048-bits

I'm trying to stop a server using Diffie Hellman key exchanges of less than 2048 bits, but I'm getting confusing results. I've run Get-TlsCipherSuite | Format-Table Name, Exchange, Cipher, Hash, ...
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1 answer
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How can a client safely post/get a (symmetric) client key to/from a key distribution center?

If you look at the above Kerberos protocol's diagram, you can find that the protocol works on the basis that the (symmetric) client key initially exists on both the client node and the key ...
1 vote
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How does Tor's second node know the key to decrypt the second layer?

I was watching this video explaining how tor works: https://youtu.be/QRYzre4bf7I It explains it with the example of 3 intermediate nodes between client and server. It says that each of the nodes can ...
1 vote
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Diffie Hellman with server public key embedded on the client

First, I realize trying to come up with your own crypto schemes is not a good idea. I'm a relatively new member of a team of developers utilizing such a custom scheme and I'm trying to come up with ...
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TLS 1.3 RSA key exchange

I have some confusion between the different public and private keys that are used in a TLS 1.3 connection. When a client makes a request to a server, I've always thought that a server's TLS x509 ...
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2 votes
1 answer
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Is it secure to share a public (RSA) key over http?

The following scenario: We have a HTTP (not HTTPS, so unencrypted) server which contains an open (RSA) public key. The general sharing of the public key should not be a problem since it is the public ...
1 vote
1 answer
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Simple Key Exchange, One Server

Posted this on Cryptography; reposting here in case it's more relevant. I am trying to better understand how TLS works. I understand in the normal use case you need various random values generated and ...
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How client and server exchanges keys over Tor network using HTTPS? [duplicate]

When someone uses a browser to connect to https://google.com via Tor network, the client needs to exchange a key with Google in order to keep all the data hidden from the exit node, right? Otherwise, ...
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2 answers
199 views

How do Routers share a key when using Symmetric Cryptography? [closed]

When a client connects to a router (standard home router) how is the key distributed to the client? If the key is sent across the network, can not someone sniff and see the key? If the key is not sent ...
4 votes
1 answer
133 views

Is it possible to use HKDF in the TPM?

Is it possible to use HKDF in the TPM? My goal is to load in a master symmetric key and derive keys from that using HKDF. I see there are other KDF functions available, but no mention of HKDF.
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How vulnerable is security if a public key is swapped by active attacker if a key check is done?

Trying to understand this from a high level conceptually. It is obvious from all information on Asymmetric encryption that a public key can be of course, public and there isn't a danger of ...
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1 vote
1 answer
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Is there any standard or protocol of key exchange between multiple nodes?

A little context: I'm working in designing a system to sign and verify data sent between modules of a bigger system. Currently the system has two parts, a central application and a SDK inside modules ...
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How does the inclusion of a subprime q value affect the Diffie Hellman equation for key exchange? [duplicate]

This is a follow on from this question: "Diffie-Hellman Key Exchange" in plain English In the answer to that question, the standard Diffie Hellman key exchange equation is derived: (g^a mod ...
2 votes
1 answer
221 views

ePassport Chip Authentication - how to verify?

I want to implement Chip Authentication for ePassport documents, and wish to validate my understanding of it. I've managed to get it up and running by using the JMRTD library, specifically the ...
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Is this scenario of static ECDH public key exchange right?

I'm thinking about the way to build encryption mechanism for 'peer-2-peer' communication. This is a mechanism I had a thought of: Alice wants to communicate with Bob First of all, Alice and Bob must ...
1 vote
1 answer
836 views

SNORT rule for detecting/preventing unauthorized VPN or encrypted traffic

Here's my not so theoretical scenario: A day-one Trojan horse attack where the attacker sets up a secure connection back to himself using a well known trusted port, such as 80 21 443. Or for instance, ...
2 votes
2 answers
192 views

Key Exchange using RSA public key without a certificate

I want to share AES key using RSA. What is the recommended/widely used format for encrypting the AES key and its attributes with the public key? I know that PKCS#7/CMS enveloped-data allows encrypting ...
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1 vote
1 answer
598 views

When is a private and public key given to a user, and why can the private key not get hacked?

Trying to understand assymetric encryption. To my knowledge, it deals with the key management problem by having each user have their own private key and public key. But when is this private and public ...
3 votes
1 answer
228 views

Why can SSH negotiatie two different encryption and authentication algorithms?

I recently found out, that according to the RFC, SSH can negotiate two different cipher (and MAC) algorithms for server-to-client-encryption and for client-to-server-encryption (check section 7.1. for ...
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Performing a simpler ssl handshake [duplicate]

Consider the following scenario: client sends hello server send a hello and its certificate client generates a key and encrypts that with server's public key server decrypts the key with its private ...
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445 views

How to securely design REST API for Password Manager app?

I want to create Password Manager where users can create their accounts and store website passwords. For the frontend, it will be a mobile app, but I need REST API as the backend data where the data ...
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Is it possible to decrypt TLS traffic through OpenSSL?

I have a web server that uses the ECDHE-RSA-AES256-GCM-SHA384 cipher suite. I noticed that when given the "(Pre)-master-secret log" file (generated by the browser), Wireshark is able to ...
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1 answer
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In Signal Messenger what is the purpose of verifying a safety number?

I've read the official page on safety numbers but they are still unclear to me. Without verification, there still is end to end encryption, so what difference does it make? Is it that a phone number ...
1 vote
1 answer
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TLS- Key exchange for session keys. Why?

I have a question about the Key Exchange Algorithm used in TLS process. I have read that the Key Exchange algorithm is used by client and server to exchange session keys. Do the client and server ...
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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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1 vote
1 answer
258 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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3 votes
0 answers
202 views

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 ...
2 votes
3 answers
341 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 ...
9 votes
8 answers
7k 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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12 votes
8 answers
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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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1 vote
1 answer
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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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1 vote
1 answer
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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 ...
0 votes
2 answers
245 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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2 votes
1 answer
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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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1 answer
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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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9 votes
1 answer
915 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 ...
2 votes
2 answers
746 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 ...
2 votes
2 answers
363 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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Why is the Diffie-Hellman 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 ...
24 votes
1 answer
3k 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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1 answer
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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 ...
2 votes
1 answer
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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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2 votes
1 answer
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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 ...
1 vote
1 answer
251 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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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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0 votes
1 answer
152 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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