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.

Filter by
Sorted by
Tagged with
1 vote
1 answer
265 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 ...
7 votes
1 answer
464 views

Can SRP be implemented using libsodium

I am using libsodium for cryptography and I want to use SRP for key exchange. The wikipedia page lists a python example, but I am not sure if and how I could convert this to libsodium function calls. ...
1 vote
1 answer
129 views

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 ...
0 votes
0 answers
33 views

ECDH or DH sharing using onion routing

I have come up with a new ECDH sharing method, where I give the common key to dozens of people in advance and then randomly select about 8 people to share the ECDH with whom I want to talk by relaying ...
1 vote
2 answers
64 views

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?
1 vote
1 answer
910 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, ...
1 vote
0 answers
45 views

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 ...
0 votes
0 answers
19 views

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 ...
3 votes
3 answers
1k 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: ...
2 votes
1 answer
114 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 ...
23 votes
2 answers
38k views

Client-server encryption technique explanation (TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256, 128 bit keys)

I opened a web page using https. When I looked at the page info provided by my browser (Firefox) I saw following: Connection encrypted: High-grade Encryption (TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256, ...
6 votes
2 answers
4k views

Role of the chosen ciphersuite in an SSL/TLS connection

When it comes to a secure TLS configuration (e.g. for HTTPS), the topic is prominently about the supported cipher suites. I want to fully understand which part of the cipher suite has which role in a ...
1 vote
1 answer
93 views

What is this scheme called and how should it work exactly?

So I was thinking about client-server communication and how to keep this private, especially from man-in-the-middle attacks. I came up with a scheme that I'm sure exists already, but I could not find ...
0 votes
1 answer
47 views

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 ...
108 votes
6 answers
32k 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 ...
1 vote
0 answers
410 views

Does Diffie-Hellman (DH) key exchange protocol lower Off-The-Record protocol (OTR) security level?

Off-the-Record protocol employes Diffie-Hellman key exchange protocol (DH). DH protocol does not provide authentication of the communicating parties and, according to many sources, is vulnerable to ...
3 votes
1 answer
139 views

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 ...
417 votes
14 answers
67k views

How is it possible that people observing an HTTPS connection being established wouldn't know how to decrypt it?

I've often heard it said that if you're logging in to a website - a bank, GMail, whatever - via HTTPS, that the information you transmit is safe from snooping by 3rd parties. I've always been a little ...
15 votes
1 answer
12k views

What are the OpenSSL standard Diffie-Hellman parameters (primes)?

I recently generated some custom Diffie-Hellman parameters which are basically just long (in the below case 4096 bit) primes. Those are then used in the key exchange process. I used the following ...
0 votes
1 answer
550 views

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 ...
13 votes
6 answers
5k views

Is (safe) encryption over compromised line impossible?

I realize something like this would be the holy grail of communications security and have never heard anything to suggest it has been done. Am just wondering. A lot of mathematicians and computer ...
5 votes
1 answer
2k views

Tor: Is a Diffie-Hellman key exchange being done over recipient of traffic?

As I was looking over Tor specifications and I noticed that when a circuit is generated then on each circuit's node a Diffie-Hellman key exchange is being done over an encrypted path on each Node as ...
6 votes
3 answers
709 views

DHE exchange and client authentication

If a server has a known public key and a Diffie-Hellman exchange is performed and signed by that key, is there any benefit to authenticating the client before establishing a secure channel instead of ...
0 votes
0 answers
208 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, ...
4 votes
2 answers
598 views

Why is random DH group recommended over a standard group?

I know in light of logjam there have been recommendations to generate your own DH group (https://weakdh.org/sysadmin.html). It seems to me that leaving this task up to the end user is much more likely ...
1 vote
0 answers
78 views

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
0 answers
85 views

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 ...
2 votes
1 answer
2k views

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 ...
2 votes
1 answer
1k views

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
105 views

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 ...
294 votes
11 answers
464k views

"Diffie-Hellman Key Exchange" in plain English

Can someone explain what the Diffie-Hellman Key Exchange algorithm in plain English? I have read that Twitter has implemented this technology which allows two parties to exchange encrypted messages on ...
0 votes
0 answers
24 views

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, ...
0 votes
2 answers
210 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
152 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.
1 vote
1 answer
150 views

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 ...
0 votes
0 answers
33 views

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 ...
9 votes
1 answer
2k views

Forward secrecy with GnuPG

I'd like to know how to implement forward secrecy using GnuPG, and I presume I need some kind of authenticated key exchange. Assuming that I have the following working already: Alice and Bob have ...
2 votes
2 answers
209 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 ...
2 votes
1 answer
243 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 ...
0 votes
1 answer
128 views

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 ...
8 votes
5 answers
26k views

Can we trust onetimesecret?

Alice: I need the file Bob: Sure, and I want to encrypt it first. Please put the strong PGP symmetric key with the copy&paste method to https://onetimesecret.com/ and send me the link. Alice. ...
4 votes
1 answer
4k views

Encryption key exchange for Tor

I've been studying how Tor works - including the great QA "Why can a Tor exit node decrypt data, but not the entry node?". I understand the concept of onion routing and multiple layers of encryption....
6 votes
1 answer
9k 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? ...
21 votes
3 answers
51k views

DEK, KEK and Master key - simple explanation

This article is intended to be a simplified explanation sans drill-down for people wanting to understand these concepts/terms. What are DEK, KEK and MEK/Master key?
5 votes
1 answer
450 views

Share or not share public key for servers?

In order to encrypt communications from our (custom) client to our (custom) servers our current scheme is a bit like this: Client uses the bundled public key A to encrypt some random key material. ...
1 vote
1 answer
677 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
244 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 ...
10 votes
1 answer
1k 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 ...
1 vote
1 answer
274 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 ...
0 votes
1 answer
114 views

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 ...

1
2 3 4 5 6