Key exchange protocols

learn more… | top users | synonyms

5
votes
1answer
131 views

How does SSH use both RSA and Diffie-Hellman?

SSH protocol 2 allows you to use DSA, ECDSA, ED25519 and RSA keys when establishing a secure connection to a server. (Keep in mind for this question that I'm only familiar with the procedure and ...
0
votes
2answers
44 views

Why do I have to use multiple Keys for each direction and purpose?

I'm currently writing an examen about 'Lessons Learned in the IT-Security'. I already found some thing, which shouldn't be done. But right now I'm in trouble finding the reasons why not to do so. ...
0
votes
0answers
10 views

Negotiate n-bits key with Diffie-Hellman protocol (or other key exchange protocol)

I've got ASCII message. I convert it to binary - then I've got 8*(ASCII message length) bits - let us assume this value will be called n. I have to negotiate key, which length (after conversion to ...
2
votes
1answer
68 views

How to establish a random OTR remote party as a specific individual?

In reading Glenn Greenwald's 2014 book No place to hide, one thing stood out to me as a bit odd. Greenwald details how Edward Snowden was insistent that Greenwald install PGP in order to communicate ...
20
votes
1answer
14k views

What key exchange mechanism should be used in TLS?

There are many key exchange mechanisms that can be used in TLS. Among them are RSA, ECDH_ECDSA, ECDHE_ECDSA, ECDH_RSA, ECDHE_RSA and others. Which of these are more cryptographically secure and can be ...
2
votes
2answers
656 views

Why should the dh keylength match rsa length in tls?

A few sources state that the DH keylength (bits of the prime) should match the keylength of rsa for TLS. For example SSL_set_tmp_dh(3) from openssl has example code on how to match the dh parameters ...
0
votes
1answer
95 views

How can I generate some public and private keys on both sides with low overhead?

We have an Authority Center (CA) generating some public and private keys for each client (more than one pair for each client). One method for sending keys to client is sharing a secret key between CA ...
0
votes
0answers
25 views

ElGamal for ECC - Not working with Edwards curves (ed25519)

I know the usual way of using encryption/decryption with ECC is DH, however, this only works with two keypairs of exactly the same kind, for example two curve25519- or two p256-keypairs. With ...
2
votes
1answer
36 views

What is 0xXXXXXXXX.asc.sig and how can I generate this?

When I am exchanging PGP keys with someone, I receive the regular 0xXXXXXXXX.asc file and regularly receive a file called 0xXXXXXXXX.asc.sig. What is this file? How can I generate one and send it ...
0
votes
1answer
55 views

Why do we encrypt ephemeral Public key in Encrypted Key Exchange

Encrypted Key Exchange can resist off-line dictionary attack Protocol : A ---> B : Ep (PK) B ---> A : Ep(Epk(K)) K is Session Key generated by B PK is an ephemeral public key ...
1
vote
1answer
98 views

Authenticated Diffie Hellman Key Exchange

It appears that the textbook version of Diffie-Hellman is susceptible to man in the middle attack and the use of digital signatures could prevent this attack from occurring. Digital signatures could ...
0
votes
1answer
363 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 ...
8
votes
1answer
845 views

How do I store Diffie-Hellman parameters in a X.509 certificate?

In there paper Authentication and authenticated key exchange Diffie, van Oorschot and Wiener recommend to insert the DH parameters into the certificate of Alice. As a result an attacker can not change ...
0
votes
1answer
58 views

How could SSL certificate affect the symmetric key length?

This article in GoDaddy support knowledge base says All of our SSL certificates support high-grade 256-bit encryption How would they not support it? The SSL certificate contains keys for ...
1
vote
3answers
218 views

Is a Diffie Hellman Ephemeral key good material for being used as a symmetric cipher algorithm key?

I am designing a secure protocol (for academic/learning purposes) and I am at the point where I need to (re)design the key exchange step. In my previous implementation, I used to rely on RSA to ...
0
votes
1answer
134 views

rolling code & keyless entry system [closed]

The security industry typically uses rolling code algorithms to authenticate sender & receivers in keyless entry systems, which is called RKE (ex: KeeLoq). In key-less smart key car system, The ...
0
votes
1answer
112 views

Key Exchange using RSA

I'm trying to do key exchange using the following scheme. Server generates an RSA-2048 key pair and sends the public part to the client Client generates an RSA-592 key pair (I have to use RSA-592 ...
1
vote
0answers
55 views

Verifying the owner of a signing key

I'm using elliptic curve cryptography (curve25519 and ed25519) for key exchange and signing. The signing and key exchange keypairs are independent. I need two users to be able to verify each other's ...
1
vote
2answers
528 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 ...
1
vote
2answers
440 views

GSM A5/1 encryption: Key management

I'm currently studying the A5/1 algorithm used for GSM encryption. I understood how thanks to the symmetric private Key and a public counter frame one can encrypt the communication between A and B. ...
2
votes
2answers
74 views

Preventing a Computational DoS Attack in Public Key Cryptosystems

I'm designing a server which accepts anonymous messages using ECIES: as in, anonymous users send the server an ephemeral EC public key, and the server uses ECDH to derive a shared secret, and some KDF ...
5
votes
2answers
880 views

Website: Pre-Shared-Key Authentication

We have this web-application with high valuable (business) data. All communication is encrypted through TLS/SSL. While I consider this a really safe protocol, it can still be compromised if someone ...
16
votes
9answers
2k views

Are there any systems out there that use a one-time pad?

I'm still new to information security, but I have read a bit about the one-time pad. The point that sticks out to me the most is that it is supposedly unbreakable. Has this method of encryption ever ...
0
votes
1answer
57 views

MITM protection, key distribution

I want to make sure each of my apps users only get their own data, and that nobody tampers with it or sniffs it in a MITM fashion. Encryption of everything should be the solution, right? But how do I ...
0
votes
2answers
106 views

What are the alternatives to ECDSA for an authentication protocol?

In an authentication protocol, S has a public/private key pair known to C, and S and C have established a secure channel (for example, using DH or ECDH, or any other key exchange protocol). C wishes ...
1
vote
2answers
323 views

How to treat/hash ECDH shared secret to use as keys for AES?

I'm doing some studies/development for a security system that would use ECDH with ephemeral keys. In my code I'm currently using a 256-bit EC, so when the two parts compute the shared secret, I get a ...
3
votes
1answer
41 views

Transferring of keys from key servers to recipients

When I download PGP keys from keyservers like so: gpg --search-keys steve@openssl.org How are the public keys transferred down to my machine? Is there a possibility of a MITM attack to serve me the ...
3
votes
1answer
696 views

ECDH and Forward Secrecy

I just read about ECDH and while getting a overview over the process, I noticed that this key exchange method does neither provide any forward secrecy, nor does it protect against replay-attacks, ...
20
votes
6answers
12k views

“Diffie-Hellman Key Exchange” in plain English

Can someone explain to me what is Diffie-Hellman Key Exchange in plain English? I have read in a non-tech news page that twitter has just implemented this technology which allows two persons to ...
5
votes
1answer
1k views

How to secure API (private key) for mobile apps

I am building a web service that has to be only accessible for iOS apps. In the future I want to expand to a mobile website to make my service also available for other mobile operating systems. Now, ...
4
votes
1answer
485 views

Diffie-Hellman key exchange

The following image attempts to explain the diffie-hellman key exchange for people not strong in maths such as myself: I do understand how the colour/paint example illustrates the idea. But I'm a ...
0
votes
1answer
78 views

In IKE protocol; what is the PRF? [duplicate]

In IKE protocol; what is the PRF ? What is "the generation of a key based on modeled random oracle hash functions"?
1
vote
0answers
118 views

SSH using pre-existing session (symmetric) keys

Is there at present a way to open a SSH connection using pre-existing symmetric session keys? In other words, if I create a list of symmetric keys can I send that list to the recipient on a CD or USB ...
0
votes
2answers
80 views

Is it safe to use a ECDSA public key as a password seed for GCM/AES?

Two peers already exchanged their ECDSA (curve secp256k1) public keys using a secure channel. They want to establish an authenticated encrypted channel between them. They will use CCM mode and with ...
214
votes
13answers
21k 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 ...
5
votes
1answer
814 views

What are the OpenSSL standard Diffie Hellmann parameters (primes)?

I recently generated some custom Diffie Hellmann 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 ...
1
vote
1answer
56 views

Evaluation of cryptosystem for authentication and keyexchange

I'm a masters student in computer science who works part time with my own company as a consultant. My lastest project is based on my bachelor thesis which handles everything except the security. The ...
1
vote
2answers
372 views

SSL/TLS : Authentication mechanism

I have these doubts regarding authentication in SSL/TLS : Will there be an authentication involved for all SSL connections ? For eg. when I browse the internet, using the most up-to-date browser, ...
2
votes
3answers
103 views

Is it a good practice to include a download URL of my GPG public key in my email signature?

I was wondering if I can put a download URL for my recipients to get my GPG public key easily in my email signature. Is this a good practice? If not, what's a good alternative?
0
votes
1answer
749 views

Which is better in “DH-group14-sha1 with hmac-sha2-256” and “DH-group-exchange-sha256 with hmac-sha2-256” from performance and security perspective?

In our product (embedded system), so far we were using diffie-hellman-group1-sha1 with hmac-sha1. But due to security concern we are planning to use diffie-hellman-group14 for key exchange and ...
1
vote
0answers
134 views

Does Diffie-Hellmann (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 ...
0
votes
1answer
119 views

Key-Exchange Algorithms VS Local Key Generation?

I was wondering the difference in term of Security, Computational cost and Network overhead between the use of : A Key-Exchange Algorithm (e.g. Diffie–Hellman) to set up a symmetric key. The ...
0
votes
3answers
190 views

What are the MitM implications of a stolen client-side private key?

Many VoIP handsets support client-side SSL authentication for auto-provisioning. Unfortunately, some devices must be programmed with their client-side keys. (Keys generated on low-entropy devices are ...
3
votes
1answer
131 views

Can we build a key exchange protocol without certificates?

Assume that the server and the client both has some secret key K. Is it possible to have a key exchange protocol with authentication between them such that MITM attack cannot hold and if the key is ...
0
votes
1answer
91 views

Key Exchange algorithm to be used for REST framework

I was required to create key exchange module for custom Rest framework which supports document level security in REST requests. Framework has its own security module which allows to encrypt parameter ...
0
votes
2answers
84 views

does a public key work with all encrypted programs

let us say, I use program "x" for my e-mail security. through them I have a public key and a private key. My friend uses program "y" for their e-mail security and consequentially have a public key ...
3
votes
7answers
267 views

How would I give an encryption key to only one person?

Let's say I have an encrypted message. I want to make it so that someone is able to decrypt it. The only way of giving it to them is online. For the purposes of this question, I can't call, mail or ...
5
votes
2answers
896 views

What is the difference between DHE and ECDH?

I learned that perfect forward secrecy is implemented through DHE and ECDH but what is the difference between these 2 key exchanges? Also can someone explain how perfect forward secrecy works? I've ...
2
votes
0answers
91 views

Main difference between Yahalom and Needham-Schroeder key exchange protocols

I am just wondering what is the main difference between the Yahalom and Needham-Schroeder key exchange protocols? Which protocol uses less computational power?
1
vote
0answers
53 views

Any Suggestion Exchanging shared key between process via port in untrusted machine (infected my malware)?

I am trying to get shared key between Firefox extension and a java program running in same machine. I am communicating both application via socket. My assumption is that malware is running in ...