Questions tagged [diffie-hellman]

The Diffie–Hellman key agreement is an anonymous, non-authenticated key-agreement protocol.

Filter by
Sorted by
Tagged with
1 vote
0 answers

How to generate DSA keypair for browserID

As a bit of a learning exercise, I'm trying to understand and implement a client for the Firefox Accounts Browser sync API. I'm up to the point where I'm trying to ask the server to give me a ...
Glenjamin's user avatar
  • 111
0 votes
1 answer

How much harm can an attacker do on the Diffie-Hellman exchange?

I'm looking at a system that uses an unprotected Diffie-Hellman exchange to negotiate a key for the session encryption. That Diffie-Hellman is not secure against man-in-the-middle attacks is textbook ...
Gene Vincent's user avatar
0 votes
2 answers

DHE Verification

I'm just struggling to get my head around this. In certificate signing with static Diffie Hellman the public key and certificate information is sent to the CA who verifies the certificate ...
Nark's user avatar
  • 549
5 votes
1 answer

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 ...
Bush's user avatar
  • 337
3 votes
2 answers

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 ...
Elrond's user avatar
  • 145
18 votes
2 answers

DH parameters recommended size?

I'm setting up EAP-TLS on my wireless router, and am currently generating DH parameters for FreeRADIUS. First, what do these parameters do? Also, what size should they be? I've been generating the ...
Naftuli Kay's user avatar
  • 6,753
20 votes
2 answers

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 ...
Matthew Clenney's user avatar
3 votes
2 answers

For DHE_RSA_.. Cipher Suites what is RSA used for?

In addition to achieving PFS with DHE, we want as little as possible to be revealed when the server's private key is revealed. So, what is RSA used for in DHE_RSA cipher suites? What does the server ...
OregonTrail's user avatar
298 votes
11 answers

"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 ...
user avatar
1 vote
0 answers

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 ...
amit's user avatar
  • 123
2 votes
1 answer

Using Diffie–Hellman key protocol to create a safe secret key

Let's say, I have a friend far from me and I want to send some secret messages to him. I have to say, I'm pretty newbie in security. That's why I'm wondering, does the Diffie–Hellman key exchange ...
Incerteza's user avatar
  • 2,257
9 votes
2 answers

What are the implications of using the same DH parameters in a TLS server?

For a DHE cipher, nginx hard-codes the Diffie-Hellman parameters to use base 2 and a fixed 1024-bit prime (modulus) if no custom DH parameters are configured. These parameters are public (sent in ...
Lekensteyn's user avatar
  • 6,068
11 votes
2 answers

1024-bit DHE vs 2048-bit RSA

Currently with apache/mod_ssl, if DHE is enabled then a 1024-bit ephemeral key will be used. I found the following quote in Adam Langley's blog: Ideally the DH group would match or exceed the RSA ...
safsaf32's user avatar
  • 213
10 votes
2 answers

Is there a key length definition for DH or DHE?

I found this in wiki The Finite Field Diffie-Hellman algorithm has roughly the same key strength as RSA for the same key sizes. The work factor for breaking Diffie-Hellman is based on the discrete ...
Zack's user avatar
  • 101
20 votes
2 answers

OpenVPN dhparam

One of the steps for setting up OpenVPN is running the command openssl dhparam -out dh1024.pem 1024. The man page tells me this 1024 value refers to the number of bits. Why is the value 1024 ...
Zoredache's user avatar
  • 653
2 votes
1 answer

ECC Brainpool Standard Curves and Curve Generation with Bouncy Castle which seed to use?

I want to implement a ECC Key Agreement with a Brainpool curve brainpoolP512r1 or brainpoolP512t1. I'm not clear about whichseed value to use (and how). In this document
hdev's user avatar
  • 247
1 vote
1 answer

OpenSSL DH modp size

If OpenSSL is configured to use a DH for key exchange, e.g. TLS_DHE_RSA_WITH_AES_128_CBC_SHA, where does it take the size for modp (or even modp itself) from? The following is a screenshot from ...
fr00tyl00p's user avatar
  • 2,339
47 votes
2 answers

Diffie-Hellman and its TLS/SSL usage

I'm struggling to understand the (non-)use of Diffie-Hellman (DH) in TLS. DH has been around for a long time now, why does almost nobody use it, yet? DH is only being used for "key sharing", why does ...
David Halter's user avatar
1 vote
1 answer

Can manual hash verification defend against a DH MITM attack?

I understand how DH key exchange is vulnerable to a MITM attack. When Alice sends Bob g, p and her public key, if she also sent a value H that was a hashing of the values g,p, and public key all ...
Jeff's user avatar
  • 133
4 votes
1 answer

How to reduce the size of a key established with Diffie-Hellman?

When I generate a key with the a Diffie Hellman method (DH), the established shared key will be of the same size as the prime which is used. As far as I have read this should be at least 2000 bits for ...
Raphael Ahrens's user avatar
19 votes
1 answer

What's the hash for in ECDHE-RSA-AES-GCM-SHA?

Presumably the SHA is for deriving the AES key from the shared secret. Where else is the hash used? ECDH just does ECC (no hashing). RSA does masking and padding but this doesn't involve the ...
Nicholas Wilson's user avatar
5 votes
3 answers

Javascript Diffie-Hellman and AES protocols

I am using the BigInteger Javascript library to create a symmetric key using Diffie-Hellman protocol. I want to create 128,160 or 192-bit keys. After some research, I have found out that I should use ...
Kheil's user avatar
  • 137
5 votes
2 answers

Should I test my SSL certificate for "RSA Shared Primes" before using it?

There are several papers from 2012 that say it's possible to factor several moduli by factoring shared primes. The link above includes python sourcecode to verify and test for this fact. Given this ...
makerofthings7's user avatar
37 votes
4 answers

Can someone explain what exactly is accomplished by generation of DH parameters?

I'm setting up a node.js server: https.createServer({ ... ciphers: 'ECDHE-RSA-AES128-SHA256:AES128-GCM-SHA256:RC4:HIGH:!MD5:!aNULL:!EDH', honorCipherOrder: true }, app).listen(443); ...
Steven Lu's user avatar
  • 977
27 votes
3 answers

How does non-ephemeral Diffie-Hellman key exchange become compromised in SSL when the RSA private key is leaked?

From my understanding, one of the major reasons we recommend Diffie-Hellman Ephemeral (e.g. DHE or ECDHE) over non-ephemeral DH, for SSL / TLS, is that compromise of the RSA private key (i.e. private ...
Polynomial's user avatar
  • 135k
56 votes
2 answers

Decrypting TLS in Wireshark when using DHE_RSA ciphersuites

How can I decrypt TLS messages when an ephemeral Diffie-Hellman ciphersuite is used? I am able to expose the premaster secret and master secret from the SSL Client. Using that, how to decrypt the ...
Kalai's user avatar
  • 811
132 votes
4 answers

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 ...
user avatar

1 2 3 4 5