Questions tagged [diffie-hellman]
The Diffie–Hellman key agreement is an anonymous, non-authenticated key-agreement protocol.
278
questions
2
votes
1
answer
3k
views
OpenSSL Generate ECDH Public Key
I am trying to use the OpenSSL command line to generate a ECDH public key that meets the following specifications:
Use a Base64 encoded X.509 SubjectPublicKeyInfo structure containing a ECDH public ...
- 123
1
vote
1
answer
279
views
Is it possible to use custom DH parameters for IKEv1 / IKEv2 /IPSEC?
While researching how to deploy TLS for web servers most securely, I have learned that using custom DH parameters is one of the key aspects.
Now I am in the process of deploying IKE / IPSEC. As far ...
- 567
2
votes
2
answers
1k
views
Why are primes reused in Diffie-Hellman key exchanges?
Reading about the Logjam attack, I learned that Diffie-Hellman exchanges often* rely on the same particular 1024-bit key. I understand that back when DH was invented, even 512-bit keys were considered ...
- 121
1
vote
2
answers
446
views
Key-exchange over the network with more than two peers
Me and my team is developing a multiplayer videogame with a Client/Server-Topology. This secures the match from clients who have the intention to cheat because of server authority but still allows the ...
- 113
1
vote
1
answer
277
views
Is there such a thing as an SSLeay/PKCS#1-style static Diffie-Hellman key?
That is, would you ever find a PEM file which starts:
-----BEGIN DH PRIVATE KEY-----
or:
-----BEGIN DH PUBLIC KEY-----
?
And if so, what is its structure?
I know static DH keys are an oddity, ...
- 111
2
votes
1
answer
397
views
Could Diffie-Hellman be used to stop people who knows the PSK from snooping on your WiFi?
One known problem with WPA2 is that anybody who knows the preshared key can snoop on the handshake and decrypt all subsequent traffic between any parties on the network. In the typical coffee shop ...
- 65.4k
6
votes
0
answers
143
views
Share diffie hellman group between servers [duplicate]
I'm deploying several servers with TLS. The servers are different but related and each having their own certificate generated by letsencrypt.
To increase the security, I'm generating my own Diffie ...
- 161
7
votes
1
answer
3k
views
Diffie Hellman Key Exchange in a messaging application
I'm currently a student that is trying to develop a messaging application on android using java that will implement diffie hellman key exchange in order to ensure that they both will be able to ...
- 71
4
votes
1
answer
3k
views
Why was running OpenSSL dhparam too fast?
I just generated Diffie-Hellman parameters and it seemed way too fast. The whole thing was over in under a second:
$ openssl dhparam -out /etc/ssl/certs/dhparam.pem 2048
This is going to take a long ...
- 275
0
votes
1
answer
1k
views
What are the requirements for private keys in Diffie-Hellman key exchange algorithm
Basically question is:
If we have pof size 2048 what sizes for private exponents should Alice and Bob choose and why?
- 103
1
vote
1
answer
649
views
How to verify the signature of DHE_RSA server parameters (TLS 1.2)?
By reading the TLS 1.2 specs I have been able to manually decrypt/encrypt pretty much all the steps of a TLS connection (DHE_RSA_AES_CBC_128_SHA cipher suite).
One of things I am missing is how to ...
- 133
4
votes
2
answers
641
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 ...
- 1,159
0
votes
1
answer
1k
views
Difference between Hybrid encryption and Diffie-Hellman key agreement?
Can someone explain me the difference between the Diffie-Hellman key agreement (DH encryption) and Hybrid encryption?
As to my knowledge DH key agreement uses public and private keys to generate a ...
- 1
23
votes
2
answers
24k
views
What is the difference between DH and DHE?
I have been reading Bulletproof SSL and TLS
Diffie Hellman is a key exchange mechanism, in which each of server and client share secret i.e. gx and gy respectively with each other where g is ...
- 447
1
vote
0
answers
136
views
DTLS and Ephemeral Diffie-Hellman [duplicate]
In the DTLS handshake, the two parties involved in the communication must authenticate each other by means of certificates, and after that they perform an ephemeral Diffie-Hellman key exchange, with ...
- 11
-3
votes
1
answer
140
views
which algorithm/hash can possibly encrypt and decrypt certain data regardless of size?
I have intercepted some data for which i don't know which algorithm has been used to encrypt this data, this data has been for sure encrypted before transmitting, to decrypt the data i should ...
- 1
5
votes
1
answer
6k
views
Is the OpenSSH server using a fallback, hard-coded DH parameter for 2048bits?
I'm toying around with OpenSSH configs and poking at the Diffie-Hellman parameters. I'm using GDSSecurity's tool to check DH settings and this page to view other SSH settings.
For funsies, I removed ...
- 1,200
5
votes
1
answer
1k
views
Is OpenSSL generating Diffie-Hellman parameters that are safe for use in TLS or SSH servers?
I would like to generate Diffie-Hellman parameters on a Debian GNU/Linux "Jessie" 8 with OpenSSL. Lets assume the system CSPRNG was seeded with some real random data.
On such a system, is the result ...
- 267
2
votes
1
answer
1k
views
Diffie Hellman prime attributes
If I generate a Diffie-Hellman prime openssl dhparam 512 -text (deliberately of small size to keep the paste size below small; I know minimum is 2048 and up), what are the different parts of the ...
- 345
0
votes
1
answer
286
views
Q: What happened to socat?
I saw elsewhere some discussions on an error (or backdoor) in socat but find it difficult to get from the (anyway not well ordered and fairly large volume) materials the essence of what had actually ...
- 1,209
0
votes
1
answer
880
views
How can a RSA-2048 certificate be vulnerable to logjam attack? [duplicate]
Most likely I am missing some fundamentals: Our web servers are secured with TLS encryption. We use RSA-2048 bit certificates. The logjam attack targets the DH algorithm. How can our web servers be ...
- 13
34
votes
2
answers
15k
views
What is the current security status of Diffie-Hellman key exchange?
There is a web site weakdh.org, whose name alone would certainly cause some feeling of uncertainty in using DH among people who are not experts IMHO. Could some knowledgeable person kindly say ...
- 1,209
2
votes
2
answers
304
views
Can a user verify the quality/safety of pregenerated SSH moduli parameters?
Many tutorials about how to mitigate the Logjam recommend regenerating Diffie-Hellman moduli. This is a resource intensive operation, especially for high-bit groups.
This made me think if it made ...
- 1,200
15
votes
3
answers
10k
views
Is 8192 Diffie-Hellman overkill?
I've finally ran SSL server test on my server and was presented with:
This server supports weak Diffie-Hellman (DH) key exchange parameters. Grade capped to B.
So I tried to generate stronger ...
- 405
0
votes
1
answer
192
views
How to encrypt something with a key? [closed]
I read a lot about security on the internet, especially how services like telegram work with their encryption and how they do it. I also heard of the Diffie-Hellman Key Exchange, which was quite ...
- 1
0
votes
2
answers
404
views
Filtering safe primes for Diffie Hellman on OpenVPN
When creating Diffie Hellman parameters for OpenSSH, there's a two-step process which looks like this to generate and filter secure primes for Diffie Hellman key exchange:
ssh-keygen -b 4096 -G ...
- 6,753
10
votes
2
answers
8k
views
In Ephemeral Diffie Hellman Key Exchange - what is actually ephemeral?
Just starting to learn about Diffie-Hellman, and it seems simple enough, but I am struggling to find any resources that explain in an Ephemeral Diffie Hellman Key Exchange, what it is that is actually ...
- 101
49
votes
4
answers
8k
views
Why is key exchange necessary at all?
Let's say "Alice" and "Bob" want to communicate with each other over an insecure network.
Using Diffie–Hellman key exchange, they can get the same symmetric key at last. However, as I understand, ...
- 503
1
vote
3
answers
3k
views
Using a stolen certificate on a server
Yesterday I asked the following question regarding what would happen if you placed a stolen certificate on your own server and edited the 'host' file so that the DNS name matched:
Could a stolen ...
- 311
11
votes
3
answers
2k
views
What DH Group size do TLS Ephemeral DHE ciphers use?
In SSL/TLS, the Client and the Server have the option to use an Ephemeral Diffie-Hellman exchange to establish a shared secret for which to seed the ensuing Master Secret and Session keys.
In the ...
- 771
0
votes
1
answer
1k
views
What's the algorithm to generate a modulus and a base for a Diffie-Hellman key exchange app?
I have a school project in which I have to write a java console application that can be used for key exchange between two people. All is fine and well, but finding good base and modulus seems to be a ...
- 103
11
votes
1
answer
733
views
Diffie-Hellman large prime number weakness. Is this concept valid? If so, how can this be remediated by end-users/admins?
So I saw this blog post on “How is NSA breaking so much crypto?”. The basic idea of this blog post is this: There is an inherent weakness in Diffie-Hellman that stems from services using the same ...
- 1,184
5
votes
2
answers
2k
views
Does changing /etc/ssh/moduli impact previously generated keys?
My company does a lot of automated file transfers over SSH/sftp with banks, etc. A recent SSH upgrade on a server dropped support for the old/weak diffie-hellman-group1-sha1 key exchange protocol in ...
- 151
-4
votes
2
answers
246
views
Does SSL doesn't work without a secondary Symmetric/Asymmetric session key?
I keep reading that Symmetric session key is used in SSL after handshake only for faster performance but isn't true a secondary session key either Symmetric or Asymmetric key generated by the client ...
- 11
1
vote
2
answers
4k
views
What algorithm should I use to avoid the error "ERR_SSL_WEAK_SERVER_EPHEMERAL_DH_KEY"?
I got a CA cert by submitting my CSR from GoDaddy, after applying a certificate to my Tomcat web server. When I access my website using Chrome or Mozilla I face the error:
...
- 11
1
vote
1
answer
3k
views
How to Build Pre-Master Secret [duplicate]
I'm implementing a TLS-like system, which uses ECDHE-RSA-AE-GCM-SHA, and I've faced two interrogations.
At the end of the handshake ( and before the ChangeCipherSpec message), both the client and the ...
- 313
2
votes
1
answer
2k
views
RSA signature on TLS
In a TLS handshake using ECDHE-RSA, the ServerKeyExchange frame must include the ECDHE ServerPublicKey, signed with its RSA private key, as specified in the RFC 4492. Got it.
Trying to implement an ...
- 313
1
vote
1
answer
1k
views
Specificity of ECDHE in a TLS handshake
It's just a short question, but I haven't find a clear answer yet...
It's in the frame of a TLS-ECDHE handshake.
Where does the specificity of the ECDHE, over the DHE, appears ?
At which point do ...
- 313
7
votes
3
answers
2k
views
Usage of Ephemeral Diffie-Hellman ciphers in 2015 and beyond
In determining TLS standards for my company, I have come to wonder why all recommendations still suggest the use of the Ephemeral Diffie-Hellman TLS ciphers starting in TLS_DHE_xxx
Background and ...
- 171
0
votes
2
answers
2k
views
Diffie-Hellman and MIM attack, and server identity
Diffie-Hellman and MIM attack:
When variants of Diffie-Hellman algorithms like DHE, ECDHE etc. are used in SSL handshake for key exchange then can it become prone to man in middle (MIM) attack.
...
- 215
10
votes
3
answers
2k
views
Is ECDH for SEC P-384 and P-521 broken in Windows 10 / Windows Server 2016 TP3?
UPDATE: Proof of concept code here, console output shown below and all involved certificates are here.
Just noticed that ECDiffieHellmanCng.DeriveKeyMaterial(...) behaves differently on Windows 8.1 ...
- 2,183
5
votes
2
answers
203
views
Where in a TLS connection can I get the signature of the content sent by the server?
I want to be able to prove that a given content returned by a HTTPS server was in fact served.
I have looked over the whole TLS protocol and I found I can use ServerKeyExchange to get the server's ...
- 51
75
votes
2
answers
100k
views
Diffie Hellman parameters still calculating after 24 hours
I have a fresh install of Arch Linux on a RaspberryPi model B. I'm setting up OpenVPN and using easy-rsa with OpenSSL 1.0.2d to generate initial keys and certificates. All went fine until I ran ./...
- 873
2
votes
1
answer
5k
views
Diffie Hellman parameters still calculating after 24 hours [duplicate]
I have a fresh install of Arch Linux on a RaspberryPi model B. I'm setting up OpenVPN and using easy-rsa to generate initial keys and certificates. All went fine until I ran ./build-dh. It is now 24 ...
- 873
1
vote
0
answers
134
views
How to inform other sysadmins their email encryption is broken [closed]
Does anyone have a good template email to use to send to remote system/mail/security administrators to alert them to the fact that emails to them would not be getting through either at all or securely ...
- 11
139
votes
3
answers
165k
views
What's the purpose of DH Parameters?
For a Diffie–Hellman (D-H) key exchange (TLS) the server generates a prime p and a generator g, which is a primitive root modulo p.
When setting up a webserver with SSL/TLS (e.g. nginx) one can use a ...
- 3,506
5
votes
1
answer
2k
views
ECDH BouncyCastle KeyAgreement length
I am attempting to obtain a shared secret using BouncyCastle's ECDH methods in C#,
however I am receiving a shared key which is much shorter than the 48 bytes I expect it to be.
I have a trusted ...
- 75
109
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 ...
- 1,352
1
vote
0
answers
306
views
How to verify the usage of dhaparameters configuration from command-line?
Although Qualys will happily do it for Internet-reachable systems, some of ours are on private networks. I'd like to be able to verify them all remotely.
Is there a "quick" recipe -- something based ...
- 111
2
votes
1
answer
2k
views
Cipher suites vulnerable to logjam
The following is a list of ciphers, how to know which ciphers are vulnerable to LogJam attack?
Client shared list of ciphers:
TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA
TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA ...
- 21