Questions tagged [diffie-hellman]
The Diffie–Hellman key agreement is an anonymous, non-authenticated key-agreement protocol.
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What are 'screened' DH groups?
Currently it's recommended to do something about the contents of /etc/ssh/moduli.
I've seen two ways:
to strip all moduli of less than 2047 bytes size from the file.
to recreate them using ssh-keygen....
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Must a Diffie-Hellman group value persist?
I've been reading about the Logjam attack on Diffie-Hellman and about how to secure our TLC-based web servers based on the recent findings.
The guide suggests that we create a Unique Diffie-Hellman ...
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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?
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What is the role of RSA in ECDHE-RSA? [duplicate]
I have read some textbooks and not found a convincing explanation.
In the cipher suite ECDHE-RSA-AES128-GCM-SHA256, what is the role of RSA in the first part (ECDHE-RSA)? This part of the cipher ...
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Do Diffie-Hellman parameters need to be recreated regularly?
Having generated 2048-bit DH params, do I need to regenerate them regularly? If so, how frequently should I do this?
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How to check if a server is not vulnerable to Logjam?
In response to Logjam I want to prove I've hardened my services.
I know that the DH param has to be 2048 bits at least and self generated. But I am unable to find a way to actually check this for ...
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How 'Logjam' attack affects openID since it uses Diffie-Hellman key exchange method?
According to the Diffie-Hellman key exchange get affected by logjam, and openID uses this to establish an association. So how this going to affect OpenID?
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What is Logjam and how do I prevent it?
I heard there is a "new" TLS vulnerability named Logjam, what does it do and how do I prevent it?
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Should diffie-hellman parameters be unique to a vhost
So I'm setting up one host to serve multiple SSL sites. I've been following various guides like https://cipherli.st/ and https://wiki.mozilla.org/Security/Server_Side_TLS and they both suggest to ...
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Unable to establish handshake using DH key exchange [closed]
I have a requirement to use the cipher suite: DHE-RSA-AES256-GCM-SHA384 I configured to use the required cipher suite on both server and client. During tests, I noticed that the handshake is failing ...
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Is Diffie-Hellman key exchange the best way to securely exchange SSH keys?
I'm designing the communication mechanism for end user devices that will communicate with a row of servers. My current plan is
on first run, a device will generate its own SSH key pair (RSA and 4096 ...
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Diffie Hellman and exchange of public key for signature
Let's assume an insecure channel.
Is it safe to exchange Alice & Bob public keys first then apply them to sign communications during the DH process? (then encrypt+sign all future communications)?
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Relationship between RSA, Diffie-Hellman Key Exchange, PKI and X.509?
I am getting confused with RSA, Diffie-Hellman Key Exchange, PKI and X.509v3.
I took a look of RSA's mathematics algorithm, it seems like a encryption algorithm, right? Generating public key and ...
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Extract pre-master keys from an OpenSSL application
Consider an application using OpenSSL which has a bug. A packet capture of the full SSL session is available, as well as a core dump and debugging symbols for the application and libraries. A RSA ...
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OpenSSL vulnerability CVE-2015-0205
I can't seem to make any sense out of the following vulnerability in OpenSSL:
DH client certificates accepted without verification [Server] (CVE-2015-0205)
=============================================...
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Does Ephemeral Diffie-Hellman require a certificate?
In Ephemeral Diffie-Hellman, the key pair is generated every time.
In practice, does this mean I never need a certificate? Or that means I need a new cert every single time?
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Is it possible to perform one-way OTR MITM?
Here's something that is bugging me recently: suppose that me and my friend establish an OTR session and - as a result of that - DH key exchange is performed. My friend verifies my key, but I cannot ...
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Is it really worth to spend time on Telegram Crypto Contest? [closed]
Telegram is running this crypto contents. But what I heard from some people on the web is that they designed the contest in such a way that they made it practically impossible to crack.
Is it really ...
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Is it feasible to create a new key for symmetric encryption for each message rather than negotiating a long lives session?
The normal method of providing an encrypted channel appears to be negotiating a session key (using Diffie Hellman or similar), then using this key for a long lived session. Even IPSec that is message ...
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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 ...
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A secure way to encrypt a connection between 2 clients securing against both passive and active adversaries
Recently I got interested in encryption and the methods behind them. So for a fun / school project I am building a program in python to encrypt data between two clients (chat and files).
I'm just ...
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Why not use symmetric encryption?
Something very simple: most of us communicate most of the time with people we already know. Alice and Bob probably have physical contact, too. Yes, there are cases when whistle-blowers want to contact ...
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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 ...
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Using Diffie-Hellman to verify SSL Certificate?
I am fairly new to encryption and I need some help. I have a problem that I'm trying to solve.
My problem is the following:
I have a Web Server and an (iOS) App that that communicate with each other....
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In OpenVPN, is the dh1024.pem file dependent on the CA?
As the question already states, I'd like to know if the dh1024.pem file, generated by ./build-dh in openvpn, is dependent on the ca.(crt|key) file.
The reason was that I needed to ./clear-all the ...
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which diffie-hellman group is needed for secure ike/ipsec
We're deploying ipsec on embedded devices and getting catastrophic performance from the diffie hellman 2048 group in ike.. afterwards the shared securet is used for 3des, sha1. ipsec negiation is ...
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How to best to secure data over HTTPS
My aim is to have an (iOS) app in which the user would login, then on sucsessful login, gain access to additional information over an encrypted webservice (undecided).
From research, I understanding ...
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it is possible to decrypt HTTPS with the (private, public) pair if it uses DHE?
Assuming you have a PCAP file with HTTPS traffic and having the key pair (private & public), it is possible to decrypt the traffic if it uses Diffie Hellman Ephemeral? Using openSSL lib for ...
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What is the simplest safe way to convey a password to another person? [duplicate]
What is the easiest way for two people – neither of whom are computer specialists and cannot meet in person – to send a password for an encrypted file that is attached to an email?
The two simplest ...
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How to password protect a Truecrypt volume using a Diffie Hellman public key exchange?
I want to send a Truecrypt volume through email. Of course, I need to password protect it, and the recipient needs to know the password too. A Diffie-Hellman public key exchange would seem to be the ...
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Understanding Diffie-Hellman key exchange
I understand the diagram up till the point where Bob and Alice do a "Public transport" of their respective mixture. I am wondering how do Bob and Alice know what secret colour to add ( circled picture ...
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How often should the DHE p and g factors be recycled?
I've been asked to enable DHE in our SMTP product. I'm stuck on this question:
How often should the product regenerate its DHE p and g parameters?
I've seen some implementations that use a cron job ...
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Does public key auth in SSH prevent most MITM attacks?
I found this article that claims asymmetric crypto signature of DH-obtained key prevents MITM:
http://www.gremwell.com/ssh-mitm-public-key-authentication
Key idea:
The value of 'signature' is a ...
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Diffie Hellman Hash MITM
I've seen an application recently that used the Diffie Hellman algorithm. It is not a Ephemeral Diffie-Hellman implementation, but rather a Diffie Hellman one. After the secret keys have been ...
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Why OpenVPN is using both certificates and DH?
I am reading about OPENVPN and I am a little bit confused. In the OPENVPN howto website, there is a step by step setup guide for generating certificates and diffie-hellman (DH) params. However, I cant ...
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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 Web browser (Firefox) I saw the following:
Connection encrypted: High-grade Encryption
(...
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How can DH provide a known secret to two parties over an unencrypted connection without it being intercepted via MITM?
Without using Private and Public keypairs, i do not understand how Diffie-Hellman is able to generate a secret key between two parties on the internet without passing something between that could be ...
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Is encrypting and subsequently sending a known clearext string after a Diffie-Hellman bad design?
I'm writing a small protocol that relies on a DH handshake, generation of a shared secret, and subsequent AES encryption/decryption using that generated secret. I want to add a built-in test message ...
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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 bit ...
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Are Telegram secret chats secure assuming MTProto isn't?
For those who don't know: Telegram is a partially open source Whatsapp alternative (Server is closed source) which offers secret chats and normal chats. Secret chats are encrypted with Diffie-Hellman ...
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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 ...
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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 ...
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Why don't more websites implement Perfect Forward Secrecy?
From what I understand, all it takes to enable PFS on a webserver is adding ephemeral cipher suites (ones that use DHE and ECDHE for the key exchange) to the list of cipher suites used in SSL/TLS ...
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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 ...
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What is the difference between Diffie Hellman generator 2 and 5?
Generating Diffie Hellman parameters in OpenSSL can be done as follows:
$ openssl dhparam -out dh2048.pem 2048
Generating DH parameters, 2048 bit long safe prime, generator 2
This is going to take a ...
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What to do with the extra bytes in ECDHE-RSA-AES-GCM-SHA?
I'm trying to implement, as an exercise, a protocol based on the cipher suite ECDHE-RSA-AES256-GCM-SHA384.
As I understand things, ECDHE is used for the key exchange, RSA for the authenticity of the ...
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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 hmac-...
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Is it safe to use Diffie-Hellman public keys as nonces to protect against replay attacks?
I have an interesting case regarding protection against replay attacks. Under the assumption that Alice and Bob have used Diffie-Hellman key exchange to establish a secure temporary session, would it ...
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How secure is Samy Kamkar's Anti-MITMA Diffie-Hellman Key Exchange Technique?
I'm currently using Diffie-Hellman to encrypt data sent across an arbitrary link (can be ethernet, Wi-Fi, USB, bluetooth, etc), and I'm not a huge fan of the potential that DH is vulnerable to an ...
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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 ...
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