Questions tagged [diffie-hellman]
The Diffie–Hellman key agreement is an anonymous, non-authenticated key-agreement protocol.
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Limit on modulus lines in OpenSSH /etc/ssh/moduli file?
I understand that OpenSSH server looks in /etc/ssh/moduli and picks a modulus at random for each Diffie-Hellman group exchange. What I am wondering is whether there is a practical limit on how many ...
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Diffie Hellman Pre Master Secret too long
As far as I understood, when using Diffie Hellman, the pre master secret is generated as follows:
Alice and Bob agree on a generator g and a prime p
Alice chooses a primary key a, calculates A = g^a ...
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What's the usage of the signature algorithm in TLS_DH_* cipher suites?
According to RFC5246 A.5 there are cipher suites TLS_DH_RSA_* and TLS_DH_DSS_*.
How / where does the signature algorithm RSA resp. DSA from the cipher suite come into play when using (non-ephermal) ...
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Possible MITM attacks on ECDH-RSA or ECDHE-RSA prevents
As I understood a simplified ECDH-RSA key exchange protocol works like below
Alice request Bob for its ECDH public key
Bob generates ECDH parameters and sign them with a CA provided RSA certificate. ...
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TLS - DHE_DSS: How does client know public DSS-server key?
I wonder where the public server key g^x for DSS authentication is communicated to the client when a DHE_DSS cipher suite is used in TLS 1.2. Precisely:
A DSS certificate contains crypto parameters (...
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Diffie Hellman Group Matching to IPSec Encryption Algorithm
I'm looking for help determining acceptable Diffie Hellman (DH) Groups for specific IPSec IKE and ESP Encryption Algorithms. The goal is to choose DH groups that provide adequate protection for the ...
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Online Diffie-Hellman Tool
I stumbled upon this website which provides a service to generate Diffie-Hellman parameters online for free to the public.
Surely using a website like this would be a bad idea to use in a production ...
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Why send HMAC in reverse direction when performing verified DH with downgrade protection?
The purpose of this procedure is that Alice and Bob perform a verified Diffie-Hellman key exchange. It goes like this:
Alice sends her supported signature schemes to Bob. It just says "supported ...
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Will changing the TLS Diffie-Hellman key exchange bit length from 1024 to 2048 cause client/browser compatibility issues?
Recently discovered the need to upgrade our DH key exchange length (used for TLS) from 1024 bits to 2048 bits (due to Logjam exploit and other factors). The question is: How will making that change ...
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What's the point of the second SA exchange in the Create_Child_SA exchange in IPsec
I have problems understanding why you would negotiate crypto-algorithms in the Create_Child_SA request in a IKEv2.
During IKE_SA_INIT you negotiate cryptographic algorithms which I assume (correct me ...
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How likely is that my ECDHE-RSA-AES256-GCM-SHA384 application will be cracked? [closed]
I am using the following chain in my cipher: ECDHE-RSA-AES256-GCM-SHA384
I am wondering if there's a weak chain in this cipher that might allow my application's communications to be cracked?
I'm new ...
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Why is the reuse of the Elliptic curve Diffie–Hellman (ECDH) public server param considered bad?
When reviewing the SSL/TLS configuration using Qualys SSL Labs, I've found that the reuse of the Elliptic curve Diffie–Hellman (ECDH) public server param was flagged.
Why is the reuse of the Elliptic ...
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Key exchange during IKE_AUTH phase of IKEv2
This is what a casual IKEv2 handshake looks like :
Initiator Responder
| ...
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What is the meaning of KEX DH host key and KEX DH H signature in SSH key exchange
During the Diffie-Hellman key exchange, the server sends a Diffie-Hellman Key Exchange Reply (31) message back to the client. This message contains the DH server f but also two other pieces of ...
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Logjam definition question
As I understand it, the Logjam TLS attack is an attack that downgrades the DHE cipher suite used by the server to DHE_EXPORT. Where the client thinks it is talking DHE 512 and the server things it's ...
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Secure application data
I have a private client/server application that trying to secure the data transmitted through public network. The encryption/decryption method is private too. Client and server uses DH key exchange ...
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When exactly is Diffie-Hellman used in TLS?
I'm aware that Diffie-Hellman is a key exchange algorithm whereas RSA is an asymmetric encryption algorithm.
I have the following questions:
During TLS handshake, will both RSA and DH be used?
(I ...
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Is ECDH easier than DH to be broken?
As I am a security newbie, this post might have lots of misconceptions about security. If so, please let me know
I've heard that ECDH is preferable to DH because its smaller key size and lower ...
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Are public/private keys needed when using Diffie-Hellman with TLS
When using RSA for key exchange in TLS, the role of the public key embedded in the certificate is clear: for asymmetric encryption when sending the master key, which the server can decode using its ...
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Is this a correct DH key exchange over RSA wirelessly?
Note: I am a network researcher, but a security newbie. Hence, this post may contain wrong understanding of security including DH and RSA. If it does, please let me know it.
I've designed a certain ...
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SSH wireshark trace and Diffie-Hellman G and P parameters
I have a problem spotting both "DH base (G)" and "DH modulus (P)" in my sshv2 trace. I scrutinized each message exchanged between both my ssh client and the ssh server, there is no trace of "DH base (...
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Generating partical Eliptic Curve Diffie-Hellman keys [closed]
I want to generate a pair of ECDH keys (64 bytes each), where the first 12 bytes of the public key will suit my format.
For example, if I have a unique sequence "13456789ABC" I'd like to use it as ...
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How is DH and RSA used together in HTTPS? [duplicate]
I'm trying to get my head around how DH and RSA are used in HTTPS.
I'm sorry if this is a duplicate.
I've done research into what RSA and DH are, but I'm trying to figure out how they are used ...
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Understanding SSL man-in-the-middle and its limitations
I’m trying to develop a good sense of how an SSL man-in-the-middle(s) (MITM) works. As I understand it, MITMs do their work in one of two ways:
Decrypt the SSL by having a copy of the server’s ...
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SSL/TLS - Certificate chain validation result in "Invalid authentication type: DHE_RSA"
I have an application that connects to a remote web service deployed on HTTPS.
Our application uses FIPS-140 Level-1 for SSL/TLS connectivity, and is based on JCE providers of RSA (the company).
com....
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Usage of Diffie Hellman key exchange in TLS [duplicate]
As far as I know, this is the process of establishing a TLS connection between a client and a web server:
Client sends a TLS request (using a packet called Client Hello) to the server.
Server answers ...
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Man in The Middle attack on secure key exchange protocols
I am going through CISSP materials and I got stuck on Secure Exchange Protocols such as Diffie Hellman and RSA. It is known that DH by itself is vulnerable to MiTM. So the answer is to use ...
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Perfect forward secrecy using XOR
I understand that Perfect Forward secrecy is meant to prevent the data sent between the client and server being decrypted in case the private key is leaked some time after the data being sent.
But ...
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Are min/max/normal groups only for the D-H parameters, with no relation to the RSA authentication/signing of the D-H parameters? [duplicate]
Using SSH (DH Group Exchange SHA256) with RSA authentication keys.
Since the initial handshake uses asymmetric algorithms (RSA, Diffie-Hellman) to handle authentication and setup of a shared secret, ...
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What are the performance differences (for client and server) between DHE and ECDHE in TLS?
My question is about the client and server performance for (EC)DHE.
I am having difficulties in understanding this picture (which is based on numbers from Ivan Ristic' book "Bulletproof SSL and TLS").
...
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Sniffing WhatsApp Traffic
I was wondering if its possible to obtain private keys for Whatsapp to be able to sniff traffic between two WhatsApp Android devices (both under my control). I understand that WhatsApp traffic is now ...
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Why is Mozilla recommending predefined DHE groups?
In a revision dated 2016-10-31, Mozilla changed their Server Side TLS recommendation from generating a random DH group to the ones published in RFC 7919. Mozilla claims:
These groups are audited and ...
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How Could A Diffie Hellman Key Exchange Work on SMS Apps on Two Different Mobile Devices?
How Could A Diffie Hellman Key Exchange Work on SMS Android Apps on Two Different Mobile Devices? It is understandable for a client browser communicating with a server, the internet data path is ...
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Should I be concerned if a Diffie-Hellman key generation is near instant?
I'm a bit new to key exchange and security, so sorry if this is a stupid question. I'm setting up an OpenVPN server on my home router, and I did a dummy run just to see if I got it all up and running (...
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ECDH vs DH secret key size
In the past couple of weeks I have been reading about DH and ECDH which are key exchanging algorithm to compute a shared secret key. According to advices, it is better to use DH with key size 2048 ...
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Does a leaked pre-shared key make the initial IKE phase 1 negotiation of Diffie Hellman vulnerable?
A pre-shared key is used for authenticating the peers and also used in protecting the DH key exchange because it's possible to man in the middle the DH exchange.
Does this mean that if an attacker ...
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How to sniff ECDH HTTPS traffic?
Our company currently sniffs encrypted RSA traffic using a network tap.
Would this still be possible using ECDH? I guess not.
Are there commercial alternatives, like placing an agent on the ...
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What does "Server Temp Key" mean in an openssl output?
I am using openssl 1.0.1e-fips. When I ran the following against my server, I get a line in the output that begins with Server Temp Key:
$ openssl s_client -cipher DHE-RSA-AES128-SHA -connect ...
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OpenVPN: How safe is a 24-7 open port static key setup? With proper encryption used. (AES256)
In a normal setup (cert), you have a strong encryption - just like here - for example, AES256. But you also use dh and the tls params. Just to be absolutely secure.
Now, if you use the static key ...
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How to Perform Encryption after Diffie Hellman Key Exchange
This feels like a silly question, but a cursory look around the internet hasn't exactly helped.
I'm implementing 1-out-of-2 oblivious transfer using DH key exchange in Python. I have successfully ...
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Usage of the permanent RSA private key in ECDHE-RSA-AES scheme
I was wondering if in SSL/TLS negotiation process, there is another role for the RSA permanent private key in ECDHE-RSA-AES scheme besides signing the DH public key for authenticating the identity of ...
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Selection of Curve in ECC for openssl 1.0.1?
I am using both version of openssl 1.0.1 and openssl 1.0.2 :
in openssl 1.0.2 have one function which is to set highest preference curve automatically.
But, in openSSL 1.0.1 there is no any function ...
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One Time Pad Algorithm without sharing keys
On my walk to work today I thought of the following encryption algorithm and could not determine the flaw. It uses one time pad's that don't need to be shared and has a Diffie-Hellman key exchange ...
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How to enable DH_RSA instead of DHE_RSA?
I generated DH parameters and set at server side. it always select cipher suite DHE_RSA? Is there any reason that DH parameter have to set server side only.
Ephemeral DH: what is changed P and g ...
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Client IPSEC VPN Key Exchange vs. Site to Site IPSEC VPN Key Exchange
Given a site to site IPSEC VPN most firewalls allow for the selection of which DH group the site to site tunnel will use to perform the key exchange prior to encrypting the traffic.
I have noticed ...
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Clarification on DH groups
Nikto reports the following via the "ssl-dh-params" NSE script:
Check results:
| WEAK DH GROUP 1
| Cipher Suite: TLS_DHE_RSA_WITH_AES_256_GCM_SHA384
| Modulus Type: Safe ...
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Secure key exchange in web between pages
In the authentification page the user writes his password, and if it is correct, he is redirected to the main page.
In the main page there is a messenger also, which uses end-to-end encryption (...
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Secure messenger in web page
I need to make the Messenger in the web page secure. For that I use encryption with AES.
So, when one person writes another, the message is encrypted, sent to the server, saved in the DB, and then ...
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Key exchange with an untrusted party
Assume there are two parties - an agent and a server. The agent must register itself to the server by sending its identifier over the internet.
And let's say we use public cryptography to encrypt ...
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End-To-End encrypted calls over GSM transport (not data / VoIP)
As the issue stands, it should be (or could be) possible, to encrypt voice, that's being passed through GSM voice call in such way, so that it's end-to-end encrypted.
Ideally in form similar to what ...
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