Questions tagged [diffie-hellman]
The Diffie–Hellman key agreement is an anonymous, non-authenticated key-agreement protocol.
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"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 ...
user15119
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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 ...
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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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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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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 ...
user10211
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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 ...
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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 ...
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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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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 ...
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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 ./...
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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);
...
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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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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 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 ...
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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 ...
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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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Is Diffie–Hellman key exchange protocol vulnerable to man in the middle attack?
Diffie–Hellman key exchange protocol vulnerable to man in the middle attack? If yes, then what type of MITM is that? I believe that is a replay attack or a relay attack, not sure though.
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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 ...
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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 ...
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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 ...
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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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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 ...
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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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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 ...
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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 ...
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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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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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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 ...
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Setup Wireshark to decrypt TLS_DHE
I have a passively sniffed traffic dump of client/server were packets are encrypted with cipher suite
Cipher Suite: TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 (0x009e)
With a Logjam attack I managed to ...
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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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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, ...
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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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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 ...
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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 ...
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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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How does TLS work (RSA, Diffie-Hellman, PFS)?
I know "How TLS works" has been discussed numerous times here and crypto, but I am still somewhat confused and would like to summarize what I know so far 1 in this giant blob of text with ...
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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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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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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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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 ...
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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 ...
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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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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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How to verify Diffie Hellman uses a "Safe" prime
I'm the developer for a web application that was recently pen tested. One of the vulnerabilities reported from the pen test is that our server uses an unsafe Diffie-Hellman prime in our key exchange. ...
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ECDH and static key encryption
It's been a while and I'm still trying to figure out if my understanding of ECC crypto is correct.
Basically from what I understood a purely asymmetric encryption is never used. Usually the ...
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Is server public key and Diffie Hellman public are the same?
I am trying to understand the working of TLS. I understand that there are various way to generate the master secret used to encrypting the data. Such as DH (Ephemeral DHE) and RSA. I understand that, ...
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RSA key exchange
I want to create a message exchange program. These messages are encrypted with the AES key, and this key is encrypted using the RSA algorithm. When I send a message from User 1 to User 2, I need to ...
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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 ...
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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 ...
