Questions tagged [diffie-hellman]

Diffie-Hellman is a method for establishing a shared secret that can be used as a cryptographic key.

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Diffie-Hellman in Https: How are prime numbers picked? [migrated]

I am trying to understand https, as I understand https uses the Diffie–Hellman method for keys exchange and then AES for encryption. But Diffie–Hellman needs two prime numbers, where do these come ...
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In which sense is Perfect Forward Secrecy perfect? [duplicate]

Wikipedia states that Perfect Forward Secrecy "is a feature of specific key agreement protocols that gives assurances that session keys will not be compromised even if the private key of the server is ...
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When does chrome generate the prime number for TLS communication?

In a TLS handshake using DH to negotiate a session key, a prime number on both sides must exist. Calculating a prime number large enough to be secure takes a litte computational time. When does ...
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how can i change DH key , enable SMTP and FTPS on plesk [migrated]

one of the clients has run a security scan for the site web that I am working on, so he found some issues that I need to fix these issues are : FTP Unencrypted Cleartext Login // solution: Enable FTPS ...
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Using Diffie-Hellman exchange on low power IoT devices

I have almost 0 knowledge of IoT, their protocols and usual device constraints. I had a discussion today with someone that has a fair amount of IoT experience and we were discussing some security ...
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DH cipher suites and DH OpenSSL Generated

I need a openssl generated diffie-hellman params for work with ECDHE or DHE cipher suites on TLSv1.2 nginx server?
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Why is the Diffie-Hellmann exchange not enough to authenticate the communication partners in IKE_SA_INIT?

The IKE_SA_INIT does create a key seed SKEYSEED from the Diffie-Hellman values and nonces. Since the exchange does sharing the secret between the communication partners, I do not understand why it is ...
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58 views

Command to check a website is vulnerable to Logjam

I am referring this post https://www.openssl.org/blog/blog/2015/05/20/logjam-freak-upcoming-changes/ and trying to see a website is vulnerable to Logjam or not. I try with www.google.com:443 but I am ...
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Is there any way to send data securely from multiple As to B in the presence of eavesdropper, without losing anonymity like in a public key exchange?

Suppose I have n subordinates at work. Any subordinate should be able to submit his or her report anonymously to me via digital means. Also suppose that I have no means of broadcasting any form of ...
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115 views

Is there a benefit to Diffie-Hellman parameter rotation?

When setting up a web server with TLS support I've generated my dhparams with openssl dhparam -C 2048 some.pem. I understand that the output in some.pem are the parameters by which DH key exchange ...
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ECDSA ECDH Man In The Middle Attack

We have a long-term key used for signing/verifying the ephemeral keys. The problem is we have to first share the long term public key with the other party. Is it possible to avoid a man in the middle ...
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Is client-side password hashing still useful when using TLS? Is TLS crackable? What about PFS? [duplicate]

Is client-side password hashing still necessary / useful when using TLS? What about TLS protocols with PFS (perfect forward secrecy) like Diffie-Hellman? Let’s say that I’m running a web application ...
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Why do predefined FFDHE parameters containt '///////////'?

Recently, Mozilla published a new and excellent version of its SSL Configuration Generator. One of the changes compared to previous versions was to use predefined FFDHE (Finite Field Diffie-Hellman ...
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Diffie–Hellman key exchange questions [closed]

at the moment I am working on a chat application, where more than two clients can communicate at the same time. I just got started with the encryption so please be bear with me. My goal is to ...
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how are symmetric keys generated in TLS [duplicate]

My confusion stems from reading that TLS handshake uses some kind of Diffie Hellmann, when I was certain that the symmetric key was generated by a digest of earlier packets encrypted with clients ...
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How to decrypt Diffie-Hellman encryption in WebRTC?

I have installed a WebRTC server application, which is designed for Contact Center solutions: communicates with internal PCs in pure RTP (agents), and with external PCs (customers) using encrypted ...
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TLS-Handshake, Server Key Exchange, Diffie-Hellman: Where does key length come from?

Where does the key length come from? In this example it is 2048 bits long: Secure Sockets Layer TLSv1.2 Record Layer: Handshake Protocol: Server Key Exchange Content Type: Handshake (22)...
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Self-signed certificates and ephemeral Diffie–Hellman key exchange protocol

If we use a self-signed certificate, is ephemeral Diffie–Hellman key exchange protocol vulnerable to a man in the middle attack?
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Diffie-Hellman with non-prime modulus

When using the Diffie-Hellman key-exchange, it is said to be important to use a safe prime. However, if a non-prime modulus with sufficient bit-length is generated, is there an attack that can be used ...
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Public key encryption confusion

I'm learning Linux, and currently SSH. But there are details that I don't really understand. I've seen and understood how Diffie-Hellman key exchanges work from a mathematical point of view, but what ...
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Is the server's private key needed in the Diffie Hellman key exchange? [duplicate]

I understand the Diffie Hellman key exchange. What I don't understand is the role the server's private key plays in it. I'm not talking about the servers generated secret. I understand that purpose ...
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How to find the DH prime value (if 1024 or 2048) from Internet?

I have to ensure that the server when communicating on the Internet needs to have DH prime value of 2048 bits or greater. I can find out the cipher suites that are used but cannot derive the DH ...
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OpenSSL - 2040 bit temporary key size, 2048 bit private key

Recently, I had an OpenVAS scan report that a TLS connection to Postfix used a temporary key size of 2040 bits, instead of the 2048 bits that I have set for my key size, and I have perfect forward ...
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Perfect forward secrecy in Instant Messaging with multiple devices

I have read multiple sites online about PFS and DH but I still have a few questions. I understand that in order to have PFS you must use different keys to encrypt messages. So your IM client could be ...
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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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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 the hope ...
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Usage of SSL_CTX_use_certificate

While building a context through openssl, if I do not provide a certificate by using the function SSL_CTX_use_certificate, would all the connections from that context default to anonymous diffie-...
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Can a DH param .pem file force the usage of only a single type of diffie-hellman exchange

Is it possible to create a diffie-hellman param .pem file to force the openssl ctx to use only a certain type of dh exchange. For example, I know that it can be used to set the length of the dh key, ...
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Understand DHE security in TLS

SSL Labs says that a website I control supports weak ciphersuites because they have DH 1024 bit, e.g. this one: TLS_DHE_RSA_WITH_AES_256_GCM_SHA384 (0x9f). I tried to connect to the website from my ...
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325 views

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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384 views

How to optimize the diffie hellman key exchange algorithm

I am making a chat feature in my app where I want to encrypt it E2EE, but the problem is when I start to calculate the public key (public key = g^private % n) it takes a decade to get it done. I need ...
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284 views

BouncyCastle and Microsoft Cng ECDH secret key mismatch

I'm trying to refactor some client-side code from BouncyCastle to Microsoft Cng. I've figured out how to convert key format(ECC key blobs) between them, but I couldn't calculate the same secret. ...
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Why Diffie-Hellman instead of just share the secret [duplicate]

I read that D-H is used to make a shared secret between parties that then they use to encrypt the messages. This is used in TLS, for example, after the server has authenticated itself with a ...
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179 views

Signal Protocol: How is identity exchanged if a key exchange hasn't happened yet?

On Signal's blog they mention that keys for accessing your profile are exchanged normally with your contacts using the Signal Protocol just like messages are (implying they are already contacts and ...
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WPA technical doubts (3)

This is the third post about the set of doubts that came up when I tried to understand WPA3. I am new to this world of cyber-security so every bit of help is welcome! Someone told me that in WPA2 ...
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Different Diffie–Hellman key per site?

I recently put each of my sites through the ssl labs analyzer and now have them all running with an A+ getting perfect scores with every metric except Key Exchange at 90. As part of this I have ...
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Advantage Of ECDH-RSA over RSA Ciphersuites In TLS

If ECDH-RSA is used for key exchange, this is what happens: The server has its public ECDH parameter embedded within its certificate. The client generates its public ECDH parameter, extracts the ...
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Diffie-Hellman protocol CA, confusing

In the Diffie-Hellman protocol, if the participants have their own private key and a generated public key. How can we determine whether or not they have a trusted CA for authentication or just the ...
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228 views

understanding MITM attack [duplicate]

hi Everyone please correct me if im wrong for my understanding for the man in the middle attack used in a variant of diffie hellman key exchange . am i right to say that a protocol is susceptible to ...
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Why use a separate key exchange method like DH during the TLS handshake [duplicate]

Ok first off I'm very familiar with the TLS handshake, the purpose of PKI and key exchange methods. My question is why use a complicated key exchange method like Diffie Hellman when the client could ...
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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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diffie-hellman size 2048 and key with size 1024

I want to increase the security of my Tomcat and to configure diffie-hellman module size 2048. I want to add to my CATALINA_OPTS -Djdk.tls.ephemeralDHKeySize=2048 What happens if I have configured it ...
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Diffie-Hellman in Android File Transfer application [closed]

I'm working on the famous android app to transfer files using WiFi-Direct technology: https://github.com/Miserlou/Android-SDK-Samples/tree/master/WiFiDirectDemo I want to implement a key exchange ...
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How can disabling Diffie-Hellman cipher for packet inspection be secure?

I have noticed that a number of network packet monitoring tools on the market today seem to have roughly the same recommended configuration parameters as described below: Disable Diffie Hellman in ...
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108 views

Exchange of public keys with DHE-RSA

The paper "Imperfect Forward Secrecy: How Diffie-Hellman Fails in Practice" by Adrian et al claims that the NSA might be able to eavesdrop on a large percentage of TLS connections, because they ...
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How to perform a MITM attack on SSH exploiting the Diffie Hellman key exchange

I have an open-ended project for a class and I picked to make a tool/use existing tools and applications to exploit the Diffie-Hellman key exchange to be able to inject, modify and delete messages ...
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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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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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Does LoraWan protocol's Over The Air Activation run Diffie Hellman?

I am looking at the LoraWan protocol specification and I want to capture the over the air activation of a device. So far I have seen the: https://zakelijkforum.kpn.com/lora-forum-16/over-the-air-...
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477 views

OpenSSL Base64 output has wrong length

I try to generate an ECDH P-256 key pair as required for web push messages. openssl ecparam -name prime256v1 -genkey -noout -out priv_key.pem ... generates the keys. openssl ec -noout -text -in ...

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