Questions tagged [key-exchange]
For questions relating to protocols for distributing public keys, and / or establishing session keys with another party. Examples of key exchange protocols include Diffie-Hellman and IKE.
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Security without TLS certificates
after getting an answer to Security over multi-streaming such as SCTP i have found that i do not have the capacity to give a public key or certificate to the other end securely (to be sure MitM cannot ...
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TLS 1.2 Handshake: How is the ECDHE public key signed by server?
I am dealing with a situation where a cipher option, such as ECDHE-ECDSA-AES128-SHA, is chosen for establishing a TLS connection. In this case, a server, when sending the ServerKeyExchange message to ...
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Where do I get prime numbers for Diffie-Hellman? Can I use them twice?
I realise it's very hard to generate suitable prime numbers and generators for the Diffie-Hellman key exchange.
What is the best way to generate them? And if I have one, can I use it twice? ...
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What steps can you take to make offline cracking of SRP harder?
In the aftermath of the Blizzard hack, what steps can I take to make offline cracking of SRP more difficult?
My question assumes that your database is already gone and that you implemented SRP more ...
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Prevent padding oracle attack on key exchange process
I found in my searches that the padding oracle attack can be used against the RSA with PKCS1PAdding or OAEP padding, and I used this algorithm for a symmetric key exchange.
How can I prevent a padding ...
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Can symmetric key cryptography provide identification?
I understand that PKI uses digital certificates to link a public key to an entity, but is there anything similar for symmetric cryptography.
If, theoretically, PKI didn't exist, how do you know you ...
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Are open wireless networks unencrypted?
When you connect to an open wireless network (that is, a wireless network without any symmetric password set) is there any sort of secure key exchange going on, or is data sent back and forth ...
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how IKE (Internet Key Exchange) protocol reacts to the replay attack?
I mean how IKE in any mode (quick,aggressive, main) responds to an attacker that tries to replay one or more messages?
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Authenticating client without hardcoding key?
A basic question, but I'm not a master and this is puzzling me-
How is it possible to authenticate a client from the server's perspective?
i.e. imagine you're the server, and you want to give the ...
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Best practices for encryption from web<-> specific client
If we want to allow sensitive data between a web server and specific client only, is there anything more that can be done besides the following?
Note that this is potentially a duplicate of ...
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What is the difference between DHE and ECDH?
I learned that perfect forward secrecy is implemented through DHE and ECDH but what is the difference between these 2 key exchanges?
Also can someone explain how perfect forward secrecy works? I've ...
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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 End to End security possible without physical contact?
I noticed that a lot of messaging start to provide "End2End" security, but I wonder how this can be possible without a key exchange between the the two clients.
To my understanding to provide real ...
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User Key pairs and Man-in-the-middle issues
I'm trying to wrap my head around how to exchange user's keys with a server.
Maybe during sign-up a JS applet generates a key-pair for the user. These keys would be used for signing subsequent ...
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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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Https certificate change effects on established secure channels
I've a question regarding https certificate changes.
Does anyone know any side-effects to changing the certificate, one signed with RSASHA1 to one signed with RSASHA256 for ex, while users already ...
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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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Distribution of key by server
I have read that in asymmetric cryptography, a system admin can generate key pairs on the server. After that, the users will be given the generated key pairs and this is an efficient way of doing this ...
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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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How to incorporate the man-in-the-middle
I am designing a web-based back-end for an online service. The service could support web based portals and mobile apps as front end.
But I am stuck on how to support third-party, i.e untrusted, web ...
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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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Why should the dh keylength match rsa length in tls?
A few sources state that the DH keylength (bits of the prime) should match the keylength of rsa for TLS. For example SSL_set_tmp_dh(3) from openssl has example code on how to match the dh parameters ...
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How can I generate some public and private keys on both sides with low overhead?
We have an Authority Center (CA) generating some public and private keys for each client (more than one pair for each client). One method for sending keys to client is sharing a secret key between CA ...
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What is 0xXXXXXXXX.asc.sig and how can I generate this?
When I am exchanging PGP keys with someone, I receive the regular 0xXXXXXXXX.asc file and regularly receive a file called 0xXXXXXXXX.asc.sig.
What is this file?
How can I generate one and send it ...
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Why do we encrypt ephemeral Public key in Encrypted Key Exchange
Encrypted Key Exchange can resist off-line dictionary attack
Protocol :
A ---> B : Ep (PK)
B ---> A : Ep(Epk(K))
K is Session Key generated by B
PK is an ephemeral public key ...
AviD♦
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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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How could SSL certificate affect the symmetric key length?
This article in GoDaddy support knowledge base says
All of our SSL certificates support high-grade 256-bit encryption
How would they not support it?
The SSL certificate contains keys for ...
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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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rolling code & keyless entry system [closed]
The security industry typically uses rolling code algorithms to authenticate sender & receivers in keyless entry systems, which is called RKE (ex: KeeLoq).
In key-less smart key car system,
The ...
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Key Exchange using RSA
I'm trying to do key exchange using the following scheme.
Server generates an RSA-2048 key pair and sends the public part to the client
Client generates an RSA-592 key pair (I have to use RSA-592 ...
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Verifying the owner of a signing key
I'm using elliptic curve cryptography (curve25519 and ed25519) for key exchange and signing. The signing and key exchange keypairs are independent. I need two users to be able to verify each other's ...
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GSM A5/1 encryption: Key management
I'm currently studying the A5/1 algorithm used for GSM encryption. I understood how thanks to the symmetric private Key and a public counter frame one can encrypt the communication between A and B.
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Preventing a Computational DoS Attack in Public Key Cryptosystems
I'm designing a server which accepts anonymous messages using ECIES: as in, anonymous users send the server an ephemeral EC public key, and the server uses ECDH to derive a shared secret, and some KDF ...
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Website: Pre-Shared-Key Authentication
We have this web-application with high valuable (business) data.
All communication is encrypted through TLS/SSL. While I consider this a really safe protocol, it can still be compromised if someone ...
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Are there any systems out there that use a one-time pad?
I'm still new to information security, but I have read a bit about the one-time pad. The point that sticks out to me the most is that it is supposedly unbreakable. Has this method of encryption ever ...
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MITM protection, key distribution
I want to make sure each of my apps users only get their own data, and that nobody tampers with it or sniffs it in a MITM fashion. Encryption of everything should be the solution, right? But how do I ...
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What are the alternatives to ECDSA for an authentication protocol?
In an authentication protocol, S has a public/private key pair known to C, and S and C have established a secure channel (for example, using DH or ECDH, or any other key exchange protocol). C wishes ...
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How to treat/hash ECDH shared secret to use as keys for AES?
I'm doing some studies/development for a security system that would use ECDH with ephemeral keys.
In my code I'm currently using a 256-bit EC, so when the two parts compute the shared secret, I get a ...
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Transferring of keys from key servers to recipients
When I download PGP keys from keyservers like so:
gpg --search-keys steve@openssl.org
How are the public keys transferred down to my machine? Is there a possibility of a MITM attack to serve me the ...
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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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In IKE protocol; what is the PRF? [duplicate]
In IKE protocol; what is the PRF ?
What is "the generation of a key based on modeled random oracle hash functions"?
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SSH using pre-existing session (symmetric) keys
Is there at present a way to open a SSH connection using pre-existing symmetric session keys?
In other words, if I create a list of symmetric keys can I send that list to the recipient on a CD or USB ...
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Is it safe to use a ECDSA public key as a password seed for GCM/AES?
Two peers already exchanged their ECDSA (curve secp256k1) public keys using a secure channel.
They want to establish an authenticated encrypted channel between them. They will use CCM mode and with ...
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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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SSL/TLS : Authentication mechanism
I have these doubts regarding authentication in SSL/TLS :
Will there be an authentication involved for all SSL connections ? For eg. when I browse the internet, using the most up-to-date browser, can ...
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Is it a good practice to include a download URL of my GPG public key in my email signature?
I was wondering if I can put a download URL for my recipients to get my GPG public key easily in my email signature.
Is this a good practice? If not, what's a good alternative?
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Key-Exchange Algorithms VS Local Key Generation?
I was wondering the difference in term of Security, Computational cost and Network overhead between the use of :
A Key-Exchange Algorithm (e.g. Diffie–Hellman) to set up a symmetric key.
The ...
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What are the MitM implications of a stolen client-side private key?
Many VoIP handsets support client-side SSL authentication for auto-provisioning. Unfortunately, some devices must be programmed with their client-side keys. (Keys generated on low-entropy devices are ...
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Can we build a key exchange protocol without certificates?
Assume that the server and the client both has some secret key K. Is it possible to have a key exchange protocol with authentication between them such that MITM attack cannot hold and if the key is ...
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Key Exchange algorithm to be used for REST framework
I was required to create key exchange module for custom Rest framework which supports document level security in REST requests.
Framework has its own security module which allows to encrypt parameter ...
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