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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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233 views

Is there a known vetted alternative to this key-exchange protocol?

I have three participants: A client A in possession of the public key Kpub A login server S in possession of the private key Kpriv Game servers B (B1, B2 etc) S and all B may share a finite number of ...
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1answer
79 views

Is There a Whitepaper or Explanation of ECDSA somewhere? [closed]

Let's say I wanted to write an implementation of ECDSA from scratch to better understand it. I can't find a raw, non-abstract explanation anywhere. I tried tracking down the sources on the wiki ...
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1answer
65 views

Is it safe to learn new keyfob by its normal open code (rolling-code)?

Part of a wireless door opener, the receiver Doorhan DHRE-2 works, according to description, with the rolling code. It looks like the receiver can register a new keyfob by listening to its normal ...
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1answer
30 views

Adding new keys to a server that doesn't accept password login

I have a Raspberry Pi with some projects on it. It is open to the internet at port 22. I have fail2ban installed and I have disabled password log in. Right now I have successfully set up a key pair ...
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3answers
565 views

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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2answers
1k views

Why should you generate SSH keys on client devices?

Most tutorials for setting up SSH recommend generating the keypair on a client machine. Why exactly is this? Assuming your communication lines are not compromised, and you delete the private key from ...
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2answers
179 views

Key-exchange over the network with more than two peers

Me and my team is developing a multiplayer videogame with a Client/Server-Topology. This secures the match from clients who have the intention to cheat because of server authority but still allows the ...
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1answer
737 views

SSH session_id in RFC 4253 (key exchange)

in RFC 4253 "SSH Transport Layer Protocol", section 7.2 specifies how session encryption and integrity keys (and IVs) are derived from the shared secret (K) and the exchange hash value (H). It uses, a ...
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2answers
198 views

ssh/scp from server to server — set permissions (no root)

I have access as a regular user (not as root) to two servers. Server A is accessible via ssh with a username and password, Server B can only be accessed using a keycard and pin. I need to set up a ...
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1answer
761 views

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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1answer
93 views

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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1answer
87 views

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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1answer
206 views

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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2answers
164 views

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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1answer
81 views

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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1answer
55 views

First setup security protocols (key transfer) in not-secure environment

This question might very well be more a confirmation than anything else, but I'm breaking my head over a problem I try to solve. I hope someone can either confirm my thoughts or tell me something I'm ...
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1answer
139 views

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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1answer
413 views

GPG: Is 'pubring.kbx' safe to share?

This public keyring pubring.kbx (as I merely guess from the name) must be safe to share publicly or is it not? Does it contain any sensitive information with respect to private keys? I want to back ...
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1answer
36 views

What is this scheme called and how should it work exactly?

So I was thinking about client-server communication and how to keep this private, especially from man-in-the-middle attacks. I came up with a scheme that I'm sure exists already, but I could not find ...
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1answer
91 views

Available alternatives for exchanging public keys for emailing

What alternatives exist for exchanging public keys with another person for sending email, except the obvious way of manually pasting the public key into an email saying, "Here is my public key"? Do ...
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1answer
611 views

TLS key exchange algorithm = Certificate signing algorithm?

My bachelor thesis is about TLS and I have a basic question about the algorithms used there. If I use e.g. a sha1WithRSAEncryption signing algorithm (RFC3279) for my certificate, that means that the ...
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1answer
186 views

CECPQ1 key exchange functionality

CECPQ1 (combined elliptic Curve and Post-Quantum Cryptography Key Exchange) is a new key exhange developed by google, which combine X25519 with NewHope (elliptic Curve KE + Post-quantum KE). Google ...
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1answer
35 views

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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2answers
786 views

PMK is what prevent to generate the PTK and decrypt the traffic?

I'm trying to establish a connection to an encrypted SSID, using scapy. My intent was basically to sniff the frames of the handshake from the victim, acting as a proxy (MITM), and redirect the frames ...
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1answer
347 views

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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2answers
82 views

Replace certificates simultaneously on remote servers?

A third party server sends us signed messages that we verify. When its certificate is about to expire, the third party generates a new key pair and sends us the new certificate. At some point, the ...
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1answer
2k views

Wireshark SSL stripping

well this question could be asked in Wireshark forums or Stackoverflow forums but, I think the question invloves development and security factors as well so i find the Information Security forum is ...
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1answer
79 views

Is there a secure method of distributing keys to network-booted diskless nodes?

I have a bit of an 'initial trust' issue. We are using CoreOS to run Kubernetes, and secure both the etcd API and the Kubernetes API servers using client certificates. We are using iPXE to boot ...
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2answers
518 views

Best encryption mechanism for message storage/exchange in client/server application

So I am building a client/server system that is similar to email idea where clients exchange messages through the server with the following main requirements (note that the clients are pre-registered ...
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1answer
76 views

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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1answer
207 views

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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2answers
937 views

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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2answers
2k views

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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1answer
1k views

Can manual hash verification defend against a DH MITM attack?

I understand how DH key exchange is vulnerable to a MITM attack. When Alice sends Bob g, p and her public key, if she also sent a value H that was a hashing of the values g,p, and public key all ...
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0answers
41 views

Is there a key exchange protocol that requires only one message? [migrated]

Say I want to exchange a secret with someone, but I only get to send one message to the other person, and then we encrypt with that secret. Diffie-Hellman and ECDH require multiple messages to be sent ...
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1answer
50 views

Authenticate Static Public Keys

How can a static ECC public key be authenticated when being shared between the client (who has just created the static ECC public key) and the CA (Certification Authority) - who will sign and send the ...
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0answers
85 views

Is this Key Exchange secure?

There is a key exchange process which I am having a look at. I am aware of key exchange algorithms such as Diffie-Hellman and the like, however as there is a method to provide an initial key out-of-...
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0answers
80 views

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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0answers
215 views

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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0answers
47 views

Why would be an attacker interested in whether a cryptographic key exchange protocol succeeded or not? [closed]

Why would an attacker want to know if a key exchange between two parties succeeded or failed? What are some motivations for wanting to know this?
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0answers
82 views

What is a KEA certificate and how it is used?

I'm currently studying IKE and IPsec in the context of VPN applications and I know that a X.509 certificate is used to provide server's public key to the client (and vice-versa in case of mutual ...
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0answers
35 views

Are all categories of assymetric key generation applicable to all categories of assymetric key exchange? [closed]

Context assumption and aim: Using asymmetric crypto to help Alice and Bob (members belonging to the same basketball club. The club has its own servers) to communicate together without the ...
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0answers
253 views

AES256 key exchange

I'm trying to get a secure way of exchanging keys between my client application and the server. The goal is to encrypt all XML messages with AES256. These XML's will be transferred to the server ...
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0answers
81 views

key hierarchy management and master key

Now, I have this equation, {{K_ab}K_bs}K_as. K_ab is encrypted by K_bs then whole packet is encrypted by K_as I think the key structure is K_as is the master key, K_bs is under K_as and K_ab is the ...
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0answers
160 views

Key Hierarchy and key Encryption

If i have two 56-bit DES keys, and I use these two key to encrypt a 256-bit AES key. Like this: K_AT encrypts K_BT and K_BT encrypts K What is the effective security of key K? Is it 2 X 56 Bits?
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107 views

Migration problem between different machines using TrouSerS TPM library

My question coincides with the question posted by Maximiliano Ezequiel. Below is a question. I could make migration process work in one single machine. I can: Export SRK public key. ...
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0answers
211 views

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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0answers
200 views

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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0answers
464 views

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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3answers
718 views

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 ...