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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124 views

Are there any actual disadvantages to a key signing party?

At the beginning of the year staff are required to attend a key signing party - after changing their keys. They are required to bring said keys on USB sticks, at the end of the party each member of ...
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6k views

What is the the meaning of “out-of-band” in “out-of-band key exchange”?

When we say "out-of-band exchange of symmetric keys", what does "out-of-band" mean?
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4answers
452 views

Can an ssh key login to a secure remote server be compromised when on a network run by a bad actor

I am in a cafe. Supposing I ssh into a secure remote server using a key pair, and supposing the cafe wifi is run by a bad actor who is intercepting traffic, can my login be compromised? I am not ...
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129 views

Why is brute forcing DH private key harder than calculating public key?

Assuming shared parameters: prime p base g Alice's private key is a and her public key is A, which is g ^ a mod p Calcuating A requires g * g * g... a times. Modulus is applied whenever necessary. ...
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139 views

Combinations of key exchange and signature algorithm in TLS

Let's say that one does not trust ECC a lot, and values confidentiality over authenticity (perhaps simply for the reason that MitM is more difficult than passive eavesdropping and decryption later on)....
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1answer
203 views

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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2answers
2k views

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, ...
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1answer
3k views

ECC Brainpool Standard Curves and Curve Generation with Bouncy Castle which seed to use?

I want to implement a ECC Key Agreement with a Brainpool curve brainpoolP512r1 or brainpoolP512t1. I'm not clear about whichseed value to use (and how). In this document http://www.ecc-brainpool.org/...
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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
46 views

How do SRP (and PAKE generally) protect against verifier leak

I have been reading into PAKE protocols, specifically starting with SRP RFC2945 The gist of the requirement on the server is that the server saves triplet (username, verifier (v), salt (s)) in the ...
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1answer
88 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
91 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
31 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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611 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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2k 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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213 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
967 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
253 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
771 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
95 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
88 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
213 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
169 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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82 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
3k views

Why Qualys SSL Server Test is giving me 80 and not 100 in Key Exchange?

My openssl ciphers -v 'CIPHER' output is the following: ECDHE-ECDSA-AES256-GCM-SHA384 TLSv1.2 Kx=ECDH Au=ECDSA Enc=AESGCM(256) Mac=AEAD ECDHE-RSA-AES256-GCM-SHA384 TLSv1.2 Kx=ECDH Au=RSA Enc=...
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1answer
62 views

TLS- Key exchange for session keys. Why?

I have a question about the Key Exchange Algorithm used in TLS process. I have read that the Key Exchange algorithm is used by client and server to exchange session keys. Do the client and server ...
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1answer
99 views

Web developer needs customer's private key

As a non security expert, I'm looking for advice from those who are. I work with company X who have hired company Y to develop their website. Company Y needs to integrate server-side online payment ...
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1answer
85 views

TPM Attestation and key exchange

I have the following problem: I have two platforms, one of them has a TPM. I need to transfer data between these two platforms, so I first determine an attestation, in order to confirm that the ...
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1answer
110 views

ECDH_SHA2_NISTP256 (KEX) Algorithm in SSH - Vulnerabilities?

My organization within my company uses this KEX Algorithm in our SSH Implementation. Another organization within my company won't connect to our servers as long as this algorithm is implemented as ...
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1answer
61 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
280 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
761 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
39 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
114 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
719 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
197 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
38 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
876 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
411 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
83 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
3k 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
89 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
577 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
215 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
1k 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
2k 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
87 views

Is it possible to decrypt TLS traffic through OpenSSL?

I have a web server that uses the ECDHE-RSA-AES256-GCM-SHA384 cipher suite. I noticed that when given the "(Pre)-master-secret log" file (generated by the browser), Wireshark is able to ...
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75 views

Examples of SSH key exchange algorithms requiring encryption-capable host keys

In the SSH spec, Section 7.1, key exchange algorithms are distinguished based on whether they require an "encryption-capable" or a "signature-capable" host key algorithm. If I ...