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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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14 views

What are some accredited security product testing and validation firms? [on hold]

I'm looking for someone like NSSLabs, Synack, Tevora, but obviously not these companies.
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1answer
25 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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1answer
112 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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0answers
32 views

What are the practical applications of the interlock protocol?

I recently dusted off my old copy of Applied Cryptography. Chapter one mentions the interlock protocol. From the wiki: Alice encrypts her message with Bob's key, then sends half her encrypted ...
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0answers
44 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 ...
2
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2answers
72 views

Can be used ECDH with static public key and parameters?

I have protocol required for privacy. Thus, I want to use hybrid cryptography. Base on my knowledge, ECDH is fast and secure. My system consists of 3 main components a trusted-server, client, and ...
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1answer
64 views

Key distribution from a central server [closed]

I have a system composed by different computers that must communicate in a real-time context. All the communications must be encrypted and this system is not connected to Internet, it's just a bunch ...
2
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2answers
108 views

TLS protocol, session key for secure connection

In Wikipedia, as part of handshaking between a client and a server, the server send a public encryption key as part of the digital certificate. Then the client uses Diffie–Hellman key exchange to ...
2
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1answer
91 views

Secure Key Storage

We have a security solution that is deployed on premise to companies with big technical infrastructures. We do real time vulnerability/configuration assessment of all critical assets in the network. ...
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1answer
33 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
80 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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3answers
108 views

Sending Encryption/Decryption keys over HTTPS

I am a newbie to the cryptographic world so bear with me. Thinking of a strategy (for securing P2P data) in which server is generating a key which should be used for AES encryption between clients ...
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0answers
37 views

Any facts that users’ secret key is stolen on some group?

I am wondering whether some severe accidents due to sharing a secret key exist in real world. A group of users or a company typically share a secret key to decrypt some shared encrypted data possibly ...
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4answers
2k views

Can we trust onetimesecret?

Alice: I need the file Bob: Sure, and I want to encrypt it first. Please put the strong PGP symmetric key with the copy&paste method to https://onetimesecret.com/ and send me the link. Alice. ...
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0answers
131 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
262 views

Why RSA is used in TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 ciphersuite [duplicate]

I try to understand where the signature is used in TLS 1.2. The ciphersuite of google.com is TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256. However, if I look at the certificate, I can find an ECDSA key ...
2
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0answers
207 views

computing the exchange hash for ecdsa-sha2-nistp256

I am writing code for an SSH server and can not get past the Elliptic Curve Diffie-Hellman Key Exchange Reply part of the connection. The client also closes the connection and says "Host Key does not ...
2
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1answer
263 views

Tor: Is a diffie-helman key exchange being done over reciepient of traffic?

As I was looking over Tor specifications and I noticed that when a circuit is generated then on each circuit's node a Diffie-Hellman key exchange is being done over an encrypted path on each Node as ...
2
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3answers
108 views

How secure is using Saving Session Feature on WinSCP?

I ssh to my AWS instances via WinSCP and it has public-private key authentication, password authentication is disabled. All the sessions are saved on WinSCP, so I click on the IP of the machine and I ...
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1answer
504 views

Why does TLS 1.3 deprecate custom DHE groups?

According to the second draft of the TLS 1.3 specification, custom DH groups have been deprecated. As we all know, hardcoded DH groups are vulnerable to a precomputation attack that allows retroactive ...
2
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0answers
85 views

Is it safe to retrieve GnuPG public/secret key with fs in Node.js?

So there is a Node.js package openpgp which is available for signing documents with GPG, but it requires public/secret key. We all know putting key right into the file is dangerous and not recommend ...
6
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1answer
313 views

Forward secrecy with GnuPG

I'd like to know how to implement forward secrecy using GnuPG, and I presume I need some kind of authenticated key exchange. Assuming that I have the following working already: Alice and Bob have ...
2
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2answers
149 views

SSH key based login is not vulenerable to MiTM attack. Is it true?

I read somewhere that when using key based login instead of a password based login, it is not possible for a Man-in-the-Middle attack to happen. This question is not about what is being more secure: ...
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0answers
46 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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1answer
348 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
60 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
297 views

Limit on modulus lines in OpenSSH /etc/ssh/moduli file?

I understand that OpenSSH server looks in /etc/ssh/moduli and picks a modulus at random for each Diffie-Hellman group exchange. What I am wondering is whether there is a practical limit on how many ...
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0answers
137 views

Key Exchange Problem

Could anybody give me a hint how to start solving this problem? Consider the following scenario, Alice and Bob want to compute a shared key, but their devices are weak, so they must rely on a ...
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1answer
383 views

Possible MITM attacks on ECDH-RSA or ECDHE-RSA prevents

As I understood a simplified ECDH-RSA key exchange protocol works like below Alice request Bob for its ECDH public key Bob generates ECDH parameters and sign them with a CA provided RSA certificate. ...
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1answer
157 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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2answers
89 views

Under what circumstances is there any real security benefit in verifying public keys in signal or WhatsApp? [closed]

Encryption is good, sure. But disclosures have revealed that both iOS and Android are so owned by intelligence services that endpoint security on all supported platforms is a joke, anyway. What ...
3
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1answer
660 views

What's the purpose of anonymous Diffie-Hellman key exchange + verification?

I attended a lecture where a procedure for solving the problem of passive attackers being able to gain knowledge about the identities of communication partners using an authenticated Diffie-Hellman ...
2
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1answer
484 views

Can you identify whether a string is a RSA public key?

I am generating RSA keys with the openssl library. I have heard that it is possible to recognise the method used to encrypt a string with AES or DES but is it possible to identify whether a string is ...
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1answer
380 views

Can an OpenPGP primary key revoke a subkey of a subkey?

I would like to have the following setup: a main Key, saved in a hardware wallet or paper wallet. Let's call this level 1. The idea is to never have to use this key again, as a sort of last resort. ...
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1answer
300 views

Is IKE aggressive mode really less secure than main mode?

This guy argues it is not: https://www.youtube.com/watch?v=DuowFgNKAIg I really confused about this. According to him, the only purpose of main mode is to make the peers anonymous, but in order to ...
4
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1answer
139 views

GPG key handling with Server

I'm using a VPS as a development machine and need gpg a) for signing git commits or e-mails (using mutt on the server) and b) for decrypting f.e. encrypted dotfiles and other files. But I don't feel ...
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0answers
64 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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1answer
33 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
1k views

SSL / TLS Ciphersuites [closed]

There's a large list of ciphersuites inside SSL / TLS. It seems like that these ciphersuites can be categorized in terms of their underlying mechanism with following categories: RSA Key Exchange (e.g....
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0answers
27 views

How to find whether HTTPS application/ website use DHE for key exchange? [duplicate]

I am not getting the result I am expecting from the above link. while executing following command openssl s_client -host www.gmail.com -port 80 output : Cipher : 0000 while executing following ...
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0answers
34 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 ...
3
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2answers
178 views

ssl - Can the attacker generate his own symmetric key if ClientHello and ServerHello are intercepted?

After reading this awesome explanation of how SSL works, I now have a confusion. The answer states that the first messages of SSL are ClientHello and ServerHello(in response to ClientHello). Both of ...
4
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2answers
2k views

Role of the chosen ciphersuite in an SSL/TLS connection

When it comes to a secure TLS configuration (e.g. for HTTPS), the topic is prominently about the supported cipher suites. I want to fully understand which part of the cipher suite has which role in a ...
4
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2answers
292 views

Is a certificate with more bits than its parent more secure?

Let's Encrypt currently issues 4096 bit RSA certificates if requested (default, however, is 2048). But its parents, intermediate "Let's Encrypt Authority X3" and root "DST Root CA X3", are both 2048 ...
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1answer
60 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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2answers
93 views

Terms for differentiating between key-exchange and public-key cryptosystem

The RSA and Diffie-Hellman protocols are part of asymmetric cryptography. But is there a word to distinguish between cryptosystem like RSA (i.e. there are two keys, one for encryption and another for ...
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2answers
581 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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2answers
1k views

What are the performance differences (for client and server) between DHE and ECDHE in TLS?

My question is about the client and server performance for (EC)DHE. I am having difficulties in understanding this picture (which is based on numbers from Ivan Ristic' book "Bulletproof SSL and TLS"). ...
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1answer
29 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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0answers
157 views

How does “Key Transparency” work?

A few days ago, Google published Key Transparency to solve the problem of verifying the key fingerprints of e.g. your chat partners. Unfortunately, I don't really understand how Key Transparency ...