for questions relating to key exchange protocols.

learn more… | top users | synonyms

0
votes
0answers
7 views

ECDH-ECDSA Combination [migrated]

I am doing research on cryptography primitives at a basic level and I faced a question on encryption methods. I understood that ECDH is an approach to for secure key exchange between two parties ...
1
vote
2answers
54 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 ...
2
votes
1answer
21 views

Can a user verify the quality/safety of pregenerated SSH moduli parameters?

Many tutorials about how to mitigate the Logjam recommend regenerating Diffie-Hellman moduli. This is a resource intensive operation, especially for high-bit groups. This made me think if it made ...
4
votes
1answer
57 views

Infinite one time pads, brute force multiple pads?

So based on my understanding using the same key for encrypting two completely random plain texts when using an otp cipher will still retain perfectly secret. This is based on the answers on this ...
3
votes
1answer
87 views

Security of Web Game over WebSockets?

Project that I'm working on depends on WebSockets to communicate between the server and client browser for all interactions within the game. I'm attending university for Computer Security, but I'm ...
3
votes
1answer
57 views

What is the best method for key exchange?

I have application working between server and client. All messages must be encrypted and decrypted. I use AES algorithm and I want method to hide the key. I found Diffie-Hellman algorithm, but my ...
1
vote
1answer
35 views

Is there a PAKE algorithm where the passwords can be tested in the first round?

I want to use PAKE for key exchange between two parties (Alice and Bob) which share a low entropy secret (a password they exchanged on a piece of papers). Alice and Bob use a software on there ...
0
votes
0answers
24 views

Can SRP be implemented using libsodium

I am using libsodium for cryptography and I want to use SRP for key exchange. The wikipedia page lists a python example, but I am not sure if and how I could convert this to libsodium function calls. ...
5
votes
1answer
84 views

Is this a safe way to verify public keys?

I want to verify a public key like this: Alice generates a public/private key pair for encryption Alice generates a public/private key pair for signing Alice signs a random 4-letter word + the ...
3
votes
2answers
42 views

What is the message called someone sends to verify a key?

Suppose Alice wants to check if Bob has a certain keypair. Alice could send some random payload to Bob and let Bob sign that payload with his private key. Alice is now able to check if the signature ...
0
votes
1answer
36 views

OpenSSL ecparam generates same private key every time?

Currently I am trying to make my web server as secure as possible and I am testing different cipher suites on the server side, some of them using ECDHE key exchange. When generating private EC keys, ...
3
votes
2answers
85 views

Encryption in peer to peer chat

For a homework assignment I'm developing a chat service that will be able to communicate within a single network. The communication channel should be encrypted with RSA. Should I generate keypairs ...
4
votes
3answers
68 views

How many keys are used in this specific TLS 1.2 connection?

That shows the mechanism of the connection. How many keys are being used in this connection? What are they? Who knows them? What is the purpose of each key?
3
votes
2answers
96 views

3rd party requires my server's public key for a secure connection?

I'm trying to integrate with a 3rd party service and they have requested our server's public key. I've sent it to them and they said they have configured it on their end. In order for me to make ...
41
votes
4answers
5k views

Why is key exchange necessary at all?

Let's say "Alice" and "Bob" want to communicate with each other over an insecure network. Using Diffie–Hellman key exchange, they can get the same symmetric key at last. However, as I understand, ...
0
votes
1answer
57 views

What's the algorithm to generate a modulus and a base for a Diffie-Hellman key exchange app?

I have a school project in which I have to write a java console application that can be used for key exchange between two people. All is fine and well, but finding good base and modulus seems to be a ...
0
votes
1answer
70 views

In Asymmetric cryptography, is the number of Private Keys limited?

My question is a bit of a leading question, because I assume that the number of Private Keys is a finite number. However, it is possible that the number is such a large number that it would ...
4
votes
2answers
210 views

Unseen.is encryption claims revisited with their proprietary, patented “xAES” algorithm

I had asked last year about the encryption claims by the web service called https://unseen.is. The very same service that had claims of "beyond army level encryption", "4096 bit keys" etc. This is the ...
-3
votes
1answer
68 views

Hiding both public and private keys for private communication between 2 servers

I've been trying to learn about deeper info security past abstract words like "tunnels" and "networks", and would appreciate some enlightenment on the following scenario: 2 servers are set up to ...
5
votes
2answers
79 views

Using plain-text phrases as public/private pair?

I'm working on an application that'll be used by relatively non tech-savvy users, and while the machines will have internet access, the app can't have any sort of hosted intermediary. The app allows ...
1
vote
2answers
42 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 ...
8
votes
3answers
672 views

What to do when you can’t protect mobile app secret keys?

We have a mobile app for iOS and Android available in the Apple and Google Play stores. The app communicates with our server’s Web Services over HTTPS. We have attackers able to spoof the app ...
2
votes
1answer
106 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. ...
12
votes
6answers
5k views

Is (safe) encryption over compromised line impossible?

I realize something like this would be the holy grail of communications security and have never heard anything to suggest it has been done. Am just wondering. A lot of mathematicians and computer ...
3
votes
2answers
364 views

DEK, KEK and Master keying - simple explentation

This article is intended to be a simplified explanation sans drill-down for people wanting to understand the concept terms. What is DEK, KEK and MEK/Master key ?
1
vote
2answers
55 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 ...
0
votes
1answer
250 views

Sharing Derived Unique Key Per Transaction (DUKPT) Base Derivation Key (BDK) with a partner

Assumptions: We have devices out in the field injected with keys derived from our one and only BDK. The devices encrypt data using the injected derived key. All our devices connect to our server ...
67
votes
5answers
7k views

Why can't I MitM a Diffie-Hellman key exchange?

After reading the selected answer of "Diffie-Hellman Key Exchange" in plain English 5 times I can't, for the life of me, understand how it protects me from a MitM attack. Given the ...
0
votes
1answer
96 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 ...
1
vote
1answer
577 views

How ECDHE is signed by RSA in ECDHE_RSA cipher

About ciphers that use ECDHE as Key Exchange and RSA as Authentication: How exactly this two algorithms work together, is ECDHE process encrypted by RSA public key? What are the DH parameters? ...
1
vote
1answer
69 views

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 ...
7
votes
2answers
208 views

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 ...
18
votes
3answers
1k views

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 ...
1
vote
0answers
42 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?
3
votes
1answer
142 views

What public GPG key do I have to publish?

I just created a master key and two subkeys. The first subkey is used for encryption, the second one for signing. Now I am wondering what public key do I have to publish on my website. Does is ...
0
votes
2answers
97 views

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 ...
1
vote
1answer
68 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 ...
1
vote
1answer
66 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 ...
2
votes
1answer
224 views

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 ...
2
votes
1answer
57 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 ...
0
votes
0answers
35 views

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 ...
1
vote
1answer
99 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)? ...
-1
votes
2answers
724 views

How do certificates stop this man in the middle attack?

Alice and Bob are trying to set up a secure conversation, but unknown to them in the middle is Eve, who can intercept and modify all packets sent between them. The communication goes as follows: ...
2
votes
2answers
271 views

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?
1
vote
1answer
294 views

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 ...
0
votes
1answer
96 views

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 ...
0
votes
1answer
252 views

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 ...
4
votes
2answers
3k views

Are VPNS vulnerable to active man in the middle attacks?

I know that with SSL/TLS, man in the middle attacks are not possible. For example if Alice and Bob are trying to communicate and Trudy is trying to perform a man in the middle attack, then when Alice ...
10
votes
1answer
4k views

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 ...
2
votes
3answers
243 views

Why do I have to use multiple keys for each direction and purpose?

I'm currently writing an examen about 'Lessons Learned in the IT-Security'. I already found some thing, which shouldn't be done. But right now I'm in trouble finding the reasons why not to do so. ...