Key exchange protocols

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Any obvious flaws in this protocol?

Are there any particular flaws in this protocol? (Yes I know about SSL) Three participants: Login Server LS Game Server GS Client C Asymmetric key-pair Kpriv Kpub Shared 128bit secret key Ksec ...
2
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1answer
170 views

Inner Workings of Public Key Encryption

After watching this video explaining PKE with tennis balls (interesting), it left me with a few particular questions that I'm having trouble finding answers to: I assume that they keys used to ...
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3answers
359 views

Secure device pairing protocol

I need to implement secure pairing between two devices based on a short shared PIN code with no trusted third party. If you think about the way bluetooth devices pair you won't be far off -- my ...
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1answer
135 views

Mutual Anonymity in key exchange

If Alice (sender) sends a private message embedded with public key of the Bob(recipient) through onion network, so in this key exchange, does Bob remains anonymous to Alice as Alice knows about the ...
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3answers
798 views

Establish a secure channel with mutual authentication given pre-shared public keys

Suppose I have a system whereby parties are identified by their public key (with some pre-selected asymmetric key algorithm). Suppose I have a party PUB1 which wants to establish a secure channel with ...
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2answers
96 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?
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83 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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3answers
110 views

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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1answer
43 views

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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2answers
363 views

Key distribution and key exchange for simple secure FTP implementation

I'm developing a simple secure file transfer protocol for a University project using openssl. I have a Client (let be C) and a Server (let be S). C will send to S messages like get, put, cd, … and S ...
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130 views

Picking exponents for Diffie-Hellman

I'm taking a class on Cryptography and the professor mentioned that given mod N and base g with a certain order, you should pick powers m and n such that they create a certain property with the order ...
2
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1answer
76 views

How to establish a random OTR remote party as a specific individual?

In reading Glenn Greenwald's 2014 book No place to hide, one thing stood out to me as a bit odd. Greenwald details how Edward Snowden was insistent that Greenwald install PGP in order to communicate ...
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93 views

Main difference between Yahalom and Needham-Schroeder key exchange protocols

I am just wondering what is the main difference between the Yahalom and Needham-Schroeder key exchange protocols? Which protocol uses less computational power?
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3answers
184 views

Cryptography key gathering tool [closed]

I am wondering if there exist a tools which can return the value of the one of the private key if the following are known: 1) Encryption Algorithm 2) Public key 3) Plain text 4) Cipher text Or may be ...
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1answer
152 views

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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2answers
187 views

How do key servers resolve conflicts?

According to the PGP network FAQ While a number of key servers exist, it is only necessary to send your key to one of them. The key server will take care of the job of sending your key to all ...
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1answer
48 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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1answer
636 views

Can you generate Diffie-Hellman parameters quickly [closed]

I am working on an android project for school and I am supposed to do a DHKE(Diffie Hellman Key Exchange). Everything works well, the problem is that it takes a lot of time (really a lot) to generate ...
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1answer
155 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 ...
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1answer
41 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 ...
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1answer
84 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 ...
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2answers
992 views

Client-server encryption technique explanation (TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256, 128 bit keys)

I opened a web page using https. When I looked at the page info provided by my browser (Firefox) I saw following: Connection encrypted: High-grade Encryption ...
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1answer
60 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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2answers
460 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
1k 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 ...
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2answers
365 views

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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1answer
421 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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58 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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154 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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512 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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3answers
262 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 ...
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144 views

Does Diffie-Hellmann (DH) key exchange protocol lower Off-The-Record protocol (OTR) security level?

Off-the-Record protocol employes Diffie-Hellman key exchange protocol (DH). DH protocol does not provide authentication of the communicating parties and, according to many sources, is vulnerable to ...
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57 views

Any Suggestion Exchanging shared key between process via port in untrusted machine (infected my malware)?

I am trying to get shared key between Firefox extension and a java program running in same machine. I am communicating both application via socket. My assumption is that malware is running in ...
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1answer
4k views

The request was aborted: Could not create SSL/TLS secure channel Exception

Let me explain my situation. I created a self-signed certificate and installed it in the Trusted Root Certification Authorities section in MMC. I then created two certificates using the self-signed ...
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1answer
238 views

Secure Encrypted Chat Protocol [duplicate]

Possible Duplicate: Is there a way to negotiate a secret between 2 parties with no prior knowledge? Imagine two clients who want to establish a secure connection over a server. Both clients ...
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2answers
956 views

Diffie-Hellman key-exchange: securing prime and base

As we know DH algorithm based upon 2 large prime numbers, which are used to be called as prime and base I am writing app which implements DH key exchange algorithm. From security point of view should ...
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Are there flaws in this simple key exchange?

I'm reviewing for a computer security exam. Here is a simple scenario: Suppose that someone suggests the following way to confirm that the two of you are both in possession of the same secret key. ...
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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 ...
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233 views

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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1answer
69 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 ...
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71 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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62 views

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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2answers
95 views

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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85 views

does a public key work with all encrypted programs

let us say, I use program "x" for my e-mail security. through them I have a public key and a private key. My friend uses program "y" for their e-mail security and consequentially have a public key ...
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131 views

Purpose of key confirmation

Among the requirements for a secure key exchange is the key confirmation. I wonder why is this step required. Even if the other party hasn't computed a correct value for the shared secret, it doesn't ...
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2k 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 ...
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130 views

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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105 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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134 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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435 views

Is the Station-to-Station protocol secure?

After I've read a lot about key exchange many sources state that the Station-to-Station is secure, since it also verifies the entity on the other side. Well how is that true, if an active Man in the ...