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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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 ...
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1answer
799 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? ...
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1answer
78 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 ...
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1answer
104 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
1k 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
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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1answer
193 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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2answers
50 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
163 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
71 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
69 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
147 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
121 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
70 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

Which is better in “DH-group14-sha1 with hmac-sha2-256” and “DH-group-exchange-sha256 with hmac-sha2-256” from performance and security perspective?

In our product (embedded system), so far we were using diffie-hellman-group1-sha1 with hmac-sha1. But due to security concern we are planning to use diffie-hellman-group14 for key exchange and ...
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1answer
2k 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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1answer
25 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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1answer
22 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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1answer
51 views

How to test TLS handshake process?

I need to test the handshake process of TLS. I thought to use inter-process communication in Linux. Is it possible or not? If not, what simulator could be used for this purpose? If yes, what do I ...
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2answers
92 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
44 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 ...
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1answer
60 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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2answers
342 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
888 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
657 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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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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46 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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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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60 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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100 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
276 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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2answers
976 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
436 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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0answers
205 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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0answers
61 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
8k 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
302 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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3answers
2k views

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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1answer
243 views

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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1answer
1k 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
1k 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 ...
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1answer
31 views

What are the requirements for private keys in Diffie-Hellman key exchange algorithm

Basically question is: If we have pof size 2048 what sizes for private exponents should Alice and Bob choose and why?
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1answer
80 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 ...
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1answer
340 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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1answer
88 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
195 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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2answers
95 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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3answers
315 views

What are the MitM implications of a stolen client-side private key?

Many VoIP handsets support client-side SSL authentication for auto-provisioning. Unfortunately, some devices must be programmed with their client-side keys. (Keys generated on low-entropy devices are ...
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1answer
72 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, ...
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1answer
84 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 ...