Questions tagged [key-exchange]
Key exchange protocols allow two parties to produce a secret session key over a public channel.
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TR-31 Key Exchange Mode of Use
Using TR-31 key exchange, how is it possible to use restrictive modes of use, such as V (Verify only)? If Alice were to generate such a key, and send it to Bob, Bob would not be able to generate a MAC ...
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Can an attacker impersonate any party in a modified Needham-Schroeder protocol?
We are doing symmetric Needham-Schroeder protocol in university. We were provided a modified protocol and needed to answer the following questions.
Original protocol:
Modified protocol:
Task
a) An ...
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TLS 1.3 key_share capture without certificate exchange
I am working on an investigation on TLS 1.3.
I've came across an article of qacafe where they shared a TLS 1.3 handshake sequence. Wireshark capture. In this capture you see that in the Client Hello a ...
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Security of keys that are as long as the data
If both communicating sides end up with the same secret 3000-bit key, is it enough to XOR each byte of the messages with each byte of the secret key to make it secure?
Wikipedia says it is, but I ...
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who creates the passkey (and how many will be created)? [closed]
Passkey is nice. The math is nice. The tech is nice. https://security.googleblog.com/2023/05/so-long-passwords-thanks-for-all-phish.html
What I still dont see after sooo many hours: what software ...
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For TLS-PSK (pre-shared key), should non-ephemeral key exchange be preferred over ephemeral one?
TLS 1.3 specify two pre-shared key exchange modes, which are psk_ke and psk_dhe_ke. The former is a non-ephemeral key exchange ...
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Key exchange from discrete logarithm only
Diffie-Hellman key exchange is sometimes informally said to be hard under the discrete logarithm assumption in the chosen group. But if I am reading literature correctly, it actually uses a stronger ...
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Linux Kernel CryptoAPI key exchange and key derivation
I have a custom network and I want to implement a symmetric key exchange and key derivation mechanism with ECDH.
I know that I need to use KPP API and ECDH helper functions, but I can't find any code ...
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How do I decrypt a key encrypted by my HSM under a ZMK?
I've generated a key using an HSM Thales PayShield and i have share it with a counterpart. I followed these steps:
i generated key usign KG console command
i use FK to form ZMK from clear components ...
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PCI compliance - use of ANSI X9.17 for export keys
we have a concern about a key export.
We completed the migration to Key Block LMK in our environment (with HSM Thales 10K).
Now, we have to exchange keys with third-parties that still use Keys in ...
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Clarification on the use of Key block Version ID with Thales HSM
Clarification on the use of Key block Version ID
For the first time since we migrated to the Key Block we are exchanging keys with third parties,
The keys were all generated by choosing Key Scheme &...
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Why NIST 800-56A rev3 does not use cross secret calculation in C(2e, 2s, ECC CDH) scheme?
In the NIST 800-56A rev3 "Recommendation for Pair-Wise Key-Establishment Schemes Using Discrete Logarithm Cryptography" in section 6.1.1.2 "(Cofactor) Full Unified Model, C(2e, 2s, ECC ...
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How does TLS 1.3 restrict the Diffie-Hellman parameters to ones that are known to be secure?
In previous versions of TLS, the choice of the Diffie-Hellman parameters was up to the participants. This resulted in some implementations choosing incorrectly, resulting in vulnerable implementations ...
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Mutual authorization using a pre-shared key
I'd like for two machines on a network to be able to prove to each other that they both have knowledge of a pre-shared secret, without revealing the secret to each other. Let's assume that all traffic ...
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Authenticated Key Exchange of Kyber.AKE
I have some questions about the setting of the one-way authenticated key exchange of Kyber.AKE as defined in section 5 of the paper.
How does $P_2$ authenticate itself to $P_1$? It is not obvious to ...
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How can I send someone a large file safely without using key exchange protocols (for encryption)?
I recently took an exam where one of the questions was roughly the following:
You need a specific way for sender S to send a large file M to a receiver R with their secret-public key pair, without ...
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Where is the cryptography library that support group signature?
Finding a cryptography library to implement various application features is not difficult nowadays, thanks to options like NaCl, Google Tink, PyCA, and OpenSSL.
However, I've been struggling to find a ...
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Two way key transport?
For a KEM mechanism like RSA, Kyber, etc. is there it usually worth doing key trapping/key encapsulation both directions in a key exchange? By this I mean: Alice wraps a symmetric key and sends it to ...
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DH Finding A Public Key from Public key and shared secret
Is there a known feasible method for determining an unknown public key from a Diffie Helman shared secret and the other public/private key pair?
This would be rarely useful, but I am curious if the DH ...
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Compute key size in Hyperelliptic Curve Cryptography
I am trying to implement a basic Diffie-Hellman key exchange using ECC and HECC of genus 2 and 3 and compare them. However, I am a bit confused about the concept of key size in HECC.
In ECC, from my ...
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A tensor-based Diffie-Hellman exchange
Below is a description of a "cube" Diffie-Hellman, based on commuting matrix actions on tensor products. Some questions:
References for something similar?
Obvious flaws, is this a terrible ...
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Why did post-quantum key exchanges go extinct?
On July 5, 2022, NIST chooses one KEM (Key Encapsulation Mechanism) as a PQC standard and 4 KEMs as four-round candidates. Why aren't there any key exchanges?
Similarly, KEMs are usually studied in ...
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What is the most secure hybrid cipher suite(Library) possible today?
What combination of public key cryptography (DH) and symmetric key cryptography is currently available that is (subjectively) as secure as possible over other ciphers (AES,curve448) when security is ...
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A perfect key exchange similar to the One Time Pad
The one time pad is unbreakable because each message could be one of many, and each one is equally likely.
Is it possible to do this with a key exchange? (So if someone records the key exchange, there ...
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McCallum-Relyea exchange on x25519 elliptic curve
Background
I have a degree in electronics engineering, I'm not bad at programming with many languages, but I'm not that good at cryptography, I'm just able to use that from libraries, and I understand ...
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RSA Key Exchange Attack [closed]
I am curious what is an attack that the RSA Key Exchange algorithm is vulnerable to that Diffie Hellman Key Exchange is not vulnerable to? I know Diffie Hellman is prone to Man in the Middle attacks ...
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Explanation of Burmester-Desmedt group key exchange and Ingemarsson-Tang-Wong (ITW) group key exchange algorithm
I know that both algorithms are similar to the Diffie-Hellman key exchange and are used for exchanging secret keys in a group but I still cannot figure out the key differences between both algorithms.
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in signed group key exchange, why do we need to sign a session id?
I have seen a few papers on (contributive) group key exchange where users create Keys and broadcast them so they can all contribute to the secret key.
In order to protect against active attackers, ...
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Can you use MITM to hijack a public key meant for key based signing?
After reading "Verify the identity of sender" , which was part of an answer on StackOverflow, I was wondering if the following is possible:
Based on part II, if I am sitting between Alice ...
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Blom's key distribution
Having a difficult time wrapping my head around the Blom's key distribution. I found an online resource to understand this but still couldn't get it.
I am attaching the screenshot from the book where ...
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Defending MITM attacks during key exchange
As far as I know, key exchanging algorithms are vulnerable to an active MITM attack.
Let A (Alice) and B (Bob) be parties with no secret information. An adversary C
playing man-in-the-middle ...
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Mapping DH / DHE p & g params to a group
I'm doing a small code that performs a simple SSL/TLS analysis and I'm stuck on determining the size of the key exchange in the case of DH / DHE.
If I take the following example (wireshark capture) :
<...
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How does TLS 1.3 provide authentication without using the public key to verify that the server has a private key?
In the TLS 1.2 handshake, after checking the certificate, the public key from the certificate was used to encrypt the data to create a symmetric encryption key, hence the authentication took place on ...
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minimal public-key authenticated encryption protocol
One party (master) wants to send data to another party (slave) over an insecure channel using public-key encryption and signature schemes such that:
master is authenticated,
data is confidential,
...
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How to evaluate efficacy of new public-key cryptosystems
Suppose I had a new public-key or key exchange protocol. How do I objectively evaluate it so as to determine if it is worth sharing with the broader community? Whenever developing a cryptosystem, it ...
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Forward-Secure AKE based on post-quantum KEM?
I am looking for authenticated key exchange protocols (AKE) based on a generic key encapsulation mechanism (KEM) and providing full/perfect forward secrecy. Optionally, the protocols should offer ...
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Encrypt messages for two-participants chat
I need a chat between two users and I obviously want to make it as secure as possible. I am, by no means, a cryptography expert, so I turn to you guys for some advice.
Because I like the idea of ...
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Can a man in the middle tell what kind of encryption you're using from a key exchange?
Encryption schemes typically are built on the idea that even if a man in the middle attacker knows exactly what kind of encryption you're using, they cannot decrypt your messages without the key.
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meaning of "zero-padding and split" procedure in HEAAN-RNS
I don't understand the meaning of step2-1 in Better Bootstrapping for Approximate Homomorphic Encryption. I understood all other parts of the algorithm. However, I have no idea why we need the "...
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In a Diffie-Hellman key exchange Find this key and compute the shared secret key k
Hi I struggling to find the answer of my schhol exam, can anyone help me .
In a Diffie-Hellman key exchange the multiplicative group of integers modulo
p is used with the parameters p = 59, g = 3 mod ...
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Commutable and Composable Asymmetric Encryption/Decryption
I have a need for the following encryption properties: $f(g(v_\text{plaintext}) = v_\text{ciphertext}$ needs to be decryptable by $f^{-1}(g^{-1}(v_\text{ciphertext}))$ and $f$ and $g$ need to be ...
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How is Diffie-Hellman linked to AES?
I have just learnt about Diffie-Hellman and AES. However, I cannot seem to understand how they link.
My initial idea was that Diffie-hellman is used to transfer a key for AES decryption. After further ...
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ECCDH: direct or with temporary ECC keypairs?
I am moving from RSA to ECC for my application.
Looking at these posts 1
2
3, they all suggest that Alice generates a temporary (ephemeral) ECC keypair eKP to send a message to Bob.
The sessionkey sK ...
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Check if pubkey belongs to twisted Edwards25519
I want to check if some pubkey belongs to twisted edwards25519 (I guess this is used for ed25519 ?) The problem is that I have in theory some valid pubkeys like:
...
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How is the shared secret generated in IPsec using DH key generation?
I have doubt like when in the IPsec we use a DH group for key exchange. It takes a prime number and $g$ value from group bit.
How does the key exchange payload and nonce help to generate the shared ...
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Is libsodium's Key Exchange system secure?
I'm building a project using libsodium's AEAD + Key Exchange system and want to write a proof justifying the security of the project. I am wondering if I can find a source detailing the exact security ...
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How to extract an AES key which resides in a TR-31 keyblock
I have a version D TR-31 keyblock (which contains an AES Key for use in CMAC), and have the ZCMK key used, what is the method which I can use to extract the key from the TR-31 keyblock? I'll do my own ...
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Are Encryption, Key Exchanges and Digital Signature the application of asymmetric encryption
Reading the wikipedia entry on asymmetric cryptography, will I be wrong to conclude that there are 3 main broad category of application for asymmetric cryptography? Mainly:
encryption
digital ...
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Need to know the key exchange value of the following cipher suites
I need to know the key exchange of the DHE-DSS cipher suites, will it be the same as mentioned in DHE-RSA?
SB_tech
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Sending encrypted message without public key from recipient (elgamal)
assume Bob and Alice use Elgamal encryption scheme. Alice wants to send Bob a message, but does not know Bobs public key. Is there a way for Alice to find out Bobs public key by receiving multiple ...
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