Key exchange protocols allow two parties to produce a secret session key over a public channel.
20
votes
1answer
1k views
Does the generator size matter in Diffie-Hellman?
For the Diffie-Hellman protocol I've heard that the generator 3 is as safe as any other generator. Yet, 32-bit or 256-bit exponents are sometimes used as generators. What is the benefit of using ...
14
votes
2answers
648 views
Is HTTPS secure if someone snoops the initial handshake?
Let's say I'm on an open wireless network that's being actively sniffed and I connect to an HTTPS site. Even though my subsequent traffic is encrypted, couldn't the sniffer use the data from the ...
8
votes
5answers
1k views
What is the post-quantum cryptography alternative to Diffie-Hellman?
Post-quantum cryptography concentrates on cryptographic algorithms that remain secure in the face of large scale quantum computers. In general, the main focus seems to be on public-key encryption ...
7
votes
7answers
3k views
Is Diffie-Hellman mathematically the same as RSA?
Is the Diffie-Hellman key exchange the same as RSA?
Diffie Hellman allows key exchange on a observed wire – but so can RSA.
Alice and Bob want to exchange a key – Big brother is watching everything.
...
7
votes
3answers
2k views
Can one generalize the Diffie-Hellman key exchange to three or more parties?
Does anyone know how to do a Diffie-Hellman or ECDH key exchange with more than two parties?
I know how to do a key exchange between 2 parties, but I need to be able to have a key agreement between 3 ...
6
votes
5answers
2k views
Why do we need asymmetric algorithms for key exchange?
In SSL protocols, both symmetric and asymmetric algorithms are used. Why is it so? The symmetric algorithms are more secure and easier to implement. Why are asymmetric algorithms usually preferred in ...
6
votes
1answer
842 views
why do we need Diffie Hellman?
my question from stackoverflow: http://stackoverflow.com/questions/11374592/why-do-we-need-diffie-hellman
Diffie–Hellman offers secure key exchange only if sides are authenticated. for ...
6
votes
1answer
301 views
Can a user of a password-protected Wi-Fi sniff on other user's communication?
Imagine a Wi-Fi network protected by WEP/WPA/WPA2. Users can join the network in case they know the pre-shared key of the access point.
Is it possible for a user A (who has successfully logged into ...
5
votes
1answer
258 views
How should I check the received ephemeral Diffie-Hellman public keys?
In my application I'm doing a DH key exchange, where both sides generate their
own ephemeral key. No static keys are used. I am trying to make my
application resistant against an active attack and ...
5
votes
1answer
268 views
GPG/PGP Verification of Revocation
How does one verify a key revocation?
After revoking a key and sending the revocation to MIT's keyserver, I noticed that the key is listed as such:
...
4
votes
1answer
440 views
advantages of a static ECDH key
What are the advantages of using static-ephemeral ECDH over ephemeral-ephemeral ECDH?
4
votes
2answers
208 views
How does the wider cryptographic community view non-abelian group based cryptography?
Is there perhaps some neural expository article on crypto systems based on non-abelian groups?
I've gleaned that Anshel–Anshel–Goldfeld key exchange is the most well-known cryptographic algorithm ...
4
votes
2answers
176 views
Can I use a key-derivation-function as the hash function H in SRP?
In the Secure Remote Password Protocol, the verifier must be stored on the server. In the case of a server compromise, an attacker could obtain these verifiers. If nobody reused passwords, this ...
3
votes
3answers
179 views
Derived Shared Key vs Distinct Keys?
I've seen a lot of 2-party applications that derive a shared key from distinct keys created by each party.
Why is this technique employed? Would it not be better to use those two distinct keys for ...
3
votes
4answers
216 views
symmetric-key cryptography based key establishment techniques
Most of the current key exchange techniques are based on public-key cryptography. Are there any key exchange/establishment techniques based on symmetric-key cryptography too ?
In my setup primary ...
3
votes
2answers
78 views
What are the potential security impacts of using CRAM-MD5 for Emails, when not using an SSL connection?
Background: My current server-provider tells me it's no problem to store the passwords in plain-text in the database, saying he has to do so because they use CRAM-MD5 for email authentication. But ...
3
votes
1answer
110 views
SSL Key Exchange
I read briefly over the TSL/SSL key exchange protocol. I have to wonder about the whole pre-master-key procedure. Wouldn't it be sufficient if the client or server encrypted a generated session key ...
3
votes
1answer
155 views
Does Identity-Based Encryption actually solve any problem?
Identity based encryption schemes [*] seem to have great potential in high-latency Delay-Tolerant and mobile, ad-hoc networks since they apparently seem to avoid the need for key negotiation and ...
3
votes
1answer
554 views
Trouble with diffie-hellman groups
Is anyone able to point me towards a known-to-be-good diffie-hellman group? I currently use group 24 (RFC5114, 2048-bit MODP Group with 256-bit Prime Order Subgroup). It came to me that this group is ...
3
votes
1answer
446 views
RSA-based authentication and key-agreement protocol
An authentication and key-agreement protocol between devices shall mutually demonstrate their identity, and establish a shared random secret $R$ suitable for securing later communications.
To that ...
2
votes
1answer
87 views
Is it feasible to break Diffie-Hellman key exchange when the implementation uses a poor-quality PRNG?
I've come across an implementation of DH in Java that uses the Random class to generate the secret integer value $a$, as shown in in Wikipedia's description of the ...
2
votes
2answers
155 views
Is EKE attackable by a brute-force password search?
So I'm trying to properly implement the EKE protocol and I'm using C# with the Windows CNG and ECDH key exchange. I need to use this because it's FIPS certified and all that jazz.
So what I'm ...
2
votes
1answer
66 views
Authentication techniques being used by QKD Systems
As its well known that QKD systems are prone to simple MITM attacks, Any idea what authentication techniques are being used in QKD to prevent them in practice
2
votes
1answer
319 views
Generalizing the conversion of Diffie-Hellman to El Gamal
How can we generalize the conversion of Diffie-Hellman to El Gamal public-key encryption scheme? The goals is to be eventually able to show that any 2-round key-exchange protocol can be converted into ...
2
votes
1answer
124 views
Is it OK to use a data-encryption key for key wrapping, too?
Our industry (area of cheap networked devices) has a standard that defines the usage of keys for both authentication and encryption using EAX mode of AES. This standard does not define key management, ...
2
votes
1answer
202 views
Verilog simulation & synthesis of Diffie-Hellman key exchange
Is there any freely available verilog implementaion of Diffie-Hellman key exchange?
I couldn't find anything using google. So, assuming its not there I started implementing on my own.
The code is ...
1
vote
3answers
349 views
Is public-key cryptography the only option in this scenario?
Two parties: a client and a server are to a agree on a symmetric key. Both the client and the server are aware of a master password. The way this is currently done ...
1
vote
1answer
85 views
Is this method for exchanging private key using RSA sound?
Bob know's Alice's public key, and he wants to make sure he's connecting to the one which has that key. Furthermore, Alice wants to verify when she gets a connection from Bob who'll give his public ...
1
vote
1answer
112 views
Implementations of Ntru TLS
I posted this in a reply to What is the post-quantum cryptography alternative to Diffie-Hellman? but since it's actually another question, it was deleted.
Has anyone come across any implementations ...
1
vote
1answer
114 views
Do Quantum Key Distribution and Physical Unclonable Functions combine, and how?
I see there's a project to combine Quantum Key Distribution, Physical Unclonable Functions, and classical crypto, in order to secure a high speed (100Gb/s) optical link.
While there does not seem to ...
1
vote
1answer
113 views
Constructing secure key exchange protocol
I have $\Pi=(Gen,Enc,Dec)$ and let it be semantically secure public-key encryption scheme. Security parameter is $n$, then the message space of plaintext is always $\lbrace 0, 1 \rbrace^n$.
By using ...
1
vote
0answers
100 views
Computer appliance protocol
I build the computer appliance system that consist of software server and multiple controllers. The system I want to build must be pluggable in the sense that when I connect a controller C to the ...
1
vote
0answers
77 views
Storing counter value of HOTP at client side [closed]
How can we store counter value on the client side in HOTP??
0
votes
1answer
58 views
What is a fair exchange scheme?
The Wikipedia entry Fair exchange has only two lines, and the only paper I can find describing such a protocol is extremely complicated.
Is this a new field in cryptology or can someone give an ...
0
votes
1answer
96 views
Why are RSA keys encoded with ASN.1 for TLS?
Browser vendors use ASN.1 encoding for RSA certificates in the TLS protocol. RSA public keys are just a number, so why do we need encode them to something else? That increases the risk of security ...
0
votes
3answers
109 views
Is it possible to ensure security with zero pre-shared information?
Is it possible to secure a communications channel against both passive (sniffing) and active (injecting / MitM) attackers without either legitimate party knowing any pre-shared information?
I know ...
0
votes
1answer
272 views
How do I generate a session key using the Diffie Hellman algorithm?
How to generate a session key between two nodes in two different subnets when the nodes don't know each other directly, using diffie hellman algorithm?
0
votes
2answers
91 views
Key Exchange and anonymity issue
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 ...
0
votes
1answer
144 views
Ways to protect flash player against MITM diffie hellman
We have a server, which sends content encrypted with AES128 or RC4 to a flash client over an insecure HTTP channel. The encryption key is negotiated using Diffie Hellman.
The problem:
Diffie ...
0
votes
0answers
44 views
“Free” key exchange in a Ed25519 PKI? [duplicate]
Assuming a PKI where everyone has a public/private Ed25519 keypair, can a secure shared secret be computed by calculating abB when Alice has keypair ...
0
votes
0answers
81 views
How to encrypt OpenVPN setup traffic [closed]
I have an OpenVPN server and a client that can successfully connect to said server. The traffic over the tunnel is encrypted. The tunnel works quite well.
However what is NOT encrypted (cleartext) is ...
0
votes
0answers
25 views
How to apply DH secret exchanging method to 3 person? [duplicate]
Possible Duplicate:
Can one generalize the Diffie-Hellman key exchange to three or more parties?
I've learned the DH, and wondering if there a way to use 3 parties to communicate with each ...
-1
votes
1answer
221 views
ECDH VS. DH benchmarking in JAVA
So basically my problem is the odd result i get when measuring the time it takes to generate a ECDH key in java vs. the time it takes to generate a DH key.
I compare the time it takes to generate:
...
-2
votes
2answers
148 views
Where to store the private key and the public key in a communication protocol
I want to create a simple secured connection protocol over TCP/IP.
I just want to connect from my mobile device to a server securely.
Firstly I thought to use an SSL connection, but I changed my ...
-2
votes
0answers
35 views
session keys in an online e-voting system [closed]
I do not have much knowledge about cryptography or public and private keys, and your help will be much appreciated. I am totally a beginner, and no one from my university can help me.
I am trying to ...
