Tagged Questions

1
vote
1answer
102 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 ...
1
vote
1answer
54 views

ECDH and Forward Secrecy

I just read about ECDH and while getting a overview over the process, I noticed that this key exchange method does neither provide any forward secrecy, nor does it protect against replay-attacks, ...
1
vote
3answers
112 views

Cryptography key gathering tool

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 ...
0
votes
1answer
103 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 ...
2
votes
3answers
142 views

Given a large enough sampling of public keys could one begin to identify a private key?

For example, an ISP or government capable of tracking millions of keys being exchanged. Would that provide a sample large enough to be able to identify the private key on either end?
0
votes
2answers
272 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 ...
3
votes
2answers
119 views

What steps can you take to make offline cracking of SRP harder?

In the aftermath of the Blizzard hack, what steps can I take to make offline cracking of SRP more difficult? My question assumes that your database is already gone and that you implemented SRP more ...
2
votes
3answers
199 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 ...
1
vote
1answer
107 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 ...
2
votes
3answers
142 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 ...
3
votes
3answers
477 views

Diffie Hellman - how large should the random number be?

When using the Diffie Hellman exchange with the second Oakley group 1024 bit Prime per RFC 2409 (*), how large should the random numbers generated by both sides be? In RFC 2631 this is called the ...
3
votes
3answers
169 views

Does the hash change the security of the Secure Remote Password protocol?

I'm implementing the Secure Remote Password protocol, and similar to this question, I'm wondering if I can use the SHA-512 hash function instead of SHA-1 currently being used. Would this help improve ...
130
votes
9answers
8k views

How is it possible that people observing an HTTPS connection being established wouldn't know how to decrypt it?

I've often heard it said that if you're logging in to a website - a bank, GMail, whatever - via HTTPS, that the information you transmit is safe from snooping by 3rd parties. I've always been a little ...
5
votes
3answers
243 views

DHE exchange and client authentication

If a server has a known public key and a Diffie-Helman exchange is performed and signed by that key, is there any benefit to authenticating the client before establishing a secure channel instead of ...
6
votes
2answers
2k views

Is 1024bit Diffie Hellman key exchange secure?

My system uses AES-256, 4096bit RSA CA key and 2048bit RSA keys for servers together with SHA-256 signing. Does using 1024bit DH key exchange lower its security? I read on one mailing list that ...
8
votes
2answers
808 views

Which cipher suites with AES cipher provide forward secrecy?

Does standard AES with RSA (reported by Opera as TLS v1.0 256 bit AES (1024 bit RSA/SHA)) provide perfect forward secrecy? Which SSL3.0 and TLS1.0 ciphers do provide forward secrecy? Which ciphers ...
7
votes
1answer
2k views

Where do I get prime numbers for Diffie-Hellman? Can I use them twice?

I realise it's very hard to generate suitable prime numbers and generators for the Diffie-Hellman key exchange. What is the best way to generate them? And if I have one, can I use it twice? ...
5
votes
3answers
957 views

Is this prime number large enough / too large for a Diffie-Hellman for AES-256?

I'm using a Diffie-Hellman key exchange to encrypt data using AES-256. The prime number I'm using is the one from the 8192bit group specified in RFC 3526 (page 6). Page 7 suggests that, with a 620 ...
8
votes
3answers
329 views

Which authentication at the end of the Secure Remote Password protocol?

For the the client and server to prove to each other that they have the same premaster shared key, the original author suggests this: M = H(A | B | K) --> <-- H(A | M | K) ...
9
votes
1answer
210 views

Optimal variable sizes in the Secure Remote Password protocol

I am implementing the Secure Remote Password protocol: U = <username> --> <-- s = <salt from passwd file> a = random() A = g^a ...
6
votes
2answers
350 views

Implementing Secure Remote Password: Constructing the verifier

The SRP protocol as described in RFC 2945 generates the password verifier: x = SHA(<salt> | SHA(<username> | ":" | <raw password>))` v = g^x % N I have three questions: why use ...
3
votes
1answer
74 views

Differing scrambling parameter generation methods in Secure Remote Protocol

RFC 2945 (The SRP Authentication and Key Exchange System) states, The parameter u is a 32-bit unsigned integer which takes its value from the first 32 bits of the SHA1 hash of B, MSB first. ...
6
votes
3answers
616 views

Using Secure Remote Password without sending the username in the clear

To initiate a key exchange using the SRP protocol the client sends the username so the server can look up the salt and password verifier. Is there a simple way to change this so that an evesdropper ...
5
votes
1answer
155 views

Using Secure Remote Password without embedding the modulus

The SRP protocol as described by the author assumes that the large safe prime modulus and generator are embedded into the client and server rather than being transmitted as part of the protocol. ...
9
votes
3answers
795 views

How to exchange RSA public keys safely between two parties?

How to exchange RSA public keys safely between two parties via internet?
4
votes
2answers
3k views

Diffie Hellman c# implementation

Hallo all, For a test project I have tried to implement the (famous) Diffie Hellman algorithm for safe key exchange. Now I have written this in C#: using System; using System.Collections; using ...
7
votes
2answers
323 views

Is there a way to negotiate a secret between 2 parties with no prior knowledge?

Is there a way for 2 parties to negotiate a shared secret (for example, a session key) without having a pre-shared knowledge? SSL does this by using asymmetric encryption. Is there any other way to ...