1
vote
1answer
75 views

What keeps the private key safe if an attacker has both clear and encrypted copies of a message and the public key?

Let's say someone obtained a message in both clear text and in its encrypted copy with asymmetric cryptography, like RSA-2048. He also has the public keys. Is the private key still undiscoverable? ...
0
votes
1answer
79 views

Public Key Authentication

Is there another way to verify someones public key without a CA signing it? A challenge-response authentication including some sort of UID of the smartphone? Smartphone A generates asymmetric key ...
1
vote
3answers
222 views

Why is RSA decryption slow?

I've been researching the disadvantages of using RSA for encryption, and one I've found repeatedly is that RSA decryption is slow, but I haven't seen an explanation as to why this is. Can anyone ...
-5
votes
1answer
135 views

What is the excellence of RSA vs my algorithm [closed]

I was wondering that what make RSA Asymmetric Cryptography Algorithm special. So I wrote a very simple algorithm that do the same work (Generate Public and Private Key) Now I want to ask you that What ...
3
votes
7answers
252 views

How would I give an encryption key to only one person?

Let's say I have an encrypted message. I want to make it so that someone is able to decrypt it. The only way of giving it to them is online. For the purposes of this question, I can't call, mail or ...
18
votes
6answers
5k views

“Diffie-Hellman Key Exchange” in plain English

Can someone explain to me what is Diffie-Hellman Key Exchange in plain English? I have read in a non-tech news page that twitter has just implemented this technology which allows two persons to ...
2
votes
0answers
70 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?
23
votes
5answers
2k views

Why is Bruce Schneier recommending symmetric crypto over public key crypto

I just read the article written by Bruce Schneier, the crypto guru. In the article, he says : Prefer symmetric cryptography over public-key cryptography. But, he doesn't shed any light as to ...
0
votes
1answer
188 views

Encrypted data transfer with middle node and asymmetric key

I'm looking forward to pass data from a node A to a node B using asymmetric cryptography, but with one (huge) constraint: When A sends data to B, it is possible that B is offline. I would like to be ...
1
vote
1answer
472 views

Is server-side cryptography with user-only access possible for email services?

I came across the Lavabit High Scalability Writeup and got curious. Do you use any particularly cool technologies or algorithms? The way we encrypt messages before storing them is relatively ...
4
votes
3answers
238 views

What SSL options should not be used?

What SSL options should be avoided, due to recently discovered weaknesses? This might include symmetric algorithms, or MAC functions.
11
votes
3answers
2k views

What specific padding weakness does OAEP address in RSA?

It's been recommended to use OAEP when padding messages to be encrypted via RSA, to prevent known plain text attacks. Can someone elaborate this in better detail? I'd specifically like to know the ...
4
votes
1answer
234 views

Potential issues with Kim Dotcom's new proposed “encrypted webmail service”

Just spotted a Reddit thread about Kim Dotcom, of MegaUpload fame, planning to produce a secure webmail system that allows people to communicate securely, without the worry of having their messages ...
4
votes
2answers
3k views

How X509 Certificates are used for Encryption

I have small doubt regarding the process of X509. I am aware of OpenPGP Encryption/Decryption, where we generate the public key and private key. We can share the public key to vendors and they can ...
4
votes
3answers
1k views

Is a 512 bit RSA key secure when used temporary?

Is a 512 bit RSA key secure when a new key gets generated and used approximately once a week? The key is only used for signing messages, not for encrypting sensitive data. This is for a system where ...
2
votes
3answers
1k views

KDC(Key Distribution Center) vs Asymmetric Key Exchange

Today I was reading notes about cryptography and I came across a problem that exists in Symmetric Key encryption, which is how to share the secret key across the network. 1st Method : Make use of ...
156
votes
8answers
64k views

Why not use larger cipher keys?

RSA Security commonly uses keys of sizes 1024-bit, 2048-bit or even 3072-bit. And most Symmetric algorithms only between 112-bit and 256-bit. I do realize that the current keys are secure enough for ...
0
votes
1answer
801 views

ECDH is better than plain RSA? [closed]

RSALabs recommend using at least 4096 bit long RSA keys to encrypt emails but we have some performance difficulty with 4096 RSA. my noob question is what is ECDH (i didn't understood from wikipedia ...
14
votes
6answers
1k views

Principle of asymmetric algorithm in plain english

I was giving a presentation to my colleagues about cryptography basics in which I explained about asymmetric algorithm and its use. One of the common question from the audience about asymmetric ...
5
votes
1answer
275 views

Most efficient key algorithm for a TLS server key?

Let's assume I want to setup a HTTPS service on a modern-but-no-so-speedy x86 server without any form of hardware cryptographic accelerator. Which key algorithm should I choose for the server key in ...
4
votes
2answers
2k views

Shared Secret, is it a public key or a private key?

Reading the Diffie-Hellman non mathematical explanation i found that some mathematical operations are performed on private-key and the recipient's public key to generate a "shared secret" on both ends ...
4
votes
4answers
724 views

Is asymmetric encryption ever recommended for long-term storage?

Is asymmetric encryption ever recommended for long-term storage of data, is it advisable for example to store data in a database such that: 1) A user enters data on a website, it is encrypted using a ...
3
votes
4answers
1k views

Asymmetric crypto: Decrypt own messages without having private key

I have built a messages system for my website. Users can send the admin messages which are stored in the DB after being AES-encrypted. I think that using asymmetric crypto (RSA through openssl) ...
1
vote
2answers
5k views

Encrypting string in javascript and decryption in java

I would like to know if someone know any library to do encryption in javascript and decryption in java. I have already tried many API, But getting not not getting same values in java. I want ...