The tag has no wiki summary.

learn more… | top users | synonyms

1
vote
2answers
24 views

What's the benefit of hybrid cryptosystem vs asymmetric for small data blocks?

It's a common belief hybrid cryptosystems are better than asymmetric only. Is that allways like that? What's the benefit of using symmetric and asymmetric encryption for small data blocks (< 100 ...
1
vote
1answer
62 views

How long can a pkcs#8 passphrase be?

A program is using a private key to read messages. To improve security, besides randomness, I'm trying to create the longest passphrase that makes sense. How long should it be? After which amount of ...
8
votes
4answers
714 views

Why the symmetric key is added to the message?

Yesterday in my class we learnt how to send a message from Alice to Bob with the achieved goals of confidentiality, integrity and authenticity. In order to have a better performance we use a hybrid ...
-1
votes
0answers
59 views

How do public/private keys work?

I have read "How does SSL/TLS work?" and "Public-key cryptography", and I know basically what happens when using a Public-key to encrypt/decrypt something. To sum up what I've read, A Public-key ...
0
votes
2answers
72 views

Why does ssh `known_hosts` file need server name?

When I push/pull repos on GitHub over SSH, sometimes there will a message about unidentified server and asks if I want to trust and add it to known_hosts. Apparently this is because GitHub has ...
2
votes
1answer
51 views

Is there any asymmetric scheme provides signature with length of 30 bytes?

I want to send short messages to cell phones.Commonly a short message is no longer than 70 bytes. I need 20 bytes or more holding information and the rest bytes are for signature provided by ...
2
votes
2answers
116 views

Receiving sensitive data uploaded on a Web server, and remotely accessing it without exposing it to theft

Edit: I mostly used my university's guidelines on how to meet DPA standards and their own. I extrapolated a bit because encryption on a VM hosted by my uni that is already probably encrypted makes ...
0
votes
1answer
61 views

Does public key auth in SSH prevent most MITM attacks?

I found this article that claims asymmetric crypto signature of DH-obtained key prevents MITM: http://www.gremwell.com/ssh-mitm-public-key-authentication Key idea: The value of 'signature' is a ...
0
votes
1answer
36 views

Public Key Transfer between two Applications

I have a Service written in c# which uses asymmetric Encryption to Encrypt Data, and a client application which Decrypts the Encrypted data received from the service. How can I do the following ...
0
votes
2answers
81 views

Encrypting using the private key in Identity-Based Cryptography

In normal asymmetric crpyto like RSA, if Alice encrypts something using her private key, Bob can decrypt it using Alice's public key. Is the same possible in Identity-Based Cryptography, where the ...
0
votes
0answers
63 views

How can I generate some public and private keys on both sides with low overhead?

We have an Authority Center (CA) generating some public and private keys for each client (more than one pair for each client). One method for sending keys to client is sharing a secret key between CA ...
0
votes
1answer
79 views

How secure is GPG symmetric encryption?

Since I am new to encryption and have recently been losing stuff, I decided to start a file that contains some passwords for online accounts and whatnot, encrypt it, back it up (and keep a single copy ...
1
vote
1answer
78 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? ...
3
votes
1answer
79 views

Recommended operational security for generating one's primary key pair?

I have been looking for an operational security guide for generating one's asymmetric key pair for (Open)PGP. I have found plenty of technical guides for how to use GnuPG to generate RSA key-pairs, ...
2
votes
1answer
59 views

Reducing asymmetric authorization token size

I would like to use an asymmetric rather than symmetric signature for authorization, since I don't want a compromised service being able to forge authorization tokens (obviously). An authorization ...
0
votes
1answer
83 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 ...
0
votes
0answers
49 views

Passing Encryption Key Across Session for Symmetrically-Encrypted DB

I'm building a database that symmetrically encrypts user data. Nothing super sensitive, I'd use a third-party if it was. The data is encrypted with a surrogate key; the user must enter a password to ...
0
votes
2answers
118 views

Asymmetric Data Storage+ No-Hash Password Storage?

Edit: removed a part of the original question; I'll break it down in a different post. I am following @Polynomial's answer to store information in a database. Here are my requirements: Only the ...
1
vote
3answers
406 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 ...
1
vote
2answers
86 views

If I change any character in a private PEM, should the public PEM be different?

I'm generating a public PEM-format key from a private PEM-format key. I noticed that if I change a few characters near the end of the private PEM that the public PEM generated from the modified ...
1
vote
1answer
28 views

Encrypting multiple blocks with an asymmetric scheme

I have a general question how asymmetric schemes are usually implemented. Typically, there is a parameter in an asymmetric scheme which limits the message length. For example the modulus in RSA. I ...
0
votes
3answers
177 views

Why is symmetric encryption still used? [duplicate]

In symmetric encryption, the key responsibility is for the two parties involved (sender and receiver). Hence, it can be more vulnerable, and can cause accountability issue in cases ofthe key is ...
32
votes
7answers
4k views

How dangerous might be publishing a public key?

Maybe this question sounds obvious, but I wonder how dangerous might be publishing a public key for an asymmetric encryption system? I know public keys are meant for encrypting messages by anyone ...
3
votes
3answers
227 views

Why do you need to encrypt symmetric key?

I'm reading this pki article and as you can see near the bottom, the quick animation and description: The sending computer encrypts the document with a symmetric key, then encrypts the symmetric ...
0
votes
1answer
100 views

Key-Exchange Algorithms VS Local Key Generation?

I was wondering the difference in term of Security, Computational cost and Network overhead between the use of : A Key-Exchange Algorithm (e.g. Diffie–Hellman) to set up a symmetric key. The ...
-5
votes
1answer
149 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 ...
2
votes
5answers
499 views

Is asymmetric encryption vulnerable to man-in-the-middle attacks?

I'm looking for ways to send private messages over a public channel, and in doing this I stumbled in asymmetric encryption, which is just perfect for what I was looking for at first - A and B ...
3
votes
7answers
259 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 ...
19
votes
6answers
8k 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
82 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?
2
votes
1answer
372 views

How can I secure IP Multicast traffic?

I'm interested in securing IP Multicast traffic for content that will be sent globally with several low bandwidth receivers. I understand that simplified Broadcast encryption takes N public keys ...
1
vote
2answers
176 views

Can any asymmetric algorithms work with only a key-sized amount of randomness?

With 397 rolls of a fair 6-sided die (not my favorite use of time, but certainly not infeasible), I could generate more than 1024 random bits. Could I use those bits to generate a keypair that could ...
0
votes
2answers
341 views

Storing email adress encrypted but deterministically

As part of an application I am developing, I am required to store user email adresses on a cloud DB. The email address is not required to be in plain text for the normal operation of the application. ...
23
votes
5answers
3k 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
212 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
2answers
592 views

How to store Encryption Key on Shared Hosting?

I am currently designed Simple Online Patient Management System, but according to country Rule, sensitive data should be encrypted when used online, I did the encryption, and all sensitive fields ...
1
vote
1answer
67 views

Hybrid Encryption System - Is this unnecessary in this case? [closed]

I have a column in my database that I need to encrypt. The column can contain any arbitrary data. What I am thinking is to generate a public and private key pair first. Store the public key in a ...
1
vote
1answer
508 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 ...
2
votes
1answer
2k views

How to encrypt a short string to a short ciphertext using an asymmetric encryption?

I am using RSA to encrypt some text, so my system has already generated private and public keys. These keys I would like to use to encrypt/decrypt a short text (16 chars). The main condition is: ...
7
votes
3answers
609 views

Is it possible to prove which public key was used to encrypt a message?

Pretty much the title: If Alice sends a message to Bob that she encrypts with Bob's public key, is it possible for Eve to prove that the ciphertext was encrypted with Bob's public key, that the ...
1
vote
1answer
943 views

How to use public key in ~/.ssh for asymmetrical encryption with OpenSSL

I want to do an asymmetrical file encryption: openssl genrsa -des3 -out private.key 4096 openssl rsa -in private.key -pubout -out public.key openssl rsautl -encrypt -pubin -inkey public.key -in a ...
6
votes
1answer
948 views

Why a symmetric key for HMAC?

I am working on securing a RESTful API and am using the Amazon AWS HMAC model as my guide. I am struggling with coming up with a secure way to store the symmetric keys on my end. What is the standard ...
2
votes
1answer
592 views

How large RSA-keys could the worlds combined computer power factorize in reasonable time?

If you combined every microprocessor on earth into one humongous computational cluster, how large RSA-keys could you factor in reasonable time (lets say a few years)? I know from reading the answers ...
4
votes
3answers
252 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.
7
votes
2answers
607 views

What asymetric scheme provides the shortest signature, while being secure?

I've had a look at several signature schemes (DSA, ECDSA for the most common ones), and am wondering about whether there exist a scheme that would have the following properties : Be asymmetric (one ...
13
votes
3answers
3k 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 ...
0
votes
1answer
666 views

Can I ensure that a public key derived from a private key is unique?

In asymmetric cryptography, is it possible to ensure that public key derived from a given private key is unique, no matter the algorithm?
4
votes
1answer
237 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
4k 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 ...
3
votes
3answers
7k views

Encrypt data within mobile app and send to web service

I'm developing a mobile application for Android and iOs. What is best practice when it comes to data encryption within the mobile application which will be sent to a web service? Basically I will ...