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0
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0answers
13 views

why DH is unbreakable and what are the facts that leads to strong DH? [duplicate]

I am new to DH and learned the basic about DH working and suspecting it can be breakable by normal MIM , then how we can use DH in plain http for sharing secret. correct me if i am wrong.
11
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0answers
474 views

Strength and length of Symmetric vs Asymmetric keys [duplicate]

There are many questions surrounding the differences between symmetric and asymmetric encryption keys. I think I've read them all at this point. But I'm still left wondering: Why does a "secure" ...
0
votes
2answers
224 views

Is an >=2048bit key with Asymmetric encryption secure enough to negotiate a Symmetric encryption key?

Let's say that a client app already knows the public key of the server to which it needs to communicate with and the client app needs to connect to the server using a normal non-secured internet ...
1
vote
1answer
141 views

“Inverted” asymmetric encryption

I am developing a system to prevent frauds in tickets. What do I need? An algorithm to generate a QR Code that will be shown to my clients in a ticket. An algorithm to validate (offline) the ...
3
votes
2answers
285 views

How Securely Store Sensitive Data on Mobile Appliation

i want to develop a mobile bank app (windows phone, android, ios) that interact with bank channel. first time when user opens application the key exchange process begins and at end of this process a ...
1
vote
1answer
123 views

All users can write only one can read system

The system I want to implement has the following requirement: All users can insert some sensitive data, but only one, master user, can see it. There is any known, already implemented solution to this ...
1
vote
0answers
45 views

SSL Asymmetric encryption newbie [duplicate]

I am relatively new to the world of cryptography and was wanting to develop a webpage which allows credit card payments. Thus, I looked into the digicert ssl service, hoping that it could do what I ...
1
vote
2answers
167 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
76 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
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4answers
763 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 ...
0
votes
2answers
211 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
86 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
131 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
2answers
425 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
2answers
65 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
165 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
1answer
105 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 ...
2
votes
1answer
389 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 ...
2
votes
1answer
104 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? ...
4
votes
1answer
105 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
70 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
87 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
0answers
89 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
164 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
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3answers
1k 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
140 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
30 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
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3answers
374 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 ...
34
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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
310 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
137 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 ...
-6
votes
1answer
189 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
829 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
272 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 ...
26
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5answers
16k 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
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0answers
97 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
507 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
193 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
439 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
300 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 ...
2
votes
2answers
697 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
69 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
562 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
3k 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: ...
8
votes
3answers
768 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
1k 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
1k 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
718 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
275 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.