Cryptography is the practice and study of logical means used to achieve information confidentiality, integrity and authenticity. It covers, among other things, encryption (making some data unreadable except for those who know a given secret element, called a key), data hashing (in particular for ...

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121 views

How to guarantee privacy on files that I store

I want to create an Android app where users from an office (typical use) can upload scanned documents to the app backend service for later use. e.g. A lawyer want to upload a sentence ...
10
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2answers
468 views

Forward secrecy for kids

In the Scouts, it is popular to use secret codes to write messages (which are simple ciphers). I want to introduce Forward secrecy to the kids so they can use it with these ciphers. So, if the ...
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2answers
385 views

Google's usage of RC4

I was reading about Google's usage of RC4 and an answer on stackexchange website stated the following: I know Google uses RC4 for most of its services, and this is the reason one shouldn't keep ...
0
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4answers
140 views

How does an encryption key work? [closed]

I'm having trouble understanding how an encryption key works. for example: if the word was 'hello' its encrypted value could be 'GHSSDgsd2', what would happen to the encrypted value if the key was ...
0
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0answers
29 views

How does an encryption key work? [duplicate]

I'm having trouble understanding how an encryption key works. for example: if the word was 'hello' its encrypted value could be 'GHSSDgsd2', what would happen to the encrypted value if the key was ...
1
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1answer
98 views

How to generate Initalization Vectors correctly

I'm working on a project that splits large files into several encrypted fixed-size blocks (e.g. 4KiB). Those blocks shall be used to be stored persistently on a storage device. Blocks are encrypted ...
1
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1answer
496 views

Help to understand secure connections and encryption using both private/public key in RSA?

I just started teaching myself cryptography, I am reading this http://www.garykessler.net/library/crypto.html to understand the basics. I am confused by Sections 3.4 and 5.3. Section 3.4 details how ...
10
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4answers
1k views

Location to store an encryption key

I'm building a secure system which stores messages on a server in a Postgresql database. The messages are stored encrypted with PHP's openssl_encrypt() function with the AES-256-CBC method. At the ...
44
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3answers
3k views

What kinds of encryption are _not_ breakable via Quantum Computers?

There's the recent article NSA seeks to build quantum computer that could crack most types of encryption. Now I'm not surprised by the NSA trying anything1, but what slightly baffles me is the word ...
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2answers
190 views

How secure are the GPG/PGP keyservers?

Importing a GPG key with a KeyID or fingerprint seems to rely on keyservers. Doesn't this invite man-in-the-middle attacks, in which someone would alter the keys to allow them to decrypt the data? ...
1
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1answer
146 views

How to safely use a Key Derivation Function to secure private data - need guidance

I have some secure data created in my client app which I wish to store on the server as backup for the user. The user already has a password to authenticate with the server. The password is never ...
0
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1answer
143 views

How can brute force scripts tell once they're found the correct key?

If you have a random block of data and you encrypt it with a key, how can a brute force script tell when it has found the correct key? Is it possible without some sort of reference to the original ...
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2answers
374 views

Is SSH secure and what are the recommended modes of operation?

Given the recent confirmation of weakened and broken encryption schemes and implementations, how does the community feel about the security of SSH? It seems there has been very little discussion ...
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1answer
124 views

Any issues with this security design for cloud storage? Server doesn't even need to know password to log someone in

I've created an algorithm I think I'm going to use for a cloud storage service I'm developing- if there are no issues or vulnerabilities with it. It's this along with TLS and forward secrecy ...
1
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1answer
54 views

How to change TEA round count? [closed]

I cribbed the public domain TEA source from wikipedia ( http://en.wikipedia.org/wiki/Tiny_Encryption_Algorithm ), looks like this - uint32_t v0=v[0], v1=v[1], sum=0, i; /* set up */ ...
3
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2answers
265 views

What are the pros and cons of using yubikey with ssd hardware encryption?

I'm considering trying out yubikey and I've recently discovered that the (crucial m500) SSD I recently bought supports hardware encryption. I think it should be possible to use a yubikey to provide ...
3
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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 ...
6
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7answers
2k views

Testing a hardware random number generator

The Raspberry Pi has a built in hardware random number generator but there doesn't appear to be any public documentation on the hardware, and even if there were it would be questionable (what company ...
4
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2answers
659 views

Is it safe to use PBKDF2 for hashing?

I would like to get a few opinions on whether it would be safe or not to use PBKDF2 to generate a hash of a password. For my purposes I'd like to assume that the hash itself will be posted on the ...
3
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3answers
130 views

How to make authenticity of text verifiable without third party services?

There is a person who wants to establish a system which allows her/him to publish texts anywhere and make it verifiable that s/he is the true origin of that text. Only the first message is not ...
4
votes
1answer
3k views

How are “security levels” of identities in TeamSpeak 3 implemented?

TeamSpeak 3 VoIP communication system uses a concept of so called identities to identify the client to the server. These identities are basically public/private key pairs. In order to prevent people ...
0
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1answer
213 views

Encrypting content using same secret key as hash?

OK - I'm trying to design a system that can provide personalised/differentiated content at minimal expense to the server. One of the designs I'm currently exploring is where the request is somehow ...
3
votes
3answers
278 views

Can a zero knowledge proof of voting be made using a trusted auth server (without client side crypto)?

Questions: Can one implement a secure voting system having all the features described below? e.g. without disclosing any individual's vote to the government server (or the third party), preserving ...
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0answers
77 views

Putty Event Log

Can anyone explain me the Step by step process of Key Exchange that takes place while accessing Linux machine using Putty ? I found the Event Log of Putty but the Various Key Exchange didn't make very ...
2
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4answers
1k views

Does using WPA2-Enterprise just change the attack model vs WPA2-PSK?

As far as I can tell based on the reading I've done so far, WPA2-Enterprise uses the same encryption and security algorithms and methods as WPA2-PSK, with the addition of using another service for ...
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0answers
39 views

What kind of security do WhatsApp and Viber use? [duplicate]

What kind of security do chat applications implement to preserve message integrity & confidentiality?
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0answers
65 views

Does the ordering of encryption and hashing matter? [duplicate]

I am now learning keyed hash function, where A and B share a secret key k. I want to know if the ordering of encryption E and hashing H matters? i.e. Is there any difference between H ◦ Ek (m) and Ek ...
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2answers
100 views

How to sign and encrypt mails using firefox

There is an option under Tools>options>Advanced>Security Devices. How to use that to encrypt and digitally signed your emails.
19
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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 ...
1
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1answer
107 views

Using secp256k1 and ECDSA with IKE

I just tried using an IKE daemon and EC certificates. I used the secp256k1 curve for key generation. The daemon claims signature scheme ECDSA-256 not supported by private key Now I am wondering ...
2
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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?
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0answers
53 views

Any Suggestion Exchanging shared key between process via port in untrusted machine (infected my malware)?

I am trying to get shared key between Firefox extension and a java program running in same machine. I am communicating both application via socket. My assumption is that malware is running in ...
0
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1answer
91 views

Transmission of messages

I am currently developing a game which will be run in a client, they will sign up for this game online and create their account there, their information will be stored into a MySQL database. I am ...
3
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0answers
112 views

BSD encryption advantages [closed]

If someone who knows about the BSD project has a moment to answer this, I'm wondering a few things about the encryption used. It's more than what I'm finding in the docs and on Wiki/Google (even the ...
0
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2answers
107 views

SSL/TLS Question [closed]

I am currently working on my SSL/TLS assignment and I got a question to ask. What is the use of a login password since it is not needed for establishing secret communication between your computer and ...
2
votes
2answers
218 views

Lightweight block ciphers definition

I've read in many papers something that looks an specialisation of the block ciphers calling them with a lightweight tag, but I couldn't found a definition. If I understand correctly, those ...
38
votes
10answers
2k views

Cryptography that looks like ordinary email

I would like to stay out of the automatic filters in place by security agencies and not be accidentally placed on a no-fly list or such. Say I'm having a political debate with a friend about democracy ...
1
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0answers
162 views

Encrypted chat using any smartphone. Is it legal? [closed]

Here's my case. We have written app for Android smartphones which allows users to exchange secured cipher messages. For key-exchange we're using elliptic curve 112 bits, for messaging we're using DES ...
3
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1answer
291 views

Symmetric encryption with different encryption and decryption keys

In the book, Applied Cryptography by Bruce Scheier, in the foundations chapter he defines symmetric encryption algorithms as algorithms where the encryption key can be calculated from the ...
-2
votes
2answers
130 views

Is this adaptation of using a One Time Pad safe?

For example, lets say there are two people named, Bob, and Jim. Bob wants to send Jim a long secret message, and he decides to use a OTP to encrypt his message. Both Bob and Jim know a secret ...
3
votes
2answers
4k views

Using AesCryptoServiceProvider in C#, should using an incorrect IV mangle just the first block?

This question was also asked on StackOverflow, but with no answers, and I thought this may be a better exchange, since I have the same question. ...
3
votes
3answers
359 views

If the code to shuffle an array is known, is it possible for the randomized shuffle to stay secure?

I recently was looking at Poker shuffles that were hacked and made to be guessable within a reasonable degree and this was because of the weakness of the shuffles. Is it possible to make a shuffle ...
2
votes
2answers
518 views

How to generate cryptographically strong pseudorandom data very rapidly?

What's the best way to go about generating a fast stream of cryptographically strong pseudorandom data without installing uncommon packages? Drawing from /dev/urandom is far too slow. I had an idea ...
8
votes
4answers
672 views

At what point does adding more iterations to PBKDF2 provide no extra security?

If my true passphrase is used only to generate a hash which is used as the cipher's actual key, doesn't that mean it's possible to try and brute force the cipher itself? I know it would take an ...
6
votes
1answer
863 views

Crypter Anti-Virus Test

I have written a very simple/basic crypter in C++ and I would like to test it. How would I go about writing a simple MessageBox program that is "tainted" so that my Anti-virus will attempt to ...
1
vote
1answer
329 views

Don't use encryption without message authentication

The text is taken from the famous answer: Lessons learned and misconceptions regarding encryption and cryptology: Don't use encryption without message authentication Alternatively, you can apply ...
0
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1answer
182 views

At what point is a cryptosystem “rolling your own”? [duplicate]

Everybody knows making your own cipher really sucks. Everybody also knows using existing cryptosystems, such as TLS, totally doesn't suck. But when is the line drawn? For example, would I be rolling ...
1
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1answer
1k views

How is the HMAC key exchanged?

Just wondering about this. Does it need a PKI to work?
2
votes
1answer
553 views

Is there any functional distributed timestamp server available? If not what about this homebrew solution?

Objective A secure Arrow of Time with unpredictable future behaviour to stop attackers or DDoS BotNets from pre-calculating proof-of-work and other gateway protections for P2P/F2F. A distributed ...
3
votes
1answer
150 views

S/Key as an alternative to UNIX passwords

There is this password system called S/Key I saw on the Internet. Can someone give me a brief description about S/Key and how it works? Can S/Key be an alternative solution to the UNIX password ...