Encryption is the process of transforming plaintext using a cipher into ciphertext to make it unreadable to anyone except those possessing the key. Decryption is the process of transforming that ciphertext back into plaintext, using the key.

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How to compare between the result of two cryptography algorithms in term of security?

How to compare between the result(hashed Value) of two cryptography algorithms in term of security? To proof that x algorithm is more secure than y algorithm.
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1answer
58 views

Drawback of ElGamal encryption

I am trying to find out some disadvantages of ElGamal cryptography but I'm not able to figure out what's wrong with the algorithm. The only one I found is that a known-plain text attack is possible in ...
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1answer
40 views

Are there cryptographic schemes that mask as unencrypted traffic?

Are there cryptographic schemes that make encrypted traffic look like unencrypted traffic?
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2answers
52 views

Why would cryptography fall apart if there were a finite number of primes?

I vaguely know that prime numbers are very important in cryptography, but I assume for most encryption methods, they tend to stay rather 'small'. Are we really using massive prime numbers for ...
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0answers
19 views

Recommendation for encryption of db fields [on hold]

Looking for java library who is capable to encrypt db fields of postgres 9.x database
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2answers
47 views

How obvious is it to decrypt numerics encrypted with a reused one time pad?

For instance say you encrypt text using the one time pad and you end up with some scrambled text that appears illegible. If you reused the key for multiple times for enough text, someone could ...
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1answer
49 views

Twofish vs. Serpent vs. AES (or a combo)

I've seen some posts and info online, but they are from 2009, 2010, 2011 or 2012, which is 3-6 years ago, which is a very long time. So I'm looking for an up-to-date answer about which of these is the ...
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1answer
53 views

Multiple keys for the same ciphertext [duplicate]

Say you have a plain text: How are you today? and you encrypt it so it becomes: LKD03Loel03skj1Q03 Now you have multiple people that need to know the plain text of this cipher text but ...
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2answers
51 views

Are there any known weaknesses with ElGamal algorithm?

I am working on a messaging system and plan to use ElGamal asymmetric encryption to protect the message contents during storage and transmission. (This would be in addition to TLS used during ...
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3answers
274 views

decrypt numbers multiplied by a certain floating point number

A friend has about 10K numbers in a an excel sheet. He wanted to encrypt these numbers in order to share the file with a 3rd party that will help him reorganize the tables. What he did, to hide the ...
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2answers
169 views

How to choose an algorithm

I have some understanding of Cryptography and I would like to know if there is a tool or website to help me choose an algorithm based on my own needs (I'm being vague in purpose). I'm looking for a ...
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6answers
8k views

Difference between encrypting something and hashing something

What is the difference between encrypting something and hashing something? in what situations would I want one or the other?
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1answer
58 views

Hashes and Ciphers [on hold]

So I'm brand new to cryptography, I'm confused on a few fundamental issues, and my normal avenues of research aren't bearing any fruit. I'm hoping someone can describe the relationship between ...
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1answer
47 views

Send an encrypted question and return answer without decryption

Oke bear with me for a minute. Once upon a time someone mentioned a hypothetical way where you would send an encrypted question to Google and Google would return an answer without decrypting it. As ...
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0answers
8 views

Acceptably secure solution for users to log in with a short unique code only (no username) [migrated]

I am creating a website whereby users are given an account by invitation only, and are sent a unique code by post. Users can then log in (at least the first time) by entering the code only. The goal ...
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0answers
38 views

websites to have people break encryptions [closed]

I have built an encrypted text editor and was wondering if there were sites out there that you could post encrypted text and have some actual smart people try and break it. I would like to test this ...
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4answers
13k views

Can you help me understand what a cryptographic “salt” is?

I'm a beginner to cryptography and looking to understand in very simple terms what a cryptographic "salt" is, when I might need to use it, and why I should or should not use it. Can anyone offer me a ...
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0answers
30 views

RSA key pair generator in “C” - HELP [closed]

So, here's my problem. Every single library i try to compile (OpenSSL, WolfSSl, PolarSSL) an other not very know gives me error on compiling to. Everthing gives the compiler a reason to just don't ...
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2answers
130 views

How to show that a function is not a PRP?

So I have to answer these questions, but I honestly have no idea what I am doing or where to begin. Can I get some advice on how to tackle these? Consider a PRP candidate function $f$ on $K = X = ...
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3answers
139 views

Brute force against computational security

One-time pad is secure under brute force with respect to either of the definitions \begin{align} \Pr[M = m] &= \Pr[M = m | C = c]\\ \Pr[C = c | M = m_0] &= \Pr[C = c | M = m_1] \end{align} ...
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0answers
34 views

How do you encrypt text using an LFSR?

How do you go about encrypting text using an LFSR? Could somebody provide an explanation and possibly a small example please?
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0answers
27 views

Substitution-permutation network

Can anyone in 6th grade English explain the steps in the Substitution-permutation network algorithm or just point a link that does so? (which is included in many of the top modern algorithms) ...
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0answers
24 views

how do u find the encryption/hash technique used in a string ? [closed]

here I have a String %63%6f%6d%6d%65%6e%74%65%64%20%63%61%6c%6c%20%74%6f%20%64%65%66%69%6e%65%64%20%6c%65%74%6d%65%69%6e%61%67%65%6e%74%6a%61%78%28%29 how to find the hash/encryption technique used to ...
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1answer
78 views

Figure out the encryption being used [closed]

There is a web API (for a game) that sends and receives data encrypted in hex format. I'm interested in accessing the api outside of the game client (mobile app). When sending a request with an ...
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1answer
57 views

Why would using a random seed with other variables be bad for ecrypting if you can't guess the key?

I asked this on stack exchange with it being code based, but someone suggested to ask here. Basically, I've done a script in python and wanted an option to encrypt the input, but I couldn't get any ...
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0answers
44 views

How does double-encryption work with a client server model

With mobile applications like Accompli (now the base for the Android Outlook application), credentials are stored. Reading from the Accompli website: Each user’s credentials are double-encrypted ...
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2answers
132 views

Given infinite unencrypted and encrypted texts, can I find the algorithm?

Given an infinite amount of both unencrypted and the corresponding encrypted text, would I be able to calculate the algorithm? I am relative new to cryptography and don't know if I would be able to ...
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1answer
182 views

What is the period of a cipher?

For the following explanation of RC4: It is a variable key-size stream cipher with byte-oriented operations. The algorithm is based on the use of a random permutation. Analysis shows that the ...
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0answers
41 views

Crypto hash function vs encryption algorithms

Why is a cryptographic hash function generally faster to execute in software than conventional encryption algorithms such as DES?
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3answers
626 views

Can I jettison MAC if I already have SHA1(M)?

I'm currently using SSL with AES-CBC and HMAC for a file transfer containing string M. Now suppose Alice already knows SHA1(M) (and the adversary does not), and she downloads M from Bob using only ...
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0answers
44 views

Encryption - How to find $\sigma$?

Alice communicates with Bill using an encryption system of type Feistel. Specifically, each block has a length of 128 bits, the algorithm has 4 rounds and the common secret key of Alice and Bill is ...
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1answer
52 views

Is it necessary to encrypt nonce in cryptographic communication?

Server and client have a pre-shared key K. Assuming that that pre-shared key is safe, so nobody other than server/client can encrypt/decrypt. Client sends a nonce N to server, server then sends back ...
4
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2answers
549 views

Is there a security analysis of CryptDB?

It's interesting to see critical thinking being applied to CryptDB in contrast to all the hoopla around it here. CryptDB is not a major theoretical breakthrough but potpourri of technologies to make ...
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1answer
46 views

How does the attacker include input before compression and encryption in CRIME?

I have read this article about the CRIME attack against TLS and SPDY. The article says that: What is not yet clear is how the attacker is including their input in the source material before it ...
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5answers
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How easily could this be cracked?

I'm looking into encrypting files like this: First, I SHA-1 hash the password. Let's say the password is something normal like "hello123", and then hashed. Then I encrypt a file using this: ...
4
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2answers
234 views

Can we say that if $P=NP$ there is no CPA secure public key encryption?

I've learned that public key encryption is based on the problem of Discrete Log (as regard to group theory) which believed to be hard. But, can we say that it doesn't matter on which problem our ...
2
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2answers
71 views

Does key derivation with known parameters add any security?

First up: this is a question about a concept that I try to wrap my head around; it is not about the specific implementation. Anyway… I have the following scenario (simplified to show the problem I ...
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2answers
64 views

General questions about cryptography for password security

I'm pretty new to this and find it quite interesting, but my brain won't process how it works so I have to ask some questions :) Why is cryptography used? Is it for extra security once the password ...
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1answer
48 views

Text in random image encoder: is it flawed?

I have created a small cryptographic programme: You input your text A random image is generated Random coordinate pairs in number equal to the chars of the message are generated. The red component ...
2
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1answer
62 views

How to construct the blind factors in practice?

I'm Implementing a protocol that uses masking techniques (or blinding factors), so we can mask a value $y_0$ as $m_0=y_0 \cdot r_0$ where $y_0 \in \mathbb{Z}_p$ and $r_0 \stackrel {R}\leftarrow ...
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3answers
767 views

Why does the recommended key size between symmetric and asymmetric encryption differ greatly?

In various articles it is mentioned that for secure communications, the recommended key sizes are 128-bit key size for symmetric encryption (which makes it $2^{128}$ possible keys?) and 2048-bit key ...
5
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3answers
1k views

Analogue encryption algorithms

I have a basic understanding of how strong encryption works on digital data. Bits can be changed so that they appear completely random and map one-to-one back to the original set, given the correct ...
2
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1answer
232 views

AES encryption takes more time to decrypt than encrypt

I am trying to find how much time an AES encryption and decryption takes for a given amount of data and key. In all the cases encryption takes way lesser processing time than decryption. I tried to ...
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1answer
91 views

Misunderstanding Broadcast Encryption

I have a secret message which I want to encrypt such that any of several different keys can open it independently. The keys can't know about each other and it has to be able to work completely ...
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2answers
68 views

Remove padding (CBC) from decrypted text

I have a bit problem with padding. Everything goes fine when I encrypt the text BUT when I decrypt I see some extra characters. Sometime's one character sometimes more and I dont know how to remove ...
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3answers
90 views

Simple multiplication as an encryption method

There was a time when I wondered about multiplication as an encryption operation. That was when I was thinking in terms of modular multiplication. But how about based around simple multiplication. ...
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1answer
56 views

Additional Data in AEAD (Chacha20-poly1305 libsodium)

I have recently been playing with Chacha20-Poly1305 with libsodium, and all of the examples state the additional data portion of the tag is stored in plaintext when encrypted. But from what I can tell ...
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2answers
103 views

Client-Server application how can data be encrypted so only clients can read it

Requirements We are building a system that connects multiple clients through a restful API. It allows the creation of groups of trusted clients. We need a way to store group shared data encrypted ...
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0answers
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compression with codebook and Cryptography

a question about the difference between code book based compression method and key based cryptography. As I know Crypto != Compression. The Shannon said Crypto is try to reduce the information of ...
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1answer
59 views

FEAL-4 Fk Function 4 Rounds

As I understood in FEAL-4 it needs 4 pair of round keys. Which means that we need to launch Fk function 4 times, but the problem occures on the 2nd round. At first round we have original 64 bits key ...