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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Public and Private key encryption in simple math

Can anybody show me (or point me to resource) how to generate public key and private key with simple math? Steps which can be reproduced in a simple calculator – so the message, keys all can be ...
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94 views

Modulo settings for successful encryption?

I saw this awesome video which shows how encryption works using "discrete logarithm". The example says: $3^x\mod17$. I understood that $3$ is called “generator”, because it has no "straight" root and ...
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297 views

Commutative Encryption with RSA scheme?

I wanted to know how I could manage to do what I'm going to tell you next, with the RSA encryption/decryption scheme. So Alice and Bob each have a public key $(n, e)$ and a private key $(p, q, d)$; ...
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Want to use ECC but am clueless [closed]

First off, I'm not an experienced cryptography or computer person, please bear with me. I have some basic experiences with PGP software though (not much of a redemption huh?). I have some data that ...
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23 views

Is TLS_RSA_WITH_RC4_128_SHA still a secure cipher to use? [duplicate]

I have read numerous times that the RC4 cipher itself is considered broken in TLS. Still many websites are using the TLS_RSA_WITH_RC4_128_SHA configuration even to date. Now, I know that sometimes ...
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How to decrypt a text which is ciphered same length key? [duplicate]

I have ten piece of ciphered texts. I know that they ciphered with a same-length key. Any idea how I can decrypt the ciphertexts? What kind of algorithms should I use? What are the points of taking ...
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101 views

Cryptography Implementation in software

I am trying to implement a password manager in C and I had a question about the proper steps in implementing the crypto. I looked at some implementations, google talks on crypto and what the standards ...
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1answer
142 views

Sequence of Encrypting RSA like Chaum Blinding scheme

I'd be a noob in cryptography but reading up a little on RSA, I do get some understanding and I want to specifically resolve this issue. UPDATED Lets say we have the following values in place: ...
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125 views

El Gamal encryption scheme and symmetric encryption scheme

Consider the El Gamal encryption scheme, a symmetric encryption scheme (KG,E,D), and the following hybrid encryption scheme having an encryption algorithm that, on input a public key (G,q,g,h), where ...
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121 views

How we transfer 128bits cipher to a 4x4 matrix for AES input?

Why the input cipher for AES encryption, can write in 4x4 matrix with 8 bits entires, and can said is 128bits? if each cell is 8bits in binary, how we said this matrix is represent 128bits?
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Index of coincidence for completely random text over k alphabets

I'm confused about /Friedman's method 2 (using a table with column of k size of key, and n/k rows, n is the total size for cipher text) \begin{equation} m = ...
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26 views

Is there a flaw in whole disk encryption vs volume or folder encryption? [duplicate]

My company just implemented whole disk encryption on all laptops (Symantec) and the concept seems flawed. Please correct me if I'm wrong, but if I have known file in plain text and that same file in ...
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214 views

Rainbow tables and blowfish

I'm thinking of implementing rainbow tables for a specific blowfish problem, but I have trouble thinking of the proper way to apply the original paper (and its application to hash functions) to ...
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135 views

Which hardware-accelerated AES-GCM implementations support encryption in-place? [closed]

By encrypt in place I mean the following. Suppose I have an input plaintext of length L and I have also allocated an extra E bytes at the start and/or end of the buffer, with E << L. So the ...
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42 views

Retrieve cryptographic key knowing cyphertext and plaintext [duplicate]

I was curious about cryptography so I started to learn about symmetric encryption. From what I understand a symmetric encryption works as follow: PlainText -> (Encrypt)K -> Cipher text -> ...
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173 views

Rabin code same message sent with different $N$

I use Rabin code with modulus $N$. Now assume that Alice sends me a message $m$ $(1\le m\le N)$ encoded by Rabin code. Unfortunately after Alice sent me the text I lose the information about the ...
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125 views

Can you show how that RSA does/doesn't provide anonymity?

Considering a CPA-secure version of RSA where the ciphertext is just a rundom element from $Z^*_N$. Does that meet the anonymity requirement in which an cpa adversary cannot distinguish between a ...
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53 views

AES and Known-plaintext attack [duplicate]

Can you help me to finding some papers that shows AES is secure against known-plaintext attack?
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1answer
100 views

Creating a secure key

Imagine that your lecturer and the undergraduate office have conducted a key exchange protocol after which both of them hold the string $X$. Yet, it is possible that a curious student sitting next to ...
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102 views

What scheme will allow merging and splitting the result of a function?

I am wondering if it's possible to have a scheme as follows. Here is the scenario: we have a set of objects (e.g. strings) {O1, O2, ..., On} we have a set of users {U1, U2, ..., Um} each user asks ...
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115 views

Cryptanalysis not based on method used to encrypt? [closed]

When doing cryptanalysis on RSA or something number theory based, there are various attacks that all seem to involve number theory (Wikipedia: RSA_(algorithm) ~ Attacks_against_plain_RSA). Similarly, ...
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156 views

PGP encryption options

I recently began using PGP desktop and found several options for my encryption capabilities. Which of these (AES, Cast, Triple DES, TwoFish, IDEA) is the most recent, firstly, secondly may the NSA not ...
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574 views

Decrypting a message without the private key using CRT

I am given 5 different encryption modulus, $N$, each ranging from 78 to 88 numbers long. Then for the encryption exponent, each has the same which is 5. Then I am given 5 different encrypted messages, ...
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How does a cracker know if they've broken AES-CBC encryption? [duplicate]

How does a cracker know if they've broken CBC or stream encryption? With hashe cracking one would know because you have the password that you started with to test. But for CBC decryption, you have a ...
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221 views

IV and Headers inside cipher text

I am a bit confused about the use of IV, and key hash. Is the key hash and IV stored inside the headers of the cipher text? Isn't it a security risk to store this header information? By key hash I ...
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openssl logs showing keyblock length of only 88 bytes instead of 136 bytes

I was decrypting TLS encrypted data from wireshark using the openssl(TLS1.0 version) TLS logs which provides the complete key block which of size 136 bytes.Now i moved to TLS(1.2 version) in that Key ...
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386 views

Non-malleable file encryption using AES XTS 256?

I'm looking to do file encryption of a bunch of individual files, some small, some quite large. The files will be write-once/read-many, so I could use CBC, however, since the read-access needs to ...
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71 views

Will D-Wave's quantum computers ruin classical encryption? [duplicate]

D-Wave has commercially available 512-qbit quantum computers now. A lot of big names are taking it seriously. Google, NASA, and USRA have joined forces to start a quantum AI lab. How far are we ...
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50 views

Conditions for proving that a signcryption scheme is secure

If I'm able to prove that any scheme satisfies confidentiality ad unforgeability conditions, will it be a valid signcryption scheme, without explicit signature and encryption parts ?
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114 views

Is OAEP reversible?

Given nothing more than some integer $m =$ OAEP($M$), is it possible to recover the original plaintext $M$? In other words, without being given the hash functions or the random string used for ...
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532 views

How compared encryption algorithm in terms of efficiency

I want to compare two cryptographic algorithms. The first algorithm is RSA, and second algorithm is ElGamal elliptic curve cryptography. Now, I’m looking for a way to compare the speed of the two ...
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220 views

Is TOTP or a timestamp encryption a better timestamp-based authentication token system?

Are there advantages to using TOTP over encrypting a timestamp with a shared secret, in cases where the readability or ease of typing the token are not important?
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1answer
216 views

NTRUEncrypt - Choose the initial random polynomial

I'm trying to implement NTRUEncrypt but encounter some problems. I've finished all the basic functions that are needed for the scheme base on this Document, but I can't find an algorithm to check the ...
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81 views

Two untrusted party want to exchange data: how to ensure each one gets the data it needs? [duplicate]

Possible Duplicate: Two untrusted party want to exchange data: how to insure each one gets the data it needs? I am trying to come up with what could maybe be a novel algorithm for an ...
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2answers
186 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
222 views

problem with “one time pad” [closed]

I am a french student and I read the post on the forums (How does one attack a two-time pad (i.e. one time pad with key reuse)?). I need your help if possible. I 'm 11 encrypted messages , all ...
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438 views

Is it possible to generate a 6-digit number using 256-bit encryption?

Reading through some documentation on a piece of software, it claims that a 4-6 digit number is created using a 256-bit encryption process for the purposes of access control. The whole process works ...
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3answers
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Does knowing common prefixes help crack blowfish?

I have strings that are if the form: {static data}{changing data} The beginning static data part is around 20 characters and is common to all strings. The last ...
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5answers
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Why can't you decrypt an encrypted message with just the public key? [duplicate]

How does asymmetric crypto work? For example, if you use PGP in emails, you generate a private key that is known only to you and a public key, which is available to everyone. Is there a simple way ...
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2answers
246 views

Why are these techniques not feasible to crack RSA?

For $d = e^{-1} \mod \phi(n)$ $$d\cdot e \operatorname{mod} \phi(n)=1$$ $$d = (e^{-1} \operatorname{mod} \phi(n))$$ With having $e$ and $n$, we can calculate the value of $d$ , the private key for ...
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3answers
220 views

Is there a way to break this encryption?

I was wondering about making up a simple system to encrypt a file: ...
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2answers
1k views

RSA PCKS1 v2.1 RSAES-OAEP algorithm

Using RSA public key (n,e) the encryption of a message is c= (m^e) mod n and the corresponding message is decrypted as ...
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Is it safe to encrypt data by simply randomizing chunks based on a permutation?

Say I want to encrypt the following text: "Today is March the 22nd, 2015". And say want to encrypt 8-byte blocks of data using the following permutation [6,3,0,1,5,7,2,4] to swap characters at those ...
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3answers
218 views

When is a cipher considered broken?

We've all read how some people claim AES is broken because there was supposedly a way to get the plain text from a cipher text faster than brute-force. But is this the definition? Is a cipher broken ...
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Pi Message Encryption [duplicate]

I created a simple yet efficient message encrypting page that will encrypt messages using Pi. Though not being an expert in this area, I am nowhere near sure how secure this is and how easy it would ...
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2answers
228 views

Encryption of a number with RSA bigger than $n$

I'm having trouble understanding why encrypting a number $m$, which is larger than $n=p\cdot q$. I've looked into the following threads: Why RSA can't handle numbers above 76? Why does plain RSA ...
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2answers
513 views

One Time Pad Question

I have a ciphertext encoded with One Time Pad. I do not know the key. How can I find the possible keys which when decoded, will result in a meaningful plain text?
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101 views

Can AES be considered as Perfectly Secure?

I am studying about the AES encryption standard, and as I know from the theory there is no known weaknesses today about this block-cipher. I would like to find out or at least to understand what ...
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Are modes of operation algorithms practical?

I took a cryptography class back in college, and now that I am working my 1st career one of the things currently on my plate is coming up with an algorithm to encrypt data before it's placed on the ...
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Strategy to crack a presumed substitution cipher

The ciphertext given is: ejitp spawa qleji taiul rtwll rflrl laoat wsqqj atgac kthls iraoa twlpl qjatw jufrh lhuts qataq itats aittk stqfj cae I've done ...