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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Secure method of encrypting data within a database

I'm designing a program which makes queries to a database stored locally which could potentially contain a lot of sensitive information. As such the information must be kept secure as possible from ...
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Standard format to encode AES cipher and random IV

As far as I understood, a secret key (same length as CBC block size) and an initialization vector (IV) are needed to decrypt a AES-256-CBC encrypted string. As the IV should better be random, it has ...
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Why would you use a weaker hash function than cipher strength?

Some cryptographic libraries (like “Bouncy Castle”) support many modes where the maximum number of bits which can be produced by the hash are significantly fewer than the cipher strength. For ...
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Implementing forward secrecy in OpenPGP with public key authentication

I am trying to consider the feasibility of implementing an encrypted file sharing system, which both provides forward secrecy but also allows public key verification. I am stuck on the marriage ...
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Image sharing without data overhead

The idea is to share $n$ images among $n$ persons so that all images can be reconstructed by someone in possession of all shares. However, there must not be any data overhead (which means the shares ...
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Can a secret message be securely transmitted within a MAC tag?

A sender wants to transmit an ultra secret code $M$ which could be either 'go', 'stop' or 'wait'. This could be any selection of code words really and adopted for any use such as transmitting short ...
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470 views

Efficient AES - Use of T-tables

I'm really in trouble! I'm trying to understand how the T-tables in AES encryption work. But I don't know if I get the point. What I understood is that they are used to reduce the whole computation of ...
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222 views

Why must IV be sent with each packet?

I was reading about Encrypt-then-MAC and everywhere I go it seems people include the IV with the ciphertext generated for each message then MAC that and send all the information concatenated. Why do ...
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249 views

Decode message $m = p * q$, where $p ^ 5 \bmod N$, $q ^ 5 \bmod N$ and $N$ are known

I been going through some cryptography exercises and stumbled across this problem. Discover message $m$. You know that $m = p * q$. Also $p ^ 5 \bmod N$, $q ^ 5 \bmod N$ and $N$ are known ...
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Calculating amount of time for brute forcing ciphertext depending on the size of the key

I am a graphic design student and for my information graphic project I have chosen the topic of the history of encryption and how the security level developed over the centuries. It’s basically an ...
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Determine the Key given ciphertexts and plaintexts?

Given two sets of plaintexts and their corresponding ciphertexts, how does one determine the key $K$? The ciphertexts are: $$C_1= (P_1 \oplus K_0) + K_1$$ and $$C_2= (P_2 \oplus K_0) + K_1$$ $K = ...
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iOS Data Protection: What is the Input of the LFSR?

Every time a file on the data partition is created, Data Protection creates a new 256-bit key (the “per-file” key) and gives it to the hardware AES engine, which uses the key to encrypt the ...
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Is there a field guide to ECC for the IT Security layman?

I'm trying to understand ECC from an IT layman's perspective and am trying to separate the theory from the standards, and understand why certain features are implemented or not implemented in the ...
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Distinguish messages

Since i cannot comment on questions, I give my own: If a secret key encrypt algorithm can encrypt messages of arbitrary length and the encrypt algorithm is probabilistic then: suppose the adversary ...
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381 views

Encryption scheme with equivalent keys?

I've long been looking for a symmetric encryption scheme (or algorithm) with equivalent keys. Let me define what I want: Symmetric encryption algorithm with encryption function $E_k$ and inverse ...
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230 views

Safely use CryptSignAndEncryptMessage?

I am developing an application that sends messages which I want to encrypt and sign. The CryptoApi offers a function called CryptSignAndEncryptMessage. The description says, what this function ...
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Explanation of part of a visual cryptography algorithm

I have been working on a project involving visual cryptography and I am stuck with the following problem. My question is related to this paper, AN IMPROVED VISUAL CRYPTOGRAPHY SCHEME FOR SECRET ...
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Has anyone heard of matrix-based “Russian Doll” encryption techniques?

I've been told that prime-number factoring is based on a "russian-doll" sequence of matrices, where a seed matrix of height Y and width X exists consisting of all zeros except for a single 1 at row Y ...
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What are the vulnerabilities of this homemade encryption algorithm? [closed]

I decided to program a relatively trivial encryption algorithm in my downtime. This algorithm takes a seed from a user (supports floating point seeds), and then adds 1 to the seed for every iteration ...
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Managing data permissions/access through asymmetric cryptography

I want to manage authorization, as 3rd-party permissions, through asymmetric cryptography. I'm concerned about how is it possible to share access of encrypted data with N entities, and be able to ...
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Secure Deduplication and Encryption in a data store

Assume: We have a centralized data store that can store whatever we need Every user is online Function $f : File \to Key$ gets access to the store, and is the same for all users. $g : Key \to File$ ...
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Pseudo-Hadamard transform, most significant bit

For clarification: The Pseudo-Hadamard transformation is a reversible transformation of a bit string that provides cryptographic diffusion. Splitting a bit string (with bit length of $2n$) into two ...
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Paper about this secure P2P idea?

Two or three years ago, I was reading something interesting, but then I lost the paper. The paper described building secure and fast P2P networks (not like tor or I2P). Unfortunately, I only remember ...
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Increasing the diffusion of the AES-CBC encryption algorithm in pycrypto for python

When encryption is done using the AES-CBC algorithm, the encryption can be thought of as chaining the cipher texts with the previous ones and an IV. However, if its on CBC mode, we give our cipher ...
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Which encryption method supports random reads?

I have a file containing 16-bit samples and I want to encrypt it, but the problem is that I need to be able to read any random 16-bit value from the file, and be to able to decrypt it, without reading ...
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Using single EC cert/keying material to derive symmetric encryption key (for storage)?

The situation involves a single party (single certificate) who would want to AES encrypt a file that they can later decrypt. Assume the EC certificate + EC keys have a purpose i.e. "File encryption" ...
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MD5 encryption in Windows batch script [closed]

I am making a script in Windows batch to have a registration and login system that stores the passwords in a SQL database using SQLite. I need a command line MD5 encryption program to encrypt the ...
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Reordering non-block-aligned parts with DES in ECB mode

I was given a ciphertext file which was encrypted using DES in ECB mode. It is known that the plainttext that was encrypted has the following form: Each line of text consists of a payroll followed ...
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How to submit a new method of encryption?

I came up with a truly new method of applying modulo-2-addition encryption function in stream ciphers which is inspired by a mechanism used to prove a mathematical theorem. How can I determine whether ...
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Is python a secure programming language for cryptography?

I know Python is a powerful programming language but is it secure for cryptography? I mean is it possible to reverse engineer the program (written in python) and discover the algorithm of cryptography ...
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How does one scale encryption strength upwards from 256-bit?

I have seen many examples of encryption up to about 256-bit. But how does one programmatically scale the logic upwards in a language such as PHP or Java to say 1024-bit or even 4096-bit and higher? ...
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Encryption vs. decryption of same plaintext

Does the same encryption algorithm given the same plaintext always produces the same ciphertext? Does this cause any security flaws?
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Practical brute-force attack on 128 bit encryption

In brute-force attack calculations cryptographers say we should assume an attacker will find the key after $2^{(n/2)}$ tries. If n=128, then n/2=64. We know that this is practical (A 64 bit key is ...
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why DES encryption uses different modes like ECB,OFB?

As without using modes we can also encrypt and decrypt data then what is the need of using modes in DES?
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Could the Enigma algorithm be classified as a Feistel network?

The Enigma algorithm is a encryption method that was developed (I believe) by the Germans in WWII. It went a little something like this: When a letter was typed on the keyboard of the Enigma ...
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Which encryption method supports random reads?

I have a file containing 16-bit samples and I want to encrypt it, but the problem is that I need to be able to read any random 16-bit value from the file, and be to able to decrypt it, without reading ...
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696 views

What is the actual difference between security through obscurity and true encryption?

In an abstract sense, aren't both the same? Don't their definitions boil down to the following? security through obscurity: trying to make sure some information cannot be obtained without knowing ...
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Can hashing become encrypting?

hashing some data and encrypting data share some similar attributes. Surely this is why "Difference between encrypting something and hashing something" has been asked. The point of this question is ...
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A mathematical explanation of the DES encryption system

I need a mathematical explanation of what does the DES encryption system really do. This means I need more explanation than the one that offers FIPS, which is more an explanation for computer ...
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Are there ANY text strings that will generate the same SHA-512 Hash output? [duplicate]

Are there ANY text strings that will generate the same SHA-512 Hash output? Please provide an example, and how you came to that conclusion. I've tried thousands of variations, including ".." vs. "." ...
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Is it safe to encrypt random data using ECB mode?

If I have 48 random bytes, is it safe to encrypt them using ECB mode? Or is there still a good reason to use another mode like CTR, CBC, etc.? Context is this: I am creating something like a TLS ...
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Is my pseudo-random initialization vector secure?

How can I know if I am generating a secure pseudorandom initialization vector? Currently I am planning to generate a pseudo-random initialization Vector using current date and time - is this secure ...
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How do I generate a number for a lottery and later proves its existence

I want to create a lottery that works like this: I choose a secret number A in the range [0:999] and publish an object B. People must try to guess the number A to win. When somebody wins, I want to ...
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Choice of MAC and handling it correctly

I have recently learned that Encrypt-then-MAC is recommended when using symmetric encryption. I have two closely related questions related to that, which is why I am posting them as one: Looking ...
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One-time pad and zero key

I'm doing some exercises before my exam, and I am stuck with task number 4 in this file: http://www.cs.umd.edu/~jkatz/crypto/f10/hw1.pdf Could you help me with this task? When using the one-time ...
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what is the state of the art algorithm to encrypt credit card data

We have a business requirement to keep credit card data. What is today's (Nov 2013) state of the art algorithm to encrypt credit card data that will be saved on disk? Additionally, I'd appreciate ...
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Keys required for cryptography

I am reading an article on cryptography at following location: http://www.entrust.com/resources/pdf/cryptointro.pdf Historically, encryption systems used what is known as symmetric cryptography. ...
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How to encrypt a short string and keep the length secret

I need to encrypt relatively short strings (generally less than 100 characters). If possible, I want to avoid leaking the length of these strings. How can I do that? The thing that came to my mind is ...
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Cipher Feedback Mode

I can't understand what CFB really is. It said in Wikipedia that CFB is same as CBC, but I find that CFB is more difficult than CBC. Can someone explain to me how CFB works. Such as how ...
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Why are RSA ciphertexts different for the same plaintext?

I am using SpongyCastle for a project in android. I have used RSA to encrypt the data and then decrypt it in another activity, the keys are stored in the shared preferences. I discovered a thing I ...