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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Decrypting Triple-DES using 2 keys in crypto tools

I'm currently working on crypto tools to encrypt/decrypt 4 blocks of messages using Triple-DES with 2 keys. So, I've reached the final cipher text, but now I have to do the reverse and get the ...
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Pailler and Gentry - homomorphic encryption

Paillier cryptosystem is a probabilistic asymmetric algorithm for public key cryptography. Doesn't homomorphic encryption schemes have regular effects on the plaintext, and does that mean Pailliers ...
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55 views

The improvement of the private key exponent in the M.Weiner Attack

I am working on attacks on RSA and came across the M. Weiner attack. The limit for $d$ in order for the attack to apply is $d <= (\frac{1}{3})N^{0.25}$. The paper states that Boneh and Durfee ...
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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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369 views

Some questions about encrypting (AES) a file with password

I'm relatively new to encrypting, and I have some questions. I intend to write a standalone C# program that will write and read an encrypted file with sensitive data using a password entered by the ...
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Is there an intuitive explanation as to why only the private key can decrypt a message encrypted with the public key?

I have just learned about using PGP/GPG for email encryption and one thing has always bugged me: How is it possible that a message encrypted with somebody's public key can be decrypted only with that ...
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How to write the encrypted message after using RSA

I have created a RSA encryption/decryption program but how do i write out the results after doing a encryption? Right now I have it so that it will just print out the decimal value of one character ...
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740 views

Generating Encryption Keys from Biometric Fingerprint Templates

How would one go about generating Encryption Keys from Biometric Fingerprint Templates extracted from a fingerprint using either Griaule SDK or DigitalPersona SDK or any other SDK that will return the ...
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1answer
86 views

Why would splitting a password output be better than separate HMACs for encryption/authentication key derivation?

In a recent question I asked here on crypto.se, an answer was given that surprised me a bit. As mentioned in the referenced question, I'm looking to derive encryption and authentication keys from ...
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2answers
111 views

Journals to read in order to keep up to date with interesting research [closed]

I'd love suggestions from crypto.stack as to academic journals to read. They can range from introductory to advanced, as long as it's free (requires no access fees). Feel free to edit this question ...
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1answer
112 views

How does CBC work with read-write volumes?

I have read an article about an attack on LUKS in CBC mode and had a look at the WP article about CBC and now I am confused. If I have understood that correctly then changing the plaintext of a block ...
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1answer
380 views

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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155 views

How do P2P clients like uTorrent maintain authenticity of files?

I am very new to concepts of cryptography so bear with me and feel free to fill in any information that may seem obvious but something you think someone may not know. At first I was under impression ...
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1answer
177 views

Is AES-256 over AES-128 weakening the original encryption?

When transfering data using TLS the browser and server agree the cipher suite to be used - so for example this could be chosen as AES-128 and is (probably) outside of my control. If I separately ...
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3answers
149 views

Is it possible to find data which makes sense when decrypted with different keys?

In theory, does a piece of data exist which, when encrypted (using any method) with a given key, makes some sense when decrypted with the wrong key? Here, a definition of "some sense" might be ...
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1answer
134 views

Hide message length in symmetric key cryptography

Is there any way to hide message length from adversary in symmetric key cryptography? Suppose we want to hide message length from active and efficient adversaries.
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541 views

How to solve cipher encrypted with Vigenère + Columnar Transposition?

Vigenère's weakness is Kasiski's test and index of coincidence. However, if you put columnar transposition on top of Vigenère, that weakness is gone. The text is now shuffled and you can't search for ...
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196 views

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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1answer
285 views

Low complexity implementation of a small blocksize cipher (< 64 bit)

Searching for "small blocksize cipher" finds a number of discussions on the topic, mostly refering to FPE. This one in particular suggests using AES as the round function of a Feistel network. The ...
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Can I decrypt the message having it encrypted with different keys?

I have some encrypted binary data I want to decrypt. I know nothing about it, but I can get it encrypted with as many different (random, unknown) symmetric keys as I want. The keys are long enough to ...
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1answer
107 views

Is it possible to combine two operations rotation and xor?

I can see many xor and rotation operations in cryptography. I just want to make some algorithms fast. So, I'm looking for a way to combine between xor rotation operations. I don't know if it is ...
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1answer
134 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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2answers
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Is it necessary to generate a private key for each encryption process?

I read about Asymmetric key cryptography like EG-ECC , RSA, ECDH. I understand the concept of mathematics to these algorithms. But I have wondered about the public key for sender and private key for ...
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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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175 views

How to retrieve the plaintext of a substitution ciphertext?

So the other day, I was piqued by a ciphertext that was trivially encoded through substitution. Solvable only because we can use our eyes to determine word boundary word detection, etc. Trawling the ...
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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

Back up an information as $n$ pieces and require exactly $n-1$ to recover it

Let $X\in \Bbb F_2^p$ be some information. How do I create $Y_1,\dots,Y_n \in \Bbb F_2^q$ so that having less than $n-1$ of the $Y_i$s gives you no information on $X$ but having $n-1$ of them allows ...
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2answers
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Size of p in ElGamal cryptosystem?

In the ElGamal cryptosystem, I was wondering whether the $m$ (message) should be less than $p$ (large prime). Because on decryption, we are getting $m \bmod p$. For $m \bmod p$ to be equal to $m$, ...
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1answer
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Why is Triple DES not vulnerable to meet in the middle attacks?

Consider the Triple DES encryption calculated as: $$C= E_{K_1}(D_{K_2}(E_{K_1}(P))).$$ For a chosen plaintext attack, given plaintext $P$, we compute the result of $D_{K_2}(E_{K_1}(P))$ and store ...
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Is RSA in a ECB-like-mode safe for bulk encryption?

Let's say I would like to communicate with my friend using asymmetric/public-key encryption, e.g. RSA. (Note: I do realize that in practice this is done through an intermediate symmetric key, but ...
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187 views

When is it safe to not use authenticated encryption?

I have read the post Why should I use Authenticated Encryption instead of just encryption? When is it safe to not use authenticated encryption? I assumed hard drive volume encryption or per file ...
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Why do we use encrypt-decrypt-encrypt (EDE) in 3DES, rather than encrypting three times?

I'm wondering why we use encrypt-decrypt-encrypt sequence in 3DES with three keys instead of three times encryption with three different keys?
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Encrypting a short phrase into two keys. both with length of 32letters

It doesn't need to be crazy secure. I wanted to figure out if there's a popular practice when encrypting a short phrase (less than 32 letter long) into two keys (two strings 32 length). Doesn't need ...
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355 views

Decrypting a small Message using RSA with a Private Key [closed]

If I have a private key of (43, 341). What would be the steps I need to take to decrypt a small message using RSA? I have looked ...
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Can I encrypt user input in a way I can't decrypt it for a certain period of time?

I run a baseball league and would like to do silent auctions for free agents. This would require teams to enter their highest bid and the highest bidder at the end of the auction period would win. ...
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DES with actual 7 byte key

Do we have any library or any mechanism where we can use true 7 byte key for DES instead of 8 byte key. I need it for keys analysis in DES and 8 byte key requirement for associated library is creating ...
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What is the limit of plaintext required to break the Vigenère encryption?

A theoretical question about the Vigenère cipher: Without any knowledge about the key (not even it's length) can we tell how much known or chosen plaintext is needed for the adversary to completely ...
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Is modern encryption needlessly complicated?

RSA, DES, AES, etc. all use (relatively) complicated mathematics to encrypt some message with some key. For each of these methods, there have been several documented vulnerabilities found over the ...
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Why Distance-128 relation in Plain texts is reflected in Cipher texts

The two text having relation as "\x10\x11" → "\x90\x91" (80+10) will have relation after encryption/decryption also in RC4. Following code clearly describes the problem I am mentioning. ...
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Difference between stream cipher and block cipher

A typical stream cipher encrypts plaintext one byte at a time, although a stream cipher may be designed to operate on one bit at a time or on units larger than a byte at a time. A block cipher ...
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reverse an identicon to its source string

Identicons are used to create unique images based on IP address or strings. Lots of programs are available to generate identicons based on an input string. My ...
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How do decryption algorithms determine whether your attempted passphrase is correct?

Judging by the algorithm on the Blowfish Wikipedia article, there is no way for the process to fail with an error. How then does GnuPG know when to tell you your password is correct when decrypting a ...
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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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1answer
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What cryptographic paradigm is appropriate for this use case?

This is a very newbie question... I have to quickly implement a solution for our application that works like this... We have a binary executable that is given a configuration file. I need to encrypt ...
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1answer
91 views

Simplified Key Wrapping to Achieve Only Confidentiality?

I'm looking for help in understanding why the algorithm described here would not deliver adequate protection of confidentiality. We don't care about other criteria such as authenticity or integrity. ...
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Is there a cryptographic method to add noise to a plaintext instead of actually encrypting it?

I'm looking for a cryptographic technique that instead of permuting a cleartext, would add noise to the cleartext to obfuscate the true text among a bunch of garbage. For example, a list of 10 ...
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Repeated Encryption using same/different Encryption systems [duplicate]

I would like to know if there are any security risks/gains from encrypting twice, i.e. $$\text{plaintext}\xrightarrow{encrypt}\text{intermediate text}\xrightarrow{encrypt}\text{ciphertext}.$$ I would ...
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XORing a header with SHA512-hash - secure?

I am writing a application that encrypts text several times and stores the result. The result looks like complete random bytes, therefore I add some random bytes at the end. To let the program know ...
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The specification of modern, non-communicating cipher machinery [closed]

I'm looking for references, papers or guidance on a class of system which I have not seen widely discussed. Consider powerful electronic machinery which remains in the custody of communicating ...
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266 views

Abstract algebra in cryptography [closed]

I have taken a course in my undergraduate on the theory part of abstract algebra.Now am interested to know how can abstract algebra be applied to cryptography.Thanks