Questions tagged [encryption]

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 does Signal Messenger's Safety Number Work?

Why do they recommend the user to verify the 60 digit code in person or via other medium of communication. How are the security codes generated and how do they function on apps like Signal and ...
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Plz help to understand this paragraph . According to concept AES is not used Feistel structure but here both are used

In Dual Watermarking in Tele-radiology using DWT for Data Authentication and Security, the authors wrote: The encryption process uses the Feistel structure consisting multiple rounds for processing ...
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RC5 vs RC6 vs CAST128 vs Loki97 vs Mars

Yes, i know the question looks kinda weird but.. i dont know i could ask in different ways. Which one is the best (considering speed & security) of these? What does the scoreboard looks like? (Im ...
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How to clock a linear feedback shift register?

I have some trouble understanding what happens when a LFSR is clocked. I have tried many examples but I do not get the correct result. Can anyone point out my errors? I have the following polynomial: ...
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Attack on LFSR key stream generator

Alright this is a question I found on one of my books: Given is a stream cipher which uses a single LFSR as key stream generator. The LFSR has a degree of 256. How many plaintext/ciphertext bit ...
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SHA-512 Encipherment via CBC

I wrote a cryptographic function that encrypts a plaintext by using a series of SHA-512 hashes that are used to encrypt the data via a simple byte-to-byte XOR. In order to prevent various attacks, I ...
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RSA p and q size to encipher a block

I have a plaintext about 18 bit size. I have to encipher it using RSA. How large have to be p and q? So M (message to encipher) = 2**18 bit I tried, using a Python coded RSA algorithm, different sizes ...
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How can we encrypt a file to be just readable (and not writable) after decryption?

Is it possible to encrypt a file (e.g., a text document) such that when a user decrypts it, he/she be able to just read the file and not be able to change the content of the file? I mean, the result ...
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Elliptic curve bilinear pairing parameters for 80-bit security level

I am reading a paper based on elliptic curve bilinear pairing groups. The author has defined the size of private key, public key etc in terms of $|\mathbb{G}_1|, |\mathbb{G}_2|$ and $|\mathbb{G}_T|$. ...
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How can I do cryptanalysis on a chaos-based cipher?

I have been reading about chaos-based cryptosystems. Every designer claims that his design is a secure system without much cryptographic analysis; however, it turns out that this is a false claim in ...
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OCB-AES: Ambiguous definition of “Encipher” in RFC document

I'm implementing an OCB-AES cipher (which is described in RFC 7253), now I have to call the AES encipher function (I'll refer to that as AES-256, described in FIPS 197) Pre-summary: I'm not sure ...
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Is chaos-based encryption legitimate?

Is chaos-based encryption a rigorous discipline? And why there are objections to it within the cryptography community? And why are many of its cryptosystems weak? And does it has a promising future? ...
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How well analyzed are giant block length ciphers? [closed]

I have heard about ciphers that have a block length of 256 megabytes. That is huge. How well are they understood by the encryption community? I'm referring to PMC Ciphers. Has anyone used such a ...
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Weakness of XORing random bytes with secret key

Side A generates 16 (high quality) random bytes and performs XOR with a 16-byte secret key, then data transfers to side B, where the same secret key is used to recover the original 16 random bytes. Is ...
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What is “electronic” in electronic codebook (ECB)?

This is an honest question regarding terminology. I believe that I understand why one mode to use a block cipher is called a codebook. But I wonder why electronic as a work appears here? Is it fair ...
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Decryption of an unknown cipher

How can I identify the cipher that encrypted the data shown below? I'm very new to this field, so I am not sure. For example: How does one know which cipher is used in the following line? How can one ...
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RSA DECRYPTION when N gives only one prime number

I am getting only 1 prime factor to some power if i factorize N for RSA decryption. So, in this case what will be the value of P and Q. P will be that one Prime Factor and then there is nothing left ...
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Decrypt RSA with known public key and modulus and the range of dp

How to decrypt RSA while given $e$,$n$ and the range of $dp$ ? ...
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Key transport vs key encapsulation?

What exactly is the difference between key transport and key encapsulation? Either they seem to be used interchangeably or I'm mixing stuff up.
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CryptDB data re-encryption and onion layers

From the CryptDB paper , I understood that the onion layers once decrypted are not re-encrypted. Only columns which are queried infrequently will be re-encrypted to higher onion layers. But if we know ...
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How to implement order-preserving encryption without CryptDB

Which cryptographic algorithm is suitable for implementing order-preserving encryption without using CryptDB?
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Does a Vigenère cipher with SHA-512 and a little foresight turn into a one-time pad? How safe can it be?

I'm doing some exercises. Of course, I have read about the weaknesses of the Vigenère cipher because it repeats the key. But what if I use a different hash every time? The hash of the "key + an ...
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686 views

What happens if CBC-mode uses the same IV for all processes?

In Cipher Block Chaining (CBC) mode, each block of plaintext is XORed with the previous ciphertext block before being encrypted. What happens if I use the same IV instead of the previous ciphertext ...
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Would Triple DES-X with 7 keys be much slower than standard Triple DES?

Since a single hardware pass of an XOR with a 64-bit key is speedy, would Triple DES-X with seven 64-bit keys used in the following manner be virtually identical in terms of code size, memory ...
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Is it possible to attack a one-time pad encrypting only slightly more than its length?

This question might be uncannily similiar to this one posted over 6 years ago, but the structure is completely different. It's written nearly everywhere that OTPs are incapable of sustaining more than ...
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How secure is the encryption with OTP and an OneRNG?

I bought an HWRND last week. What do you think, how secure is the encryption with that and the OTP? See the OneRNG theory of operation here.
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Where to start? decrypting .enc files [closed]

I'm looking for a simple way to brute force a series of .enc files. My particular use case is that I have a CD containing purchased photos from a photographer that is no longer in business, and there ...
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What uses are there (if any) for asymmetric message encryption?

What uses are there (if any) for asymmetric encryption of a message, instead of hybrid encryption? Specifically, I'm not considering asymmetric encryption of a symmetric key (eg old TLS RSA key ...
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What is the need for Diffie-Hellman key exchange when we have asymmetric encryption?

I am new to cryptography and I am having a hard time understanding what is the need for DHKE procedure. I think I fully understand the principle in which it happens and also the mathematics behind it ...
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Managing master keys used in PBKDF2 and HMAC (store, rotate)

My use case: I have few master keys, I use each for a specific operation (e.g. one for encrypting user's data and another for creating JWT signatures etc...). I use these master keys in two specific ...
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Encryption and decryption of Request and response for REST API

I am working on encryption/decryption for the rest of the API. The client here can be mobile, desktop, web browsers, etc and all the requests will be made to an https endpoint. The main goal here is ...
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Should I protect the salt before storing it in a database or use a pepper (secret salt) instead?

If I protected the salt or used a pepper (secret salt) and an attacker got access to the database he can't do a rainbow table attack on a targeted user (a famous or important person). Should I use a ...
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Is RSA encryption with a private key the same as signature generation?

It is often said that RSA encryption of a cryptographic hash with a private key is the same as signing (signature generation). And that verification consists of decryption using a public key. Is RSA ...
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Recognizing and decrypting custom cipher with known plaintext and ciphertext

I've been trying to reconstruct an encryption algorithm that produces a known ciphertext from a know plaintext. I have done some analysis: the algorithm operates on single bytes a plain text can be ...
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Comparing two private values and extracting the ciphertext corresponding to the minimum value

How can I solve this problem: I have a directed graph of nodes that can be malicious and all of them have a private value. Consider a node "B" with private value "BPrivateValue = b&...
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PRNG For RSA (ANSI_X9.31)

I have a query please , I want to know how to generate random numbers using ANSI_X9.31 algorithm for RSA Algorithm please . Thank u
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Help in understanding exactly how lattices are used as one-way functions for hashing

In my long-distance cryptography course, an assignment covers lattice-based cryptography. It is hard, and I am lost. There is no one to help me. Thus far, I have understood that: Lattices are a ...
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Using Alberti Disks to Create a Strong Cipher

Could one use three different disks set at different positions and encrypt a strong message? For example: Wheel 1: A = J Wheel 2: A = E Wheel 3: A = B The first letter is encrypted using 1, and then ...
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Does asymmetric order-preserving encryption exist?

As I understand from this post, mapping from plaintext space to ciphertext space is the fundamental point of all order-preserving encryption. So the only way that we let someone encrypt an arbitrary ...
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What is the difference between CBC and GCM mode?

I am trying to learn more about GCM mode and how it differs from CBC. I already know that GCM provides a MAC, which is used for message authentication. From what I have read and from the code snippets ...
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Can CPA secure scheme be converted to CCA secure?

I would like to know if there are some methods or techniques that can convert a public key encryption scheme from CPA secure to CCA secure?
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Key Scheduling of the International Data Encryption Algorithm (IDEA)

How is key scheduling done in the International Data Encryption Algorithm (IDEA). I did some research, but to no avail. I could not understand this statement from Wikipedia: ...further groups of ...
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Creating nested messages in OpenPGP

I need to create a nested message in OpenPGP (my understanding is that the protocol itself should support it). Let's say I have Payload ("Time in Lordran is ...
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Zero knowledge RSA public key

Suppose Bob has $k>1$ RSA public keys $(e_i, n_i)$ without any knowledge of their corresponding private keys. Alice also has all the public keys, but also has a private key for only one of them, ...
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How does Authentication-Key Recovery for GCM work?

In his Paper "Authentication weaknesses in GCM" Ferguson describes, how some bits of the error polynomial can be set to zero, thereby increasing significantly the chance of a forgery. Q: ...
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Which encryption technique should be adopted to keep the search functionalities?

I am in exactly the same situation as described in this post. I must be able to encrypt data from a client workstation then send it to an untrusted server (encrypted at rest), then decrypt it only on ...
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Does reusing IV in AES-CBC weaken it?

Rsynccrypto allegedly uses AES-CBC with a twist: If the last few bytes of plaintext meet a condition*, then stop, pad the current block and start encrypting new block from the current position in file ...
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Modifying an Enigma machine to allow unchanged letters

One of the biggest flaws of Enigma was that a letter couldn’t represent itself because the route through the machine was one-way. I was thinking a quick fix could be to introduce a rotor position that ...
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What is the correct order of operations for one-time pad cipher when using subtraction and mod 10 arithmetic?

What would be the proper order of operations for OTP encryption/decryption when using subtraction and mod 10? E.g. P - K = C or K - P = C Most of the sources I have seen do not cover this topic or I ...
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The security level of secret share compared to homomorphic encryption

I want to compare additive secret share to Paillier encryption. However, I haven't found out how to set the parameters in such a way that the security level is consistent. Additive secret share (...

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