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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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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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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Existence of encryption schemes where $F_{k}^{-1} \big( F_{k}(A) + R \big) = A + O(R)$

Is there a encryption scheme in literature, where I can do something like $$F_{k_1}^{-1} \big( F_{k_2}(A) + R \big) = A + O(R)$$ where, $A$ is a $m \times n$ real matrix, $R$ is a $m \times n$ real ...
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Counter Mode with a sequence of zeros bits plaintext, is it secure?

I had a quiz last week in computer security course. There was a confusing question that I am still looking for a good and clear answer. First, I know that counter mode with a good block cipher is ...
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What does K stand for in frequency analysis

It was from frequency analysis lecture and the professor mentioned but I cannot recall. The K value for English was .067, German was .076. The lowest K was Russian which was .056. When the frequency ...
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Automatic generation of secure passwords with the least inconvenience for a user

I'm working on a web site for a private company that should allow them to upload files, which will be later retrieved by their affiliates. The site will be available from a public Internet using ...
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331 views

CPA security of a stateless and deterministic encryption system

Why can no stateless and deterministic encryption system be IND-CPA secure? Is there a formal proof for it?
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113 views

RSA generation of private key using public key

In RSA private key generation e*d ≡ 1 mod φ e is public, also n is public. How to prove mathematically, generation of ...
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Can RSA encryption produce collisions?

In RSA, a message is encrypted by $m^e \pmod N$. $N$ is the modulus, $m$ is the message and $e$ is the public exponent. (I know that $m$ should not be greater than $N$.) My question is, can $m^e$ be ...
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184 views

The perfect way of using IV in CTR mode

I understand that it is necessary to use the same IV for both encryption and decryption in the CTR mode. I'm thinking about the case when I concatenate the secret ...
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Decrypt files with original file CTB-Locker [closed]

I have problem called CTB-Locker. It encrypted all of my files on computer and since I have lot of documents that are very important I am in problems! As I read online CTB-Locker uses "elliptical ...
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DES Encryption Algorithm all 64 bits for key instead of 56 bits

Would a DES algorithm that uses all 64 bits for the key instead of just the 56 bits be more secure? I have been thinking about it but those 8 bits used for parity are very useful and but including ...
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Is signing a message just encrypting it with private key? [duplicate]

I have a simple question, When I sign a message (in RSA) does the program encrypt the text with my private key? Because I can decrypt it with my public key. Yes or no. Is signing a message just ...
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Why can't you just clone encrypted data and use it?

Let's take a contactless card for example (one for public transport lets say (i.e. MiCard)), the data is encrypted on the card and encrypted on the reader as far as I know. So how come somebody who ...
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RSA: how does it work and how is it more secure than symmetric systems

Before starting the question, I know that RSA is naturally a key exchange cryptosystem rather than an antilogarithm fully implemented for encrypting and decrypting data since the length of the secret ...
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126 views

Will current encryption always remain secure? Is there mathematical proof?

Current encryption algorithms, such as AES, RSA, elliptic curve, etc. work based on known mathematical problems. I am specifically interested in the RSA. Will such security always remain secure? One ...
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40 views

Cipher for human interpretation [duplicate]

Please suggest algorithms to encrypt and decrypt text messages that can be easily performed by human in a considerably short time. It doesn't have to be really secure, but sufficient to fool ...
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51 views

Is it possible: Derived key based on variable number of private keys?

I have a MySQL database that I want to encrypt with AES_ENCRYPT() and have to provide access to a variable and possibly changing number of users. Is it possible to derive an encryption key based on a ...
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134 views

Automated testing of cipher security for import/export compliance [closed]

What do we know about systems that automatically test and grade cipher security. The application in mind would be for checking for compliance with import/export regulations. I imagine a system that ...
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129 views

RSA signing security

I'm curious about the security of RSA signing with the same public private key pair when the same message is sent multiple times. It's my understanding that once you generate the hash of the message ...
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Exploration of Blum Micali Security By Seed Size

I'm new to cryptography and am most intrigued by mathematically based pseudo random number generators. With reference to the Blum Micali algorithm: $X_{i+1} = G^{X_i} \bmod P$ can security be ...
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I have a keyword and cipher text but cannot decode it please help! [closed]

coded text: ij gj hnev xudmyx hn igim umif obaxidyw kxzq si the key is JULIET, but i cannot figure out how it is used. Any help would be awesome!
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Is ASCON cipher broken?

http://eprint.iacr.org/2015/030 present several attacks of ASCON but does not have a conclusion section. I'm having troubles estimating what are the consequences on the use of ASCON. What's your ...
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What cryptanalysis is possible against two independent keystreams XORed against plaintext?

If a wise person was unsure about which commercial cryptography standards are truly secure from the fascist powers that be, it would seem the obvious option for companies and individuals is to now use ...
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158 views

Using hash of plaintext as nonce in NaCl secretbox- bad idea?

I need a nonce to encrypt my stuff using NaCl secretbox. I will be transmitting the nonce along with the ciphertext, which I have been told is OK to do. It occurs to me that one could simply use the ...
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Many Time Attack [closed]

How i can XOR these two cipher texts encrypted by using same key First ...
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514 views

How secure is file header encryption for large files?

I'm having trouble location information about whether or not encrypting a file's header is good enough. The files in question are media files that range in size from 500mb to 4GB. If I had no ...
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Deduplication: Encrypting the SHA-256 hash of a file chunk

I'm designing a data storage system that should be both able to deduplicate data that share the same encryption key, and be reasonably secure. I know that this kind of encryption quality can be ...
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In what way is XXTEA really vulnerable?

I'm looking at using the XXTEA algorithm to encrypt a small amount of data (say, less than 32KB) in the context of a software licensing algorithm. That is, we wish to make it difficult (not ...
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293 views

Share encrypted files without giving master key

Imagine I have four files I want to encrypt. I have master key, and from that master key I derive four keys, one for each file: ...
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106 views

Public key encryption [duplicate]

I am not getting whole idea behind Public Key Encryption technique. As according to fact, public key encryption method uses two keys a public key known to everyone private key known only to recipient ...
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298 views

fuzzy commitment implemenation to make secure biometric template

I want implement some ideas from an article that is about making secure biometric templates using fuzzy commitment and fuzzy vault. I need to implement just the fuzzy commitment (fuzzy commitment is a ...
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Interested in learning cryptography [duplicate]

I'm interested in learning cryptography outside the university(studying civil engineering). I was always interested in computer sciences and programing and in mathematics. I always try to program ...
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Encryption for a short packet size

I have an 8051 microcontroller with a radio that can send packets with up to 32 bytes and I want to have the messages encrypted. It is a sensor network so I really only want to send one packet per ...
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How will Cryptography be changed by Quantum Computing?

I realise this isn't a 'yes or no' question, and I apologise for asking something that could be seen as a discussion thread, but I had to ask. I'm currently doing an EPQ in CS (specifically how QC ...
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what is it called when encrypt('a') + encrypt('a') == encrypt('aa')?

So normally if you do encrypt('a') twice in a row you'll get the same result. But sometimes (as is the case in SSH) this is not desirable. You want encrypt('a') + encrypt('a') == encrypt('aa'). What ...
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Transforming a key into a seed with the most entropy

I'm making a very simple encrypter in C# which is basically a Stream cipher. The user enters a key(password), converted to a seed for a pseudo-random generator, and the pseudo-random generator ...
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If I know the salt, can I decrypt the commitment?

Say, I salt my key(K) with y. So, my new Key is K' = Salt(K+y). Now, Alice sends commitment = E[K',M] to Bob. Bob knows the salt(y), but not K nor K'. Can Bob decrypt the message?
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How much extra information is in an RSA public key?

I'm trying to calculate the size of an RSA public key in Ruby. I've retrieved the key in PEM format, and once I've decoded the base64 part from the PEM format, I get the size in bytes. What I find is ...
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can anyone give the java code to encrypt files using paillier [closed]

I want to implement encryption on personal files using paillier encryption. Is it possible to encrypt files using this encryption..
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Possible to know who is the owner of a message encrypted with RSA public key

Given the scenario in which I want to send 10 messages either to Stalio or Olio. I encrypt these messages with their respective public keys using textbook RSA, before sending the messages to their ...
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Is AES-GCM length extension attack possible using authenticated decryption?

I am looking to encrypt a piece of data using AES-GCM with a full 16-byte GCM Tag and send it over the network using UDP. Is it safe to assume using the AEAD nature of AES-GCM that performing ...
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Why shouldn't I use ECB encryption?

I'm using Java to generate encrypted strings, and I get this warning at build time: ECB encryption mode should not be used So I'm wondering why I shouldn't use ECB and what I can use instead?
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Encryption and HMAC in a PSKC file

This is the PSKC standard https://tools.ietf.org/rfc/rfc6030.txt In Section 6.1 6.1. Encryption Based on Pre-Shared Keys They have the following ...
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Embedded devices Authentication, Integrity and Confidentiality

Embedded devices send messages to the server. The server occasionally sends messages to individual devices(Reboot, upgrade firmware etc) After some research this is my ad-hoc solution: 1) Each ...
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Why are primes important for encryption

Why are primes so important? Why can't we just use a random number? My guess is that it's because finding a random prime require more computing power, than finding a random number. Can anybody confirm ...
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91 views

Encrypting decryption key

What's that property called when a scheme is secure even if you encrypt the decryption key? Some schemes have problems when your plaintext is the decryption key (or just the key if symmetric).
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Does a cryptosystem provide unconditional security if and only if it provides perfect secrecy?

Is unconditional security and perfect secrecy one and the same thing, i.e a cryptosystem provides unconditional security if and only if it provides perfect secrecy ? I've wondered about the above and ...
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Can a cryptosystem be unconditional secure if the same key $k \in \mathcal K$ is used for more than one encryption?

Can a cryptosystem be unconditional secure if the same key $k \in \mathcal K$ is used for more than one encryption ? I know that the one-time-pad doesn't have perfect secrecy and doesn't provide ...
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Formal relationship between encryption and random number generators?

Cryptographically secure random number generators seem to have similar properties to symmetric encryption: initial seed is permuted to produce a random numbers (key and ciphertext) given the seed, ...