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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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Given a cipher text, How to start the attack on it? How to identify what cipher has been used to encrypt it?

I have a cipher text which contains english alphabets only. How to figure out what method has been used to encrypt it. It doesn't seems a good idea to try all known encryption methods.
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One-Time-Pad with multiple keys?

Would it be more secure if we used multiple keys in a One-Time-Pad encryption?
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31 views

Plaintext Size Limit for ECIES with AES-128 CBC mode

Using the ECIES (Elliptic Curve Integrated Encryption Scheme), is there a limit size of plaintext? (what is the maximum allowed number of bytes to be encrypted with ECIES).
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Identify encrypton method [on hold]

I'm trying to emulate the ID parameter in my system but can't able to as I don't know the encryption method. Can anyone please help me - Here is the thing I'm trying to do. I successfully generate ...
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Converting PHP encrypt/decrypt to Node.js [on hold]

I have been trying to find out how to make this: ...
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1answer
57 views

Best practices for saving encrypted user data without a database

We are setting up a web application which requires users to submit sensitive data. Since entering all the required data may take a long amount of time, we want to give them the option to save their ...
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Please Tell me about book or article that Explain about Mathematical Background Of DES Encryption Algorithms [on hold]

Please Tell me about book or article that Explain about Mathematical Background Of DES Encryption Algorithms?
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What does libsignal use the registrationId for?

I am playing around with the libsignal at the moment and i was noticing that in the different documentation for libsignal-js or libsignal-java one of the first steps is always to generate a so called "...
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Derivable encryption key - BIP0032 parallel

I wish to find an asymmetric encryption algorithm that supports key derivation, BIP0032 style. Meaning that I have some SEED [PRIV] and I give someone some public data [PUB], then given new public ...
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101 views

Creating new cryptographic algorithm instead of using known algorithm

Does it invent a new cryptographic algorithm in case of military encrypted communications makes the communication safer? Keeping the structure and behavior of the protocol unknown is an advantage?
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2answers
61 views

Search Over Encrypted Data

I'm doing a research about how to search over encrypted data as the title said. And, I saw cryptDB used a cryptographic scheme from Song et.al's article Practical Techniques for Searches on Encrypted ...
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1answer
27 views

Is it acceptable to add a setup algorithm in the public key encryption?

I saw in the paper How to Use a Short Basis: Trapdoors for Hard Lattices and New Cryptographic Constructions at page 29 that key generation algorithm of PKE can use a common random matrix $A$. Is it ...
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How to decrypt a simple substitution cipher where space is also encrypted by a character

I am trying to decrypt a text data encrypted with a simple substitution method with 2 steps. First, shift the alphabet of the source text by a few characters. For example, if we shift by 2 characters,...
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110 views

What's the best block cipher mode of operation for RSA?

I know that you should never use RSA with any block cipher mode of operation, but theoretically, what's the best block cipher mode (safest) we can use with RSA encryption - without adding any kind of ...
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What choices of $a$ and $b$ of the affine cipher lead to proper encryption functions [duplicate]

Suppose I consider the affine cipher defined by $E(x) = ax + b \bmod n$ on the standard alphabet of 26 letters. Which choices of $a$ and $b$ lead to proper encryption functions? Using the ...
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2answers
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Why can´t an attacker find the key if he has the plain text, the IV and the ciphertext? [duplicate]

I am reading a book about web security and they are now talking about AES CBC. After reading the chapter I was wondering, can an attacker compute my secret key if he has access to the IV, the plain ...
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2answers
479 views

Can AES be used with a static key?

I am making an embedded system for a project that uses AES. As I cannot accommodate key generation (hardware constraints) I am using a static key. I can use another small algorithm to create dynamism ...
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42 views

Digital Signature Verification failed using SHA256withRSA in Python [migrated]

I am trying to validate the digital signature with given certificate files for the offline aadhaar KYC verification application. This instruction is given in the documentation for the verification. ...
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78 views

What is meant by the term “hostile environment”? [closed]

I come across many time a term called ”hostile environment” in cryptographic literature. What does “hostile” mean exactly? Is it unknown third parties which are responsible for handling and routing ...
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1answer
181 views

why do we asume that in the registration process communication is over the secure channel?

I was reading some research papers and saw that in Registration phase/process it is always assumed that communication is over the secure/private channel, whereas, all of the phases communication is ...
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Is there a way of “bitwise” decrypting a corrupt Bitlocker encrypted raw HDD-image [migrated]

I'm facing a situation, where I'd like to decrypt a "corrupted" Bitlocker protected drive (Windows 10 Partition) by using the known 48-digit recovery key. Corrupt means, I executed a restore (Windows ...
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2answers
95 views

Lightweight block ciphers that support decryption with minimal overhead?

Lightweight block ciphers are mostly expressed for encryption routine and efforts are made to keep it as light as possible mostly in terms of gates count and power usage although some try to keep ...
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If Kerckhoff's Principle holds, why do we need a cipher at all?

I understand Kerckhoff's principle, in a very practical sense, that the best attack that can be performed on a given cryptographic algorithm should be only as practical, if not less practical, than an ...
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What are some shuffling algorithms I can implement?

I am building a mixnet and right now I am looking for an algorithm that can give me a random, secret permutation when applied to the corresponding inputs. The correspondence of the inputs and outputs ...
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2answers
91 views

Safely erasing encrypted data

My secret message is encrypted in a byte buffer with AES-128 in CBC mode. The first 16 bytes are the IV and the message follows contiguously. If I want to securely delete this message is it enough ...
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1answer
223 views

Decrypting Ciphertext with partial Key Fragment using LFSR and Berlekamp-Massey

Edit Does the state register (the LFSR) always have to remain with 16 bits (I'm assuming yes). If so, are we shifting the register right by one (lfsr>>1) ...
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1answer
143 views

Bit Flipping Attack on CBC Mode

To perform a bit flipping attack, the previous block is modified by using XOR. This results in an altered plaintext. However, now the ciphertext of the previous block is altered, hence it will result ...
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ECDSA Message Recovery from Two Encrypted Messages with Signatures and Public Key

I am currently working on a problem where I have two encrypted messages, their corresponding signatures, and the public key. Furthermore, the value of $r$ is the same in the two signatures. I am ...
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1answer
53 views

Are there any practical use cases for performing homomorphic operations on encrypted Strings?

Does anybody know which practical use cases there are to operate on encrypted strings? Even niche problems that can be solved using homomorphic encryption on strings are interesting to me, but not ...
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1answer
73 views

What is the most secure way to check that a given masterkey is valid?

For the purposes of learning, I'm writing a small utility that allows encrypting a list of passwords using a single master key (using AES-256 and PBKDF2) Before encrypting or decrypting any password ...
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1answer
90 views

Is an IV useless for encrypting database IDs?

In my scenario I need to build a pseudo-anonimization service: a machine that given a plainID return a chiperID and vice-versa. <...
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1answer
523 views

Why doesn't the GCM spec use a more efficient multiplication algorithm?

NIST SP 800-38D § 6.3 Multiplication Operation on Blocks describes a multiplication algorithm that, in my testing, appears to be a good amount slower then algorithm 2.40 (arbitrary reduction ...
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1answer
42 views

RSA - are we able to encrypt into any possible ciphertext in $Z_n$ given a specific key?

Given a public key $(e,n)$, if we are free to choose the plaintext does that mean we are able to generate any possible ciphertext in $Z_n$ ? Because if we were given $e$ we can say that the ...
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1answer
63 views

RSA - source and image - all are possible?

Given a key $e = 3$ (the public exponent for RSA) and a group of numbers, say $Z_n^*$ (the multiplicative group of $n = pq$, where $p$ and $q$ are primes as requested by RSA). I can find the ...
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1answer
230 views

Would this mode of operation be safer?

Here the key stream is used as keys for the second level of block cipher encryption. I guess this is not vulnerable to: padding oracle attack because it is basically counter mode stream cipher ...
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Writing to /root/workspace doesn't break the files inside encrypted partition [migrated]

I have made full disk encryption on my hard disk exactly as in this guide https://web.archive.org/web/20180428191153/http://thesimplecomputer.info/full-disk-encryption-with-ubuntu Partition table: ...
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1answer
109 views

What restrictions exist for publishing on strong encryption in USA?

In the past, there were export and other restrictions on publishing information, source code or otherwise making new strong cryptographic items available without prior government approvals. There are ...
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3answers
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Is there a counter mode of encryption where the key is being changed for every block of data?

I thought like encrypting an IV concatenated with a CTR but instead of XOR-ing this output with the plaintext this output should be used as a temporary key for another encryption block that actually ...
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29 views

DSA signature creation using hash oh the message

I am trying to understand how i can create DSA signature. the arithmetic uses H(M) and it is given a random nunber for the hashing result.( written- lets assume it is 121). Is the number really random ...
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Creating a login system [migrated]

I am working on a project where users create a one time use account in a uwp app, then those credentials are entered into a website, where they are used to grant access to a one time use link, then ...
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Is there any stateless authenticated and encrypted communication protocols?

It's like TLS but stateless. In TLS, a handshake is established in at least one round for the key exchange. Thus TLS is stateful. Suppose we want to have an authenticated and encrypted communication ...
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2answers
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Choosing a Random Number Generator algorithm to encrypt a message

What are the best cryptographically secure pseudo-random number generator algorithms, and what are their strengths/weaknesses? I can't seem to come up with a list of them (or maybe I do, but they ...
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1answer
40 views

Combining secret/public keys

Suppose that we have three authorities which each of them generate one secret/public key for Alice. It means that Alice has three secret keys and three related public keys. Suppose that Alice combines ...
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1answer
69 views

Attacks on one-time pad, given a property of keys

An adversary $A$, eavesdrops $n$ cipher-texts, $c_{1}, c_{2} ..., c{_n}$. It also knows a value $v$ and a function $f$ such that $$f(k_{1}, k_{2}, ..., k_{n}) = v$$ where, $k_{i}$ is used to encrypt $...
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1answer
102 views

RSA exercise with known $n$ and $e$

Bob decides to use $n = 697 \rightarrow 17 × 41$ and $e = 33$ as his public key for an RSA cryptosystem. Show that the decryption exponent is $97$. Find the encrypted form of the message $17$.
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1answer
87 views

Computational Complexity of SHA-3 (SHAKE128)

Please, I got the question "what is the computational complexity of SHA-3 (SHAKE128)"? What does that mean and how can I calculate that?? *I am using SHA-3 (SHAKE128) in my mechanism to hash fix ...
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1answer
47 views

El Gamal Signatures, Need help explanining a step, Where does the “775” come from? Image included

I understand all of the previous steps, but I don't understand what is happening to "S2" in that the number "775" showed up. Where does the 775 come from? I can't seem to get it, and I've tried ...
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1answer
115 views

Explaining Chaotic Cryptography

I will venture myself into studying chaotic cryptography. However, I find it hard to explain what chaotic cryptography entails to those that have some knowledge of cryptography. Neither can I explain ...
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1answer
47 views

Hash Collision Probabilities

Please give help! how can I calculate the probability of collision? I need a mathematical equation for my studying. Assume, I am using SHA256 to hash 100-bits. Thus: SHA256 {100} = 256-bits (hash ...
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1answer
48 views

The goal, the method, and the interface of the signcrypt primitive.

Some time ago, I proposed making the site more educational by teaching correct cryptographic programming. The proposal had had somewhat good reception, but was met with cold ice as there had been ...