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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1answer
52 views

Create a ciphertext that decrypt to different plaintexts with different keys in RSA

(This is inspired by this question 1; have also read this question 2 but it's one-time pad) I would like to know, given two message $m_1$ and $m_2$, as well as public keys $(e,n_1)$ and $(e,n_2)$, ...
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157 views

Why is a proxy needed in proxy re-encryption?

Context Here's the usual proxy re-encryption scenario: Alice, with key pair $(pk_a, sk_a)$ encrypts a message $m$, producing $c = encrypt(pk_a, m)$ Alice saves $c$ on an untrusted storge provider (...
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1answer
86 views

How to implement GSW13 using Helib or SEAL?

I want to implement the homomorphic encryption scheme proposed in GSW13, and make some changes to it, but seems that there is no library that has already been implemented it. Since this is a ...
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How hard is it to guess a 8 digit PIN?

Say that there are different live situations where you have to select own PIN numbers. Can someone say if it is possible to guess a 8 digit pin within 3 tries, given any methods or resources? Is ...
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3answers
170 views

Negotiate a secure connection without certificates?

I would like to have a simple experience for a user for setting up a secure connection between two computers against a MITM attack. Something like the following: A number (possibly base64) appears ...
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2answers
2k views

Is using 7-8 random words from all words of a language as password a good idea?

The Bitcoin Bip-39 dictionary has 2048 words. And a random 24 of them are pretty secure together. What if the source is bigger (all words in the language) but there are only about 7-8 words? These ...
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31 views

How challenge response password recovery mechanism works with disk encryption? [migrated]

For the sole purpose of learning, I am trying to figure out how disk encryption software is able to recover password of an encrypted disk using a challenge response mechanism. Th recovery process ...
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20 views

complexity of ElGamal ECC and Menezes-Vanstone ECC?

How to compute the complexity of ElGamal ECC and Menezes-Vanstone ECC?
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1answer
114 views

How safe is my method

I'm building a website. I have an API which takes 2 parameters: delete_user(user_id, hash). And there is method to evaluate hash using SHA512: ...
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48 views

State of the Twofish encryption cipher - is it broken?

Twofish was one of the finalists in the last cipher competition together with Serpent and AES, where AES won. Do you know of any cryptanalysis on Twofish and if its considered "broken" or still ...
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1answer
84 views

AES-256 mix column code generating output bigger than 8 bits [closed]

I'm implementing AES-256 in JavaScript with block size 128 bits and I understand every thing about AES except MixColumn transformation. So I copied this code from ...
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1answer
129 views

Using Caesar crypt, then encrypting the output with PGP, then encrypting that with AES-256

Is that possible? Well, of course it is, but if you decrypt it, will it show the actual message in the final output? This isn't me actually doing this in practice, just if it is possible. Lets say ...
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1answer
332 views

AES-256 will double the size of photo after encryption?

I am currently working on my JavaScript project where I am also trying to encrypt attachments with AES-256. Right now I am testing it and I am getting this results. For photo file which has size ...
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2answers
370 views

What are the advantages of AES-128 cascade vs AES-256?

Ok so let's say I have some top secret data ~ 50-100 MB and I need it to be protected. The cipher operation mode and the KDF is irrelevant for this example. Let's just assume we use ...
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0answers
419 views

Key size, performance, and security tradeoffs for AES GCM / CCM

AES can be used with 128, 192 or 256 bit keys and each one appears to have a performance vs security trade-off (What is the effect of the different AES key lengths?, What are the practical differences ...
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1answer
63 views

Problem with AES-128 AddRoundkey Step

I'm trying to self-learn the AES-128 algorithm and ran into a snag while following these slides I found online: https://kavaliro.com/wp-content/uploads/2014/03/AES.pdf For the sixth round in the ...
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1answer
1k views

Choice between AES-128 and AES-256 for password protection in MS Office

Why are we still using the default of AES-128 when password protecting a Microsoft Word document. My answer is and always has been - because its good enough and MS don't recommend changing to AES-256. ...
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0answers
47 views

What is the formula to calculate password entropy? [closed]

I saw in another thread: Is using 7-8 random words from all words of a language as password a good idea? These calculations: If we assume that English has 171,476 words. Then with 8 words the ...
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0answers
19 views

What is the best way to encrypt whole partitions with Ed448-Goldilocks?

I like crypto, but I'm a bioanalytical chemistry person by trade. I like this algorithm and was wondering if I could use it to encrypt partitions like a MBR that prompts a passphrase, like BitLocker.
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25 views

Is there a program i can use to find a hidden message in a BMP file?

I am working on a puzzle and think there is a message hidden in one of the files that is a BMP file. I am wondering if there is a program somewhere that could find it?
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1answer
165 views

Large Volumes of Asymmetric Encryption

First of all, I apologize in advance if I use any incorrect terminology. I am just getting my feet wet when it comes to cryptography and there is a lot to learn. For the past 12 months, we have been ...
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24 views

Would these Vigenere cipher use cases be considered secure? [closed]

I've a couple of questions about my knowledge of the modern and secure use cases of vigenere. I'd like to know whether or not they'd be considered secure by todays standards - By that I mean easily ...
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2answers
61 views

Is there something like a secure hashmap?

TL;DR: Is there such a thing as a hashmap whose contents cannot be read unless you have the right encryption key, and where each encryption key only works for a specific key value pair? More context: ...
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1answer
179 views

Does the transposition cipher have a network application?

So I'm reading a chapter in my networking book, and it talks about substitution and transposition ciphers. I know that most network security uses public key or symmetric encryption, but I wonder ...
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0answers
24 views

How to securely store / generate a private key for client side encryption when using SQRL as login? [closed]

I am a developer who until now has done very little with encryption. Steve Gibson's explanation of SQRL (Secure, Quick, Reliable Login) has solved a lot of problems for me regarding encryption, most ...
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How can I decrypt the encrypted text of GitHub opensource project? [closed]

In Github I found this gfwlist text, but this is not plaintext, it's encrypted text, we know GitHub is a opensource code manage platform, why it is encrypted? and there do not give a decryption ...
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21 views

default value for rsa_padding_mode in openssl cms command [closed]

I am trying to generate the signature for a file using openssl cms command. Wanted to understand what is the default value for rsa_padding_mode. I did not specify anything for this parameter and I ...
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1answer
49 views

Proving the right encrypted message was sent

Total amateur to crypto here but I've searched and searched and am at the extent of my knowledge. I've gone down several avenues to satisfy what I'm looking for but I'm just going to describe what I'd ...
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1answer
60 views

openssl encryption salt length

when i was reading the latest source code of openssl, i found openssl enc has an 8-byte (64-bit) salt length; because the same ...
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2answers
60 views

PRNG next bit test

I would like to know whether a specific PRNG satisfy the next-bit test or not. will satisfying all of NIST statistical tests on PRNG guarantees passing the next-bit test? Or is there a specific ...
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1answer
70 views

Double 3DES/TDES Encryption

If 3DES/TDES (officially TDEA or Triple DEA - Triple Data Encryption Algorithm) encryption is used twice, using 6 different keys K1-...
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1answer
52 views

RSA: How to compute plaintexts knowing ciphertexts, public key and relation between plaintexts

I'm trying to solve an exercise where you have to compute two plaintexts $p_1$ and $p_2$, knowing the corresponding ciphertexts $c_1$ and $c_2$ and the public key, of which $e=3$, and $n$ is a large ...
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1answer
89 views

Cipher comparison chart/table?

I'm more of a visual person, so a chart or table layout usually works best to help me "see". I'm just trying to locate a resource that shows me where the various ciphers fall in relation to each ...
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Niederreiter cryptosystem sources

I want to study about Niederreiter cryptosystem and I want your opinion about sources, papers, etc. I found stuff on the Internet but I want to know if there is a good source that you may know. I want ...
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2answers
680 views

Is direct RSA encryption of AES keys secure?

I am wondering: If we take this scheme/procedure and each of it seems very secure (to me at least), is it truly secure or is there a vulnerability hidden in the process? This is the scheme: Bob has ...
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1answer
45 views

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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1answer
16 views

decrypting el gamal encrypted messages in regards to k being used

i am trying to understand the differences of using k in the following scenarios to better understand the protocol and most importantly the consequences of using such k. so i wonder, some user, call ...
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0answers
17 views

attacks and defenses on multi party Diffie-Hellman protocol

I tried to create a 4 partied Diffie-Hellman implementation for 4 people using its cyclic group property. However, I am not sure regarding those 2 issues, and would appreciate if you could elaborate ...
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1answer
41 views

Trapdoors for Lattices: CCA-secure encryption

In Trapdoors for Lattices:Simpler, Tighter, Faster, Smaller, Micciancio and Peikert proposed a CCA-secure encryption. However, I am confused about the step in decryption algorithm (p.36 Lemma 6.2.). ...
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2answers
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Is there any vulnerability in this scheme?

We want to design a symmetric encryption scheme. Note that the following things are true for our system: The plaintext P will change every time for a given user. A user will choose a password which ...
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2answers
121 views

What encryption to choose from the SSL library in python 3?

I've been researching some of the types of encryption that the python SSL library uses. Among them the best I've seen are: ECDHE-RSA-AES256-GCM-SHA384 TLSv1.2 Kx = ECDH Au = RSA Enc = AESGCM (256) ...
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3answers
251 views

How secure is XOR-CBC?

How secure would this be? To be clear, I mean replacing the block cipher encryption step in the Wikipedia diagram explaining CBC with plain old XOR? EDIT: Replace ...
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2answers
77 views

Multiple (RSA) public key encryption how to verify others received the same information? Non-deterministic encryption

I have an RSA system between multiple parties. Alice takes the targets (Bob and Oliver) public keys and encrypts a message using them and sends it to them. All parties know each other's public keys ...
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1answer
46 views

Why is the second XOR operation in OCB mode necessary?

In Rogaway's OCB mode, the offset (derived from the key) ist XOR-added twice: Once to the plaintext block, and a second time after the Encryption. I am wondering, why the second XOR operation is ...
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1answer
80 views

Is more ECDHE or RSA currently recommended?

Lately I have seen that many websites warn us of changing RSA for ECDH, and that the latter is much better if we use its "ephemeral" form or better known as ECDHE. So is ECDHE recommended to use more ...
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1answer
72 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 ...
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1answer
74 views

EL Gamal Attack without a secret key

I have the following data where all the inputs are Big Integers, group size $p$, group generator $g$ public key of the receiver $y$ $c_1$ and $c_2$ Random Number as well I am trying to execute an ...
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2answers
145 views

The importance of randomness in the creation of a key

Why does it matter what kind of random number generation is used during key generation? E.g. this answer states ...
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3answers
688 views

Benefits of signing RSA-encrypted data?

I recently came across this (PDF) journal article, which describes what it calls "A New Design Of A Hybrid Encryption Algorithm" (which I must say, doesn't sound very novel, even in 2014!): An AES ...
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0answers
28 views

Server stored, encypted messaging app

For my personal research, I have to create a messaging app, but security is only important part of application, security from MITM (man in the middle attack), at device end, and at server level. (note:...