Questions tagged [decryption]

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mono-alphabetic substitution cipher with turkish language

There is a 96 character text encrypted. I've been dealing for 2 days and I couldn't figure it out. Could you help ? Turkish alphapet: ABCÇDEFGĞHIİJKLMNOÖPRSŞTUÜVYZ
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1answer
52 views

When is a cryptosystem or its algorithm (like RSA) considered efficient?

When is a cryptosystem (like RSA) or its algorithm for keygeneration, encryption and decryption of messages considered efficient? Is there some bound in complexity which splits both efficient and not ...
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2answers
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What type of encryption is this? [closed]

2018000010 - YjRxEBukq Encrypted O6at6Op6sGcAfLoBPhx8Xm89qWEZcw2jkmIxmqM27wAd0V1fWtuVmh9ofPX5n803Q7mnaWsWXRq2TA+1vUbj+TB62jJXNGhJPh17chGPTC3hTKVnItlpHSotwneieheRNUC0M/+zXyu8Ag8iQxP/NSFY2QO7vXwK/...
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1answer
166 views

Asymmetric Cryptography decryption

I am new to cryptography, i know essential part of asymmetric cryptography but is it possible to decrypt 617 decimal digits (2,048 bits) with RSA ? How it can be factored?
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51 views

Need answers to some questions I'm curious about [closed]

When more computational time is required to encrypt or decrypt the plaintext or cipher text? Which parameter reduces the performance speed of the cryptographic algorithm? How can we improve that ...
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1answer
41 views

number of operations for Elgamal cryptosystem

In page 408 of Hoffstein, Piper, and Silverman's Introduction to Mathematical Cryptography, it says "Roughly speaking, in order to achieve $k$ bits of security, encryption and decryption for ...
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26 views

How can I find the key if I have Plain text and Cipher Text [closed]

I'm trying to obtain the key with plain text and cipher text. I guess the encryption algorithm is Vernam Cipher as it works with binary data rather than letters Plain text : 1011 0101 110 Cipher ...
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36 views

I need to know if there's any way that UUDHD could be decrypted into HTTPS. Not sure if this is enigma or what [closed]

Alrighty. Name says it all, I have a string of text I need to decode, but I'm not sure how. If I can find out how to decode UUDHD into HTTPS, then that should let me be able to decode the rest. It's ...
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0answers
28 views

How can you decipher a encrypted message, m, given only that it is not coprime to N

is anybody able to help with the following question?
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19 views

Design flaws in the round-key generation mechanism of Data Encryption Standard (DES) [duplicate]

I am beginner in Cryptography, I want to ask that what are two design flaws in the round-key generation mechanism of Data Encryption Standard (DES) that can lead to the occurrence of weak and semi-...
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31 views

Confused in selecting the encryption method for mobile number and email encryption

I'm new in cryptography and I'm developing a mobile app that gets user_name, E-mail ID, and ...
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36 views

What is the best encryption algorithm for having a “master” decryption key

I'm kind of a noob at cryptography so sorry if this doesn't make sense. Here is my scenario: Somebody inputs their email into a form, their email is encrypted and only they have the decryption key to ...
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60 views

What measures can I do to prevent decryption of encrypted data?

This is entirely hypothetical, I'm working on securing some data and I want to make sure we do this properly. If I have a list of information which is encrypted (say, using a 256 bit encryption key) ...
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0answers
237 views

RSA factorization . How should I choose a to have a smaller computational complexity?

Given $N=p*q$ Solving these four with odd $x$ and $N$ with $h$ varying from $0$ to $7$ and with $a >= 1$ and $x >= 3$, assigning at $a$ value to our choice such that [1] $[8*(96 k² + 24 k + 1)...
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1answer
74 views

Encryption & decryption in AES CBC mode - Which is faster?

I wrote a small code to compute the time consumption by the AES in CBC mode, I noticed that the encryption is faster than the decryption, my question: Is my result correct? If yes, why is the ...
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1answer
51 views

The way to break Diffie-Hellman(small nonprime number)

i am wondering how to break DH(small nonprime number). Let's say we don't know: $a$: Alice's private key $b$: Bob's private key And we know: $N$: nonprime number $p$,$q$: $N = p * q$ ($p$ and $q$...
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Does multiple substitutions increase security? [duplicate]

Yes, because the attacker must decrypt the cypher text twice No, because it is equivalent to a single substitution Maybe, depending on the complexity of each substitution
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1answer
50 views

AES 5-round Square attack, how to choose plaintexts?

I know that we need to generate a delta-set (with 256 plaintexts). During the attack, we guess 4 bytes of round 5 key and 1 bytes of round 4 key, which allows us the byte at one position of the state ...
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33 views

What is the exact algorithm for encryption and decryption with hummingbird-1 cryptography?

I have really googled the entire internet but could not find a clear algorithm for hummingbird-1 cryptography.The problem emerges in the decryption module: What is the initial value of state register ...
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39 views

Unable to determine plaintext from ciphertext

Given the letter-number cipher: a=00, b=01, c=02, etc., encrypt the word 'hi' and decrypt its ciphertext using RSA. The public key is (5,35) and the private key is (29,35). I know that 'hi' is ...
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2answers
71 views

How is asymmetric cryptography safe if one of the keys is public?

Let's suppose $A$ is sending a message $m$ to $B$ using asymmetric cryptography. To guarantee the authenticity of a message, $A$ encrypts $m$ with $A$'s private key: $E(m, k_A) = m_A$. Then, $A$ ...
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1answer
43 views

Finding IV in AES-128 having partial Key and plaintext

Let's suppose we have the plaintext, 14/16 char of the key and the first 2 and the last 36 chars of encrypted data (that is 64 char long). What I want is to find the IV. The cipher algorithm is AES (I ...
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2answers
48 views

What's a relatively fast way of checking if a string is decrypted English?

I asked this on Stack Overflow but I was told to ask here. I'm writing a program that decrypts text encrypted using a Vigenere cipher. It's been working very well so far, but my current issue is that ...
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2answers
119 views

How to decipher an ADFGVX cipher?

I got introduced to the ADFGVX cipher, and it seems very tedious to decipher such ciphertexts. If I do not have access to the key square and the keyword, and I am just given the ciphertext and a ...
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1answer
43 views

Enforce weak RSA in TLS

I'm going to give a small talk on the mathematical background of RSA. My audience will consist mostly of software engineers and to make the mathematical stuff tangible, I wanted to demonstrate how to ...
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2answers
103 views

Relationship between $N$ and $\phi(N)$ in the RSA algorithm

Recently I started learning how the RSA algorithm works and there is one single part of the computation which really confuses me and can't get over it. Let's say I chose 2 prime numbers, namely $P ...
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1answer
191 views

How to decrypt using CRT, and then verify by encrypting without CRT?

Here is the actual question that I need to answer: An RSA encryption scheme has the set-up parameters $p = 31$ and $q = 37$. The public exponent is $e = 17$. Decrypt the ciphertext $y = 2$ using the ...
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2answers
111 views

A doubt about Diffie-Hellman Key Exchange

I have a doubt about the Diffie-Hellman problem: Is it possible to send a message to someone using only the Diffie–Hellman key exchange? Since it's called a key exchange can you only make a key?
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1answer
71 views

RSA Decryption: Doubts: knowing p or $\phi(n)$ can lead to find private exponent?

I have some doubts about RSA (the public key $n$ and $e$ is public): Note $n = pq$ and $\phi (n) = (p-1)(q-1)$ 1) Say if some hacker knew $p$, why would it be easy for them to find $q, \phi (n), d$? ...
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71 views

Finding a dataset to benchmark cryptographic algorithms

I’m planning to compare cryptographic algorithms in terms of encryption/decryption time, memory used etc. and for that I’m in need of a standard dataset consisting of plaintexts of different bit sizes ...
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Three Pass Protocol Question!

Alice and Bob have agreed to use the Three Pass Protocol. p=1009 Alice chooses the encryption exponent e_A = 101 Bob chooses the encryption exponent e_B = 209 Now Alice and Bob send three ...
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81 views

How do I prove that a user encrypted the data?

I am using homomorphic encryption, and I need to check whether or not a user's data is actually encrypted. For example, an eCommerce website pulls data from a user called Alice and wants to prove to ...
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41 views

Bitslice DES decryption

I would like to implement fast DES decryption using Bitslice technique. Without bitslice DES technique, I have already done decrpytion in this source code by changing the for loop from 15 to 0. In ...
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2answers
194 views

One-Time Pad: True or False

Suppose a message $M$ was encrypted with a one-time pad. If we learned the first half of the original text is some substring $s$, would we have a better chance of cracking the rest of the message? Is ...
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1answer
55 views

How can a derived key be verified to be the right key?

Assuming I am using some derivation function to generate encryption key from the string to encrypt a file. How that string is later verified during decryption? If user enters wrong password/string, ...
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3answers
186 views

Would creating a custom human language be stronger protection than encrypting a known human language?

There are some languages that people haven't been able to read (Cretan Hieroglyphics for example). Does that mean that you can better protect data by making your own language than by encrypting an ...
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I know my passphrase. I don't remember specifically how I entered it

First if this is the wrong place to post this please forgive me. I know my passphrase. I don't remember specifically how I entered it. ex. If the phrase is "The house at the end is blue and white. I ...
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31 views

How to recover deleted-recovered windows efs-encrypted files?

I'd some EFS-encrypted files on a HDD which were deleted unintentionally. I used a data recovery software to restore them, but afterward, windows does not recognize those recovered files as encrypted ...
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1answer
58 views

Proof that Niederreiter Cryptosystem is correct

I read about Niederreiter Cryptosystem. I understood the Key Generator, encryption and decryption of the cryptosystem, but if I want to prove that is a correct cryptosystem, what should I do?
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1answer
61 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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781 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
71 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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1answer
136 views

My RSA decryption doesnt match answer

Break the RSA code whose key is $(n, e) = (8369428283, 1234567)$. Find the deciphering key and then decipher the message under the assumption that the plaintext consists of 7-letter blocks in the ...
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2answers
230 views

Construct another ciphertext that decrypts to same message without knowing key in Elgamal

I read about ElGamal from various resources and I was wondering if the following is true. Would appreciate if you could elaborate on it so I can understand better: Is it possible to construct, given ...
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1answer
219 views

What is AES subkey? [closed]

I saw the AES algorithm that at the end of algorithm the buffer that stored in the beginning of algorithm the encrypt/decrypt key. now is store the last subkey. What is the last subkey? Why do I ...
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1answer
68 views

RSA: least significant bit position in key

How can I show that $C' = 2^e·C^* \bmod N$ when it is decrypted will add zero bits in the least significant bit position of the key? I am not sure if the cause is multiplying by a ciphertext which ...
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1answer
78 views

Encrypt data. Create 5 keys. Just 3 keys are needed for decryption

I would like to encrypt some data and create 5 keys. These keys are stored in different places. If I want to decrypt the data I just need 3 of these 5 keys. Is there a way to do this?
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77 views

How to decrypt a combination of transposition and substitution cipher text

I'm having problems decrypting a cipher text that has an transposition cipher applied to it but also a substitution cipher. I don't know in which order they were applied. Does anyone know what steps I ...
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25 views

How would you decrypt an affine cipher with only the ciphertext? [duplicate]

If I have only the ciphertext but the alphabet and the value of a and b are all unknown ... how would I go about this? I understand decryption with the key and alphabet, that is fairly easy but if we ...