Questions tagged [decryption]

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I need help deciphering this [closed]

I'm not sure if this is the right place to ask this, but I need help deciphering this code. Message is as follows: "I,Zdg F\ух|Rю.DpьфоF}"rxVдrGGMjWяьеmqлiWaюeBseцюagаmьFsa-j|=d,фgdмeZvйwfmHlArцxπ"...
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2answers
55 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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46 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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Any idea what this Encrypted text says? [closed]

" 31 30 5c 6c 67 6d 62 6f 61 5g 36 35" It seems to be Hex, but the answer is wrong. This is what I get: 10\lgmboa65. Any different ideas?
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Does anyone know of any tools that can decrypt CTR, CFB, and OFB modes in DES? [closed]

I have the key, ciphertext, and IV for all 3 messages. Don't really know what I'm doing with programming it and haven't found any working tools online for them.
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2answers
93 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
81 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
102 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
95 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
63 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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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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21 views

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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71 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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35 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
175 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
53 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
178 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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65 views
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37 views

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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28 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
54 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
59 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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2answers
735 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
43 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
133 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
144 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
121 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
61 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
63 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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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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24 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 ...
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1answer
156 views

Need help cracking a vigenere cypher with period 2

how do you crack a long vigenere cipher when the key is unknown , I have tried a frequency analysis but I'm not making any progress
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52 views

Decryption of RSA with e that has no inverse

I'm studying the RSA protocol and I was wondering if there was any way of decrypting a message if the $e$ doesn't have an inverse $\mod (p-1)(q-1)$. Usually, you have to choose a value of $e$ that is ...
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1answer
79 views

RSA - Calculating $d$ given $\varphi (N)$ and $N$

From this discussion, I know that if I know $\varphi (N)$ and $N$ (where $N=pq$, $p$ and $q$ prime), then I can very easily get $p$ and $q$. Suppose I have the encrypted message $c$. I want to get ...
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Using Viterbi algorithm to decrypt Vernam cipher

I'm reading a book on cryptography and it mentions the Viterbi algorithm being used to decrypt Vernam cipher if the same key is used multiple times. According to the book the Viterbi algorithm takes ...
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How are side-channel attacks executed? What does an attacker need to execute a side channel attack?

I've been reading about side-channel attacks on Wikipedia, and it seems that some of these can only be executed on the victim's computer. (I am specifically asking about the side-channel attacks ...
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1answer
80 views

Secure encryption to store credit card data

I need an encryption algorithm that would be secure enough to store credit card data. So it should be reasonably secure. Here's what I've come up with. I'd appreciate any constructive criticism. Is ...
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179 views

Known Plain-text Attack [closed]

How can I find the known plain text P2 based on the given information? Assuming that the encryption is made using a common initialization vector and the mode used for encryption is OFB. ...
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1answer
321 views

OpenSSL: How to maintain padding from encryption after decryption?

One of my professors mentioned in class that there is a way of using PKCS#7 padding to have the padding persistent after decryption. For example, if I encrypt a 20-byte file using ...
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1answer
220 views

“hex” vs. “base64” encoding when enciphering

Examining different implementations of encryption / decryption with cipher on Node.js, I paid attention that some implementations use hex encoding: ...
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0answers
67 views

Possible deciphering methods for the steganography on an old check? [closed]

This check was deposited in the 1930s, and it was issued by OCBL (an old bank in Singapore). The checks issued by this bank had an interesting feature - an obfuscated pattern printed on the back of ...
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1answer
40 views

Is it possible to find what is the random generated key if I know the plaintext and ciphertext? [closed]

Is it possible to find what is the key with only plaintext and ciphertext? For example, My plaintext is: hi My ciphertext is: 0x1db5
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4answers
199 views

Is an invulnerable code possible (including brute force attack)?

If I double encrypted a text with for example AES wouldn't it be invulnerable to bruteforce attacks due to the computer not knowing when it has reached the plain text? Plain text->1st layer of ...
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1answer
97 views

NaCl allows decryption with the same public key as for encryption

I followed the description here: Public-key authenticated encryption: crypto_box and created an example that encrypts a message with Bob's public key and signs it with Alice's secret key : ...
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2answers
228 views

Is this toy RSA demonstration flawed?

I want to present the basics of how RSA works to an audience of beginners in cryptography. The problem is that I am lightyears from being an expert. After reading about how RSA works in wikipedia, ...
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1answer
88 views

How secure is a 40 bytes hexadecimal string AES256 encrypted with 50 bytes random password

Problem Assume I have a 40 bytes hexadecimal ASCII string and a 50 bytes random password. ...
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54 views

Subexponential algorithms that apply only one of factoring and discrete logarithm?

Shor (quantum polynomial), Number Field Sieve (subexponential), Pollard rho (square root) all have both factoring and discrete logarithm over $\mathbb F_p^*$ variants. What are the subexponential ...
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1answer
86 views

Are there any asymmetric key encryption/decryption algorithms?

When it comes to encrypting some data (where data being something of a large size), symmetric key cryptosystem is predominant. Symmetric key algorithms like AES, DES, Blowfish, IDEA etc. are ...
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1answer
89 views

Cryptography on programming

In pursuit of understanding a randomly found topic I was interested in learning the connection between integer programming and cryptography and found Lenstra Jr.'s Integer Programming and Cryptography....