Questions tagged [decryption]

In cryptography, encryption is the process of encoding information. This process converts the original representation of the information, known as plaintext, into an alternative form known as ciphertext. Only authorized parties can decipher a ciphertext back to plaintext and access the original information.

Filter by
Sorted by
Tagged with
26
votes
2answers
5k views

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 ...
14
votes
1answer
12k views

How long does it take to crack RSA 1024 with a PC?

Using an Intel Core i5 CPU, how long does it take to crack RSA using a key size of 1024 bit (generated using a secure key pair generation function)? Suppose for instance that we have thousands of ...
12
votes
13answers
2k views

Cryptography elements needed for a story

Note: following Maarten Bodewes's answer, I edited this post to make it clearer. I'm writing something partly driven by the need to crack a few encrypted files. This is what needs to happen in the ...
7
votes
1answer
490 views

Why does the Bombe not consider the Ringstellung when determining stecker pairs?

I am doing research on the Bombe Machine, and I read that when the Bombe tries to find the stecker (plugboard) partners of letters, it only needs to use the rotor types and arrangement and also the "...
6
votes
3answers
2k views

Good layperson analogy for password and encryption keys

NOTE: QUESTION UPDATED. SEE BOTTOM OF THIS POST. I'm writing something where I need to make someone come across as though they know cryptography. I don't know enough, but as cryptography plays only a ...
6
votes
3answers
229 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 ...
5
votes
4answers
5k views

How can I force slow decryption in the browser?

I have a string that I will encrypt on the server. I then want to send the encrypted string along with a decryption method for it to be decrypted in the browser. I want the decryption to take some ...
5
votes
0answers
1k views

Can I alter encrypted data without decrypting it? [duplicate]

I didn't find a direct solution for it. Can I modify encrypted data without accessing it? If there is an example, I would appreciate it.
4
votes
2answers
579 views

Advantages and possible usages of encryption schemes with probabilistic decryption

We can define deterministic and probabilistic encryption; Deterministic $c = E(k,m)$, and Examples are textbook RSA, block ciphers in ECB mode. Deterministic encryption fails to achieve CPA security....
4
votes
2answers
492 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 ...
4
votes
1answer
53 views

Why are the indicator drums of a Bombe machine labelled from A to Z clockwise?

I am researching the Bombe Machine, having just completed a project on the Enigma Machine. I visited The Rutherford Journal - The Turing Bombe, and it claimed that The scales on the three ...
3
votes
2answers
1k views

Encryption and decryption with Diffie-Hellman

I don't understand how it works. I only found explanations about the key exchange, but what about the actual encryption and decryption? Do you use the session key $K$ with a symmetric algorithm? Do ...
3
votes
2answers
287 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, ...
3
votes
2answers
1k 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 ...
3
votes
2answers
139 views

How to correctly implement an archetypal encrypt-then-MAC AES-CTR + HMAC mode cipher?

I've created an AES implementation in Python as a learning experience (mainly for encrypting/decrypting files), and wanted to make sure that I haven't made any huge mistakes in my logic (of course, ...
3
votes
1answer
68 views

What is the exact meaning of the public key cryptosystem properties in New Directions In Cryptography by Diffie and Hellman

I'm quite new to cryptography and don't have much mathematical knowledge. I'm studying cryptography, especially public key algorithms. I have some basic knowledge of public key algorithms so I know ...
3
votes
1answer
52 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 ...
3
votes
0answers
72 views

Decrypt the same ciphertext to multiple messages of my choice if I can use any key I want to decrypt

In a modern secure encryption scheme, is it possible(both theoretically and practically) to encrypt a message using a key to get the following ciphertext c = Enc(M1,k1) and later find another key so ...
3
votes
0answers
81 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 ...
3
votes
0answers
72 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 ...
2
votes
3answers
498 views

Will Fernet’s key function at any timeframe?

I’m very new to cryptography and I need to use a symmetric cryptography approach. My simple question is, will the key always at any time be able to decrypt the encrypted text? The encrypted text may ...
2
votes
4answers
252 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 ...
2
votes
1answer
1k views

What are the smallest possible RSA private and public keys?

I'm trying to understand what the smallest possible RSA public and private keys are. When using $p = 2, q = 3$, the encryption function doesn't encrypt. So I have to shift one prime to get $p = 3, q = ...
2
votes
2answers
174 views

FOR AES GCM decrypt function, Does the output(PT) depend on Tag value(T)?

According to spec, FOR GCM decrypt function input is IV, A, C, and T. As mentioned below: 5.2.2 Authenticated Decryption Function Given the selection of an approved block cipher, key, and an ...
2
votes
2answers
154 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 ...
2
votes
3answers
830 views

Need help cracking a Vigenère cypher with a period of 2

How do you crack a long Vigenère cypher when the key is unknown? I have tried frequency analysis, but I'm not making any progress.
2
votes
2answers
599 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 ...
2
votes
1answer
126 views

What is the correct order of operations for one-time pad cipher when using subtraction and mod 10 arithmetic?

What would be the proper order of operations for OTP encryption/decryption when using subtraction and mod 10? E.g. P - K = C or K - P = C Most of the sources I have seen do not cover this topic or I ...
2
votes
1answer
137 views

Zodiac unsolved 340 cipher decryption in 2020

This is a rather general question, but I'd really appreciate your (experts, in my view) opinion on this subject. I was wondering if, using current tech like machine learning, quantum computers and ...
2
votes
1answer
105 views

How to encode and decode message into polynomial form on NTRU

This question is based on a previously asked question. How to make a message into a polynomial on NTRU encryption? I am tasked to implement NTRU with toy parameters such as $N=7$ or $N=11$ and I have ...
2
votes
1answer
897 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: ...
2
votes
1answer
78 views

It possible to encrypt .bmp bitmap files using Stream Cipher Chacha20?

Maybe this sounds like a stupid question. I'm sorry for that. I just wanted to know is it possible to encrypt a bitmap image file like *.BMP, and generate the ciphertext which is an obscure bitmap ...
2
votes
1answer
5k views

Encryption and decryption of Request and response for REST API

I am working on encryption/decryption for the rest of the API. The client here can be mobile, desktop, web browsers, etc and all the requests will be made to an https endpoint. The main goal here is ...
2
votes
2answers
175 views

Forgery attack on Poly1305 when the key and nonce reused

Introduction: I've tried to find how reusing one-time key compromises itself but only found information that it breaks the encryption entirely, it is written everywhere. But since no methods to reuse ...
2
votes
0answers
38 views

Is there a way to find the two generator polynomials of a JPL sequence?

I am decoding a binary sequence that was detected as an unpractically long LFSR by the Berlekamp-Massey algorithm. First of all, the generated sequence is far longer than it needs to be and since it ...
2
votes
2answers
819 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 ...
2
votes
0answers
83 views

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 ...
2
votes
0answers
645 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. ...
2
votes
0answers
78 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 ...
1
vote
4answers
172 views

Are there any cryptographic algorithms, which lets the user apply some modifications on the encoded data, without decoding it?

I would like to encode some data with a key, and send it to a third party. They don't know the key to decode it, but I would like to make it possible for them to apply some modifications on it. Then ...
1
vote
2answers
194 views

How can RSA be used to compactly sign and encrypt?

How can RSA be used for digital signature with message recovery and encryption, providing transmission of a small message with confidentiality and authentication simultaneously, small cryptogram size, ...
1
vote
1answer
204 views

Why "encipher" instead of "encrypt" and "decipher" instead of "decrypt"?

According to a book I am reading, Applied Cryptography by Bruce Schneier, the ISO 7498-2 standard uses the terms “encipher” instead of "encrypt" and “decipher” instead of "decrypt" ...
1
vote
1answer
249 views

I do many searches but can't find any explanation about "AES analysis using entropy"

I found this scenario in CRYPTOOL2 templates but there is no explanation how entropy is used. There is just a short description "This template shows how to use a brute-force search to attack an ...
1
vote
2answers
1k 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 ...
1
vote
1answer
115 views

Are there any tools to analyze cryptographic algorithms performance?

How can I analyze a cryptographic algorithm performance to make a table and charts comparing them. I have seen several papers but there's no paper explaining how it is exactly done. As comparing data ...
1
vote
1answer
449 views

How RSA-OAEP decrypt a Symmetric Key message?

In an RSA-OAEP encrypted symmetric Key (AES for example) message. The message is then decrypted by the other party when R is a Random Number That other party doesn't know about. so How it can retrieve ...
1
vote
1answer
637 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 ...
1
vote
1answer
73 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 ...
1
vote
1answer
2k 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 ...
1
vote
1answer
82 views

Can we sign and encrypt with RSA keys of both sender and receiver?

By using RSA encryption, it is possible to "encrypt" sign with sender's private key and then with receiver's public key, and decrypt with receiver's private key and then with sender's public ...