Questions tagged [cryptography]

Questions relating to cryptographic topics such as encryption/decryption and hashing. (Not for use with trivial ciphers.)

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1answer
82 views

Encrypting a user's file with a key that isn't stored but only known by the user

I want to make some kind of file vault. I want to store encrypted files in a MySQL table, and the key to encrypt/decrypt them is never stored but only known to the user (that's the goal, anyway). The ...
-2
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1answer
301 views

Symmetric cipher [closed]

Can someone please review this algo and say if it has some weak places and/or what kind of algo is this (caesar, block etc)? ...
2
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0answers
746 views

Converting [UInt32] -> [UInt8] -> [[UInt8]]

I am trying to speed up my current implementation of a function that converts [UInt32] to a [UInt8] which in turn is split up ...
3
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1answer
999 views

Implementation of Ceaser's Cipher in Python

This is my implementation of a Ceaser's Cipher in Python using OOP principles. I'm looking for feedback for any code starting from the function build_shift_dict (...
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1answer
194 views

Some kind of encryption in C++

It's my university task. Can I get some opinions on it? ...
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1answer
766 views

Encrypting and decrypting strings using Caesar cipher

I was inspired by a solution in Think Python: How to Think Like a Computer Scientist. I structured mine (into two functions) according to it, and used the technique used in ...
3
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1answer
229 views

Encryption functions intended for production

I want to know if these encryption functions are ok for a live production application. Based on resources here and here and here I have put together these three functions. Purpose This code is for a ...
4
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1answer
304 views

AES Encryption/Decryption

Where I currently work I'm tasked with writing a good encryption and decryption code which will have DEK as well as KEK. Haven't started on KEK yet. I have already told them, that we need expert help, ...
5
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1answer
2k views

Using SHA-512 for encryption/decryption

It occurred to me that if SHA2 can be used to derive keys from passwords, then it might as well be good enough to generate random data that can be xored with a plaintext to encrypt and the other way ...
2
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3answers
3k views

Implement Transposition cipher in c++

I try to implement the encryption by Columnar transposition. Input: key_secret and Text_to_encrypt, both of them are in lower. Output: encrypted_text. The code works fine but I have some questions: ...
2
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2answers
2k views

Simple ActiveRecord attributes encryption in Rails 5+

The task at hand was to ensure that certain columns in the database are encrypted in case the database data is stolen. I have a feeling that a lot can be improved here (naming, DSL, encapsulations) ...
2
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1answer
2k views

Signing a String using an identity and trust from a PKCS #12 Bundle

One of the requirements of a third-party SDK I am integrating with is to sign an identifier string with the identity from a p12 certificate. This code loads a p12 certificate from the application's ...
2
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1answer
7k views

AES-128 Encryption/Decryption of NSData

I recently found an Objective-C extension on NSData that encodes and decodes data with AES-128. I made an attempt to port this code to Swift 2.2: NSData+AES.swift ...
3
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2answers
280 views

DIY String Encryption

I was asked to make a String encryption utility without using encryption API. I basically had to come up with my own encryption methodology! the program was to be able to encrypt a string and decrypt ...
2
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2answers
1k views

String Encryption

I was asked to make a String encryption utility without using encryption API I basically had to come up with my own ecryption methodology! the program was to be able to encrypt a string and decrypt a ...
3
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2answers
588 views

AES class security

I am using the AES class (which I think I got from another post on Stack Overflow) for encrypting strings to a database. How robust and secure (would it be easy to break) is this class? Is there any ...
2
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3answers
6k views

String hash generator

There is a lot of code duplication because it generates hashes using multiple cryptographic hash algorithms. How can I improve this code? ...
2
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2answers
232 views

Intel® TinyCrypt: AES-128/CTR to encryption/decryption of 2D arrays

I need to encrypt/decrypt 2D arrays (double pointers) using AES-128/CTR using Intel TinyCrypt (written in C). The following are two helper methods to simplify the library usage. Any comments would be ...
4
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0answers
3k views

Generating public/private RSA key pair programmatically, using it for JWTs

In my app I'm using JSON Web Tokens for authentication purposes, using the pyjwt library. Instead of using static keys and/or worrying about key distribution, the server generates a public/private key ...
7
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1answer
729 views

Steganography with AES encryption

I created a small program that hides arbitrary files in png images using steganography - it encodes the files in the two least significant bits of every channel, so using a 4-channel png we can encode ...
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0answers
578 views

API with security through a private and public key

I want to make users login into an app. The code on my server serves a "token". This is based on a salt that is saved for each user, the login date, expDate and the ...
8
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3answers
3k views

Implementing AES encryption in Java

I'm not a security expert, but while checking over our AES implementation for our flagship product, I've noticed some strange things, like the output length having a relation with the input length and ...
5
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1answer
832 views

PyCrypto AES-256 CTR wrapper secure for public use?

I have tried to write a more user-friendly AES CTR wrapper with PyCrypto, but I'm not sure if it's safe enough. I mean, by default there is IV=1 for CTR and in documentation it's said that IV is ...
2
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1answer
655 views

CUDA brute force 48 bit key

I have a cryptographic function with two 24 bit keys. I have two blocks of input and two blocks of output, and want to brute force the keys using CUDA. Overview: The function is composed to two ...
0
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1answer
202 views

Effective ways to find partial sha1 collision

I need to find 2 different string and compare their hash value. Both string must contain "abc". I looking for the first eight character that are the same and stop. I have been running for more than 24 ...
12
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1answer
14k views

Secure way to store and load password in app config

I am trying to figure out a good way to store and load a password in the application configuration of my C# application. To achieve this I use the BouncyCastle library and the DPAPI from Windows. To ...
2
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0answers
2k views

Simple Java Encryption/Decryption

I am a beginner at Java programming, and I'm always curious about how to make code more efficient or learn what I am doing wrong. I just started learning about cryptography, and this is a simple ...
13
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1answer
473 views

.NET 4.5 licensing subsystem using RSA-4096 strong name key, SHA256 signed XML, and assembly signature enforcing

Abstract For the past week I have been looking at taking advantage of the .NET 4.5 improvements to code signing and XML signing to produce a licensing subsystem I can use to license my own products. ...
4
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1answer
51 views

AES Wrap function

This code is supposed to implement RFC 3394 which also described in this PDF at page 11. Are there any weak places or formatting issues in attached source? Or maybe some places are not explicit ...
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2answers
203 views

File-encryption utility application

I made a simple file-encryption utility application for a little school project. I'm really interested in cryptography, and tried my best while making it. Can you see it, and give me feedback? The ...
8
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1answer
5k views

Encrypting strings in Golang

This is a an example application for testing some encryption and decryption functions in Golang. The functions encryptString(), ...
0
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1answer
906 views

Implementation of authenticated encryption

My application needs to implement authenticated encryption using C#. There is a .NET class called encryptAndAuthenticate, but it is only supported on windows 8 or ...
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3answers
1k views

Encryption algorithm using CTR mode

I am using CTR mode (it is a cipher in itself) in this code. I just wanted to see what you thought about it before I finish it. (Yes, I know that the plaintext length and key length must be highly ...
4
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2answers
3k views

AES and RSA using javax.crypto

So I am assuming that I did something wrong, and my AES and RSA encryption and decryption classes are insecure. I plan on using them for a larger project, and want to make sure I didn't completely ...
2
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0answers
1k views

LockBox TwoFish string encryption and decryption

I'm using TurboPower LockBox for the first time, and using the TwoFish algorithm to first encrypt a password, and later retrieve the password by decrypting the generated hash. I would like to know ...
4
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1answer
94 views

T-SQL Secure String Comparison

The previous version of my function was scalar-valued and employed a WHILE loop to do the comparison, this is SLOW. This new version is tabled-valued and uses a typical tally table in place of the ...
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0answers
139 views

XOR 256 Block Encrypting and Decrypting

I am quite new to Go but have found it to be very useful for my use case (game server). I have a routine that encrypts/decrypts the game packets which was written in C++ which can be seen here and ...
3
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2answers
73 views

Finding a pair of words from two files with a particular MD5

I have two txt files. Both contain 60k+ words in a list. I put together some code to loop through each file and concatenate the strings ...
7
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1answer
1k views

Encryption Algorithm in C#

I'm coding a "encryption" algorithm for learning and and don't know how good is it or how could I make it better: ...
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2answers
346 views

Saving encrypted files

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7
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1answer
7k views

BouncyCastle implementation with X509Certificate signing, KeyStore generation, and Socket creation

The following is a (somewhat messy) implementation of the BouncyCastle cryptography library. I create a self-signed certificate (hopefully correctly), store it in a Java KeyStore, and use it to create ...
4
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2answers
5k views

One Time Pad algorithm for encryption and decryption

I have written my own one time pad algorithm for encryption and decryption, but I would like to listen to your opinions about its correctness and eventually how could I improve it. My idea was to keep ...
3
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1answer
5k views

Secure RSA encryption with PyCrypto

I'm coding a very simple reverse shell in python, and I want to encrypt the communication between the server and the client. The idea is to exchange an AES key using RSA then use it to encrypt ...
12
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2answers
2k views

Diffie-Hellman in JavaScript

Diffie-Hellman is a key exchange that allows 2 people to share a symmetric key without interaction beforehand. First, a person shares an equation; in this case, we use: $$3^x \mod{17}$$ Next, each ...
4
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5answers
3k views

XOR encryption program in C

I've written a program that encrypts files (or stdin) with a user-specified key from 1 to 255. This "encryption" is very insecure, but still a bit better than ROT13 ...
10
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3answers
312 views

What an Enigma! (Machine Simulator)

I've made this some time ago for an assignment and I was wondering how it could be improved both in terms of performance and best practices for C code. ...
5
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1answer
783 views

Custom encryption

I made a custom encryption library/class which allows to en-/decrypt Strings with a custom charset. I think you'll get what I mean with that when you take a look at ...
6
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2answers
4k views

Java conversion of base 16 to base 64

I wrote a solution in Java to solve the problem here. I use BigInteger to convert first from base 16 to base 10, then base 10 to base 64. This seems quite ...
3
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1answer
95 views

Sorting dictionary according to letter patterns

I've written a JavaScript dictionary sorting algorithm, which takes a .txt file (the dictionary), and loads it via node's file system. The purpose of this algorithm is to sort every word into its ...
7
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1answer
278 views

Encrypt message for sending over non secure network

wRecently needed to swap keys with a colleague on the other side of the country. This script encrypts a file using the other persons public key that is stored on github. It outputs a script that will ...