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
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
271 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
964 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
544 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
219 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
709 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 ...
1
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0answers
556 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
786 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
622 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
201 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
12k 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
468 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
50 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 ...
3
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2answers
201 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
854 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 ...
1
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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 ...
1
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0answers
132 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
335 views

Saving encrypted files

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7
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1answer
6k 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
306 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
737 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
94 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
273 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 ...
3
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3answers
276 views

Checking an MD5 of a device

The point of this code snippet is to calculate and compare an MD5 obtained from a USB device connected to the computer against a database to check its validity. ...
6
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2answers
3k views

BouncyCastle Diffie Hellman

I want to write a complete diffie Hellman example for bouncy castle that includes key generation, key exchange, encryption, and decryption. I also want to verify that if Alice is initiating a ...
5
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2answers
156 views

Hashing user passwords

I've written a Java class that will provide the utility of, in essence, hashing user passwords for an Android app that integrates Couchbase mobile into it, and then, checking whether or not the ...
5
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2answers
648 views

An AES Cryptography Wrapper

I built this wrapper over the System.Security.Cryptography.Aes encryption/decryption so that one need only instance the class and call the appropriate methods. This makes it much simpler to work with ...
4
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3answers
5k views

Cipher decryption and encryption

I'm brand new to C# and I've started to make a cipher decryption program. The code works and runs fine, apart from the odd exception. I'm just looking for ways to improve my code and make more ...
3
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3answers
318 views

A hash-signature-type which tests on comparing against normal strings

I decided to throw this together today figuring it would be cool to add to my repertoire. Before we always had performed this "task" externally. Find the value we want to compare, hash it and compare ...
3
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2answers
151 views

Program to retrieve key/message from a multiple times used one time pad

I wrote a program to retrieve the key/messages from 10 different ciphers which were all encrypted with the same key with an xor one-time-pad method via crib dragging. To do this, I wrote a python ...
2
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1answer
156 views

T-SQL Constant Time Comparison

Explanation is in the function. Please point out any egregious errors: ...
3
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2answers
3k views

Getting a hash string for a very large file

After reading about large files and memory problems, I'm suspecting that my code below may be inefficient because it reads the entire files into memory before applying the hash algorithm. Is there a ...
6
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2answers
8k views

Simplified DES encryption

This is one of my first Python scripts and I was wondering if it meets the correct conventions. Also are there things that you would write different? I am looking for some good comments so I can start ...
1
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0answers
161 views

T-SQL Totp (Rfc6238 SHA2_256) Implementation

Using my previous function as a base I've come up the following: ...
4
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1answer
360 views

MD5 hash generator

I made this code for a simple WinForm for my school project where I want to add other hash and encryption algorithms. I have made it following the algorithm of the official RFC 1321 and the Wikipedia ...
4
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2answers
490 views

Encryption wrapper

I am writing an encryption class using Crypto++. The idea is that the client connects using RSA (encrypt, decrypt) with username, password, 32 byte key. The server will then return using the stream ...