Generate Encryption Key With Diffie Hellman

11.04.202011.04.2020

Security on cloud has been a hot topic. Even the tech giants like google and amazon spend hefty capital to strengthen their security. We, here have implemented a secure text transfer using diffie-hellman key exchange algorithm.

Diffie Hellman Group
Generate Encryption Key With Diffie Hellman Lyrics
Wireshark Diffie Hellman

Diffie-Hellman Key Exchange

One of the brute approaches for secure transfer can be that user A can encrypt the using a key and later the key could be shared with user B. This approach can work up to an extent but it always has a risk of third-party eavesdroppping. We needed a system in which two users, without knowing the secret key, can independently generate same key at both ends. This key could later be used to encrypt and decrypt the text. The diffie-hellman key exchange algorithm comes into picture.
Diffie–Hellman key exchange (DH) is a method of securely exchanging cryptographic keys over apublic channel and was one of the first public-key protocols named after Whitfield Diffie andMartin Hellman. DH is one of the earliest practical examples of public key exchangeimplemented within the field of cryptography.
In public key cryptosystem, enciphering and deciphering are governed by distinct keys, E and D,such that computing D from E is computationally infeasible (e.g., requiring more than 10^100instructions). The enciphering key E can thus be publicly disclosed without compromising thedeciphering key D. This was the main ideology behind Diffie-Hellman Key Exchange Protocol.Each user of the network can, therefore, place his enciphering key in a public directory. Thisenables any user of the system to send a message to any other user enciphered in such a way thatonly the intended receiver can decipher it. As such, a public key cryptosystem is a multiple accesscipher. A private conversation can therefore be held between any two individuals regardless ofwhether they have ever communicated before. Each one sends messages to the other enciphered inthe receiver’s public enciphering key and deciphers the messages he receives using his own secretdeciphering key.

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Working example of Diffie-Hellman

Public-Key Cryptography and Diffie-Hellman Certificates Public-Private Keys. Cryptography takes the original message, and produces an encoded version by using a special piece of information known to the sender and receiver.

p is a prime number
g is a primitive root modulo of p

Alice and Bob agree to use a modulus p = 23 and base g = 5
Alice gets her private key (key which she should not share with anyone) generated as 4.
Thus, public key generated for Alice shall be 5^4 %23 = 625%23 = 4
Bob gets his private key (key which he should not share with anyone) generated as 3.
Thus, public key generated for Bob shall be 5^3 %23 = 125%23 = 10
Now, Alice gets the public key of Bob and generates a secret key. i.e.(public key of Bob ^ Private Key of Alice) mod p=> (10^4 ) % 23 => 10000 % 23 => 18
On the other side, Bob also uses a similar method to generate a secret key i.e.(public key of Alice ^ Private Key of Bob) mod p=> (4^3 ) % 23 => 64 % 23 => 18

Dependencies

I am writing a test harness in java for an existing program. As part of this i need to generate a Diffie Hellman key pair and pass the public key to the other program in its raw (i.e unencoded bytes).
Create a Diffie-Hellman key by calling the CryptGenKey function to create a new key, or by calling the CryptGetUserKey function to retrieve an existing key. Create a Diffie-Hellman private key BLOB by calling the CryptExportKey function, passing PRIVATEKEYBLOB in the dwBlobType parameter and the handle to the Diffie-Hellman key in the hKey.
For our webserver or VPN server, you want to use unique Diffie-Hellman parameters but you don’t know how to generate the.pem file using OpenSSL. Solution: Use this command to generate the parameters and save them in dhparams.pem: openssl dhparam -out dhparams.pem 4096. This command generates Diffie-Hellman parameters with 4096 bits.
What if we could dynamically generate a key? What if there was some way that both a client and a server could agree upon an encryption key without ever having to tell each other the actual key? Enter the Diffie-Hellman key exchange. Diffie-Hellman Explained.
Mar 17, 2016 s 1 and s 2 are the individuals’ “secrets”, only used to generate the symmetric key; Remember this: RSA is used to come up with a public/private key pair for asymmetric (“public-key”) encryption.Diffie-Hellman is used to generate a shared secret in public for later symmetric (“private-key”) encryption.

Code Explanation

This implementation can be explained in two parts

stand-alone-application
web-application

stand-alone-application

This portion deals with encryption and decryption of file
The file is encrypted using AES algorithm
Menu option also helps to toggle the menu to upload and download files

src/stand-alone-application/DH.py: This file deals with generating keys using diffie-hellman. It generates three keys: Private Key, Public Key, Secret Key (used for encryption and decryption)
src/stand-alone-application/ENCDEC.py: This file is used for encoding and decoding using AES algorithm.
src/stand-alone-application/thrain.py: This file acts as a mediator and connect the main program with other code files.
src/stand-alone-application/main.py: This file deals with the GUI. It is the main file [yeah, trust me!].

web-application

Once file is encrypted it has to be uploaded on an online directory. Another directory is needed where public-key of all the users is stored. Thus, we built an online directory and hosted it on cloud. The unique thing about hosting is that dynamic files are being generated while adding a new user or uploading a text file. Thus, we needed a cloud service which could run the program and incorporate the dynamic files. We tried free services like pivotal and heroku but then amazon AWS came to our rescue.
src/web-application/app.py Contains the website in python-flask which acts like a directory.

Hosting on AWS

Diffie Hellman Group

fork this repository
create an amazon EC2 instance.
Select and create Amazon Linux AMI 2018.03.0 (HVM), SSD Volume Type
While creating the machine, toggle to menu Configure Security Group menu.
Here, enable port SSH, HTTP, RDP and in port, change Source to Anywhere
Download and keep the publicKeyPair.pem file
Install putty and puttygen
Open puttygen, select the publicKeyPair.pem and generate a private key. Now, save it as Save private key
Open the AWS machine dashboard ad copy the IPv4 Public IP of the instance created
Open putty
In putty, copy the IP in Host Name(or IP address)
In putty, toggle the SSH>Auth and here, select the private key you generated.
Click open and voila! The terminal of instance opens
Enter 'login as:' ec2-user
Enter following command
$sudo bash
$yum install python-pip
$yum install git
$pip install flask
Now, clone the forked repository on local machine
In src/web-application/app.py, comment on line 169 and uncomment line 168
Update the github repository
On the terminal of instance, clone the repository and enter command
$python app.py