One-time pad encryption

Basic Java Swing application to demonstrate one-time pad encryption.

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Table of Contents

• About the project
• Usage
• Technical details
• Architecture
• Performances test
• License

About the project

This is a simple GUI application (in French) to demonstrate the use of the One-time pad encryption technique for encrypting / decrypting data (text and files).

Application has been built on November 2008 using Netbeans IDE 6.5.

It uses the Swing Application Framework and was compiled with Java 6.

Usage

Run the provided .jar file :

java -jar "dist/ProjetCrypto.jar"

Then just use the UI :

From the Option menu, you can configure :

• byte packet size (1024, 2048, 4096) : byte packet size for file processing
• random or fixed seed (alternated 0 and 1)
• write seed or not : if yes, seed will be written in the mask before generating next bits
• LFSR (see technical details below)

When dealing with files, I use the following naming convention :

• original file : filename.ext
• encrypted file : crypte_filename.ext
• key file : cle_filename.ext
• decrypted file : decrypte_filename.ext

Technical details

Security is done by using a Verman type scheme with a Linear Feadback Shift Register (LFSR) based on a pseudo-random generator.

Following LFSR have been implemented :

1. Xn = Xn-5 ⊕ Xn-6 ⊕ Xn-15 ⊕ Xn-16
   

   Short secret key (the seed) is constituted of X0, X1, ..., X15 values (16 bits)

2. Vn = Vn-5 ⊕ Vn-13 ⊕ Vn-17 ⊕ Vn-25
   Xn = Xn-7 ⊕ Xn-15 ⊕ Xn-19 ⊕ Xn-31
   Yn = Yn-5 ⊕ Yn-9 ⊕ Yn-29 ⊕ Yn-33
   Zn = Zn-3 ⊕ Zn-11 ⊕ Zn-35 ⊕ Zn-39
   

   In this case, the secret key consists of 25 + 31 + 33 + 39 = 128 bits, and the secret bit generated after each iteration is given by b = Vn ⊕ Xn ⊕ Yn ⊕ Zn.

3. Xn = Xn-5 ⊕ Xn-13 ⊕ Xn-17 ⊕ Xn-25 ⊕ Xn-32 ⊕ Xn-40 ⊕ Xn-44 ⊕ Xn-56 ⊕ Xn-61 ⊕ Xn-65 ⊕ Xn-85 ⊕ Xn-89 ⊕ Xn-92 ⊕ Xn-100 ⊕ Xn-124 ⊕ Xn-128
   

   Short secret key (the seed) is constituted of X0, X1, ..., X127 values (128 bits)

Thus, a sequence of bits of the same length as the message to be encrypted will be generated. And as the data is in binary form, the method is reduced to a particularly simple calculation and very effective in practice. The message to be encrypted is presented as a sequence of bits, and the key is another sequence of bits, of the same length. The bits of the plain text are treated one by one, by combining each one with the bit that has the same rank in the key, and then applying a XOR operation.

Decryption is done by combining the encrypted data with the bits of the key. The XOR operation being simple in computer science, these treatments can be performed at very high speed.

Here is a picture representing the secret bit generation for the 128 bits LFSR (n°2) :

Architecture

Application architecture :

All interesting stuff is located in file ProjetCryptoView.java (yes I don't used any MVC pattern at that time!)

Performances test

Here are some tests about file encryption (text, image, sound, video) under different computers (1,2 and 4 cores) to evaluate the performances :

1. Computer 1 (laptop) :
   • AMD Athlon M 2600+@2,0ghz
   • 1 x 256Mo PC2700@133mhz
   • 30Go IDE 5400tr/min 2Mo
2. Computer 2 :
   • Intel Core 2 duo E6700@3,3ghz
   • Corsair 2 x 1Go PC6400PRO@413mhz 4-4-4-12
   • 2 x Maxtor SATA II 160Go 7200tr/min 8Mo raid0
3. Computer 3 :
   • Intel Quad Core Q6600@2,9ghz
   • Corsair 2 x 1Go PC6400C4@406mhz 5-5-5-18
   • 2 x Maxtor SATA II 500Go 7200tr/min 32Mo raid1

Files :

• Name : test1.txt, Type : text txt, Size : 790 bytes
• Name : test2.jpg, Type : image jpg, Size : 46 467 bytes
• Name : test3.mp3, Type : sound mp3, Size : 3 637 961 bytes
• Name : test4.avi, Type : video avi, Size : 310 971 920 bytes

Computer 1 :

File	LFSR n°1 - 1024 bytes	LFSR n°1 - 2048 bytes	LFSR n°1 - 4096 bytes	LFSR n°2 - 1024 bytes	LFSR n°2 - 2048 bytes	LFSR n°2 - 4096 bytes
test1.txt (790 o)	00:00:00:080	00:00:00:040	00:00:00:020	00:00:00:010	00:00:00:020	00:00:00:020
test2.jpg (46,47 Ko)	00:00:00:231	00:00:00:180	00:00:00:341	00:00:00:421	00:00:00:430	00:00:00:431
test3.mp3 (3,64 Mo)	00:00:06:099	00:00:07:370	00:00:08:562	00:00:10:435	00:00:12:938	00:00:16:053
test4.avi (310,97 Mo)	00:10:50:726	00:12:28:306	00:14:03:764	00:16:51:624	00:24:21:078	00:29:52:878

Computer 2 :

File	LFSR n°1 - 1024 bytes	LFSR n°1 - 2048 bytes	LFSR n°1 - 4096 bytes	LFSR n°2 - 1024 bytes	LFSR n°2 - 2048 bytes	LFSR n°2 - 4096 bytes
test1.txt (790 o)	00:00:00:000	00:00:00:000	00:00:00:000	00:00:00:000	00:00:00:000	00:00:00:000
test2.jpg (46,47 Ko)	00:00:00:032	00:00:00:050	00:00:00:062	00:00:00:063	00:00:00:062	00:00:00:078
test3.mp3 (3,64 Mo)	00:00:01:375	00:00:01:782	00:00:02:078	00:00:02:344	00:00:02:938	00:00:03:640
test4.avi (310,97 Mo)	00:02:15:875	00:02:36:265	00:02:58:688	00:03:33:532	00:04:28:391	00:05:57:500

Computer 3 :

File	LFSR n°1 - 1024 bytes	LFSR n°1 - 2048 bytes	LFSR n°1 - 4096 bytes	LFSR n°2 - 1024 bytes	LFSR n°2 - 2048 bytes	LFSR n°2 - 4096 bytes
test1.txt (790 o)	00:00:00:000	00:00:00:000	00:00:00:000	00:00:00:000	00:00:00:000	00:00:00:000
test2.jpg (46,47 Ko)	00:00:00:016	00:00:00:062	00:00:00:078	00:00:00:047	00:00:00:063	00:00:00:109
test3.mp3 (3,64 Mo)	00:00:01:563	00:00:02:062	00:00:02:735	00:00:02:859	00:00:03:906	00:00:04:828
test4.avi (310,97 Mo)	00:02:38:112	00:02:59:754	00:03:38:968	00:04:08:622	00:05:10:354	00:06:58:720

License

General Public License (GPL) v3

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.