General Question

The fear of every surveillance society: citizens protecting their own privacy with strong cryptography

General Question

Post by Tubbieh on Thu Dec 09, 2010 4:11 pm
([msg=50339]see General Question[/msg])

I have a encrypted version of a file and the unencrypted version of the same file, is there any way to figure out the encryption method, and come up with decryption program or what ever?
Tubbieh
New User
New User
 
Posts: 3
Joined: Thu Dec 09, 2010 4:08 pm
Blog: View Blog (0)


Re: General Question

Post by Goatboy on Thu Dec 09, 2010 4:31 pm
([msg=50341]see Re: General Question[/msg])

Look up Known Plaintext Cryptanalysis.
Assume that everything I say is or could be a lie.
1UHQ15HqBRZFykqx7mKHpYroxanLjJcUk
User avatar
Goatboy
Expert
Expert
 
Posts: 2753
Joined: Mon Jul 07, 2008 9:35 pm
Blog: View Blog (0)


Re: General Question

Post by msbachman on Thu Dec 09, 2010 6:10 pm
([msg=50345]see Re: General Question[/msg])

Curious, how do you know you have identical files without knowing the encryption method? You have to decrypt it to know, correct?
"I'm going to get into your sister. I'm going to get my hands on your daughter."
~Gatito
User avatar
msbachman
Contributor
Contributor
 
Posts: 685
Joined: Mon Jan 12, 2009 10:22 pm
Location: In the sky lol
Blog: View Blog (0)


Re: General Question

Post by Goatboy on Thu Dec 09, 2010 6:14 pm
([msg=50346]see Re: General Question[/msg])

Depending on the method used to encrypt, you may be able to get by with only part of the file. For example, a ZIP file may contain many encrypted documents, and you might have just one of them. Or let's say you have the decrypted version of a document, and you know that many others are encrypted the same way. You could use this knowledge to work out the key.
Assume that everything I say is or could be a lie.
1UHQ15HqBRZFykqx7mKHpYroxanLjJcUk
User avatar
Goatboy
Expert
Expert
 
Posts: 2753
Joined: Mon Jul 07, 2008 9:35 pm
Blog: View Blog (0)


Re: General Question

Post by Tubbieh on Thu Dec 09, 2010 7:44 pm
([msg=50350]see Re: General Question[/msg])

After a bit of researching I found out that i can use [adaptive] chosen plaintext. How can I go about discovering the cipher with this method?

edit:

Just to clarify I have a bunch of files[1.txt,2.txt,3.txt,4.txt,...100.txt] in encrypted and unencrypted form. I can put in any numbers or text I want, im trying to figure out the cipher. [That didn't clarify at all]...

-- Thu Dec 09, 2010 10:57 pm --

msbachman wrote:Curious, how do you know you have identical files without knowing the encryption method? You have to decrypt it to know, correct?


I have a program that encrypts my own files [so I have the original and the decrypted], and I want the cipher so I can decrypt other peoples files too :D.
Tubbieh
New User
New User
 
Posts: 3
Joined: Thu Dec 09, 2010 4:08 pm
Blog: View Blog (0)


Re: General Question

Post by msbachman on Fri Dec 10, 2010 7:19 am
([msg=50368]see Re: General Question[/msg])

I have a program that encrypts my own files [so I have the original and the decrypted], and I want the cipher so I can decrypt other peoples files too


If you post the program, I am sure that people would find it a fun challenge.
"I'm going to get into your sister. I'm going to get my hands on your daughter."
~Gatito
User avatar
msbachman
Contributor
Contributor
 
Posts: 685
Joined: Mon Jan 12, 2009 10:22 pm
Location: In the sky lol
Blog: View Blog (0)


Re: General Question

Post by Tubbieh on Fri Dec 10, 2010 11:05 pm
([msg=50388]see Re: General Question[/msg])

Byond, Its a game engine. A simplified version of C++. The only thing is getting the encrypted and decrypted files is extremely hard to explain. I can post the Files if you guys want or whatever.
Tubbieh
New User
New User
 
Posts: 3
Joined: Thu Dec 09, 2010 4:08 pm
Blog: View Blog (0)



Return to Crypto

Who is online

Users browsing this forum: No registered users and 0 guests