Extract PrivateKey Information

Question

2.33/5 (3 votes)

See more:

Hi All,

I am working on a small project based on PKI.
And i needed some information about extracting the PrivateKey from the Digital Signature.

Is there any way in which i can extract the PrivateKey information from the custom .p12/.pfx Certificate i have installed into the browser ?

Google suggested a few methods of using openssl to do this. But I am not sure as how how i have to use them.

I would like some suggestion as to how I can get the privateKey information from the Digital Signature using php/javascript.

I am looking for these information in the client machine. I am not talking about the information in the Server side.

Posted 22-Apr-11 4:46am

ZeeroC00l

Updated 22-Apr-11 19:38pm

v2

Add a Solution

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Sergey Alexandrovich Kryukov · Accepted Answer · 2011-04-22T13:06:00

Solution 1

No way.

If you read about asymmetric encryption and think about it, you will understand, that if such method existed it would defeat the purpose if ciphering or digital signature.

All this is based on the idea of one-way function, see http://en.wikipedia.org/wiki/One-way_function[^]. The algorithm representing a one-way function is believed or proven to have not backdoor (http://en.wikipedia.org/wiki/Backdoor_(computing)[^]).

Perhaps you need better understanding of public-key cryptography. Please read http://en.wikipedia.org/wiki/Public-key_cryptography[^].
To understand digital signature, read http://en.wikipedia.org/wiki/Digital_signature[^].

—SA

Posted 22-Apr-11 13:06pm

Sergey Alexandrovich Kryukov

Updated 22-Apr-11 19:18pm

v3

Comments

ZeeroC00l 22-Apr-11 22:45pm

Thanks for the Information. :)

I read those articles and now its clear that I can't extract privateKey, but is it possible to use the digital Signature directly to encrypt/decrypt a message ?? (i.e. Use the signature as a key in encrypting/decrypting the message)

Sergey Alexandrovich Kryukov 22-Apr-11 23:32pm

Wait, wait! What do you mean "use digital signature to encrypt/decrypt"?
No. Perhaps you need to explain your ***ultimate*** goals.

I think you misunderstood the signature. The signature task is something in reverse to the problem of secret communication, but technology is the same. Look at the example of Alice and Bob in the article on public-key cryptography. One of them can decrypt with private key, but anyone can encrypt as the other key is public. Digital signature is kind of reversed situation: anyone can "decrypt" (read signed message, run signed application), but only the owner of the private key can "encrypt" (sign assembly, create another message impersonating the original author, an owner of the private key). In both cases, the same mathematics/algorithm works: generate pair of key: what is encrypted with one key is decrypted with its counterpart. The difference is only which one to open to the public. The communication in the opposite direction needs another pair of keys...

--SA

Sergey Alexandrovich Kryukov 23-Apr-11 1:19am

I added one more reference -- on digital signature good to understand how it works.
See the last sentence and link in my updated answer.
--SA

ZeeroC00l 23-Apr-11 1:26am

Thanks for the answer :) Now things are clear..
My goal was to encrypt a message using the key available in the Digital Signature.
And when you mention that extracting the privateKey would be a security violation, I thought it might be possible to use the Digital signature file itself directly to encrypt the message.

ZeeroC00l 23-Apr-11 1:27am

Is there any other way in which i can encrypt a message using the information present in the Digital Signature ?

Sergey Alexandrovich Kryukov 23-Apr-11 22:33pm

I don't see any sense in it. This is not the purpose of this file to do encryption. You did not answer my question about the ultimate goal. Essentially, I asked "why do you want to use digital signature", you answered "because I want to encrypt using digital signature". The question remains "why would you want it". What's the ultimate goal? Secret messages? Use known techniques of key distribution or even exchange the pubic key on each message. You answer the question about the goal including the technique in the answer. But you don't really want to use this technique or don't answer why.
--SA

ZeeroC00l 23-Apr-11 23:49pm

My goal was to exchange a message between two users in encrypted form. As you said "secret message". Sorry that i didnt answer your question as to what was my ultimated goal, yours suggestion clarified my doubt. So I didn't answer that question.

I am using xor cipher for encrypting the message for now. I will give a try to the method you suggested, i.e. to use the key distribution of exchange of public key.

Sorry, my Answer was incomplete in the previous comments.. Hope i have answered all the doubts that I had raised with this question.

BR//
Harsha

Sergey Alexandrovich Kryukov 24-Apr-11 0:03am

No problem at all. You can use, for example, RSA class to generate key, encryption and decryption. For better performance, it can be used for secret passing of the symmetric key used for further communications or immediate exchange of messages (a pair of keys per each direction).
--SA