Re: Share and store RSA - public key in java server and vice versa
Re: Share and store RSA - public key in java server and vice versa
- Subject: Re: Share and store RSA - public key in java server and vice versa
- From: Devarshi Kulshreshtha <email@hidden>
- Date: Thu, 12 Jun 2014 08:31:12 +0530
Because of all the problems I faced I finally decided to use a third
party library - Chilkat
Here is the link: http://www.chilkatsoft.com/crypt-objc.asp
On Mon, May 19, 2014 at 10:56 PM, Jens Alfke <email@hidden> wrote:
>
> On May 19, 2014, at 3:06 AM, Devarshi Kulshreshtha
> <email@hidden> wrote:
>
> 5. Used - wrapSymmetricKey:keyRef: method defined in SecKeyWrapper
> class (CryptoExercise example) for encryption, and passed key obtained
> from step 3 and data to encrypt obtained from step 4 to it
>
>
> I think you’re misusing wrapSymmetricKey. The NSData you pass into it is not
> the message itself; it’s a raw symmetric key. The idea is that you create a
> symmetric key at random (probably 32 bytes for an AES-256 key), wrap
> (encrypt) that key using the recipient’s public key, encrypt your actual
> message using the symmetric key, and then send both the wrapped key and the
> encrypted message to the recipient.
>
> Problem: getting error - too much data for RSA block
>
>
> Yup. RSA can only encrypt a block of the same size as its key, so if you’re
> using RSA-2048 the maximum block size is 256 bytes. The padding formats used
> with RSA don’t support messages longer than that. In practice, the only
> things RSA encrypts are symmetric keys, never messages.
>
> (If you’re not familiar with concepts like wrapping and padding, you should
> really read a good book on cryptography before proceeding. It’s actually
> rather dangerous to work on this kind of stuff without a solid understanding
> of the principles, because the crypto building blocks can easily be misused
> to create systems that are insecure and easily exploited.)
>
> —Jens
--
Thanks,
Devarshi
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