OAKLEY 5 group in Diffie-Hellman

Hi everyone!
I'm developing an SRTP implementation using the MIKEY key exchange protocol (for compatibility with a draft on SIP crypto info exchange) and, therefore, need an implementation of the oakley 5 group of Diffie- Hellman.
My question is as follows:
If I use the following code does the paramGen use the OAKLEY 5 scheme to generate the parameters? I've tried to look at the API for information on what actually happens when inputing 1536 bit prime size, but I find nothing.
AlgorithmParameterGenerator paramGen = AlgorithmParameterGenerator.getInstance("DH");
paramGen.init(1536);I'd be grateful for any information and/or suggestions.

If I use the following code does the paramGen use the
OAKLEY 5 scheme to generate the parameters? I've
tried to look at the API for information on what
actually happens when inputing 1536 bit prime size,
but I find nothing.
AlgorithmParameterGenerator paramGen =
AlgorithmParameterGenerator.getInstance("DH");
paramGen.init(1536);
paramGen.init(1536) does not work for the default JCE Provider (the max value allowed is 1024).
I guess that the OAKLEY scheme is not used because the implementation predates OAKLEY RFC (1998), but it's better to check the source code (that you can download from http://wwws.sun.com/software/communitysource/j2se/java2/download.html
You can check also Bouncycastle's implementation, (http://www.bouncycastle.org ) but it's meant to be compatible with JCE's, so it probably does not use the OAKLEY scheme as well.

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Alexis wrote:
>
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>
I don't understand what you mean. The code snippet I posted is from OpenJDK source code. It catches any exception that is thrown from the call to create a DH public key from the X509 encoded key spec. new DHPublicKey(((X509EncodedKeySpec)keySpec).getEncoded()) If your encoding is incorrect then you will not know why. X509 encoded keys have a specific ASN.1 structure.
>
Considering you have the public key on the card, you should try using the javax.crypto.spec.DHPublicKeySpec using the three key components from the card key.
>
for that I need to know which value of my byte[] area corresponding to "y","p" and "g". In addition I think on my card I have create an elliptic curve for diffie-hellman method (KeyPair.ALG_EC_FP) and on my client (java) I use "DH" method.
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Edited by: claymore1977 on May 26, 2009 4:47 PM

claymore1977 wrote:
Which is simple enough, so I assumed that simply stripping off the first 4 bytes off the byte[] would yield a viable PublicKey, but I get the above error.Too simple. If you look at the Javadocs for X509EncodedKeySpec, you can see that it is much more complicated beast that contains object IDs in addition to the DH public bytes. You could try to get openssl to build the more complicated X509EncodedKeySpec, but I see below that you have found a simpler solution.
>
>
Additionally, I have tried to modify the code to use a DHPublicKeySpec instead of a X509EncodedKeySpec:
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