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Hi

I'm making tests with JC 2.2.2 and would like to know what is supposed to give back the KeyAgreement ECDH function when it is called. The JC 2.2.2 API guide states that this function follows the notation of IEEE 1363. However, if for example you make tests with public and private keys of the type LENGTH_EC_FP_112 (where any field element is 14 bytes long), after calling the "generateSecret" method you obtain a byte array of 20 bytes. The problem is that the ECDH method is supposed to provide a field element (of 14 bytes), so I don't know what those 20 bytes represent. Does anybody know what this KeyAgreeement implementation is suppossed to produce?

Here's a sample of my code:

try {
keyPair = new KeyPair(KeyPair.ALG_EC_FP, KeyBuilder.LENGTH_EC_FP_112);
keyPair.genKeyPair();

ecPublic = (ECPublicKey)keyPair.getPublic();
ecPrivate = (ECPrivateKey)keyPair.getPrivate();

baECPublic = new byte[100];
baOut = new byte[100];

keyAgreement = KeyAgreement.getInstance(KeyAgreement.ALG_EC_SVDP_DH, false);
keyAgreement.init(ecPrivate);
short lenW = ecPublic.getW(baECPublic, (short) 0);
short lenOut = keyAgreement.generateSecret(baECPublic, (short) 0, (short) lenW, baOut, (short)0);

apdu.setOutgoing();
apdu.setOutgoingLength((short) lenOut);
apdu.sendBytesLong(baOut, (short) 0, lenOut);
}
catch(Exception e)
{
ISOException.throwIt((short) 0x4401 );
}

Thanks in advance.