public static KeyPair Extract(KeyPair masterKey, String ID, Random rnd)
{
//user public key is ID+ public parameters
BFUserPublicKey pk = new BFUserPublicKey(ID, (BFMasterPublicKey)masterKey.Public);
Pairing e = ((BFMasterPublicKey)masterKey.Public).Pairing;
//user private key: hash(ID)->point Q
//sQ, s is the master private key
byte[] bid = null;
bid = Encoding.UTF8.GetBytes(ID);
Point Q = BFUtil.HashToPoint(bid, e.Curve, e.Cofactor);
BigInt s = ((BFMasterPrivateKey)masterKey.Private).Key;
Q = e.Curve.Multiply(Q, s);
BFUserPrivateKey sk = new BFUserPrivateKey(Q, (BFMasterPublicKey)masterKey.Public);
return(new KeyPair(pk, sk));
}
public static PublicKey ExtractPublic(KeyPair masterKey, String ID)
{
BFUserPublicKey pk = new BFUserPublicKey(ID, (BFMasterPublicKey)masterKey.Public);
return(pk);
}
public BFUserPublicKey Public(string id)
{
BFUserPublicKey userKey = (BFUserPublicKey)BFCipher.ExtractPublic(master, id);
return(userKey);
}
