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javacryptographybouncycastleelliptic-curvesecp256k1

Elliptic Curve DSA in Bouncy Castle - what do h and n stand for?

I am trying to re-construct an ECPublicKey (generated by a smart card) in java with BouncyCastle.

I have this code, found from an example online:

KeyFactory keyFact = KeyFactory.getInstance("EC");
ECNamedCurveParameterSpec paramSpec = ECNamedCurveTable.getParameterSpec("secp256k1");
ECParameterSpec params = new ECNamedCurveSpec("secp256k1", paramSpec.getCurve(), paramSpec.getG(), paramSpec.getN(), paramSpec.getH());
ECPublicKey ecPublicKey = (ECPublicKey) keyFact.generatePublic(new ECPublicKeySpec(w, params));

(w is an ECPoint made of the x and y values I have from the smartcard)

What are n and h? Are they the cofactor and order of the cofactor of g, or something else?

Is there anymore values I need to get from the card to re-construct the key?

Solution

  • N is de order of G and h is the cofactor

    id recommend looking at this

    https://www.secg.org/sec2-v2.pdf