| package org.bouncycastle.crypto.agreement; |
| |
| import java.math.BigInteger; |
| |
| import org.bouncycastle.crypto.BasicAgreement; |
| import org.bouncycastle.crypto.CipherParameters; |
| import org.bouncycastle.crypto.params.ECPrivateKeyParameters; |
| import org.bouncycastle.crypto.params.ECPublicKeyParameters; |
| // BEGIN android-added |
| import org.bouncycastle.math.ec.ECCurve; |
| // END android-added |
| import org.bouncycastle.math.ec.ECPoint; |
| |
| /** |
| * P1363 7.2.1 ECSVDP-DH |
| * |
| * ECSVDP-DH is Elliptic Curve Secret Value Derivation Primitive, |
| * Diffie-Hellman version. It is based on the work of [DH76], [Mil86], |
| * and [Kob87]. This primitive derives a shared secret value from one |
| * party's private key and another party's public key, where both have |
| * the same set of EC domain parameters. If two parties correctly |
| * execute this primitive, they will produce the same output. This |
| * primitive can be invoked by a scheme to derive a shared secret key; |
| * specifically, it may be used with the schemes ECKAS-DH1 and |
| * DL/ECKAS-DH2. It assumes that the input keys are valid (see also |
| * Section 7.2.2). |
| */ |
| public class ECDHBasicAgreement |
| implements BasicAgreement |
| { |
| private ECPrivateKeyParameters key; |
| |
| public void init( |
| CipherParameters key) |
| { |
| this.key = (ECPrivateKeyParameters)key; |
| } |
| |
| public int getFieldSize() |
| { |
| return (key.getParameters().getCurve().getFieldSize() + 7) / 8; |
| } |
| |
| public BigInteger calculateAgreement( |
| CipherParameters pubKey) |
| { |
| // BEGIN android-changed |
| ECPoint peerPoint = ((ECPublicKeyParameters) pubKey).getQ(); |
| ECCurve myCurve = key.getParameters().getCurve(); |
| if (peerPoint.isInfinity()) { |
| throw new IllegalStateException("Infinity is not a valid public key for ECDH"); |
| } |
| try { |
| myCurve.validatePoint(peerPoint.getXCoord().toBigInteger(), |
| peerPoint.getYCoord().toBigInteger()); |
| } catch (IllegalArgumentException ex) { |
| throw new IllegalStateException("The peer public key must be on the curve for ECDH"); |
| } |
| // Explicitly construct a public key using the private key's curve. |
| ECPoint pubPoint = myCurve.createPoint(peerPoint.getXCoord().toBigInteger(), |
| peerPoint.getYCoord().toBigInteger()); |
| ECPublicKeyParameters pub = (ECPublicKeyParameters)pubKey; |
| if (!pub.getParameters().equals(key.getParameters())) |
| { |
| throw new IllegalStateException("ECDH public key has wrong domain parameters"); |
| } |
| ECPoint P = pubPoint.multiply(key.getD()).normalize(); |
| // END android-changed |
| |
| if (P.isInfinity()) |
| { |
| throw new IllegalStateException("Infinity is not a valid agreement value for ECDH"); |
| } |
| |
| return P.getAffineXCoord().toBigInteger(); |
| } |
| } |