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Normalise elliptic curve points.

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akwizgran
2014-01-16 15:35:25 +00:00
parent a168a7ba89
commit 14e1cd6072
2 changed files with 9 additions and 6 deletions
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8
briar-core/src/org/briarproject/crypto/Sec1KeyParser.java
View File

@@ -9,6 +9,7 @@ import org.briarproject.api.crypto.PublicKey;
import org.spongycastle.crypto.params.ECDomainParameters; import org.spongycastle.crypto.params.ECDomainParameters;
import org.spongycastle.crypto.params.ECPrivateKeyParameters; import org.spongycastle.crypto.params.ECPrivateKeyParameters;
import org.spongycastle.crypto.params.ECPublicKeyParameters; import org.spongycastle.crypto.params.ECPublicKeyParameters;
import org.spongycastle.math.ec.ECCurve;
import org.spongycastle.math.ec.ECPoint; import org.spongycastle.math.ec.ECPoint;
/** /**
@@ -50,13 +51,14 @@ class Sec1KeyParser implements KeyParser {
BigInteger y = new BigInteger(1, yBytes); // Positive signum BigInteger y = new BigInteger(1, yBytes); // Positive signum
if(y.compareTo(modulus) >= 0) throw new GeneralSecurityException(); if(y.compareTo(modulus) >= 0) throw new GeneralSecurityException();
// Verify that y^2 == x^3 + ax + b (mod p) // Verify that y^2 == x^3 + ax + b (mod p)
BigInteger a = params.getCurve().getA().toBigInteger(); ECCurve curve = params.getCurve();
BigInteger b = params.getCurve().getB().toBigInteger(); BigInteger a = curve.getA().toBigInteger();
BigInteger b = curve.getB().toBigInteger();
BigInteger lhs = y.multiply(y).mod(modulus); BigInteger lhs = y.multiply(y).mod(modulus);
BigInteger rhs = x.multiply(x).add(a).multiply(x).add(b).mod(modulus); BigInteger rhs = x.multiply(x).add(a).multiply(x).add(b).mod(modulus);
if(!lhs.equals(rhs)) throw new GeneralSecurityException(); if(!lhs.equals(rhs)) throw new GeneralSecurityException();
// We know the point (x, y) is on the curve, so we can create the point // We know the point (x, y) is on the curve, so we can create the point
ECPoint pub = params.getCurve().createPoint(x, y); ECPoint pub = curve.createPoint(x, y).normalize();
// Verify that the point (x, y) is not the point at infinity // Verify that the point (x, y) is not the point at infinity
if(pub.isInfinity()) throw new GeneralSecurityException(); if(pub.isInfinity()) throw new GeneralSecurityException();
// Verify that the point (x, y) times n is the point at infinity // Verify that the point (x, y) times n is the point at infinity

7
briar-core/src/org/briarproject/crypto/Sec1PublicKey.java
View File

@@ -1,8 +1,8 @@
package org.briarproject.crypto; package org.briarproject.crypto;
import org.briarproject.api.crypto.PublicKey; import org.briarproject.api.crypto.PublicKey;
import org.spongycastle.crypto.params.ECPublicKeyParameters; import org.spongycastle.crypto.params.ECPublicKeyParameters;
import org.spongycastle.math.ec.ECPoint;
/** /**
* An elliptic curve public key that uses the encoding defined in "SEC 1: * An elliptic curve public key that uses the encoding defined in "SEC 1:
@@ -23,9 +23,10 @@ class Sec1PublicKey implements PublicKey {
public byte[] getEncoded() { public byte[] getEncoded() {
byte[] encodedKey = new byte[publicKeyBytes]; byte[] encodedKey = new byte[publicKeyBytes];
encodedKey[0] = 4; encodedKey[0] = 4;
byte[] x = key.getQ().getAffineXCoord().toBigInteger().toByteArray(); ECPoint pub = key.getQ().normalize();
byte[] x = pub.getAffineXCoord().toBigInteger().toByteArray();
Sec1Utils.convertToFixedLength(x, encodedKey, 1, bytesPerInt); Sec1Utils.convertToFixedLength(x, encodedKey, 1, bytesPerInt);
byte[] y = key.getQ().getAffineYCoord().toBigInteger().toByteArray(); byte[] y = pub.getAffineYCoord().toBigInteger().toByteArray();
Sec1Utils.convertToFixedLength(y, encodedKey, 1 + bytesPerInt, Sec1Utils.convertToFixedLength(y, encodedKey, 1 + bytesPerInt,
bytesPerInt); bytesPerInt);
return encodedKey; return encodedKey;