Générer ECPublicKey à partir de ECPrivateKey

Question

J'essaie de générer une clé publique à partir d'une clé privée et d'une courbe connue. Ci-dessous mon code:

// Generate Keys 
ECGenParameterSpec ecGenSpec = new ECGenParameterSpec("secp256r1"); 
KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("ECDSA", "BC"); 
keyPairGenerator.initialize(ecGenSpec, new SecureRandom()); 
java.security.KeyPair pair = keyPairGenerator.generateKeyPair(); 
ECPrivateKey privateKey = (ECPrivateKey) pair.getPrivate(); 
ECPublicKey publicKeyExpected = (ECPublicKey) pair.getPublic(); 

// Expected public key 
System.out.print("Expected Public Key: " + 
     BaseEncoding.base64Url().encode(publicKeyExpected.getEncoded())); 

// Generate public key from private key 
X9ECParameters ecp = SECNamedCurves.getByName("secp256r1"); 
ECDomainParameters domainParams = new ECDomainParameters(ecp.getCurve(), 
     ecp.getG(), ecp.getN(), ecp.getH(), 
     ecp.getSeed()); 
ECPoint Q = domainParams.getG().multiply(privateKey.getS()); // is this correct? 
KeyFactory kf = KeyFactory.getInstance("ECDSA", "BC"); 
ECPublicKey publicKeyGenerated = 
     (ECPublicKey) kf.generatePublic(new X509EncodedKeySpec(Q.getEncoded(false))); // exception here 

// Generated public key from private key 
System.out.print("Generated Public Key: " + 
     BaseEncoding.base64Url().encode(publicKeyGenerated.getEncoded())); 

Cependant, quand je l'appelle: kf.generatePublic(new X509EncodedKeySpec(Q.getEncoded(false))) je reçois l'exception: java.security.spec.InvalidKeySpecException: encoded key spec not recognised (pas mon mal orthographié)

I semble je ne calcule pas correctement Q, mais je ne suis pas sûr où est mon erreur.

Merci pour l'aide!

Answer 1

Dans le cas où mon futur moi a besoin de la solution:

// Generate Keys 
ECGenParameterSpec ecGenSpec = new ECGenParameterSpec("secp256r1"); 
KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("ECDSA", "BC"); 
keyPairGenerator.initialize(ecGenSpec, new SecureRandom()); 
java.security.KeyPair pair = keyPairGenerator.generateKeyPair(); 
ECPrivateKey privateKey = (ECPrivateKey) pair.getPrivate(); 
ECPublicKey publicKeyExpected = (ECPublicKey) pair.getPublic(); 

// Expected public key 
System.out.print("Expected Public Key: " + 
     BaseEncoding.base64Url().encode(publicKeyExpected.getEncoded())); 

// Generate public key from private key 
KeyFactory keyFactory = KeyFactory.getInstance("ECDSA", "BC"); 
ECParameterSpec ecSpec = ECNamedCurveTable.getParameterSpec("secp256r1"); 

ECPoint Q = ecSpec.getG().multiply(privateKey.getD()); 
byte[] publicDerBytes = Q.getEncoded(false); 

ECPoint point = ecSpec.getCurve().decodePoint(publicDerBytes); 
ECPublicKeySpec pubSpec = new ECPublicKeySpec(point, ecSpec); 
ECPublicKey publicKeyGenerated = (ECPublicKey) keyFactory.generatePublic(pubSpec); 

// Generated public key from private key 
System.out.print("Generated Public Key: " + 
     BaseEncoding.base64Url().encode(publicKeyGenerated.getEncoded()));