java.lang.IllegalArgumentException: string curve25

Question

I'm trying to generate a key pair using the /java bouncy castle 1.52 implementation for curve 25519 what gives me

java.lang.IllegalArgumentException: string curve25519 not an OID

Here is my code:

public KeyPair generateKeys() throws NoSuchAlgorithmException,
        NoSuchProviderException, InvalidAlgorithmParameterException {
    ECParameterSpec ecSpec = ECNamedCurveTable.getParameterSpec("curve25519");
    KeyPairGenerator g = KeyPairGenerator.getInstance("ECDSA", "BC");
    g.initialize(ecSpec, new SecureRandom());

    return g.generateKeyPair();
}

the result of this code is a stacktrace below:

java.lang.IllegalArgumentException: string curve25519 not an OID at org.bouncycastle.asn1.ASN1ObjectIdentifier.(Unknown Source) at org.bouncycastle.jcajce.provider.asymmetric.ec.BCECPublicKey.getEncoded(Unknown Source) at org.bouncycastle.jcajce.provider.asymmetric.ec.BCECPrivateKey.getPublicKeyDetails(Unknown Source) at org.bouncycastle.jcajce.provider.asymmetric.ec.BCECPrivateKey.(Unknown Source) at org.bouncycastle.jcajce.provider.asymmetric.ec.KeyPairGeneratorSpi$EC.generateKeyPair(Unknown Source) at com.poc.databank.encryption.BouncyCastleEncryption.generateKeys(BouncyCastleEncryption.java:22) at com.poc.databank.encryption.BouncyCastleTest.testApp(BouncyCastleTest.java:16) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:606) at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44) at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17) at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50) at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238) at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63) at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236) at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53) at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229) at org.junit.runners.ParentRunner.run(ParentRunner.java:309) at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50) at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)

I checked the bouncy castle code and figured out that the curve25519 is registered in CustomNamedCurves class as

defineCurve("curve25519", curve25519);

but not as

defineCurveWithOID("secp192k1", SECObjectIdentifiers.secp192k1,
            secp192k1);

I understand that there should be a reason for this. Please help me to found out a way how I can generate a key pair uising curve25519.

Answer 1

You need to get curve parameters in X9.62 format and convert them to JCE format

X9ECParameters ecP = CustomNamedCurves.getByName("curve25519");
ECParameterSpec ecSpec=new ECParameterSpec(ecP.getCurve(), ecP.getG(),
        ecP.getN(), ecP.getH(), ecP.getSeed());

Then produce ECDSA key as normal

Provider bcProvider = new BouncyCastleProvider();
KeyPairGenerator g = KeyPairGenerator.getInstance("ECDSA", bcProvider);
g.initialize(ecSpec, new SecureRandom());
KeyPair keyPair = g.generateKeyPair();
Assert.assertNotNull(keyPair);

I believe curve25519 has no Object Identifier assigned to it. But probably it doesn't excuse inability to find curve by name.

Answer 2

@divanov I got the following compilation error when I run your code

error: constructor ECParameterSpec in class ECParameterSpec cannot be applied to given types;
ECParameterSpec ecSpec=new ECParameterSpec(ecP.getCurve(), ecP.getG(),
^
required: EllipticCurve,java.security.spec.ECPoint,BigInteger,int
found: ECCurve,org.bouncycastle.math.ec.ECPoint,BigInteger,BigInteger,byte[]
reason: actual and formal argument lists differ in length

Has the method signature changed? May be we could use org.bouncycastle.jcajce.provider.asymmetric.util.EC5Util

X9ECParameters ecP = CustomNamedCurves.getByName("curve25519");
ECParameterSpec ecSpec = EC5Util.convertToSpec(ecP);