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package org.bitcoin;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import com.google.common.base.Preconditions;
/**
* This class holds native methods to handle ECDSA verification.
* You can find an example library that can be used for this at
* https://github.com/sipa/secp256k1
*/
public class NativeSecp256k1 {
public static final boolean enabled;
static {
boolean isEnabled = true;
try {
System.loadLibrary("javasecp256k1");
} catch (UnsatisfiedLinkError e) {
isEnabled = false;
}
enabled = isEnabled;
}
private static ThreadLocal<ByteBuffer> nativeECDSABuffer = new ThreadLocal<ByteBuffer>();
/**
* Verifies the given secp256k1 signature in native code.
* Calling when enabled == false is undefined (probably library not loaded)
*
* @param data The data which was signed, must be exactly 32 bytes
* @param signature The signature
* @param pub The public key which did the signing
*/
public static boolean verify(byte[] data, byte[] signature, byte[] pub) {
Preconditions.checkArgument(data.length == 32 && signature.length <= 520 && pub.length <= 520);
ByteBuffer byteBuff = nativeECDSABuffer.get();
if (byteBuff == null) {
byteBuff = ByteBuffer.allocateDirect(32 + 8 + 520 + 520);
byteBuff.order(ByteOrder.nativeOrder());
nativeECDSABuffer.set(byteBuff);
}
byteBuff.rewind();
byteBuff.put(data);
byteBuff.putInt(signature.length);
byteBuff.putInt(pub.length);
byteBuff.put(signature);
byteBuff.put(pub);
return secp256k1_ecdsa_verify(byteBuff) == 1;
}
/**
* @param byteBuff signature format is byte[32] data,
* native-endian int signatureLength, native-endian int pubkeyLength,
* byte[signatureLength] signature, byte[pubkeyLength] pub
* @returns 1 for valid signature, anything else for invalid
*/
private static native int secp256k1_ecdsa_verify(ByteBuffer byteBuff);
}
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