在本地Java中从私钥字符串派生EC公钥，使用secp256k1曲线。

要在本地Java中从私钥字符串派生EC公钥，并使用secp256k1曲线，可以使用Java加密库中的Bouncy Castle库。以下是一种解决方案的代码示例：

首先，确保已将Bouncy Castle库添加到Java项目中的依赖项中。

import org.bouncycastle.crypto.digests.SHA256Digest;
import org.bouncycastle.crypto.params.ECPrivateKeyParameters;
import org.bouncycastle.crypto.params.ECPublicKeyParameters;
import org.bouncycastle.crypto.signers.ECDSASigner;
import org.bouncycastle.crypto.signers.HMacDSAKCalculator;
import org.bouncycastle.jce.ECNamedCurveTable;
import org.bouncycastle.jce.spec.ECNamedCurveParameterSpec;
import org.bouncycastle.math.ec.ECPoint;
import org.bouncycastle.util.encoders.Hex;

import java.math.BigInteger;
import java.security.KeyFactory;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.Security;
import java.security.spec.ECPoint.Fp;
import java.security.spec.ECPrivateKeySpec;
import java.security.spec.ECPublicKeySpec;

public class EcdsaExample {
    public static void main(String[] args) throws Exception {
        // 添加Bouncy Castle库的提供者
        Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());

        // secp256k1曲线参数
        ECNamedCurveParameterSpec spec = ECNamedCurveTable.getParameterSpec("secp256k1");

        // 从私钥字符串派生EC私钥
        String privateKeyString = "私钥字符串";
        BigInteger privateKeyValue = new BigInteger(privateKeyString, 16);
        ECPrivateKeySpec privateKeySpec = new ECPrivateKeySpec(privateKeyValue, spec);
        KeyFactory keyFactory = KeyFactory.getInstance("EC", "BC");
        PrivateKey privateKey = keyFactory.generatePrivate(privateKeySpec);

        // 从EC私钥派生EC公钥
        ECPoint publicKeyPoint = spec.getG().multiply(privateKeyValue);
        ECPublicKeySpec publicKeySpec = new ECPublicKeySpec(publicKeyPoint, spec);
        PublicKey publicKey = keyFactory.generatePublic(publicKeySpec);

        System.out.println("私钥: " + privateKey);
        System.out.println("公钥: " + publicKey);
    }
}

请确保将“私钥字符串”替换为实际的私钥字符串。此代码示例使用Bouncy Castle库中的ECDSASigner类来派生公钥。