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首页 > 解决方案 > Curve25519 公钥是 309 字节，私钥是 587。不应该是 32 字节吗？

java - Curve25519 公钥是 309 字节，私钥是 587。不应该是 32 字节吗？

问题描述

我正在尝试使用 bouncycastle 在我的 java 程序中实现curve25519，这是我想出的代码：

package crypto;

import org.bouncycastle.asn1.x9.X9ECParameters;
import org.bouncycastle.crypto.ec.CustomNamedCurves;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.jce.spec.ECParameterSpec;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import java.security.*;

public class Curve {

    public KeyPair generateKeyPair() throws NoSuchAlgorithmException, InvalidAlgorithmParameterException {
        X9ECParameters ecP = CustomNamedCurves.getByName("curve25519");
        ECParameterSpec ecSpec = new ECParameterSpec(ecP.getCurve(), ecP.getG(), ecP.getN(), ecP.getH(), ecP.getSeed());
        KeyPairGenerator keyGen = KeyPairGenerator.getInstance("EC", new BouncyCastleProvider());
        keyGen.initialize(ecSpec);
        return keyGen.generateKeyPair();
    }

}

我的主要方法：

package crypto;

import java.nio.charset.StandardCharsets;
import java.security.InvalidAlgorithmParameterException;
import java.security.KeyPair;
import java.security.NoSuchAlgorithmException;
import java.util.Base64;

public class Test_Curve {

    public static void main(String[] args) throws NoSuchAlgorithmException, InvalidAlgorithmParameterException {
        Curve curve = new Curve();
        KeyPair keys = curve.generateKeyPair();
        System.out.println(keys.getPrivate().getEncoded().length);
        System.out.println(keys.getPublic().getEncoded().length);
        System.out.println(new String(Base64.getEncoder().encode(keys.getPrivate().getEncoded()), StandardCharsets.US_ASCII));
        System.out.println(new String(Base64.getEncoder().encode(keys.getPublic().getEncoded()), StandardCharsets.US_ASCII));
    }

}

这是我从程序中得到的输出：

587
309
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
MIIBMTCB6gYHKoZIzj0CATCB3gIBATArBgcqhkjOPQEBAiB/////////////////////////////////////////7TBEBCAqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqYSRShRAQge0Je0Je0Je0Je0Je0Je0Je0Je0Je0Je0JgtenHcQyGQEQQQqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqq0kWiCuGaG4oIa04B7dLHdI0UySPU1+bXxhsinpxaJ+ztPZAiAQAAAAAAAAAAAAAAAAAAAAFN753qL3nNZYEmMaXPXT7QIBCANCAAQrALerSrNmYi5/OYIDQo3cfvrxiMDTiNF9DrF7HEjIDgcwqTAxgznbdXo1eS4j6qK43enyCGRuD1gl4748Qjvj

但是，这对我来说似乎不正确。我读到 curve25519 公钥应该是 32 字节，这显然不是。我已经完成了尽职调查，并从谷歌中提取了几个示例并进行了尝试，但仍然遇到了同样的问题。任何帮助是极大的赞赏。

标签： javabouncycastlepublic-keydiffie-hellman

解决方案

Curve25519 不是 X9/Weierstrass 曲线。您所做的将与其他实现不兼容，这些实现都使用 Bernstein 对称为 X25519 的仅 X 蒙哥马利形式 Diffie-Hellman 或称为 Ed25519 的 Edwards 形式签名（通常没有预哈希）的规范。Java 对所有非对称密钥（公共和私有）使用的密钥编码不仅仅是密钥本身，而是一种包含元数据的通用编码，X.509 SPKI 或 PKCS8并通过首先将此曲线强制为 Weierstrass 形式（对于 X9）然后通过使用显式且长期过时的 X9 形式来生成未命名ECParameterSpec的形式，您会极大地膨胀元数据。

取而代之的是使用算法 "X25519"或"ED25519"两者KeyPairGenerator和后续KeyAgreement或Signature分别。标准编码仍将比原始密钥长，但要少得多。要获得原始密钥，在 Oracle/Open 中适当地使用{XEC,EdEC}{Public,Private}Key由算法相关的实现（提供者）类实现的接口。（编辑）Recent Bouncy（1.65 以上）在足够新的 Java 上运行也可以做到这一点；否则，AFAICS 您必须获取通用 (ASN.1) 编码并对其进行解析——Bouncy 确实单独公开了该 (ASN.1) 功能（通过其“轻量级”API 而不是 JCA）（并且大约从一开始就已经存在）。

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